NATIONAL ROAD TRANSPORT COMMISSON

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NATIONAL ROAD TRANSPORT COMMISSON Powered By Docstoc
					NATIONAL ROAD TRANSPORT COMMISSON

 DIESEL EXHAUST AFTER TREATMENT
           TECHNOLOGIES
                and
   The POTENTIAL for RETROFITING
               to the
       EXISTING DIESEL FLEET




                    PREPARED BY Alross Pty Ltd
                              September, 2000
FOREWORD


The National Road Transport Commission is taking a comprehensive approach to
reducing emissions from the diesel fleet. Through its work with the Motor Vehicle
Environment Committee, the NRTC has contributed to setting new vehicle emission
standards, improving fuel quality and proposals for improving in-service emissions
performance.

The Diesel Emissions National Environment Protection Measure (Diesel NEPM),
currently being developed by the National Environment Protection Council in
conjunction with the NTRC, will present a range of strategies to improve emissions
from the current diesel fleet. This report shows that one of these strategies; the
retrofit of exhaust after-treatment devices such as catalysts and particle traps, is
capable of reducing exhaust emissions at a cost.

The report examines the issues that governments and private businesses will need to
address in considering the role of exhaust after-treatment devices in improving in-
service emissions from diesel vehicles. It is intended to contribute to the current level
of knowledge regarding the potential for emission reductions in Australia from the use
of these devices. The report was prepared by an independent consultant and does not
necessarily represent the views of the NRTC.

A draft Diesel NEPM and in-service emission standards is being circulated for public
comment in the first quarter of 2001. Stakeholders wishing discuss exhaust after-
treatment issues or any other aspects of the Diesel NEPM and in-service standards can
contact:

Tim Eaton
Senior Project Manager
Safety and Environment

Ph 03 9321 8444
Email eatont@nrtc.gov.au




                                           2
CONTENTS

                                                              Page
EXECUTIVE SUMMARY                                              4
INTRODUCTION                                                   8
BACKGROUND                                                     9
DIESEL EMISSIONS                                              11
DIESEL RETROFIT TECHNOLOGIES                                  13
      Oxidation Catalyst                                      13
      Diesel Particulate Trap                                 17
      Catalytic Conversion of NOx                             19
      Selective Catalytic Convertor                           20
      Other Technologies                                      21
      Technology Summary                                      23
      Field Performance                                       23
COSTS                                                         25
      Equipment Costs                                         25
      Installation Costs                                      25
      Impact of Retrofit Technology on Fuel Efficiency        26
      Cost Effectiveness                                      27
EXISTING PROGRAMS for RETROFIT
of HEAVY DUTY DIESEL VEHICLES                                 29
OPTIONS for AUSTRALIA                                         32
      Basic issues                                            32
      Technical Issues                                        32
      Program Design Parameters                               34
      Incentives                                              34
      Performance Assessment                                  35
      The Sanctions Structure                                 36
      The Target Fleet                                        36
THE OPTION SET                                                37
IMPLEMENTATION PARAMETERS AND OUTCOMES                        38
      Option 1 – Urban Buses                                  38
      Option 2 - Vehicles Owned by/Contracted to Government   40
      Option 3 – Heavy Haulage Fleet                          41
COMMENT                                                       42
CONCLUSIONS                                                   45
REFERENCES                                                    46

ATTACHMENTS
ATTACHMENT 1   REVIEW OF EMISSION CONTROL                     50
               STRATEGIES
ATTACHMENT 2 US EPA URBAN BUS PROGRAM AND                     73
            EXTENSIONS
ATTACHMENT 3 UK CLEANER VEHICLES TASK FORCE                   78
              Final Report
ATTACHMENT 4 LONDON TRANSPORT BUSES                           80
                “Buses: a cleaner future”
ATTACHMENT 5 BASIC MODEL                                      83



                                      3
LIST OF TABLES and FIGURES
Table 1. Comparison of Emission Standards for Heavy-duty Diesel     11
Vehicle Engines in Australia, Europe, the United States and Japan
Table 2. Fuel-Sensitive Technologies for Diesel Engines             11
Table 3. Performance of a Particulate Trap                          18
Table 4: Effect of of Fuel Consumption Penalty                      27
Table 5: Cost-effectiveness – Effect of Distance Travelled          28
Table 6: Effect of Emission Rate on Cost Effectiveness              28
Table 7. Option 1 - Retrofit of Sydney Urban Bus Fleet)             39
Table 8. Option 2 - Retrofit of Government Owned/Operated Fleet     40
Table 9. Option 3 - NSW Long Distance Transport Fleet               41
Table 10. Impact of Variations in Retrofit Unit Costs on Cost       42
Effectiveness, Option 3 Parameter Set
Table 11. Variation in Cost Effectiveness with Annual Distance      43
Travelled, Option 3 Parameter Set
Table 12. Effect of Emission Rate on Cost Effectiveness, Option 3   43
Parameter Set
Table 13. Variation in Cost Effectiveness with Fuel Efficiency      44
Penalty, Option 3 Parameter Set

Figure 1. Conversion of CO and HC in a Diesel Oxidation Catalyst    15
Figure 2. PM performance of Diesel Oxidation Catalyst               16

ABBREVIATIONS

ADR            Australian Design Rule
CNG            Compressed Natural Gas
CO             Carbon Monoxide
CRT            Continuously Regenerating Trap
DOC            Diesel Oxidation Catalyst
DPF            Diesel Particulate Filter
EU             European Union
GST            Goods and Services Tax
HC             Hydrocarbons
I/M            Inspection and Maintenance
LNC            Lean NOx Combustion
LPG            Liquefied Petroleum Gas
MECA           Manufacturers of Emission Controls Association
NEPC           National Environmental Protection Council
NEPM           National Environmental Protection Measure
NESCAUM        North-East States for Coordinated Air Use Management
OEM            Original Equipment Manufacturers
PM             Particulate Matter
PM-10          Particulate Matter less than 10 Microns diameter
SCC            Selective Catalytic Converter
SCR            Selective Catalytic Reduction
SOF            Soluble Organic Fraction
STA            State Transit Authority
UN ECE         United Nations Economic Commission for Europe
US EPA         United States Environmental Protection Authority


                                         4
EXECUTIVE SUMMARY
This study set out to assess issues involved in determining the future role for
programs to retrofit heavy diesel road vehicles exhaust systems with after treatment
devices to improve their emissions performance. The study required assessment of
existing and potential technology and the identification of technologies suitable for
use on vehicles in Australia.

Diesel exhaust after treatment technology has been used for large stationary engines
for some time. Development of the technology for road vehicles and in particular
heavy road vehicles has been driven by air quality concerns and by the more stringent
emissions performance requirements now coming into effect. The technology has
been first developed for new vehicles as part of the emissions management system.

Concerns regarding air quality in large cities led to the development of technology for
retrofitting to the existing fleet. There have been a number of major programs in US
and Europe which have demonstrated the potential benefits of retrofit programs.

The study assumes that commercial diesel fuel in Australia will move to low sulphur
content (50 ppm) in accordance with the current agreed timetable.

Technology
There are three basic approaches to “retrofit” programs1 to reduce emissions from
the existing diesel fleet of heavy road vehicles :
         Oxidation catalysts
         Particulate traps
         Engine rebuild kits

The last approach, engine rebuild kits has been demonstrated as effective, but has
largely been developed for US sourced engines. The study therefore focusses on the
first two technologies.

Oxidation catalysts significantly reduce emissions of HC, CO and to a lesser extent
TPM. The oxidation catalyst is not effective in reducing NOx emissions. The units fit
in the exhaust line or inside the muffler. In some cases manufacturers offer a
replacement muffler unit incorporating the catalyst.

Particulate traps significantly reduce the level of TPM, but have less effect on HC and
CO. Particulate traps do not significantly affect the level of NOx emissions. The units
fit into the exhaust line in a similar way to oxidation catalysts.

Retrofit units which effectively combine oxidation catalysts and particulate traps offer
the prospect of high performance reduction in PM as well as HC and CO.

Technologies to reduce NOx emissions are developing. The most promising appears
to be the selective catalytic converter. The units are more complex that oxidation
catalysts and particulate traps and require some form of catalyst (commonly urea)


1MVEC is addressing a range of approaches to reduce heavy vehicle emissions, including
fuel quality, in-service maintenance and alternative fuels


                                            5
which raises issues of storage and replenishment. Selective catalytic converters are
now being offered on some new vehicles.

Public concern regarding “diesel smoke” has led to a focus on the reduction of PM
emissions in retrofit programs. While this tends to favour the particulate trap, the
higher unit cost of the particulate trap has led to some concentration on the use of
oxidation catalysts in retrofit programs. However, the unit costs of both oxidation
catalysts and particulate traps is decreasing as production builds up.

If the primary concern is PM reduction, the higher cost of the particulate trap is offset
by the better performance in PM reduction. There are other factors which impact on
the cost effectiveness of both oxidation catalysts and particulate traps. These include
the unit costs, the annual vehicle travel, the emission rates of the target vehicles and
the potential for fuel efficiency penalties.

Programs in Other Countries
There are a significant number of retrofit programs in other countries:
        US where the EPA Urban Bus program is being extended to heavy vehicles
        UK, where the is a broad program to improve air quality through a
           number of retrofit and other options
        Europe, where there are a number of urban vehicle programs,
        South America where there are several bus programs
        Hong Kong and Bangkok, where new bus programs have been announced.

These existing programs provide a range of experience and options for consideration
in developing programs in Australia.

Retrofit Programs for Australia
The development of a retrofit program needs to take account of a number of policy
issues:
         Institutional structure, including incentives and sanctions
         Capital Costs
         Target fleets
         Cost effectiveness

The institutional structure involves incentives (including requirements), sanctions and
monitoring. There is a range of options for incentives, ranging from some form of
rebate to inclusion of retrofit in alternative compliance programs. The requirements
approach ranges from government decisions for government owned/operated fleets to
statutory requirements applying to all vehicles in the category of interest.

The capital costs are dominated by the relative costs of oxidation catalysts ($2,500
and particulate traps ($6,000). These costs can be expected to drop as production
builds up. The development of combined units will also affect the capital cost
structure. The installation costs for oxidation catalysts and for particulate traps
would be similar, with costs varying according to the physical constraints for each
type of vehicle and the packaging of the retrofit unit (brackets, lugs etc to facilitate
changeover).




                                             6
The target fleets are a key aspect of program design. The urban bus fleet in major
cities has obvious attractions for retrofit. The fleet is essentially under government
control, it has a large degree of homogeneity and most of the emissions take place in
the urban areas. The government owned/operated fleet has similar attractions,
although the degree of travel in the urban areas is less. The heavy duty road
transport fleet poses different problems, requiring careful development of a program
through consultation with industry.

Three options are addressed in the report:
        Urban buses
        Government owned/operated fleets
        Heavy haulage fleet

Each option is defined for a particular region as the air quality/emission management
issues are essentially regional. Robust data is not easily available and a number of
assumptions have been made. In designing a specific program, specific data would
be available.

The following outcomes were identified:
Option/Target Fleet                    Retrofit                 Cost Effectiveness
                                     technology                 $/kg PM reduction

Option 1                          Oxidation catalysts                  39.13
Urban Buses
                                   Particulate trap                    31.31

Option2 –                         Oxidation catalysts                  26.46
Government
owned/operated fleet               Particulate trap                    21.16

Option 3-Heavy haulage            Oxidation catalysts                  16.29
fleet
                                   Particulate trap                    13.03


The outcomes are dependent on:
        Unit cost – cost effectiveness improves as unit costs reduce
        Annual distance travelled - cost effectiveness improves as distance
          travelled increases
        Emission rate – cost effectiveness improves as emission rate increases
        Fuel efficiency penalty – cost effectiveness deteriorates as fuel efficiency
          penalty increase.

For current cost and performance estimates, particulate traps are consistently more
cost effective. The higher initial cost of the particulate trap raises program cost
issues and has led to some preference for oxidation catalysts in existing programs.

These factors identify some of the key issues in designing a retrofit program:
        Choose high utilisation vehicles


                                           7
          Examine unit costs carefully
          Minimise fuel efficiency penalties by proper matching of retrofit units to
           the vehicle engines.

In summary, there are two field proven commercially available technologies for
exhaust after treatment for heavy duty diesel engines:
       Oxidation catalysts
       Particulate traps.

The technology is evolving rapidly and new developments offer considerable promise.
Retrofit programs offer a cost effectiveness of $10-40/kg PM reduction, depending on
program parameters.




                                           8
INTRODUCTION
This project was carried out for the National Road Transport Commission (NRTC) as
part of the preparatory work for a Diesel National Environmental Protection Measure
(NEPM). The principal contactor was Alross Pty Ltd (Dennis McLennan), with
Parsons Australia (Peter Anyon) and Michael Mowle providing technical support and
information.

Project Objectives
The project objectives are set out in the project brief as follows:
   The key objective of this study is to provide information that will assist policy
   makers in determining the future role of retrofitted exhaust after treatment
   technologies in improving emissions from the diesel fleet. This will be achieved
   by:
   1. providing an inventory of diesel exhaust after treatment technologies
        (focusing on catalyst technologies) that are existing or under development;
   2. identifying the key features of these technologies;
   3. identifying whether any of these technologies are suitable for use on the
        existing diesel fleet and;
   4. identifying issues associated with retrofitting exhaust after treatment
        technologies to the existing diesel fleet.

Study Approach
The study approach was based on guidance in the project brief. The technology part
of the study is based on current information held by the project team, updated where
appropriate from publicly available data. The scenario and option set section of the
study is based on simple analytical approaches which will provide useful guidance for
agencies considering the development of programs.




                                          9
BACKGROUND
The regulation of diesel emissions in Australia began with the introduction of
Australian Design Rule 70 in 1995. ADR 70 was based on the UN ECE R49 and R83
and allowed certification to three alternative standards, the EU Directives (reflecting
the technical conditions of the ECE regulations), the US EPA 1991 and the Japanese
standard. ADR 70 was seen as a “first step”, recognising the realities of the world
scene and the Australian market.

The new vehicle standards have now been revised in line with the agreements reached
during the GST negotiation process. Essentially, Australia will follow ECE standards,
recognised as the “international” standards, and representing effective best practice
and will progressively implement the tighter standards based on the “Euro” group of
standards. For heavy vehicles, certification to the US EPA Standard will also be
recognised.

The problem is that new vehicle standards have a significant time delay in permeating
the fleet to a significant extent. The problem of the emissions of the existing fleet,
and programs to manage those emissions, is a significant issue. The “In Service
Emissions Study”, carried out by the Federal Office of Road Safety was the first
serious attempt in Australia to develop robust, quantitative data to help policy
development in this area (for cars).

The current program of work on diesel emissions is based on a broad approach to
managing diesel emissions. It encompasses new vehicle standards, in-service
management and programs to reduce emissions from the existing fleet.

There are two fundamental aspects of diesel emissions:
        particulates and smoke
        gaseous emissions.

To the public, the “smoke” and odour aspects are very visible and this has led to a
focus on these issues in many jurisdictions. Public support for the management of
smoke and odour is likely to be strong, while programs to manage gaseous emissions
are not likely to generate the same level of support.

Studies indicate that the issue of diesel engine NOx emissions is also important, as
diesel engine vehicles will be a major contributor to the future growth of NOx
emission levels in urban conurbations.

This project is aimed at the issue of technology and options for retrofitting suitable
vehicles in the current diesel fleet with equipment to reduce exhaust emissions. The
project draws on experience overseas to identify current and emerging technologies
that might have application in Australia. The issue of emissions from older diesel
engines has been recognised world wide, and there are a number of major programs in
place. The US EPA “Urban Bus Program is well documented and relies on incentives
derived from the air quality management programs to encourage retrofit. The
program has now been extended to heavy vehicles. The EPA program is very
structured, with a range of approved packages and products, and extensive monitoring
and evaluation.



                                           10
The London Bus Program is quite different in that a major focus was on particulate
matter and “diesel odour”, and the incentive came from government. There are a
range of other initiative (taxis, medium trucks) specifically aimed at improved air
quality in London. A key focus of these programs is the reduction of particulates and
“diesel odour”. However the high capital cost of particulate traps lead to a focus on
oxidation catalyst technology for implementation..

There are other city focussed programs in Europe based on the development of “no
go” areas in the city for diesel vehicles not fitted with emissions reduction technology
(eg the Swedish three cities program).

There are programs in South America focussed on urban buses, and a range of
demonstration projects in several countries aimed at validating new technology. A
major program to retrofit urban buses in Hong Kong and Bangkok were recently
announced.

The technology for diesel retrofit has developed from the technology required to meet
the very tight proposed emission standards in Europe and America. Some of the
technology derives from technology used for diesel engines used in mining and
stationary equipment.

The issue of fuel quality is relevant to retrofit technologies. Several of the
technologies available are sensitive to fuel sulphur content. For the purpose of this
study, it is assumed that the proposed Australian fuel quality program (diesel fuel
sulphur content reduced to a maximum of 150ppm by 2005 and 50ppm by 2006) will
be implemented. These standards are required to allow the use of appropriate
technologies to meet the proposed emission requirements (Review of Fuel Quality
Requirements for Australian Transport – Coffey Geosciences 2000). The proposed
fuel sulphur standards were also endorsed as part of the GST Package negotiated
between the Government and the Australian Democrats. Retrofit program proposals
will assume the availability and use of low sulphur diesel fuel.




                                           11
DIESEL EMISSIONS
The emission standards for diesel engines are set out below:

Table 1: Comparison of Emission Standards for Heavy-duty Diesel Vehicle
Engines in Australia, Europe, the United States and Japan

Pollutant            ADR70/00        Euro2       Euro3      Euro4      Euro5       US        Japan
                     1997/99         1995        2000       2005       2008        1998      2004
CO g/k W/hr          4.5             4.0         2.1        1.5        1.5         15.5      2.22
HC g/k W/hr          1.1             1.1         0.66       0.46       0.46        1.3       0.87
NOx g/k W/hr         0.36            0.15        0.1        0.03       0.02        0.1       0.18
PM g/k W/hr          0.36            0.15        0.1        0.03       0.02        0.1       0.18

Notes: Test procedural differences mean that direct comparisons of standards are not necessarily valid
       ADR 70/00=Euro1 or US 94 or Japan 94. The ADR is shown here as the Euro1 limits.

Source: Review of Fuel Quality Requirements for Australian Transport
       Coffey Geosciences 2000

To achieve these limits, a range of technologies is in use or emerging. These are
summarised below:


Table 2: Fuel-Sensitive Technologies for Diesel Engines

Technology                 Availability         Sensitivity Fuel Quality    Key Fuel Parameter and
                                                                                  Threshold
                       Now        Emerging
Computerised fuel                                        Low
and engine
management
Direct fuel                                              Low
injection
Common Rail                                              Low
High Pressure
Injection
2-way catalyst                                           High              Sulphur  30 ppm
De-Nox catalyst                                          High              Sulphur  5-10 ppm
Continuously                                             High              Sulphur  30 ppm
regenerating
particulate trap *
Particulate                                              Low
filtration *
On board                                                Medium             Sulphur  150 ppm
diagnostics
*These technologies could today be considered to have moved to “available now”

Source: Review of Fuel Quality Requirements for Australian Transport
       Coffey Geosciences 2000

The first three technologies are engine technology, and are only suited to treatment of
the existing fleet where engine rebuild programs allow the incorporation of advanced



                                                 12
technology in existing engines. The US EPA Urban Bus program does encompass
engine rebuild technology, and has achieved significant results. Other programs focus
on fitting specific devices outside the engine to achieve emissions reductions.

The US engine rebuild programs are based on engines used in urban buses in the US.
The Australian urban bus fleet is predominantly based on European engines, and
engine rebuild programs are not well developed for these engines. If European
developments continue to focus on devices fitted after the engine, it is unlikely that
engine rebuild programs similar to the US programs will develop in the short term.

Consequently this project does not substantively address engine rebuild programs.
The NESCAUM Report, 1997, sets out guidelines for managing an engine rebuild
program. It may be necessary to work with European agencies to encourage the
development of rebuild packages focussed on emissions reduction.

This project does not encompass the role of “in-service” management (I/M) programs
in managing diesel emissions. It is recognised that an effective I/M program could
achieve significant emissions reductions through focussing on the gross emitters in the
fleet. For this project, the focus is on technologies which could be used to support a
program to retrofit particular diesel engine vehicle fleets.




                                          13
DIESEL RETROFIT TECHNOLOGIES
The technologies available for diesel retrofit essentially fall into three groups:
        oxidation catalysts
        particulate traps
        selective catalytic converters.

The first two technologies are now well established and available off the shelf. The
components have been developed to be installed directly in the exhaust line or as
muffler replacements, and installation is simple. There is no electronic control
circuitry, and there are no moving or working parts. There is, however, the issue of
regeneration for particulate traps, which is discussed under “Filter (Trap)
Regeneration”.

Selective catalytic converters are not yet generally on offer as retrofit technology,
being mainly developed to help vehicle manufacturers reach the new emission
performance standards. SCCs by their nature require storage and metering equipment
as part of the unit, and may require linkage to the engine management system.
Installation and operation will be more complex than for the oxidation catalytic
converter or the particulate trap.

Oxidation Catalyst (2-way Catalyst)
A diesel oxidation catalyst is designed to cause desirable chemical reactions in the
exhaust gas stream without being consumed itself. The physical device is a
honeycomb structure contained in a stainless steel jacket and commonly replaces the
muffler in a retorfit installation. The honeycomb surface is coated with the catalytic
precious metals that induce the desired oxidation reactions.

Diesel oxidation catalysts were first introduced in 1970s in underground mining as a
measure to control CO. Today, oxidation catalysts are used on many diesel road
vehicles, primarily to control particulate matter and hydrocarbon emissions to meet
emissions performance requirements.

Early diesel catalysts utilised very active oxidation formulations such as platinum on
alumina. They were very effective in oxidising emissions of CO and HC as well as
the SOF portion of diesel particulates.

A downside of earlier catalysts was that they also oxidised sulphur dioxide, which is
present in diesel exhaust from the combustion of sulphur containing fuels. The
oxidation of SO2 leads to the generation of sulphate particulates and may significantly
increase total particulate emissions despite the decrease of the SOF fraction.
Newer diesel oxidation catalysts are designed to be selective, i.e., to obtain a
compromise between sufficiently high HC and SOF activity and acceptably low SO2
activity.

Applications of Diesel Oxidation Catalyst
Diesel oxidation catalyst (DOC) technology promotes a range of oxidation reactions
utilising the excess oxygen present in diesel exhaust at all engine operating
conditions.




                                            14
The oxidation reactions may also be combined with selective catalytic reduction
(SCR) and lean NOx catalyst (LNC). SCR systems are used in to reduce NOx
emissions through selective reaction with a reducing agent, such as ammonia or urea,
which is injected upstream of the catalyst bed. The lean NOx catalyst, intended to
reduce nitrogen oxides in an oxidising atmosphere from mobile engines, is now
becoming a commercial reality for new vehicles. Pressure to improve urban air quality
will provide the incentive for the development of the technology for the retrofit
scenario.

Increasingly stringent emission standards, such as Euro3 and 4, are likely to transform
the emission control catalyst into a standard component of diesel powered vehicles.
Future catalysts will also have to exhibit at least some NOx reduction activity in
addition to their oxidation functions.

The U.S. Urban Bus Retrofit/Rebuild Requirements which became effective in 1995
triggered the widespread use of catalysts on urban buses. Several systems that have
been certified by the EPA under the bus retrofit program utilise diesel oxidation
catalysts, either alone or in conjunction with other emission controls.

Gaseous Phase Performance
The diesel oxidation catalyst is an effective device to control carbon monoxide and
hydrocarbons emissions from diesel engines, including the PAH and hydrocarbon
derivatives such as aldehydes.

Figure 1 depicts an example catalyst performance. The catalyst shows no activity at
low exhaust gas temperatures. As the temperature increases, so does the oxidation rate
of CO and HC. This is called catalyst "light-off". At high temperatures the catalyst
performance stabilises to form the characteristic plateau on the light-off curve. For
simple oxidation catalysts such as Pt/Al2O3, the conversion of carbon monoxide is
higher than that of hydrocarbons at any given temperature.

            Figure 1.      Conversion of CO and HC in Diesel Oxidation Catalyst




                                           15
Particulates Performance
Diesel particulate matter is composed of three major fractions including the
carbonaceous particulates, the organic particulates (SOF), and sulphates (SO4). Each
of the fractions shows different reactions in the diesel oxidation catalyst. The
composition of raw exhaust particulates and the particulates after the DOC is
schematically depicted in Figure 2.

Experimental data shows that the diesel oxidation catalyst is virtually inactive in
respect to the carbonaceous particulate material or black soot. The carbon fraction of
diesel particulates remains essentially unchanged as the gas passes through the
catalyst.

The organic fraction (SOF) of diesel particulates, composed of high boiling
hydrocarbons, is very effectively oxidised in the catalyst contributing to a decrease in
the TPM emissions. After a full catalyst light-off is reached, the conversion of SOF
shows little change with further temperature increase. This is similar to the light-off
curve for gas phase conversions.

As noted above, the sulphate fraction of diesel particulates (SO4) is increased in the
DOC due to the oxidation of SO2 with subsequent formation of sulphuric acid,
reactions (3) and (4).

This is a counter-productive process, leading to an increase in TPM emissions in the
diesel oxidation catalyst. The intensity of the sulphate production increases with
exhaust gas temperature and becomes difficult to control at about 400°C. These
processes are shown graphically in the following chart:


                    Figure 2 PM Performance of Diesel Oxidation Catalyst
                               Source: Johnson Mathey 1998




                                            16
Special catalyst formulations are used to suppress that process, making the diesel
oxidation catalyst a viable PM reduction approach.

Low sulphur fuels minimise sulphate production and increase the benefit of the diesel
oxidation catalyst, but in practice, if sulphur is present in the fuel, there is always a
temperature above which PM emissions will start to increase. If sulphur-free fuel is
used, the highly active platinum/alumina based catalyst systems are still the best
choice for both the particulate and the gas phase emission control.

Sulphur levels in Australian fuel today vary from 500ppm to 5,000ppm. While it is
possible to formulate oxidation catalysts to work effectively with higher sulphur
levels, the performance of the catalyst suffers. The Report of the Findings of the
Expert Reference Group2 found that, while ultra low sulphur fuel (0.005%) gave the
best results, low sulphur fuel (0.05%) with an oxidation catalyst still gave marginally
better results for minimising PM10 exposure than CNG or LPG.

Deactivation of Diesel Catalyst
Deactivation of the catalyst was an issue in the development of effective oxidation
catalysts for heavy duty diesel engines. The main cause for the deactivation of diesel
catalysts is poisoning by sulphur, as well as by lubrication oil additives. Phosphorus
is the most common oil-derived catalyst poison.

Sulphur can be found uniformly distributed over the catalyst length and the washcoat
depth, while phosphorus is selectively adsorbed at the catalyst inlet and in a thin,
outer washcoat layer.

Since diesel engines typically burn larger quantities of oil than their gasoline
counterparts, the diesel catalyst must be more resistant to the oil and its additives.
Under the cooler modes of operation, unburnt oils and their additives deposit within
the catalyst washcoat. Unlike the organic portion of the oil, the additives remain after
the oil is catalytically oxidised. Substances such as phosphorus, zinc, and calcium
oxide accumulate on the surface or within the catalyst. The oil-derived poisons result
in an irreversible catalyst deactivation.

In most countries, diesel fuel contains significant quantities of sulphur, several times
higher than those present in gasoline. The maximum sulphur content in the US and
Europe on-road diesel fuels is 0.05% by weight, but in Australia can often exceed
0.12%. Fuel sulphur may be another source of catalyst deactivation.

Sulphur poisoning is frequently reversible by high temperatures, under which the
sulphur compounds decompose and are released from the catalyst washcoat.
However, due to the low diesel exhaust temperatures, in many diesel engine
applications the conditions needed for catalyst regeneration may never be reached.

Field experience with low sulphur fuels confirms that effective and durable oxidation
catalysts are now available for heavy duty diesel engines in the circumstances
expected to apply in Australia. Manufacturers also advise that they can now


2   Euro2 and Beyond - Fuel for Transperth’s Bus Fleet


                                               17
formulate catalysts to work with higher sulphur levels in fuels, but performance
suffers.

Summary
The oxidation catalyst is a proven technology, available on a commercial basis for
retrofit programs. Installation is simple.

Oxidation catalysts reduce the level of HC and CO emissions and reduce PM by
oxidising the sulphur content of the PM. They do not effect NOx emissions. The
performance of the oxidation catalyst is affected by the level of sulphur in the fuel..
This will not be significant for Australia because of the commitment to move to low
sulphur (0.05%) fuel.

Diesel Particulate Trap
Diesel particulate traps physically capture diesel particulates preventing their release
to the atmosphere. Diesel particulate traps generally replace the muffler in the
vehicle. Diesel traps work primarily through a combination of deep-bed filtration
mechanisms, such as diffusional and inertial particle deposition. The most common
filter materials are ceramic wall-flow monoliths and filters made of continuous
ceramic fibres.

The issue with particulate traps is regeneration to “clean” the trap i.e. get rid of the
accumulated particulate matter. A number of methods have been developed to
regenerate diesel filters. Passive filter systems utilise a catalyst to lower the soot
combustion temperature. Active filter systems incorporate electric heaters or fuel
burners to burn the collected particulates.

Diesel traps are most effective in collecting the solid carbonaceous fraction of diesel
particulate matter. The effectiveness of diesel traps in controlling the organic fraction
of particulate matter (SOF) depends on the type of trap and on its operating
conditions. Depending on the circumstances, it may be lower than the SOF abatement
effectiveness of the diesel oxidation catalyst.

All diesel traps of practical importance are diesel particulate filters (DPF). The terms
"diesel trap" and "diesel filter" are frequently used as synonyms. Some of diesel filter
materials show quite impressive filtration efficiencies, frequently in excess of 90%, as
well as acceptable mechanical and thermal durability.

Diesel traps are currently the most efficient emission control measures to reduce
diesel particulate emissions.

The most important issue with diesel traps is filter regeneration. Soot generated by
diesel engines is characterised by low bulk density and, therefore, high volume. Due
to the high volumes of generated particulates, it is necessary that the filter is
regenerated, either periodically or continuously, during the regular engine operation.
The on-vehicle filter regeneration is most commonly realised by oxidising (burning)
of soot in the filter.




                                            18
Filter (Trap) Regeneration
In an ideal situation, particulates that enter the filter are oxidised in a continuous or
almost continuous manner. The filter maintains an approximately constant, moderate
soot load, which produces an acceptable pressure loss. Continuous regeneration does
not produce high temperature peaks due to the exothermic combustion of soot. Thus,
there is little thermal stress on the filter material. Rapid regeneration occurs when a
high load of soot becomes "ignited". Such regeneration, also called "uncontrolled" or
"run-away" regeneration, is the opposite to the ideal, continuous regeneration mode.
The "ignited" soot load burns rapidly releasing high quantities of heat, raising filter
temperature, and eventually, causing damage (melting, cracking) to the filter material.

In passive systems the soot combustion temperature is lowered to a level allowing for
auto-regeneration during regular vehicle operation. This can be achieved by
introducing an oxidation catalyst to the system. The catalyst can be placed directly
onto the trap surface or added to the diesel fuel as fuel additive.

In active systems, the catalyst is supplied through a fuel additive. The active
ingredients of available fuel additives include iron, cerium, copper, platinum, or
mixtures of metals. There are obvious problems with the fuel additive approach in
terms of reliability.

A different principle has been utilised in the CRT (continuously regenerating trap),
where the catalyst, placed upstream of the filter, is used to generate nitrogen dioxide
which then oxidises the collected soot. This approach has been used by Johnson
Mathey to produce a unit which in effect, combines the oxidation catalytic converter
with a particulate trap in a single unit designed to replace the muffler on a diesel road
vehicle. The CRT unit provides significant reductions of hydrocarbons and CO
combined with the high performance on particulate reduction, but does not address the
NOx issue

Another approach is to actively trigger regeneration by raising the temperature in the
trap, using electric heaters or fuel burners. Active trap systems are much more
complex than passive filters. They require sophisticated hardware, including an
electronic control unit to trigger and control the regeneration process. They have been
effective in areas like fork lift trucks, which tend to stay in one area and can access a
“regenerating” station periodically, or urban buses which return to depot regularly.
The passive filters, due to their simplicity, are a more attractive approach.

The following table illustrates the effects of a typical (active) trap on the emissions of
a heavy duty engine, using the US Federal HD Urban Bus Cycle.

Table 3: Performance of a Particulate Trap

       Engine Baseline                     Trap                Trap Efficiency
           g/bhp·hr                        g/bhp·hr                  %
Nox    5.0                                 4.3                  14
HC     0.7                                 0.6                  14
CO     2.5                                 3.0                 -20
PM     0.350                               0.053                 85



                                            19
An average regeneration interval of the trap was 4.2 hours. The duration of
regeneration was 6.5 minutes. The heater power consumption during that period was
150 A at 24 V.

One problem is that periodic trap regeneration leads to increases in back pressure as
soot builds up. The increase in back pressure leads to a drop in fuel efficiency and
increased emissions. While continuous regeneration avoids this particular problem,
the evidence suggests that a particulate trap will lead to a modest increase in back
pressure and a fuel efficiency loss of up to 1%.

 Summary
Particulate traps are a proven technology available on a commercial basis. The key
issue with a particulate trap is the removal of accumulated particulate matter (soot).
Continuously regenerating traps resolve the issue by oxidising the “soot” during
normal operation. Other regeneration approaches which are more complex and
require additional active equipment, are not well suited to road vehicle applications.

A particulate trap is effective in reducing particulate levels (90% reduction), but does
not have a significant effect on other emissions.

Catalytic Conversion of Nox
Oxidation catalytic converters are effective in reducing HC, CO and to some extent
particulates. Particulate traps primarily focus on particulate matter. Combined unit
give significant reductions of HC, CO and PM. Neither of these technologies is
effective in reducing NOx.

Oxides of nitrogen can be very efficiently reduced from exhaust gases of rich-burning
engines, such as those used in today's gasoline-powered cars. The three-way catalyst,
which has been developed for that purpose, promotes a non-selective reduction of
NOx by other exhaust gas components such as carbon monoxide and hydrocarbons.

High NOx reductions can be only achieved if the engine operates close to the
stoichiometric air to fuel ratio. Since the presence of oxygen in the exhaust gas rapidly
deteriorates the NOx performance of the three-way catalyst, that technology is
ineffective in controlling nitrogen oxides emission from diesel engines.

A catalyst capable of reducing NOx in exhaust gases from lean-burning engines, i.e.,
in the presence of oxygen, is called a lean NOx catalyst (LNC). This technology is
being very actively pursued by engine and vehicle manufacturers to achieve the
performance levels of the new emission standards. This applies not only for diesel
NOx reductions, but also for gasoline engines, where lean burn offers very significant
fuel consumption (and hence greenhouse) benefits.

The following catalytic approaches have been investigated for the NOx control in lean
exhaust gases:
    NO decomposition catalyst
    Selective catalytic reduction with nitrogen containing compounds (ammonia,
       urea)


                                           20
      Selective catalytic reduction with hydrocarbons
      NOx trap-catalyst systems.

Although initially promising, Catalytic Decomposition of NO has proven to be a
difficult reaction to realise. The decomposition of NO on Cu/ZSM5 is subject to
inhibition by water, is very sensitive to poisoning by SO2, is effective only at low
space velocities, and the catalyst activity and selectivity are not satisfactory [Iwamoto
1991]

The most promising current retrofit technology to reduce emissions of NOx appears to
be the selective catalytic converter.

Selective Catalytic Converter
Selective catalytic converters are fitted in the exhaust line in a similar structure to a
muffler or as part of a muffler structure. The device also requires an active system to
inject the reducing agent (eg urea) ahead of the catalyst bed. An obvious corollary is
the need to periodically replenish the reducing agent supply and the issue of
appropriate action (alarms, positive action to close down engine) if the supply of
reductant runs out.

Selective Catalytic Reduction (SCR) of NOx can be achieved if a reducing agent is
injected into the gas upstream of the catalyst bed. SCR processes utilising nitrogen-
containing reductants such as ammonia or urea are commercially available for
stationary diesel engines and for industrial sources.

Although considered in the past not to be an attractive option for diesel trucks and
cars, the use of ammonia, or preferably urea, is now becoming a commercial reality in
some light and heavy duty diesel applications. One issue is the carriage and
replenishment of the reagent and the associated issue of means to ensure the reagent is
replenished appropriately. Peugeot has announced a system for light vehicles based
on urea injection, understood to require replenishment at 50,000 km.

A number of catalysts have been found to promote Selective Catalytic Reduction of
NOx by hydrocarbons, alcohols, or other combustion gases [Shelef 1995]. Reduction
by HC is less susceptible to sulphur poisoning than the NO decomposition process
and higher conversion efficiencies have been demonstrated. Some manufacturers are
developing HC based selective catalytic reduction technology.

In the case of diesel application, diesel fuel was the obvious source of hydrocarbons
necessary for the reaction, and the computerised Common Rail post-injection
techniques outlined previously, now make this approach both feasible and
economically attractive.

While the use of diesel fuel to support the reaction has attractions in terms of technical
simplicity for a modern diesel engine, the effectiveness in terms of NOx reduction is
significantly lower than that achieved with an ammonia based catalyst. Consequently,
where the primary objective is to meet stringent emission requirements, manufacturers
are more likely to develop ammonia based technology.




                                            21
The other factor mitigating against the diesel fuel based systems is that it would not be
suited to older engines which do not have computer control and common rail
injection. It is therefore likely that ammonia based systems will be developed for
retrofit applications.

In the selective catalytic reduction, the hydrocarbons selectively react with NOx,
rather than with O2, to form nitrogen, CO2, and water. One consequence of this is
some trade off between NOx emissions and CO2 emissions.

The catalyst-reductant system has to be optimised to promote the desired selective
reaction and suppress the undesired reactions with oxygen. Catalyst selectivity
depends on several factors including the catalyst formulation, the hydrocarbon species
used for the reaction, and the HC/NOx ratio.

Summary
The selective catalytic converter technology is currently being introduced in some
new vehicles as part of the emissions management system to meet the new emission
standards. Selective catalytic converter technology focuses on the reduction of NOx,
emissions, which are not addressed effectively by oxidation catalysts or particulate
traps.

The technology is more complex, requiring active systems to supply the catalyst. It is
not yet developed for retrofit applications.

Manufacturers are developing a combined selective catalytic converter/continuously
regenerating particulate trap device which is said to achieve low NOx levels as well as
reductions in HC, Co and PM. Cost targets are in the range $4,000-$5,000 and
physical size target is to simply replace the conventional muffler.

Other Technologies
NOx Trap - Catalyst Systems
The concept of NOx traps is to incorporate NOx trapping compounds into the catalyst
washcoat, with a controlled release under favourable catalysing conditions.

In Temperature Regenerated NOx Traps, these compounds adsorb NOx during
periods of low exhaust gas temperature then, at higher temperatures, the stored NOx
would be released and reduced in the catalyst. Several materials, including various
types of zeolites, have been evaluated as candidates for temperature regenerated NOx
traps.

Another, different NOx trap/catalyst technology is based on acid-base washcoat
chemistry. It involves trapping NOx during lean driving conditions and releasing it
under short periods of deliberately induced rich operation. The released NOx must be
catalytically converted to nitrogen as happens in current three-way catalyst.

This "rich spike regeneration" trap concept was originally developed primarily for
gasoline engines, but work is underway to utilise this technology for diesel NOx
reduction also.




                                           22
The catalyst washcoat combines three active components: an oxidation catalyst, a
trap, and a reduction catalyst. First, nitric oxide reacts with oxygen on oxidation
catalyst sites (e.g. platinum, Pt) to form NO2. Then the NO2 is adsorbed by an alkaline
earth oxide trapping material (e.g. barium oxide, BaO), forming barium nitrate. The
oxidation of NO and adsorption of NO2 occurs during the lean engine operation.
During a rich exhaust spike the barium nitrate decomposes producing mostly nitric
oxide which is reduced on reducing catalyst sites (e.g. rhodium, Rh). The entire
trap/catalyst system is very simple and, in fact, similar to the three-way Pt/Rh catalyst
technology. It is certainly a potentially attractive technology for lean burn gasoline
engines. The necessary rich regeneration periods may be more difficult to implement
in the diesel engine.

The following are some of the issues which are currently being resolved:
    High temperature limitations related to the decomposition temperature of
       barium nitrate in the catalyst washcoat. (This issue is probably not critical for
       diesel applications);
    Deactivation of the trap by sulphur. Sulphur compounds form barium sulphate
       which is more stable than barium nitrate. Desulfation of the trap could be
       performed by applying high concentrations of reductants or by exposure to
       high temperatures (above 500°C). However, some barium sites appear to be
       permanently and irreversibly poisoned by sulphur [Dou 1998];
    The impact of phosphorus and zinc, known poisons of the 3-way catalyst, on
       the NOx trap is still not fully understood;
    Vehicle driveability problems can occur during the brief but necessary
       periodic mixture enrichment.

Mixture enrichment needs to be carefully applied. In-cylinder enrichment creates
high particulate emissions, and exhaust system enrichment requires not only that a
reductant be injected but, first of all, that the oxygen levels in the exhaust gas be
lowered. Post-injection using common rail injection systems are likely to provide the
answer to this problem.

Plasma Exhaust Treatment
Non-thermal plasma technologies have the potential to reduce several diesel and
automotive exhaust emissions including NOx, particulate matter, and hydrocarbons.

The focus in plasma research is on nitrogen oxides reduction. Since oxidation
reactions dominate during plasma discharges in lean exhaust, the plasma alone is
probably ineffective in reducing NOx. Instead, combined plasma-catalyst systems
have been proposed and are investigated.

Early reports indicate that plasma may enhance the catalyst selectivity and removal
efficiency. Today's plasma exhaust treatment technologies are in their early stage of
development.

It is still impossible to predict whether or not they will become a viable emission
control option.




                                           23
Summary
Selective catalytic converters are currently being introduced as part of emissions
management to meet new vehicle emission standards. The on-vehicle technology is
more complex than the oxidation catalyst or the particulate trap, involving active
systems. The technology is not currently available as a retrofit option.

Other options to address NOx are still in the development phase and not available as
retrofit options.

Technology Summary
There are two technologies at the commercial stage for retrofit of heavy road vehicle
engines:
        Oxidation catalyst
        Particulate trap.

Selective catalytic converter technology is at the production stage for some new
vehicle applications, but not yet developed for retrofit applications.

The performance of the currently available devices suited to retrofit is summarised
below:

 Technology                               Performance
                       NOx             HC           CO                   PM            Installation
  Oxidation
   Catalyst            Low          Effective        Effective         Modest            Simple
  Particulate
     Trap              Low            Low              Low             Effective         Simple


Field Performance
There are many variables affecting the field performance of retrofit equipment. These
include:
        Technology of the retrofit equipment
        Engine technology
        Engine condition and tune
        Design optimisation
        Vehicle duty cycle – urban vs highway.
        Fuel Quality.

There is some data available (NESCAUM Report, Oct 1997) which suggests that
oxidation catalytic converter and particulate trap performance as set out below:

Device                          HC Reduction      CO Reduction      PM Reduction
Oxidation catalytic converter   50-90%            50-90%            25%
Catalysed particulate trap      50-90%            50-90%            90%

Other tables in the same report show the wide variability actually achieved in the
field. The report suggests that for planning purposes, the performance of oxidation
catalytic converter be taken to be a 40% reduction for CO, a 50% reduction for HC
and a 20% reduction for PM.


                                          24
The UK Cleaner Vehicles Task Force Report suggests the following performance in
reducing particulates:

Equipment                     PM Reduction
Particulate Trap                  95%
Oxidation catalyst Pre Euro       50%
Post Euro 1                       40%
Post Euro 2 and 3                 30%

Information published by MECA (1997) suggests the non-catalysed particulate traps
will have very little effect on NOx or CO emissions while giving similar performance
in PM reduction.




                                         25
COSTS
Equipment Costs
The data on unit costs for retrofit equipment is variable. Manufacturers data is
generally optimistic, and unit costs often vary dramatically with production volume.
Information provided by MECA suggests that costs could be:
       Oxidation catalytic converter          $1,500-4,500
       Particulate trap                       $5,000-10,000

A Johnson Mathey publication suggests selective catalytic converters could be of the
order of $3,300-4,000

Data in the March 2000 report of the Commission for Integrated Transport suggests
that the costs for particulate traps for heavy vehicles would be of the order of $9,000,
with a slightly lower cost for buses. The Cleaner Vehicles Task Force final report
suggests the following costs:
                                         2000                 2005
        Particulate traps                $7,700-11,000        $5,500
        Oxidation catalysts              $1,650-4,400         $1,650-4,400

Discussions with manufacturers suggest oxidation catalytic converters for an urban
bus could be between $1,500 and $3,000, depending on the work involved in
installation. The same source suggests particulate trap costs would be of the order of
$9,000-10,000.

NELA (A Review of Dynamometer Correlations In-Service Strategies and Engine
Deterioration) suggests costs could be as high as $10,000-15,000 per vehicle for
oxidation catalytic converters and particulate traps. This is not consistent with other
sources, and could reflect early data when production levels were low.

It is important to note that unit costs generally increase with engine capacity and
power. To achieve optimum performance, it is essential that the retrofit unit be
properly matched to the engine. There have been some instances where smaller
(cheaper) units were fitted as an economy measure, leading to unsatisfactory emission
performance.

Installation costs
The oxidation catalysts and particulate traps are essentially in line devices and can
replace the muffler. A common retrofit issue is the physical placement of the retrofit
unit. Buses in particular do not generally offer space for additional units or large units
in the exhaust line. Replacement of the existing muffler is therefore the most popular
approach. In some instances, the choice has been to actually fit the retrofit unit inside
the existing muffler casing. It is worth noting that some manufacturers offer retrofit
units as muffler replacements, with all necessary fittings. Such units are specified to
meet the performance of OE mufflers. The structure of the retrofit elements is such
that with appropriate installation, noise is not an issue.

A program which linked retrofit to muffler replacement programs would offer some
savings, but would be constrained by the timing of muffler replacement.




                                           26
The point is that installation is simple. There are no active components and the units
are largely maintenance free. Where retrofit is combined with muffler replacement,
installation costs are essentially zero. Where the units can be installed by simply
cutting the exhaust pipe to take the retrofit unit, installation costs would be minimal.
Where the units are fitted inside the muffler, installation costs might be of the order of
$1,000.

Maintenance costs are minimal. Oxidation catalysts do not require routine
maintenance. Some reports suggest that continuously regenerating particulate traps
may benefit from periodic reversal of the element to “blow out” any accumulated soot
particles.

Impact of Retrofit Technology on Fuel Efficiency
The primary impact of retrofit technology on fuel efficiency derives from the potential
increase in back-pressure. Fitting a device in the exhaust line can lead to some
increase in back-pressure, with a consequent increase in fuel consumption. The effect
is generally small, and consequently difficult to establish authoritatively.

The problem is compounded by the fact that back-pressure effects vary with engine
load. MECA (June 1999) notes that the back pressure from fitting a particulate trap
can lead to fuel economy penalties of 1-2% at or near full load conditions. However,
for engines operated largely at part load conditions – common for heavy road vehicles
– the fuel economy penalty is claimed to disappear. The MECA paper also notes that
properly sized oxidation catalysts have “little or no” impact on back-pressure and
hence fuel economy. The paper goes on to note that fuel borne catalysts used in
combination with oxidation catalysts may generate a fuel economy improvement.

Another aspect of the fuel economy issue derives from the fact that some particulate
traps use fuel injection as the basis for regeneration. This clearly has a direct impact
on fuel efficiency. Continuously regenerating traps would not give this effect.

The UK Cleaner Vehicles Task Force analysis uses specific fuel economy penalties in
calculating costs and benefits:
        Oxidation Catalyst        0.5% fuel economy penalty
        Particulate Trap          1.0% fuel economy penalty

The key to minimising fuel economy impacts lies in properly matching the retrofit
equipment to the engine. The performance of oxidation catalysts can be significantly
degraded if the unit is not properly matched to the engine, and the impact on fuel
efficiency will be increased. Similar considerations apply to the matching of
particulate traps to the engine.

The matching issue could be significant for a voluntary program, where there would
be a financial temptation for owners to fit the cheapest unit. Some programs require
the retrofit equipment to be marked or labelled with the appropriate engine
information so that inspectors can ensure that correctly sized units are fitted.

While detailed information is not available, it is possible to estimate the annual cost of
a 1% increase in fuel consumption for a heavy vehicle. The following table sets out
the parameters and changes in cost effectiveness.


                                            27
Table 4: Effect of Fuel Consumption Penalty

   Retrofit   Unit Cost    Annual      Fuel         Fuel       PM        Fuel Cost       Cost
 Technology                Travel   Consumption    Penalty   Emission                Effectiveness
                                                             Reduction                 $/kg PM
                 $          km         km/L          %          kg          $         Reduction
Oxidation      2,500      100,000       4            0          27          0           13.33
 Catalyst
Oxidation      2,500      100,000       4           0.5         27         100          16.93
 Catalyst
Particulate    6,000      100,000       4            0          81          0           10.58
   Trap
Particulate    6,000      100,000       4           1.0         81         200          13.05
   Trap



These figures are ball park estimates, and should be treated as such. As noted, the real
“in use” fuel penalty may be much lower than 1% for a particulate trap if the duty
cycle is largely mid-range, which is reasonably typical for heavy-duty road
vehicles. There are also arguments that the real world “in use” fuel penalty for
oxidation catalysts is negligible.

The key point is that reliable data on the fuel efficiency impact of fitting an oxidation
catalyst or a particulate trap to a heavy vehicle is difficult to obtain other than by on-
road testing in a typical operations context. Consequently, the cost estimates must be
treated with caution. The same caveats apply to the PM emissions from a heavy
vehicle and the reduction in PM emissions from retrofit. However there is some
reasonable data in these areas, but much less data for the impact on fuel efficiency.

Cost Effectiveness
The cost effectiveness issue is important in designing retrofit programs. The basic
cost variables are :
         retrofit installation cost including the device itself - $K
         life of retrofit equipment (L years) and
         fuel cost penalty – if any – Fp%.

The other key variables are the annual vehicle travel (Tkm), the fuel consumption
(Fc km/l), fuel price($C/litre)), the PM emission rate (Pg/km) and the emission
reduction expected from the retrofit (R%).

The objective function or measure of cost effectiveness is taken to be the annual cost
per kilogram of PM reduction. The capital cost of the retrofit is assumed to be
depreciated over life of the equipment

The following relationships are simplistic, but give an indication of the cost
effectiveness of a retrofit program for each vehicle:
         Annual PM emitted                           = TxP/1000 kg
         Annual PM reduction from retrofit           = TxPxR/1000 kg
         Annual fuel cost penalty                    = $(T/Fc)xFpxC
         Total annual costs                          = $(K/L + (T/Fc)xFpxC).




                                              28
             Cost per kilogram of PM Reduction (cost effectiveness)
                     = (Total annual costs)/(Annual PM reduction from retrofit)
                     = (K/L+(T/Fc)xFpxC)/(TxPxR/1000)
                     = 1000{K/(LxTxPxR) + (FpxC)/(FcxPxR)}

The capital component of the annual cost per kilogram reduction of PM reduces as the
annual vehicle travel increases while the fuel related component of the annual costs is
independent of the annual distance travelled. This emphasises that it is important to
select the target fleet carefully.

The following table sets out some indicative cost effectiveness outcomes for a typical
set of assumptions for a heavy vehicle.

Table 5: Cost-effectiveness – Effect of Distance Travelled

  Retrofit        Retrofit      Fuel        Fuel       Fuel       PM Emission     PM          Annual       Cost
  Capital        Equipment   Consumption   Cost *   Consumption      Rate       Reduction     Travel   Effectiveness
   Cost             Life                              Penalty                                             of PM
                                                                                                        Reduction
2 way           7years       4 km/L        90       0.5%          0.9           30%         50,000      $30.16
catalyst                                   c/L                                              km           /kg
$2,500
2 way           7years       4 km/L        90       0.5%          0.9g/km       30%         100,000     $16.93
catalyst                                   c/L                                              km           /kg
$2,500
2 way           7years       4 km/L        90       0.5%          0.9km         30%         150,000     $12.50
catalyst                                   c/L                                              km           /kg
$2,500
Particulate     7 years      4 km/L        90       1%            0.9g/km       90%         50,000       $22.4
trap                                       c/L                                              km            /kg
$6,000
Particulate     7 years      4 km/L        90       1%            0.9g/km       90%         100,000     $13.05
trap                                       c/L                                              km           /kg
$6,000
Particulate     7 years      4 km/L        90       1%            0.9g/km       90%         150,000    $9.52/kg
trap                                       c/L                                              km
$6,000
* fuel cost does not reflect significant fuel price rises in third quarter 2000

If the PM emission level is assumed to be 0.5 g/km instead of 0.9 g/km the cost
effectiveness deteriorates by a factor of 1.8. For annual travel of 100,000 km, Table 6
sets out the correction in cost effectiveness.

Table 6: Effect of Emission Rate on Cost Effectiveness

Change in cost                        PM rate                             Cost effectiveness
                                        g/km                                  $/kg PM
Oxidation catalyst                    0.9                                 16.93
Oxidation catalyst                    0.5                                 30.48
Particulate trap                      0.9                                 13.03
Particulate trap                      0.5                                 23.49




                                                     29
EXISTING PROGRAMS FOR RETROFIT OF HEAVY DIESEL VEHICLES
There are a number of well known programs to retrofit urban buses. The US EPA has
an extensive program in place, and the program has been extended on a voluntary
basis to other heavy vehicle fleets. The program relies on the US EPA air quality
arrangements to provide the incentive for state and regional jurisdictions to put
specific programs in place. The technology is largely focussed on oxidation catalytic
converters, although the combined continuously regenerating particulate trap is likely
to become popular.

The program requires approval of each retrofit product for each engine type, and the
approvals are available on a web site. There are extensive monitoring programs to
provide assurance that the equipment is installed and operating correctly.
Attachment 2 provides more detail on the program.

The London Bus program is a sub-set of a range of programs developed to address the
area of in-service vehicle emissions. Technology employed was primarily oxidation
catalyst (for cost reasons), although a primary focus was PM and odour. There is a
similar program in Germany, but specific details are not currently available.

The broader initiatives of the UK Cleaner Vehicles Task Force (Attachment 3)
include a range of proposals to reduce emissions from diesel vehicles. These include
vehicle tax reductions for retrofitted vehicles (taxis and lorries), and are aimed at
setting up a commercially viable incentive structure for vehicle owners.

There are a number of other programs in Europe. Some are focussed on urban buses
and some are broader programs based on “low emission” areas (the three cities
program in Sweden). Low emission areas are defined as areas only accessible to
vehicles meeting particular emission performance limits. Typical examples would be
the central areas of major cities or “dormitory” areas. Issues of vehicle identification
arise and there are obvious enforcement issues.

The Swedish program13 was introduced in1996. It placed restrictions on the types of
heavy vehicles which can be used in the most heavily polluted central areas of
Stockholm, Goteborg and Malmo. A special exemption can be issued for older
vehicles if they are retrofitted with approved kits. The performance requirements for
approved kits have led to a tendency to favour combined catalyst/trap units, achieving
high levels of PM and hydrocarbons reduction.

A problem with the first program was that it unintentionally allowed engine
replacement with the same (say Euro 0) type of engine, leading to a lower
achievement level than was expected. This has now been rectified.

Low emission areas could be integrated with modern electronic tolling technologies to
monitor the vehicles going into and out of areas. A flag in the tolling system could
either initiate the sanction systems or to charge a premium for high emitting vehicles.




3   MECA March 1998


                                           30
Australian Studies
There are two relevant Australian Studies:
        NSW EPA Study – Diesel Emissions Reduction Project, Final Report
        WA Report on the Findings of the Expert Group – Euro2 and Beyond,
           Fuel for Transperth’s Bus Fleet.

Both studies were undertaken in the context of major bus fleet purchasing decisions
for the urban transports system in each city. The studies do, however, provide useful
information on managing diesel engine emissions. Some of the conclusions are
relevant to the retrofit issue.

The NSW study considered a range of issues including 2 way catalysts and set out to
consider issues such as cost, maintenance, performance and the general effect on
driveability, engine performance and fleet operations. For the purposes of the current
study, the key findings were:
         The installation of catalysts using standard commercial (1997) fuel led to
            decreases in CO and THC, but increases in PM, considered to be due to the
            formation of sulphates. This was due to the high sulphur content of
            commercial diesel fuel;
         Use of low sulphur fuel led to improved performance in respect of PM;
         No overall effect on NOx was observed;
         There was no effect on driveability, maintenance and engine performance;
         A reduced platinum content catalyst achieved reductions in TPM even
            when using commercial diesel fuel;
         Catalyst maintenance was negligible.

The study concluded that “oxidation catalysts fitted to the vehicles reduced
substantially the emissions of CO and THC. However, they were inefficient at
reducing TPM emissions even with the use of low sulphur fuel and caused these
emissions to increase substantially when used with commercially available diesel fuel.
As expected, no overall changes in NOx emissions were observed.”

These conclusions are not inconsistent with the general literature, although the general
conclusion is that 2 way catalysts do reduce TPM (around 30%) when used with low
sulphur fuel

The Transperth study was aimed at helping determine the most appropriate
fuel/engine technology package for servicing Perth’s transport system. The study
considered CNG, LPG and diesel options. Of particular interest for the current study
are the findings that:
         “ultra low sulphur (0.005%) diesel with a continuously regenerating
            particulate trap gives the lowest full cycle CO2 emissions per kilometre,
            followed by ultra low sulphur fuel (0.005%) diesel with an oxidation
            catalyst’
         Low sulphur diesel (0.05%) ranks second to LPG for low emissions of air
            toxics
         Low sulphur (0.05%) diesel combined with an oxidation catalyst is
            marginally better for minimising the populations exposure to PM10 when
            compared with CNG and LPG”



                                           31
          Diesel (0.2% sulphur) has marginally less impact on worsening the
           population’s exposure to smog produced”.

The Transperth study led to a program to fit oxidation catalysts to new diesel buses as
they are delivered. The units are fitted inside the vehicle muffler.




                                          32
OPTIONS FOR AUSTRALIA
Basic Issues
There are several issues to be considered in developing the option set:
        National vs State/Territory
        Target Fleets
        Fuel quality.

There is a distinct advantage in developing options focussed on regions rather than
national approaches. The pragmatic reason is that the action will be based on
state/territory powers, and not on national powers. The second consideration is the
fact that air quality issues tend to be regional rather than national in character. The
third reason is that the option set is intended to give agencies some discretion in how
they might approach the issue of in-service diesel emissions. A diesel emissions
model based on a particular fleet in a particular region can be simply applied to
another region by changing the relevant parameters. Finally, some options are based
on the existence of an I/M program. It is likely that some, but not all, jurisdictions
will implement such programs.

Target fleets are an issue because there are a range of opportunities for government to
influence the retrofit of diesel engine vehicles. Urban bus fleets, for instance, offer
particular opportunities and the benefits are largely in major urban centres. The
particular set of circumstances allows government to directly influence the retrofit of
this fleet. Government owned or contracted heavy vehicle fleets offer a similar
opportunity. The heavy haulage fleet in general is quite diverse and a different
approach would be required.

In considering target fleets, it is important to remember that the benefits from a
retrofit program will decline over time as newer low emission vehicles penetrate the
fleet. Older, high emission vehicles will tend to move to lower annual useage
activities i.e. used only in peak period. This trend will reduce the potential benefits
from a retrofit program over time. The nature of a retrofit program will also change
over time to a program based on upgrading the performance of post ADR 70 vehicles.

Fuel quality is an issue because some of the emerging technology requires low
sulphur fuel to be effective. For this project, it is assumed that Australian diesel fuel
contain progressively less sulphur (to 50ppm by 2005), as proposed in the “Measures
for a Better Environment Package” in the Prime Minister’s Statement on the Goods
and Services Tax, June 1999.

Technical Issues
As discussed earlier, there are effectively three established approaches to reducing in-
service emissions from heavy duty highway diesel engines:
        1. Diesel oxidation catalytic converter
        2. Engine rebuild kits
        3. Particulate traps.

Diesel oxidation catalytic converters are available for many engine families, and are a
well established technology. Units are available as a direct replacement for the
existing muffler, without any other modifications to the vehicle. If appropriate



                                            33
incentive/sanction structures are in place, the reduction in diesel in-service emissions
can be significant.

Selective catalytic converter technology is at an advanced stage of development, but is
not yet widely field proven and generally requires on-board storage of a reductant
(most commonly urea), which needs to be periodically replenished.

Engine rebuild kits targetting emission reduction are available for many US-sourced
engines, but have the disadvantage that they only apply when an engine rebuild is due.
Given the long periods between engine overhaul, this limits their effect on fleet
emissions in the short term. However, an engine rebuild incentive program could
offer significant longer term emission reductions. The attraction of engine rebuild
programs is the opportunity to incorporate some more recent engine technology and
the benefits in terms of emissions reductions across the board. One problem is that
engine rebuild programs would require significant and intrusive monitoring programs
to ensure that the appropriate rebuild kit was in fact installed and continued to
perform in the field.

Particulate traps have traditionally had some complications in terms of regeneration
(dealing with particulate matter build up in the trap). Manufacturers now offer the
continuously regenerating particulate trap. Particulate traps have been demonstrated
in the field and can be considered a reasonably well-established technology.

Oxidation catalysts and particulate traps are effective in reducing particulate matter
and visible smoke, as well as hydrocarbons and carbon monoxide (the latter two are
not a significant issue for diesel vehicles). They are not, however, effective in
addressing NOx emissions. As noted above, new technologies are emerging to
address NOx emissions – selective catalytic converters. This technology is well
advanced, but not yet substantially field proven. It is being developed by OEM and
specialist exhaust treatment companies to meet the tighter emissions requirements. At
this stage, there is little evidence of a significant priority being given to the retrofit
issue, but this can be expected to change as the new vehicle equipment is proven in
the field.

Given the limitations on the timing of engine rebuilds and on the availability of
certified rebuild kits, the primary option set will consider oxidation catalytic
converters and continuously regenerating particulate traps. In deciding between the
two technologies, the issues to be considered are:
         Two way catalytic converters reduce particulate matter, hydrocarbon and
            CO emissions
         Particulate traps focus on particulate matter and odour
         Particulate traps offer a significantly higher level of particulate reduction.
         Catalytic converters have a claimed life of up to 600,000 km
         Particulate traps need a regeneration mechanism – several are on offer,
            ranging from periodic electrical regeneration to continuous regeneration
            through fuel additives or catalytic coatings
         Capital costs are generally lower for catalytic convertors
         Cost effectiveness in terms of cost/kg reduction in PM is broadly
            compatible.



                                            34
Program Design Parameters
The key issues in designing a program for retrofit are:
      1. The incentive structure
      2. The performance assessment structure
      3. The sanctions structure
      4. Target fleets
      5. Alternative compliance approaches.

Incentives
The incentives can be by way of inducements or requirements. Inducements might
include:
       1. registration rebates for retrofitted vehicles
       2. permit rebates for retrofitted vehicles
       3. inspection rebates
       4. direct funding of part or all of the cost of retrofit.

One disadvantage of incentives based approaches is the potential cost to revenue.
Most incentives involve some loss in revenue or direct cost to government. This can
be alleviated by measures such as introducing special inspection charges, which can
then be rebated for complying vehicles. There is also the difficulty in predicting take-
up, and therefore effectiveness.

The “requirement” approach is more suited to fleets which are owned or contracted to
government e.g. bus fleets, garbage disposal fleets. In these circumstances,
government can direct that government owned fleets comply and make compliance a
condition of contract for contracted fleets. Changing the conditions of contract would
be generally restricted to contract renewal, and hence may have a significant time
scale. The costs would be borne directly by the relevant agencies – a contract
condition approach would presumably be reflected in the tender price. Competitive
pressures could lead to some cost absorption by operators. In the case of urban bus
fleets, there would be limited opportunities to recover costs through the fare box, and
the costs would generally need to be addressed through the operating subsidies – a
direct cost to government.

There is always the mandatory approach, backed by legislation. This is the approach
for new vehicles, but has traditionally not been favoured for existing vehicles. There
are some precedents, where equipment has been required for existing vehicles for
safety reasons e.g. urban buses.

The attraction of the mandatory approach is that it impacts on all subject vehicles
equitably, has no revenue implications and is transparent. The disadvantages are the
natural resistance of operators to imposed costs, and the difficulty in targeting
particular fleets. The highly competitive nature of the road transport industry makes it
particularly cost sensitive. In today’s climate, a mandatory approach would be likely
to meet significant resistance.

An incentive could be provided by incorporating the retrofit requirements as part of an
alternative compliance package. This would avoid the revenue implications of direct
financial incentives while prioritising some choices for operators.



                                           35
Performance Assessment
It would generally be necessary to develop an assessment structure to ensure that
eligible vehicles were in fact fitted with working retrofit equipment of the appropriate
type for the engine, and that the vehicle continued to perform within limits. This
would be particularly important for incentive based systems, where there would be a
temptation to make false claims to gain the incentive benefit.

There would be some attraction to linking the assessment program to the annual
vehicle inspection. Heavy vehicles are normally required to undergo an annual
inspection. Where an emissions I/M program is in place, this would be a simple
matter, although the technology required might be complex. The successful
development of simple test procedures to measure particulate emission levels would
be a major benefit to performance assessment. These issues are under investigation as
part of the preliminary work on the diesel NEPM.

There should be sufficient information available from overseas experience to make it
unnecessary to carry out testing in Australia to establish the performance of individual
products. A national register of diesel engine families and approved retrofit products
could be set up on a website to provide information for operators.

The performance assessment program would need to provide assurance that eligible
equipment for the particular engine was in fact fitted to the vehicle, and could range
from simple inspections on a random basis to sophisticated verifications procedures to
measure emissions performance.

Performance assessment could be linked to an annual emissions I/M program, which
could also be linked to the incentives program. Work is already well advanced in
Australia to develop highly cost-effective diesel vehicle I/M programs, and some $30
million of Federal Government funding is available to assist States and Territories to
establish such programs.

The issue of the development of a roadside test procedure to confirm that the retrofit
equipment is operating effectively also needs to be addressed. It would be highly
desirable for the annual inspection to be supplemented by random roadside tests.

The performance assessment program would vary depending on the nature of the
retrofit program. A program based on vehicles owned/operated by government would
generate a different assessment program to an incentive based program.

The first type of program could be based on agreements between the operator and the
relevant government agency on the retrofit program, and a regular audit process to
ensure that the program is implemented. For equipment with a defined life, the audit
process would need to encompass the replacement of the retrofit equipment at the
appropriate time.

The performance assessment program for an incentives based retrofit program would
need to identify eligible vehicles for which the incentive has been claimed, and then
put in place a process to inspect the vehicles, either on a random roadside basis or
through an annual inspection.



                                           36
Another approach would be to modify the alternative compliance programs to
encompass retrofit of eligible diesel vehicles. This approach would have the
advantage of much lower investment for agencies coupled with good assurance of
compliance.

The Sanctions Structure
The sanctions structure is linked to the assessment structure. An I/M program
provides the opportunity for a range of sanctions for non performance – fines, default
notices, contract penalties. An alternative compliance approach would offer a
different range of sanction opportunities. The sanctions structure is not developed in
detail in this paper.

The Target Fleet
The target fleet is an important element of a program. There is a need to profile the
target fleets to help identify suitable vehicle models and help design incentives. This
data is not readily available at present, but could be collected through representatives
of government and privately owned fleets.

The urban bus fleet is an attractive target fleet. The links exist to require retrofit of
suitable vehicles – ownership or service contracts. The vehicles do most of their
travel in urban areas where air quality is a sensitive issue. It would be desirable to
target major urban areas in the initial phases. There is considerable overseas
experience in this sector. For bus fleets on permit operation, the conditions of permit
could encompass a retrofit requirement.

Heavy vehicles owned or on contract to government agencies offer another target fleet
with strong direct links to achieve retrofit. While the outsourcing of government
functions/fleets has reduced government owned fleets, the ensuing contract
arrangements offer a direct avenue to require compliance as part of contract
conditions. This approach would have a built in time delay because the
implementation would be tied to contract negotiation.

The heavy haulage fleet, local and long distance, is a target fleet that generally does
not offer direct links to require retrofit of suitable vehicles. Further, the fleet has a
significant component of owner drivers/small fleet owners and is well known to resist
the imposition of additional cost elements. There would need to be strong incentives
to offset the costs of retrofit. There is the possibility of including retrofit as part of an
alternative compliance package which would tie retrofit to other benefits of alternative
compliance.

The light commercial and 4WD fleets may also come under consideration.
Significant numbers of these vehicles are fitted with diesel engines, mainly of
Japanese origin. Much of the travel of these vehicles is in urban areas, but the
vehicles are not generally long life compared to heavy duty diesel vehicles, where
engine rebuilds are common. Consequently the economics of emissions reduction
equipment may not be attractive.




                                             37
THE OPTION SET
This option set assumes that there is some cost/performance trade-off in the emissions
reductions that might be achieved through either technology. There is some attraction
in allowing a choice of technology, given that both technologies are well established
and of comparable cost and effectiveness.

While there is some evidence of a progressive deterioration in emissions performance
over time, the effect is of secondary significance. Consequently, a single emission
rate will be used for the analyses.

The range of factors that may influence the option set is quite extensive. For the
purpose of this project, it is necessary to identify a restricted option set that identifies
the key factors and allows informed policy discussion to take the issues further. The
proposed target fleets are:
       1. Urban Bus Fleet in Major Cities (publicly and privately owned) –
           requirements approach
       2. Heavy Duty Vehicle fleet owned or contracted to Government –
           requirements approach
       3. Heavy Duty Vehicle Fleet – incentive approach or alternative compliance
           approach.

             TARGET FLEET         INDUCEMENT         IMPLEMENTATION         COST STREAM
OPTION 1     Urban buses          Direction by        Direct action for    Costs built in to
                                  government           government owned     fare structure or
                                                       fleets               direct government
                                                      Condition of         subsidy
                                                       contract for
                                                       privately
                                                       owned/operated
                                                       fleets
OPTION 2     Government           Direction by        Direct action for    Costs built in to
             owned/contracted     government           government owned     unit costs or direct
             heavy duty fleet                          fleets               government
                                                      Condition of         subsidy
                                                       contract for
                                                       privately
                                                       owned/operated
                                                       fleets
OPTION 3     General Heavy        Rebate of           Statutory            Potential reduction
             duty Fleet           inspection costs      Framework to        in potential
                                  or include in         rebate inspection   revenues to
                                  alternative           fees                operator of
                                  compliance          alternative          inspection facility
                                  package               compliance          Retrofit costs
                                                        procedures          borne by vehicle
                                                                            owner and passed
                                                                            on to customers




                                              38
IMPLEMENTATION PARAMETERS AND OUTCOMES
The key data element is the current in-service emission rate for the target fleet.
Reliable data is scarce, and assumptions will need to be made. The NEPC In-Service
Emissions Pilot Program and the recently completed Diesel Testing project should
provide more robust data on which to estimate current diesel fleet emission factors.

It would also be very useful to validate claims made for catalyst and trap emission
reductions when vehicles are operating in congested flow traffic. Most available data
relate to tests done using a more free-flowing certification drive cycle.

There is also a need to collect reasonably detailed data on the target fleet. It is
important to identify the most suitable vehicles in the fleet. Some vehicles will be
simply unsuitable – about to be replaced, engine in poor condition. Others will not be
cost effective because the annual travel is low. The program should focus on high
annual travel vehicles with suitable engines. Many fleets can be grouped into high
useage vehicles and peak period or standby vehicles. Such a subdivision of the fleet
would allow more effective programs to be developed.

Option 1 - Urban Buses
Fleet operators would need time for a retrofit program. There would also be the
question of suitability – some older buses may not be suited to the fitting of catalytic
converters. Vehicles approaching an engine rebuild would generally not be
considered suitable for retrofit as the engine would be worn and could adversely affect
the performance of the additional equipment e.g. contamination from combustion
products of lubricating oil.

Where services have been outsourced or are privately provided, there may be
protracted negotiation required, and the outcomes might be tied to contract
renegotiation.

The example is based on Sydney. The STA Sydney bus fleet is 1,574 buses, and this
has been increased to 3,000 to reflect the privately owned fleet. This figure is subject
to correction when data is available.




                                           39
Table 7: Option 1 - Retrofit of Sydney Urban Bus Fleet

Parameters

      Target cities                 Sydney
       Time-scale                                                  5 years
        Fleet size          Sydney urban bus fleet            3,000 (estimate)
    Fleet penetration                                    Linear to 90% from year 2
                                                                  to year 5
     Fleet suitability                                   Assume 80% fleet suitable
      PM reduction             Two way catalyst                Assume 30%
                                Particulate trap               Assume 90%
  Annual vehicle travel                                    33,800 (STA Annual
                                                                   report)
Current PM emission rates                                Assume average. emission
          g/km                                               rate of 0.9 g/km
    Avg. Cost/vehicle          Two way catalyst                    $2,500
                                Particulate trap                   $6,000
 Life of Catalyst or Trap                                          7 years

Outcomes

  Annual PM reduction          Two way catalyst                 21,900 kg
                                Particulate trap                65,700 kg
  Cost-effectiveness of        Two way catalyst            $39/kg PM Reduction
  measure ($/kg PM)             Particulate trap           $31/kg PM Reduction




                                      40
Option 2 - Vehicles Owned by/Contracted to Government
Option 2 targets heavy vehicles owned/contracted to government. The specific fleet
to be targeted could be quite small for a demonstration project covering government
owned fleets to quite large if the program covered all vehicles owned/contracted to
government. The second target fleet would involve a longer time scale as there would
be a need for contract negotiations.

Data on the relevant fleet size is not presently available, but it is worth noting that the
cost per gram of particulate reduction is constant for the same annual kilometres
travelled. The total reduction in particulate will, of course vary with the fleet size.

The option presented assumes the relevant fleet size to be 500 vehicles. The fleet
penetration is assumed to be 80% over a five year period. The relatively high
penetration is based on the assumption of a requirements based approach ie a
government decision implemented by the relevant agencies through direction or
contract requirements. The time scale allows for the timing of contract negotiations.

Table 8: Option 2 Retrofit of Government Owned/Operated Fleet

Parameters

        Time-scale                       5 years
        Target Fleet           Government owned heavy           Say Sydney Assume 500
                                      vehicle fleet                    vehicles
     Fleet penetration         Linear to 80% from year 2
                                        to year 5
      Fleet suitability        Assume 80% fleet suitable
       PM reduction                Two way catalyst                   Assume 30%
                                    Particulate trap                  Assume 90%
   Annual vehicle travel         80,000 (estimate) km
                                    (NEPC Report)
    PM emission rates            Arterial 0.432 g/km                  Assume
                                 Highway 0.238g/km              commercial/arterial rate
                                 Commercial /arterial                0.9 g/km
                                       0.865g/km
   Average cost/vehicle            Two way catalyst                      $2,500
                                    Particulate filter                   $6,000
  Life of catalyst or trap               7 years

Outcomes

  Annual PM Reduction               Two way catalyst                   8,770 kg
                                    Particulate filter                26,309 kg
   Cost-effectiveness of            Two way catalyst             $16/kg PM Reduction
         measure                     Particulate trap            $13/kg PM Reduction




                                            41
Option 3 – Heavy Haulage Fleet
This option assumes an incentive structure based on an inspection fee rebate. To be
attractive, the rebate would need to cover costs of retrofitting over say three years.
The annual rebate would therefore need to be in the range $300 - $1,500.
Alternatively, the scheme could be based on an alternative compliance arrangement
where annual inspections were not required for accredited vehicles. The cost structure
would again need to reflect the annual costs, and allow for recovery of costs over a
reasonable period.

An alternative approach would be to declare a defined area around the city centre as a
“low emission” area, and require that, say, only Euro 2 or retrofitted heavy diesel
vehicles be allowed in the “low emissions” area. This would require some form of
identification for complying vehicles, and a separate sanctions regime. This approach
has been tried in some countries.

The fleet modelled is the total heavy haulage fleet, assumed to be the articulated
vehicle fleet. Given that the scheme would, to a certain extent, require an I/M
program to be in place, the option is taken to encompass the NSW articulated vehicle
fleet.

Table 9: Option 3 NSW Heavy Haulage Fleet

Parameters

       Time-scale                                                    5 years
       Target Fleet            NSW articulated vehicle     14590 (NEPC report Nov
                                       fleet                          99) 0
     Fleet penetration                                     Linear to 30% from year 2
                                                                    to year 5
    Fleet suitability                                      Assume 70% fleet suitable
  Annual vehicle travel                                     81,200 (NEPC Report)
     PM reduction                Two way catalyst                Assume 30%
                                  Particulate trap               Assume 90%
        PM emission Rates       Arterial 0.432g/km                   Assume
                                Highway 0.238g/km           commercial/arterial rate
                                Commercial /arterial          rounded to 0.9 g/km
                                     0.865g/km
    Avg. Cost/vehicle            Two way catalyst                    $2,500
                                  Particulate trap                   $6,000
 Life of Catalyst or Trap                                            7 years

Outcomes

  Annual PM Reduction             Two way catalyst                 67,200 kg
                                   Particulate filter             201,500 kg
   Cost-effectiveness of          Two way Catalyst          $16.29/kg PM Reduction
         Measure                   Particulate trap         $13.03/kg PM Reduction




                                          42
COMMENT
The key variable in determining cost is the annual vehicle travel. The figures for the
government owned fleets and for the articulated vehicle fleet are the same because the
average annual travel assumed is the same. The cost-effectiveness of the articulated
fleet is 0.4 that of the Sydney bus fleet because the average annual travel assumed for
the bus fleet is 0.4 times the travel of heavy articulated vehicles.

The cost effectiveness of the two-way catalyst is similar to that of the particulate trap
because the greater particulate reduction of the trap is offset by the lower cost of the
catalyst. These figures would need verification in examining a particular proposal, as
the costs and performance parameters are evolving rapidly.

It is important to note that this area is developing rapidly, and the costs of two-way
catalysts and particulate traps are reducing as production volumes increase. In
addition, combined units are now being offered by manufacturers at competitive
prices, and some manufacturers are offering retofit units as muffler replacement units,
ready to install – all necessary brackets and fitting already on the unit. SCR units are
being developed rapidly to address the NOx issue. However, some of this technology
is not yet being offered for retrofit programs.

The cost effectiveness of the options is directly affected by the unit cost of the
equipment. The cost figures used in option 3 are middle range. The following table
shows the variation in cost effectiveness with unit cost:

Table 10: Impact of Variations in Retrofit Unit Costs on Cost Effectiveness –
Option 3 Parameter Set

   Retrofit Technology             Retrofit Unit Cost             Cost Effectiveness
                                           ($)                          $/kg
    Oxidation Catalyst                    500                            3.3
                                         1,500                           9.8
                                         2,500                          16.3
                                         3,500                          22.8
     Particulate Trap                    5,000                          10.6
                                         6,000                          13.0
                                        10,000                          21.7
                                        12,000                          26.6




                                           43
The cost effectiveness also varies inversely with the annual distance travelled. The
following table shows the variation in cost effectiveness for option 3 for a range a
range of annual distance travelled.

Table 11: Variation in Cost Effectiveness with Annual Distance Travelled –
Option 3 Parameter Set

   Retrofit Technology         Annual Distance Travelled           Cost effectiveness
                                                                       $/kg PM
    Oxidation Catalyst                  50,000 km                         26.5
                                        81,200 km                         16.3
                                       100,000 km                         13.2
                                       150,000 km                          8.8
     Particulate Trap                   50,000 km                         21.2
                                        81,200 km                         13.0
                                       100,000 km                         10.6
                                       150,000 km                          7.1


As the annual emissions from a vehicle are proportional to the annual distance
travelled by the vehicle, careful selection of high utilisation vehicles within the target
fleet will improve the cost effectiveness of the program. In most fleets, this would
mean first consideration would be given to the newer vehicles in the fleet, as these
tend to be used more intensively and thus have the highest annual distance travelled.

It is also important to note that the actual emission rates might be quite variable. It
has been suggested that major fleets are generally well maintained, while the
maintenance of small fleets may be quite variable. This can have a significant effect
on the real life emission rates, and consequently, the cost effectiveness of a program.

An example of this is the urban arterial emission rate for articulated vehicles. The
rate used above (.865g/km) is taken from the NEPC Fleet Characteristics study.
Indications from other studies are that a rate as low as 0.5 g/km might be more
appropriate. The impact of this change on the cost effectiveness of Option 3 is set out
below.

Table 12: Effect of Emission Rate on Cost Effectiveness
Option 3 Parameter Set

 Retrofit Technology            Emission Rate            Cost Effectiveness

  Oxidation Catalyst               0.9 g/km                 $16.3/kg PM

                                   0.5 g/km                 $29.3/kg PM

    Particulate Trap               0.9 g/km                 $13.0/kg PM

                                   0.5 g/km                 $23.5/kg PM




                                              44
The lower particulate emission rate gives rise to a significant deterioration in the cost
effectiveness of retrofit of around 80%.

Finally, there is the issue of the impact of retrofit on fuel efficiency. As noted earlier,
the is some dispute regarding the magnitude, if any of the fuel efficiency effect. The
following table shows the impact on the cost effectivess of Option3 of assuming the
fuel efficiency penalty estimates from the UK “Cleaner Vehicles Task Force” ( 0.5%
penalty for oxidation catalysts, 1% penalty for particulate traps).

Table 13: Variation in Cost Effectiveness with Fuel Efficiency Penalty

   Retrofit Technology           Fuel Efficiency Penalty           Cost Effectiveness
                                                                        $/kg PM
    Oxidation Catalyst                     0.0%                           16.3
    Oxidation Catalyst                     0.5%                           20.0
     Particulate Trap                      0.0%                           13.0
     Particulate Trap                      1.0%                           15.5


In summary, the cost effectiveness of a retrofit program can be significantly improved
by careful selection of the most suitable vehicles from within the target fleet.

In general, given the assumptions on relative performance in PM reduction, the
particulate trap is marginally more cost effective than the oxidation catalyst.
However, the significantly higher initial capital cost remains an issue for retrofit
program designers.




                                            45
CONCLUSIONS
The main conclusion from this study is that there is established technology available
to allow the development of Diesel Exhaust After treatment programs that would
generate significant reductions in emissions from diesel engines in service.

The two main technologies (and there is some convergence in technology) are the
oxidation catalyst and the particulate trap. The emission reductions are in PM, HC
and CO.

The issue of NOx is yet to be addressed in field tested technology for retrofit
programs. The selective catalytic converter technology is promising and is now on
offer for some new vehicles. Time will tell if the technology will be developed for
after treatment programs.

If jurisdictions wished to establish diesel exhaust after treatment programs in
Australia, there is a range of options that could be considered. Government owned or
contracted fleets are an attractive option because there are mechanisms available to
achieve a high level of retrofit.

The commercial road transport fleets can be encompassed in a retrofit program, but
there is a need for effective incentive to achieve reasonable take-up levels.

There is also a need to collect data on the target fleet. The calculations in this paper
are based on averages, as this is a paper on issues rather than a specific program
design. When developing a specific program, it is desirable to have quite detailed
information on the target fleet. The program should be targeted at high useage
vehicles to achieve a high cost-effectiveness. Fleets with a high peak load component
– urban buses – do not achieve high average distances travelled each year. It might be
desirable to sub-divide the fleet on the basis of annual useage as well as engine type to
achieve the best outcomes. In most cases, the fleet will have a component that is in
use all day, and a component largely restricted to peak periods.

Another issue to consider is that the problem of exhaust emissions from the existing
fleets is inherently of a declining nature. As new vehicles with lower emissions
penetrate the fleet, the annual travel of the older, high emissions vehicles declines.
Thus the opportunity for retrofit programs is essentially of a temporary nature, and
programs would need continual monitoring and review. Over time, the focus of the
retrofit programs would change from upgrading the emissions performance of pre-
ADR70 vehicles to one of upgrading the emissions performance of ADR 70 vehicles
to later emissions performance levels.




                                           46
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Breuer J, Bruck, Diewald R, Hirth P (Emitec GmbH), 1997. Temperature
Examinations on a Metal Catalyst System. SAE 971028.
Chattopadhay A, Kolbenschmidt AG, 1992. (German language). Variable Valve
Timing as an Integrated Solution for Combustion Engines. SAE 927155.
Cheng W K, Hamrin D, Heywood J B, Hochgreb S, Min K, Norris M (Massachusetts
Institute of Technology), 1993. An Overview of Hydrocarbon Emissions Mechanisms
in Spark-Ignition Engines. SAE 932708.
Cleaner Vehicles Task Force, UK, 1999., First report of the Cleaner Vehicles Task
Force “Driving the Agenda”.
Cleaner Vehicles Task Force, UK, 2000. Technology and Testing: Working –Group
Report.
Cleaner Vehicles Task Force, UK, 2000. The Final Report of the Cleaner Vehicles
Task Force.



                                         47
Collins N R, Chandler G R, Brisley R J, Andersen P J, Shady P J, Roth S A (Johnson
Matthey), 1996. Catalyst Improvements to Meet European Stage lll and ULEV
Emissions Criteria. SAE 960799.
Commission for Integrated Transport, 2000. UK Pollution from older vehicles.
Cox and The Apelbaum Consulting Group Pty Ltd, 1999. The Australian Diesel Fleet
– Existing Vehicle Characteristics and the Modelling of Transport Demand, Vehicle
Populations and Emissions.
Crane M, Thring R, Podnar D, Dodge L (Southwest Research Institute), 1997.
Reduced Cold-Start Emissions using Rapid Exhaust Port Oxidation (REPO) in a
Spark-Ignition Engine. SAE 970264.
Day P (Corning Inc), 1997. Substrate Effects on Light-Off – Part ll: Cell Shape
Contributions. SAE 971024.
Dingli R J, Watson H C, Palaniswami M, Glasson N (University of Melbourne), 1996.
Adaptive Air Fuel Ratio Optimisation of a Lean Burn SI Engine. SAE 961156.
Dunleep K G, Meszler D (Energy and Environment Analysis Inc), 1996. Emission
Control Technology to Comply with FTP Revisions. SAE 961115.
Fekete N and Kemmler R (Mercedes-Benz AG), Voigtlander D et al (Daimler-Benz
AG), Strehlau W et al (Degussa AG), 1997. Evaluation of NOx Storage Catalysts for
Lean Burn Gasoline Fueled Passenger Cars. SAE 970746.
Fraidl G, Piock W, Wirth M (AVL List GmbH), 1996. Gasoline Direct Injection:
Actual Trends and Future Strategies for Injection and Combustion Systems. SAE
960465.
Gulati S, Jones L (Corning Inc), Brady M, Baker R (Chrysler Corp), Kessler B,
Zammit M (Johnson Matthey CSD-NA), Snider B, Rajadurai S (Walker
Manufacturing), 1997. Advanced Three-Way Converter System for High
Temperature Exhaust Aftertreatment. SAE 970265.
Hanel F (ALPINA GmbH & Co), Otto E (BMW AG), Bruck R, Nagel T and Bergau
(EMITEC AG), 1997. Practical Experience with the EHC System in the BMW
ALPINA B12. SAE970363.
Hertl W, Patil M, Williams J (Corning Inc), 1996. Hydrocarbon Adsorber System for
Cold Start Emissions. SAE 960347.
Houston R, Cathcart G (Orbital Engine Company), 1998. Combustion and Emissions
Characteristics of Orbital’s Combustion Process Applied to Multi-Cylinder Direct
Injection 4-Stroke Engines. SAE 980153.
Jackson S D, Williams P A (University College London), Ma T (Ford Motor Co),
1996. Development of a Fuelling System to Reduce Cold-Start Hydrocarbon
Emissions in an SI Engine. SAE 961119.
Kobayashi T, Yamada T, Kayano K (N E Chemical Corp.), 1997. Study of NOx Trap
Reaction by Thermodynamic Calculation. SAE 970745.
Kubsh J, Brunson G (W R Grace and Co), 1996. EHC Design Options and
Performance. SAE 960341.


                                         48
London Transport Buses, c. 1998. Buses: a cleaner future. Bus emission and air
quality in London.
Luoma M (Kemira Chemicals Oy), Harkonen M, Lylykangas R (Kemira Metalkat
Oy), Sohio J (University of Oulu), 1997. Optimisation of the Metallic Three-Way
Catalyst behaviour. SAE 971026.
MECA, 1997. Emission Control of Diesel Fuelled Vehicles.
MECA, 1999. Demonstration of Advanced Emission Control Technologies Enabling
Diesel-powered Heavy-duty Engines to Achieve Low Emission Levels, Final Report.
NELA, 2000. A Review of Dynamometer Correlations, In-Service Strategies and
Engine Deterioration.
Nelson English, Loxton and Andrews Pty Ltd, 1991, Study on Potential to Improve
Fuel Economy of Passenger Motor Vehicles, Part 1 – Study. Prepared for Department
of Transport and Communications, Federal Office of Road Safety.
NESCAUM, 1998, Heavy Duty Diesel Emissions Reduction Reduction Report -
Retrofit Rebuild Component.
Patil M, Hertl W, Williams J, Nagel J (Corning Inc), 1996. In-line Hydrocarbon
Adsorber System for ULEV. SAE 960348.
Petit A (Renault), Jeffrey J G (Esso), Palmer F H (CEC), Steinbrink R (GM-EA Opel
AG), 1996. European Programme on Emissions, Fuels and Engine technologies
(EPEFE) – Emissions from Gasoline Sulphur Study. SAE 961071.
Robnett J, Van Vuuren W N, Siemens Automotive, Molitor M Sealed Power
Technologies HY-Lift Corp, 1993. Performance Characteristics of an Electro-
Hydraulic Variable Valve Timing System: Lost motion principle. SAE 937102.
Roychoudhury S, Muench G, Bianchi J, Pfefferle W (Precision Combustion Inc),
Gonzales F (Ford Motor Co), 1997. Development and Performance of Microlith
Light-Off Preconverters for LEV/ULEV. SAE 971023.
Scussel A, Simco A, Wade W, 1978. The Ford PROCO Engine Update. SAE
790699.
Shimasaki Y, Kato H (Honda R&D Co Ltd), Abe F (NGK Insulatots Ltd), Hashimoto
S (NGK Locke Inc), Kaneko T (NGK Ceramics USA Inc), 1997. Development of
Extruded Electrically Heated Catalyst System for ULEV Standards. SAE 971031.
Steinbrink R (GM-Europe), Cahill G F (PSA), Signer M (IVECO), Smith G (Ford
Europe), 1996. European Programmes on Emissions, Fuels and Engine technologies
(EPEFE) – Vehicle/Engine technology. SAE 961067.
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1999. Air Assisted Gasoline Direct Injection.
Thos J, Rieck J and Bennett C (Johnson Matthey), 1997. The Impact of Fuel Sulphur
Level on FTP Emissions – Effect of PGM Catalyst Type. SAE 970737.
Toyota Motor Corporation, 1997. Car(e) for the Earth. Toyota Automotive Eco-
Technologies. PR-E-9710.



                                        49
Transport -Coffey Geosciences Pty Ltd, 2000. Review of Fuel Quality Requirements
for Australian.
Umehara K, Yamada T, Hijikata T, Itchikawa Y, Katsube F (NGK Insulators Ltd),
1997. Advanced Ceramic Substrate: Catalytic Performance Improvement by High
Geometric Surface Area and Low Heat Capacity. SAE 971029.
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US EPA, 1998. EPA Staff Paper on Gasoline Sulphur issues. Environmental
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System for ULEV. SAE 960343.
Yamada T, Nagatomo S, Suzuki Y, Kanano K (N E Chemical Corp), 1996. Impact of
Revised FTP on Emissions and New Modifications Required for Catalysts. SAE
960793.
Zahn W, Kollmann K, Mikulic L, Mercedes Benz-AG, 1995. (German language).
Modern Measures for Reduced Exhaust Emissions of Passenger Cars with Spark
Ignition. SAE 957062.


ATTACHMENT 1

REVIEW OF EMISSION CONTROL STRATEGIES
There is now an almost endless catalogue of technologies, and combinations of
technologies, to control vehicle emissions and/or to reduce fuel consumption. This
part of the report summarises the most significant, commercially available and near-
term strategies.

Not all strategies are used in all vehicles. Some engines, because of their design, size
or fuel type may require fewer controls than others in order to meet regulated
emission limits. Some technologies can only be applied to specific fuel or engine
types.

It is also important to note that, for most light duty vehicles (ie cars, station wagons
etc up to 2.7 tonnes), tailpipe emission levels (apart from CO2) are generally not a
direct function of engine size or fuel consumption. Standards for light duty vehicles
generally set a maximum g/km emission level regardless of the engine size or vehicle
mass. In these vehicles, manufacturers may, for commercial reasons, incorporate only
the minimum controls necessary to meet regulated emission limits.

Hence a vehicle powered by a large six cylinder engine with a range of highly
effective emission control strategies may well have lower emissions than a small three
or four cylinder engine with only minimal controls.




                                           50
On the other hand, CO2 emissions, for any given fuel, are directly proportional to the
rate of fuel consumption, so emissions of this gas tend to increase with vehicle mass.

It should also be noted that some technologies may have a “swings and roundabouts”
effect, in that they tend to improve one aspect of emissions at the expense of another.
For instance, lean burn technology can greatly improve fuel consumption (and hence
CO2 emissions), but cause NOx emissions to increase significantly.

Fuel selection itself is also a major factor in determining emission levels. Gasoline
tends to have high air toxics and low regulated gas emissions; diesel has very low CO
and HC, but high NOx and fine particulate emissions. LPG and CNG have very low
air toxics and particulate emissions, but HC (non-reactive) can be a problem for CNG.

Beyond the “direct” influences of technologies and fuels, there is also the important
issue of maintaining the emissions performance of vehicles at an acceptable level
throughout their operating lives. Whether achieved through accredited fleet
management systems or through regulated inspection / testing programs, this “whole
of life” approach to vehicle emissions performance is being increasingly recognised as
an essential element in emissions management.

Less well recognised, but potentially of some significance, is the role of fuel additives
in achieving and maintaining lower emission levels and, possibly, in reducing fuel
consumption. This is a contentious area and there is considerable scepticism about
some of the claims made for these products.

Nevertheless, the oil industry routinely adds detergent formulations to commercial
petrol in order to maintain fuel injector performance, and similar benefits are widely
acknowledged to flow from the use of similar additives in diesel engines.

Summary of Fuel Consumption and Emissions Reduction Technologies
The strategies outlined below each fall into one of three categories, viz:
 Fuel management and in-engine controls, which are primarily aimed at optimising
   combustion to achieve clean, efficient and properly timed burning;
 exhaust after-treatments, which clean up residual pollutants in the exhaust stream;
   and
 body/transmission/running gear enhancements, aimed at reducing or smoothing
   the load on the engine.

0        Diesel Vehicles.

(a)     Engine Controls

    0    Computerised fuel management
    1    Direct fuel injection
    2    Turbocharging
    3    Variable valve timing and/or lift geometry
    4    Low-friction bearings and pistons
    5    Roller cam followers
    6    Multi-valve heads (3 or 4 valves/cylinder)


                                           51
(b)        Exhaust After-treatment

      7     2-way catalyst
      8     De-NOx catalyst
      9     Particulate traps (accumulating or continuously regenerating)
      10    Particulate filtration


(c)        Body/Transmission/Running Gear

      11    Lightweight components (plastics, magnesium, aluminium, composites,
            high-strength steel)
      12    Improved aerodynamics
      13    Low rolling resistance tyres



Defining a Baseline
Many of the above technologies are already commonplace in vehicles commercially
available in Australia. However, because their application is far from uniform, it is
difficult to define a clear baseline against which the potential for future improvements
can be measured.

It is very clear, nevertheless, that the Government's recent decision to adopt Euro4
emission standards for diesel engines, and either Euro3 or Euro4 for spark-ignition
vehicles, will be a major challenge for the motor industry. Inevitably, manufacturers
will be pushed into employing virtually every technique in their repertoire in order to
meet the new regulations.

In the context of this review, only engine and exhaust after-treatment technologies are
considered.
For diesel engines, the baseline is taken as the current mainstream technologies that
have been adopted in meeting Euro1 and, increasingly, Euro 2 standards. In general,
the baseline for Australia would then include:
 (a)    Engine Controls

      0     Computerised fuel management
      1     Direct/common rail fuel injection
      2     Turbocharging

(b)        Exhaust After-treatment

      3     2-way catalyst
      4     De-NOx catalyst
      5     Particulate filters/traps (accumulating or continuously regenerating)




                                             52
THE CRITICAL TECHNOLOGIES
The key issue in this part of the study is to identify those technologies:
(a)    that are now being developed for commercial application in order to
       concurrently achieve major emission and fuel consumption reductions, and
(b)    which, in combination with other technologies may be dependent on fuel
       quality for effective function and durability.
They are tabulated below and have been classified into current and emerging
technologies, together with an indication of their dependence on fuel quality.


                  Table 1: Fuel-Sensitive Technologies for Spark-Ignition Engines
                                                                 Availability           Sensitivity to
                                                                                        Fuel Quality
                    Technology                             Now           Emerging     High / Med / Low

Computerised engine management                                                              Low

Knock sensors                                                                               Low

Exhaust gas oxygen (EGO) sensors                                                            Low

Exhaust gas recirculation                                                                   Low

Multi-point fuel injection                                                                  Low

Sequential fuel injection                                                                   Low

Variable valve timing / lift (VVT)                                                          Low

Lean burn                                                                                 Medium

Stratified charge, gasoline direct injection                                                High

Advanced catalyst formulations                                                              High

On board diagnostics                                                                      Medium
Note: Availability "Now" is defined as a technology that is standard or optional equipment on a
wide range of vehicle models. . All “Now” technologies are under continuing development and
refinement. "Emerging" means limited commercial availability or proven technology likely to be
commercially available in the near future.




                                                53
                           Table 2: Fuel-Sensitive Technologies for Diesel Engines


                                                                     Availability        Sensitivity to
                                                                                         Fuel Quality
                     Technology                                 Now          Emerging   High / Med / Low

Computerised fuel and engine management                                                     Low

Direct fuel injection                                                                       Low

Common Rail High Pressure Injection                                                         Low

2-way catalyst                                                                              High

De-NOx catalyst                                                                             High

Continuously regenerating particulate trap *                                                High

Particulate filtration *                                                                    Low

On board diagnostics                                                                      Medium

* The rate of development of technology is such that these technologies today would
be considered as “available now”
THE CRITICAL FUEL QUALITY PARAMETERS
Diesel
There is a clear correlation between some fuel properties and regulated diesel
emissions. Drawing general conclusions is, however, difficult due to such factors as
inter-correlation of different fuel properties, different engine technologies, or engine
test cycles.
In heavy-duty engines increasing the cetane number lowers HC, CO, and NOx
emissions, while reducing fuel density lowers NOx and PM but increases HC and CO.
Light-duty engines show a different fuel sensitivity than the heavy-duty engines.
Sulphur increases PM in both classes of engines. Sulphur is also known to interfere
with several diesel emission control strategies, especially in relation to particulate
emissions reductions. The influence of sulphur on the effectiveness and durability of
the key diesel emission reduction technologies are discussed in the following sections.
The combustion of engine lubrication oil, although not strictly a fuel issue, is also
relevant because diesel engines typically burn significant quantities of oil. Some of
the products of combustion, notably phosphorous, zinc, and calcium oxide accumulate
on the surface or within catalysts or particulate traps. These oil-derived poisons can
result in an irreversible catalyst/trap deactivation.
DIESEL TECHNOLOGIES
Computerised fuel and engine management
The use of computerised engine control for both heavy and light-duty engines has
been rapidly growing since the late 1980s. This technology has proved to be a
powerful tool for achieving reductions of all regulated diesel emissions and for
delivering significant improvements in fuel economy.
Compared with older, mechanical arrangements, electronic systems provide much
more precise control over fuel, air and exhaust gas recirculation (EGR). Moreover,
this control is executed over the engine lifetime, compensating for engine wear and
deterioration. Additionally, as required in an increasing number of applications,


                                                     54
engine emission controls can be supported by on-board diagnostic (OBD) systems,
which activate a malfunction indicator in the vehicle when an emission fault is
detected.
Typical electronic control systems for diesel engines include a range of sensors, a
microprocessor (the electronic control unit, or ECU), and a set of actuators. The
sensors measure physical variables and pass the information in the form of electrical
signals to the controller. Examples include crank speed, boost pressure, intake
manifold temperature and pressure. The actuators perform mechanical actions as
directed by signals from the microprocessor. Examples of actuators are EGR valves or
variable geometry turbochargers. The system generally covers:
   0      Fuel quantity control
   1      Fuel timing control
   2      Boost pressure control
   3      EGR control.

1       Fuel Quantity Control

The optimal fuel requirements for the entire operating range of a given engine are
determined by analysis, testing and computer modelling as part of the engine's design
and development. These parameters are then stored by the ECU as a three-
dimensional map of fuel supply versus engine speed and throttle position.
The engine controller will first calculate the fuel rate from the map. This demanded
fuel rate is then compared with other computed fuel rates needed to satisfy other
engine conditions, for example the airflow limited fuel rate. The lowest useable fuel
rate value is selected and passed to the fuelling system.

2       Fuel Timing

Injection timing is one of the most important factors influencing combustion and the
resulting emissions. All important engine performance parameters, including specific
fuel consumption, emissions of NOx, PM and HC are strongly influenced by injection
timing.
Mechanical fuel system have fairly limited injection timing capabilities. They usually
require hardware changes in order to modify injection schedules. The timing schedule
of mechanical systems has very few degrees of freedom, so that handling such
anomalies as cold start advance or low coolant temperature advance requires
additional mechanical elements. Furthermore, cam-driven fuel systems typically
exhibit a relationship between injection timing and fuel injection rate, which can
influence injection pressure and duration.
In contrast, electronic control allows command of injection timing in response to
engine load, engine speed, or ambient conditions. Exhaust emissions can be optimised
over a wide range of engine speeds and loads, through implementing injection timings
that optimise emissions and fuel consumption over local regions of the operating
spectrum.
The electronic injection control also allows for much better accuracy of the injection
timing. Some engines [Bauder 1990]i, use an injector needle lift sensor to provide
feedback, with a claimed injection timing accuracy of ±1 degree of crankshaft
rotation.




                                          55
3        Boost Pressure

Practically all today's automotive diesel engines are turbocharged. Modern
turbochargers, including the wastegated turbocharger and variable geometry
turbocharger technologies, allow control of the intake manifold (boost) pressure and,
thus, the air flow rate to the engine cylinders. A wastegate bypasses some of the
exhaust gas around the turbocharger turbine at high speeds to prevent excessive boost
pressure and airflow.
Many mechanical wastegate systems develop inaccuracies through their inability to
adapt to wear and friction over their operating life, with consequential adverse effects
on engine performance.
Electronic wastegate control is now treated as an integrated engine control strategy,
with true closed-loop control of the boost pressure, compensated for manufacturing
variability and changes during engine lifetime, as well as environmental conditions
including altitude.

4        EGR Control

Exhaust gas recirculation (EGR) is now increasingly used as a means to control NOx
emission. Gas to be recirculated is drawn from the exhaust manifold upstream of the
turbocharger and transferred to the intake manifold through an EGR valve. The
amount of EGR is electronically controlled in response to various parameters,
including the throttle position and ambient conditions. Most current implementations
use open-loop EGR.
Different degrees of EGR control are possible. In the simplest open-loop system, the
EGR valve is closed by the ECU during start-up and when the engine coolant is below
prescribed temperature. A more sophisticated implementation of the open-loop EGR
control involves modulating the EGR valve according to a valve position schedule
stored as a look-up table in the ECU.
Direct and Common Rail High Pressure Fuel Injection
Direct injection (DI) involves firing a cloud of finely atomised fuel directly into the
combustion chamber at an optimum point in the engine cycle. Older, indirect
injection systems for diesel engines simply entrain fuel into the inlet air stream so
there is little control over the ignition timing.
In heavy duty engines, DI has been used for many years, with increasing levels of
technical sophistication and ever-increasing operating pressures. A key feature of
high-pressure systems is that they can provide good fuel atomisation, which is needed
for low particulate and hydrocarbons emissions.
Since the early 1990s commercial competition and regulatory action have also pushed
manufacturers of light duty diesel vehicles towards using a high pressure direct
injection combustion process.
The most recent commercialisation of high pressure DI is Common Rail technology.
Instead of an injector pump sending a timed "pulse" of fuel to each cylinder's injector
in turn, the fuel is continuously pressurised and held at this high pressure in a tubular
reservoir (the common rail), to which all the computer controlled injectors are
connected. A computer-controlled signal actuates each injector at exactly the correct
time in the cycle.
A common rail system typically includes the following components:
     High pressure fuel pump
     Rail for fuel storage and distribution


                                           56
   Electro-hydraulic injectors
   Electronic control unit (ECU).




                                     57
                   Figure 1. Schematic of the common rail injection system




The injectors open and close in microseconds, allowing the system to precisely meter
the quantity, timing and pressure of fuel injection to a degree of accuracy that was
never previously possible.
To maximise atomisation efficiency, fuel in the rail is typically pressurised to around
1,350 bar (approximately 20,000psi) - twice the pressure of a modern, conventional
direct injection diesel engine.
This accurate control also enables the pilot injection of a very small charge of fuel just
before the main injection, which then produces a complete and progressive burn. This
softening of the ignition reduces noise by around 3dBA [Citroen 1999].
Pilot injection also helps to reduce NOx emissions because the reduced size and later
timing of the main injection with pilot, compared to the no pilot case, gives a more
retarded heat release for the main injection.
This reduces cylinder pressure and mean gas temperature, and hence NOx formation,
in the region soon after TDC where there is the highest rate of diffusion burning.
Thus, the NOx generated by early burning of a small quantity of pilot fuel appears to
be more than offset by reduced NOx formation from the main injection.




                                             58
Post-Injection
The common rail also has the capability of introducing fuel post-injection, which is
used with some catalytic emission control technologies. These technologies include
the following NOx catalysts (which are discussed in later sections):
     passive diesel particulate filter systems
     lean NOx catalysts utilising selective reduction with hydrocarbons
       NOx traps which require a "rich exhaust" condition for regeneration.
Passive particulate filter systems rely on the exhaust gas temperature and, usually, a
catalyst or fuel additive for regeneration. Post-injection of fuel may be used to
periodically increase the exhaust temperature to enhance the filter regeneration. A
filter system utilizing such engine management strategy has recently been developed
by Peugeot.

SUMMARY: Common Rail systems are characterised by the following advantages:
   High injection pressures and good spray characteristics are possible even at
    low engine speeds and loads.
   Capability to deliver stable, small pilot injections can be used for decreased
    NOx emissions and noise.
   Option for post injection that may be used together with such emission control
    technologies as particulate filters, lean NOx catalysts, or NOx traps.

2-way Catalyst (Diesel Oxidation Catalyst)

5        Introduction

Diesel oxidation catalysts were first introduced in 1970s in underground mining as a
measure to control CO. Today, oxidation catalysts are used on many diesel road
vehicles, primarily to control particulate matter and hydrocarbon emissions.
Early diesel catalysts utilized very active oxidation formulations such as platinum on
alumina. They were very effective in oxidising emissions of CO and HC as well as
the SOF portion of diesel particulates.
A downside of earlier catalysts was that they also oxidised sulphur dioxide, which is
present in diesel exhaust from the combustion of sulphur containing fuels. The
oxidation of SO2 leads to the generation of sulphate particulates and may significantly
increase total particulate emissions despite the decrease of the SOF fraction.
Newer diesel oxidation catalysts are designed to be selective, i.e., to obtain a
compromise between sufficiently high HC and SOF activity and acceptably low SO2
activity.

6        Applications of Diesel Oxidation Catalyst

Diesel oxidation catalyst (DOC) technology promotes a range of oxidation reactions
utilising the excess oxygen present in diesel exhaust at all engine operating
conditions.
The oxidation reactions may also be combined with selective catalytic reduction
(SCR) and lean NOx catalyst (LNC). SCR systems are used in to reduce NOx
emissions through selective reaction with a reducing agent, such as ammonia or urea,
which is injected upstream of the catalyst bed. The lean NOx catalyst, intended to


                                          59
reduce nitrogen oxides in an oxidising atmosphere from mobile engines, is now
becoming a commercial reality.
Increasingly stringent emission standards, such as Euro3 and 4, are likely to transform
the emission control catalyst into a standard component of diesel powered vehicles.
Future catalysts will also have to exhibit at least some NOx reduction activity in
addition to their oxidation functions.
The U.S. Urban Bus Retrofit/Rebuild Requirements which became effective in 1995
triggered the widespread use of catalysts on urban buses. Several systems that have
been certified by the EPA under the bus retrofit program utilise diesel oxidation
catalysts, either alone or in conjunction with other emission controls.

7       Reactions in diesel oxidation catalyst

Diesel oxidation catalyst can be used to reduce the following emissions:
     gas phase hydrocarbons (HC),
     the organic fraction of diesel particulates (SOF),
     carbon monoxide (CO).
The emission reductions in the DOC occur through the chemical oxidation of
pollutants. These processes can be described by the following chemical reactions.
[Hydrocarbons] + O2 = CO2 + H2O                                        (1)
CO + 1/2O2 = CO2                                                       (2)
Hydrocarbons are oxidised to form carbon dioxide and water vapour. Reaction (2)
describes the oxidation of carbon monoxide to carbon dioxide. Since carbon dioxide
and water vapor are non-toxic, the above reactions bring an obvious emission benefit.
Some of the oxidation reactions that may occur in the diesel catalyst can produce
undesirable products and act counter-productively to the catalyst purpose. Oxidation
of sulphur dioxide to sulphur trioxide with the subsequent formation of sulphuric acid
(H2SO4), described by reactions (3) and (4), is certainly the most important of these
processes.
2SO2 + O2 = 2SO3                                                       (3)
SO3 + H2O = H2SO4                                                      (4)
When the exhaust gases are discharged from the tailpipe and mixed with air, their
temperature decreases and the gaseous H2SO4 combines with water molecules. These
highly aggressive sulphate particulates increase the total particulate matter emissions
from the engine.


8       Gaseous Phase Performance

The diesel oxidation catalyst is an effective device to control carbon monoxide and
hydrocarbons emissions from diesel engines, including the PAH and hydrocarbon
derivatives such as aldehydes.
Figure 2 depicts an example catalyst performance. The catalyst shows no activity at
low exhaust gas temperatures. As the temperature increases, so does the oxidation rate
of CO and HC. This is called catalyst "light-off". At high temperatures the catalyst
performance stabilises to form the characteristic plateau on the light-off curve. For
simple oxidation catalysts such as Pt/Al2O3, the conversion of carbon monoxide is
higher than that of hydrocarbons at any given temperature.




                                          60
            Figure 2.      Conversion of CO and HC in Diesel Oxidation Catalyst
                             Source: Johnson Mathey 1998


9        Particulates Performance

Diesel particulate matter is composed of three major fractions including the
carbonaceous particulates, the organic particulates (SOF), and sulphates (SO4). Each
of the fractions shows different reactions in the diesel oxidation catalyst. The
composition of raw exhaust particulates and the particulates after the DOC is
schematically depicted in Figure 3.
Experimental data shows that the diesel oxidation catalyst is virtually inactive in
respect to the carbonaceous particulate material or black soot. The carbon fraction of
diesel particulates remains essentially unchanged as the gas passes through the
catalyst.
The organic fraction (SOF) of diesel particulates, composed of high boiling
hydrocarbons, is very effectively oxidized in the catalyst contributing to a decrease in
the TPM emissions. After a full catalyst light-off is reached, the conversion of SOF
shows little change with further temperature increase. This is similar to the light-off
curve for gas phase conversions.
As noted above, the sulphate fraction of diesel particulates (SO4) is increased in the
DOC due to the oxidation of SO2 with subsequent formation of sulphuric acid,
reactions (3) and (4).
This is a counter-productive process, leading to an increase in TPM emissions in the
diesel oxidation catalyst. The intensity of the sulphate production increases with




                                           61
exhaust gas temperature and becomes difficult to control at about 400°C. These
processes are shown graphically in the following chart.

                    Figure 3. PM Performance of Diesel Oxidation Catalyst
                               Source Johnson Mathey 1998
Special catalyst formulations are used to suppress that process, making the diesel
oxidation catalyst a viable PM reduction approach.
Low sulphur fuels minimise sulphate production and increase the benefit of the diesel
oxidation catalyst, but in practice, if sulphur is present in the fuel, there is always a
temperature above which PM emissions will start to increase. If sulphur-free fuel is
used, the highly active platinum/alumina based catalyst systems are still the best
choice for both the particulate and the gas phase emission control.

10       Deactivation of Diesel Catalyst

The main cause for the deactivation of diesel catalysts is poisoning by sulphur, as well
as by lubrication oil additives. Phosphorus is the most common oil-derived catalyst
poison.
Sulphur can be found uniformly distributed over the catalyst length and the washcoat
depth, while phosphorus is selectively adsorbed at the catalyst inlet and in a thin,
outer washcoat layer.
Since diesel engines typically burn larger quantities of oil than their gasoline
counterparts, the diesel catalyst must be more resistant to the oil and its additives.
Under the cooler modes of operation, unburnt oils and their additives deposit within
the catalyst washcoat. Unlike the organic portion of the oil, the additives remain after
the oil is catalytically oxidized. Substances such as phosphorus, zinc, and calcium
oxide accumulate on the surface or within the catalyst. The oil-derived poisons result
in an irreversible catalyst deactivation.
In most countries, diesel fuel contains significant quantities of sulphur, several times
higher than those present in gasoline. The maximum sulphur content in the US and
Europe on-road diesel fuels is 0.05% by weight, but in Australia can often exceed
0.12%. Fuel sulphur may be another source of catalyst deactivation.
Sulphur poisoning is frequently reversible by high temperatures, under which the
sulphur compounds decompose and are released from the catalyst washcoat.
However, due to the low diesel exhaust temperatures, in many diesel engine
applications the conditions needed for catalyst regeneration may never be reached.
Lean NOx (De-NOx) Catalyst
Methods for catalytic reduction of nitrogen oxides under lean exhaust conditions
include selective catalytic reduction with urea or ammonia, selective catalytic
reduction with hydrocarbons, and NOx trap/catalyst systems.
Reduction with ammonia, originally used only in stationary applications, is now
becoming available for road vehicles [Peugeot]. Several catalyst systems have been
proposed for the reduction of NOx with hydrocarbons, including a copper substituted
zeolite ZSM5 catalyst, which is active at high temperatures, and a platinum/alumina
catalyst, exhibiting low temperature activity. Both these catalysts have narrow
operating temperature windows and still require improvement.
NOx traps are the newest technology which is being developed for partial lean burn
gasoline engines but is also considered for diesel engines. The traps adsorb nitrogen
oxides during lean engine operation and require short enrichment "spikes" for the
desorption and reduction of NOx using post-injection techniques.



                                               62
11       Catalytic Reduction of NOx

Oxides of nitrogen can be very efficiently reduced from exhaust gases of rich-burning
engines, such as those used in today's gasoline-powered cars. The three-way catalyst,
which has been developed for that purpose, promotes a non-selective reduction of
NOx by other exhaust gas components such as carbon monoxide and hydrocarbons.
High NOx reductions can be only achieved if the engine operates close to the
stoichiometric air to fuel ratio. Since the presence of oxygen in the exhaust gas rapidly
deteriorates the NOx performance of the three-way catalyst, that technology is
ineffective in controlling nitrogen oxides emission from diesel engines.
A catalyst capable of reducing NOx in exhaust gases from lean-burning engines, ie, in
the presence of oxygen, is called a lean NOx catalyst (LNC). This technology is being
very actively pursued not only for diesel NOx reductions, but also for gasoline
engines, where lean burn offers very significant fuel consumption (and hence
greenhouse) benefits.
The following catalytic approaches have been investigated for the NOx control in lean
exhaust gases:
     NO decomposition catalyst
     Selective catalytic reduction with nitrogen containing compounds (ammonia,
        urea)
     Selective catalytic reduction with hydrocarbons
     NOx trap-catalyst systems.
The decomposition of nitric oxide to elements is described by the following equation:
2NO = N2 + O2
Although initially promising, Catalytic Decomposition of NO has proven to be a
difficult reaction to realise. The decomposition of NO on Cu/ZSM5 is subject to
inhibition by water, is very sensitive to poisoning by SO2, is effective only at low
space velocities, and the catalyst activity and selectivity are not satisfactory [Iwamoto
1991].
Selective Catalytic Reduction (SCR) of NOx can be achieved if a reducing agent is
injected into the gas upstream of the catalyst bed. SCR processes utilising nitrogen-
containing reductants such as ammonia or urea are commercially available for
stationary diesel engines and for industrial sources. If ammonia is used, the main
selective reaction is given by the equation:
4NO + 4NH3 + O2 = 4N2 + 6H2O
Although considered in the past not to be an attractive option for diesel trucks and
cars, the use of ammonia, or preferably urea, is now becoming a commercial reality in
some light and heavy duty diesel applications
A number of catalysts have been found to promote Selective Catalytic Reduction of
NOx by hydrocarbons, alcohols, or other combustion gases [Shelef 1995]. Reduction
by HC is less susceptible to sulphur poisoning than the NO decomposition and higher
conversion efficiencies have been demonstrated.
In the case of diesel application, diesel fuel was the obvious source of hydrocarbons
necessary for the reaction, and the computerised Common Rail post-injection
techniques outlined previously, now make this approach both feasible and
economically attractive.
In the selective catalytic reduction, the hydrocarbons selectively react with NOx,
rather than with O2, to form nitrogen, CO2, and water.
{HC} + NOx = N2 + CO2 + H2O


                                           63
The competitive, non-selective reaction with oxygen is given by:
{HC} + O2 = CO2 + H2O
The catalyst-reductant system has to be optimised to promote the desired selective
reaction and suppress the undesired reactions with oxygen. Catalyst selectivity
depends on several factors including the catalyst formulation, the hydrocarbon species
used for the reaction, and the HC/NOx ratio.
0       NOx Trap - Catalyst Systems

The concept of NOx traps is to incorporate NOx trapping compounds into the catalyst
washcoat, with a controlled release under favourable catalysing conditions.
In Temperature Regenerated NOx Traps, these compounds adsorb NOx during
periods of low exhaust gas temperature then, at higher temperatures, the stored NOx
would be released and reduced in the catalyst. Several materials, including various
types of zeolites, have been evaluated as candidates for temperature regenerated NOx
traps.
Another, different NOx trap/catalyst technology is based on acid-base washcoat
chemistry. It involves trapping NOx during lean driving conditions and releasing it
under short periods of deliberately induced rich operation. The released NOx must be
catalytically converted to nitrogen as happens in current three-way catalyst.




                                          64
This "rich spike regeneration" trap concept was originally developed primarily for
gasoline engines, but work is underway to utilise this technology for diesel NOx
reduction also. The NOx trapping/reduction mechanism is illustrated in the figure
below:




                       Figure 4. NOx Trapping / Reduction Mechanism

The catalyst washcoat combines three active components: an oxidation catalyst, a
trap, and a reduction catalyst. First, nitric oxide reacts with oxygen on oxidation
catalyst sites (e.g. platinum, Pt) to form NO2. Then the NO2 is adsorbed by an alkaline
earth oxide trapping material (e.g. barium oxide, BaO), forming barium nitrate. The
oxidation of NO and adsorption of NO2 occurs during the lean engine operation.
During a rich exhaust spike the barium nitrate decomposes producing mostly nitric
oxide which is reduced on reducing catalyst sites (e.g. rhodium, Rh). The entire
trap/catalyst system is very simple and, in fact, similar to the three-way Pt/Rh catalyst
technology. It is certainly a potentially attractive technology for lean burn gasoline
engines. The necessary rich regeneration periods may be more difficult to implement
in the diesel engine.
The following are some of the issues which are currently being resolved:
     High temperature limitations related to the decomposition temperature of
        barium nitrate in the catalyst washcoat. (This issue is probably not critical for
        diesel applications).
     Deactivation of the trap by sulphur. Sulphur compounds form barium sulphate
        which is more stable than barium nitrate. Desulfation of the trap could be
        performed by applying high concentrations of reductants or by exposure to
        high temperatures (above 500°C). However, some barium sites appear to be
        permanently and irreversibly poisoned by sulphur [Dou 1998].
     The impact of phosphorus and zinc, known poisons of the 3-way catalyst, on
        the NOx trap is still not fully understood.
     Vehicle driveability problems can occur during the brief but necessary
        periodic mixture enrichment.
     Mixture enrichment needs to be carefully applied. In-cylinder enrichment
        creates high particulate emissions, and exhaust system enrichment requires not
        only that a reductant be injected but, first of all, that the oxygen levels in the
        exhaust gas be lowered. Post-injection using common rail injection systems
        are likely to provide the answer to this problem.
Continuously Regenerating Particulate Trap
Diesel particulate traps physically capture diesel particulates preventing their release
to the atmosphere. Diesel traps work primarily through a combination of deep-bed



                                           65
filtration mechanisms, such as diffusional and inertial particle deposition. The most
common filter materials are ceramic wall-flow monoliths and filters made of
continuous ceramic fibres.
A number of methods have been developed to regenerate diesel filters. Passive filter
systems utilize a catalyst to lower the soot combustion temperature. Active filter
systems incorporate electric heaters or fuel burners to burn the collected particulates.
Diesel traps are most effective in collecting the solid carbonaceous fraction of diesel
particulate matter. The effectiveness of diesel traps in controlling the organic fraction
of particulate matter (SOF) depends on the type of trap and on its operating
conditions. Depending on the circumstances, it may be lower than the SOF abatement
effectiveness of the diesel oxidation catalyst.
All diesel traps of practical importance are diesel particulate filters (DPF). The terms
"diesel trap" and "diesel filter" are frequently used as synonyms. Some of diesel filter
materials show quite impressive filtration efficiencies, frequently in excess of 90%, as
well as acceptable mechanical and thermal durability.
In fact, diesel traps are the only emission control measures which reduce diesel
particulate emissions with high efficiencies.
The most important issue with diesel traps is filter regeneration. Soot generated by
diesel engines is characterized by low bulk density and, therefore, high volume. Due
to the high volumes of generated particulates, it is necessary that the filter is
regenerated, either periodically or continuously, during the regular engine operation.
The on-vehicle filter regeneration is most commonly realized by oxidizing (burning)
of soot in the filter.
Filter Materials

12       Wall-Flow Monoliths

Wall-flow monoliths are by far the most common type of diesel traps. They have been
utilised in the majority of commercial diesel trap systems. The monolithic filters are
derived from flow-through supports used for automotive catalytic converters. The
channels are alternately plugged at each end in order to force the diesel aerosol
through the porous walls. Thus, the walls of the structure act as a filter.




                                           66
Monolithic filters are usually made of a synthetic ceramic composition originally
developed for automotive catalytic converters. The material has a very low thermal
expansion coefficient, which makes the material resistant to extreme thermal cycling.
It also exhibits high temperature resistance (~1,200°C) and good mechanical strength.
The filtration mechanism in ceramic monoliths is usually a combination of depth and
surface (cake) filtration. In the initial phase, diesel particulates are collected in the
pores within the walls through inertial and diffusional deposition. With increasing
filter load, however, a layer of soot may be build at the surface of the inlet monolith
channels. After that layer develops, it acts as a filtration cake.

13       Ceramic Fibres

Continuous ceramic fibres were first researched as diesel filters in 1980's for urban
bus applications. A typical design of fibre filters involves ceramic yarn wound around
a perforated metal tube or knitted into 3-dimensional structures.
     Both wound and knitted ceramic fibre filters work through practically pure
        depth filtration mechanisms. Therefore, they tend to be less prone to clogging
        when overloaded with soot. They are also characterised by good thermal
        shock resistance. As a drawback, the filtration efficiency of fibre filters is
        lower than that of wall-flow monoliths.

14       Wire Mesh Filters

Traps made of packages of wire mesh are another example of deep-bed filters. They
are characterised by a high void volume (up to 95%) and a tendency for blow-off of
the accumulated soot. Today, they seem to attract little attention.
The attractiveness of wire mesh filters in the past was related to their potential
compatibility with a variety of regeneration methods, including catalyzing with
alumina-based washcoat or electrical regeneration.

15       Ceramic Foams

Ceramic foam filters have large, mostly open, circular pores of 250 to 500µm in
diameter and pore density of 20 to 30 pores per cm2. The foam is manufactured by
impregnating a polyurethane foam matrix with ceramic paste. The parts are then
calcined to decompose the polyurethane and obtain the rigid ceramic structure. The
filters can be made, quite similar to the wall-flow monoliths, of either cordierite or
silicon carbide.
Inertial deposition is the major filtration mechanism in ceramic foams. Typical
filtration efficiencies are relatively low, usually between 60 and 70%. Due to low soot
holding capacity, large filter volumes are needed with ceramic foams.
Filter (Trap) Regeneration
In an ideal situation, particulates that enter the filter are oxidised in a continuous or
almost continuous manner. The filter maintains an approximately constant, moderate
soot load, which produces an acceptable pressure loss. Continuous regeneration does
not produce high temperature peaks due to the exothermic combustion of soot. Thus,
there is little thermal stress on the filter material.
Rapid regeneration occurs when a high load of soot becomes "ignited". Such
regeneration, also called "uncontrolled" or "run-away" regeneration, is the opposite to
the ideal, continuous regeneration mode. The "ignited" soot load burns rapidly



                                           67
releasing high quantities of heat, raising filter temperature, and eventually, causing
damage (melting, cracking) to the filter material.
In passive systems the soot combustion temperature is lowered to a level allowing for
auto-regeneration during regular vehicle operation. This can be achieved by
introducing an oxidation catalyst to the system. The catalyst can be placed directly
onto the trap surface or added to the diesel fuel as fuel additive. Active ingredients of
available fuel additives include iron, cerium, copper, platinum, or mixtures of metals.
A different principle has been utilized in the CRT Trap, where the catalyst, placed
upstream of the filter, is used to generate nitrogen dioxide which then oxidizes the
collected soot.
The second approach is to actively trigger regeneration by raising the temperature in
the trap, using electric heaters or fuel burners.
Active trap systems are much more complex than passive filters. They require
sophisticated hardware, including an electronic control unit to trigger and control the
regeneration process. The passive filters, due to their simplicity, are a more attractive
approach.
The following table illustrates the effects of a typical (active) trap on the emissions of
a heavy duty engine, using the US Federal HD Urban Bus Cycle:

        Engine Baseline       g/bhp·hr With Trap g/bhp·hr Trap Efficiency %

 NOx                   5.0                          4.3                     14

  HC                   0.7                          0.6                     14

  CO                   2.5                          3.0                     -20

  PM                 0.350                        0.053                     85

An average regeneration interval of the trap was 4.2 hours. The duration of
regeneration was 6.5 minutes. The heater power consumption during that period was
150 A at 24 V.
Plasma Exhaust Treatment
Non-thermal plasma technologies have the potential to reduce several diesel and
automotive exhaust emissions including NOx, particulate matter, and hydrocarbons.
The focus in plasma research is on nitrogen oxides reduction. Since oxidation
reactions dominate during plasma discharges in lean exhaust, the plasma alone is
probably ineffective in reducing NOx. Instead, combined plasma-catalyst systems
have been proposed and are investigated.
Early reports indicate that plasma may enhance the catalyst selectivity and removal
efficiency. Today's plasma exhaust treatment technologies are in their early stage of
development.
It is still impossible to predict whether or not they will become a viable emission
control option.
On board diagnostics
On-board diagnostics (OBD) is a system designed to monitor the performance of
vehicle's emission controls, such as catalytic converters, diesel traps, evaporative
emissions, engine misfire, etc., and to detect emission faults. OBD systems are or will
be required by emission regulations in several countries. In the U.S., OBD systems


                                            68
are currently required on light duty vehicles (up to 6,350 kg GVW in California and
3,850 kg GVW federal) fueled by gasoline, diesel, or alternative fuels. In Europe,
OBD requirements will be introduced in 2000 (phase-in schedule until 2005) for light
duty vehicles and in 2005 for heavy duty vehicles.
Generally, there will be differences between requirements for diesel and gasoline
fueled vehicles. The following components or systems are typically subject to OBD
monitoring:
     Emission after-treatment devices (catalysts, traps)
     Engine misfire
     Fuel system
     EGR system
     Air conditioning system (CFC refrigerants)
     Evaporative system, secondary air system, oxygen sensor (gasoline engines).




                                         69
TECHNOLOGIES FOR IN-SERVICE AND MAINTENANCE PROGRAMS

Most of the foregoing discussion has focused on the technologies required to allow
vehicles (or engines) to meet the increasingly stringent certification standards.
However, there is little value in these standards if vehicles are allowed to deteriorate
during their service life. Australian research (FORS, 1995) has clearly shown that
badly-maintained or defective vehicles can have emission levels many times higher
than when new.
To ensure that vehicles continue to operate cleanly over their whole service life, there
is a growing trend towards the adoption of programs designed to encourage (or
require) good vehicle maintenance. Most commonly known as Inspection and
Maintenance (I/M) programs, they usually involve the periodic inspection and/or
testing of vehicles to ensure that they have not been tampered with and that their
emission control systems are still effective.
Over the years, many approaches to emissions I/M programs have been taken to try
and find the optimum cost/benefit trade-off. These have included simple visual
inspections, remote sensing, idle testing and loaded testing using rolling road (chassis)
dynamometers.
There is now general consensus that the only reliable way of checking a vehicle's
emissions is to test it while the engine is operating under loads equivalent to those
encountered during normal driving conditions. This is particularly the case for
catalyst-equipped vehicles, where the computerised emissions control equipment does
not start to function until the vehicle is being driven under load. Furthermore, NOx
levels are insignificant during idling or lightly loaded operations.
To ensure that testing is done in a controlled and repeatable manner, emissions
measurements need to be done using a rolling road (chassis) dynamometer, together
with appropriate gas measuring equipment. For diesel engines smoke opacity
measurements will almost certainly be included. Currently there is no low-cost
technology to measure fine particulates in real-time, but this situation may change in
due course.
Loaded (dynamometer) testing has an important role to play in ensuring that I/M
repairs are properly done, particularly when a vehicle is failed because of excessive
smoke emissions (probably the most common cause of diesel vehicle failure). High
smoke levels are often caused by over-fuelling, but cutting back fuel delivery too
much can result in NOx levels rising dramatically, beyond a certain point.
Hence, to avoid creating a new problem when fixing another, it is essential to monitor
both smoke (or particulate) emissions and NOx to achieve the optimum balance where
both are close to their minimum values. The following chart illustrates this
phenomenon:




                                           70
As can be seen from the nest of curves on the above chart, the Particulates / NOx
trade-off becomes more pronounced with advancing technology levels, making the
need for loaded testing more important than ever on the latest technology vehicles and
engines.




ATTACHMENT 2

US EPA URBAN BUS PROGRAM AND EXTENSION TO HEAVY VEHICLES

This summary is based on the “NorthEast States for Coordinated Air Use
Management” (NESCAUM) Report of March 1999, which addressed the issues
involved in expanding the use of retrofit pollution control technologies through the
development of consistent guidelines for such policies. The programs would make
use of the technology developed for the Urban Bus program to address the in-service
emissions of the existing diesel heavy vehicle fleet.

The Urban Bus Rebuild/Retrofit program was initiated in 1993 to reduce the
emissions of urban busses with engines built before 1993. It is estimated 10,000 of



                                          71
         42,000 eligible vehicles have been retrofitted or rebuilt. Two States have also
         undertaken retrofit programs.

         The need for retrofit programs for heavy duty diesel fleets is demonstrated by the fact
         that 33% of all NOx and 80% of all PM in the NE states of USA comes from heavy
         duty diesel engines.

         The recommendations of the report are based on discussions of a workgroup
         organised by NESCAUM. The report included input from state and federal staffs,
         EPA, testing laboratories, engine manufacturers and control equipment manufacturers.

         The report recommendations of primary interest for this study are:
                 The extended program should be able to use technologies certified for the
                    urban bus program without further testing. The states should be able to
                    claim 20% reduction for PM, 40% reduction for CO and 50% reduction for
                    HC
                 For all technology not certified for the urban bus program, the equipment
                    manufacturer, using independent third party verification, should conduct a
                    similar certification program
                 There should be a program of verification of the performance of the
                    retrofit equipment in service
                 A website should be developed showing certified equipment and the
                    relevant acceptable engine families.

         The last section of the report outlines model policies for retrofit programs.

         The key aspect of the proposed program is that it fits under the US EPA air quality
         program, and allows jurisdictions to claim “State Implementation Plan (SIP)” credits.
         This provides the incentive to set up a retrofit program, which might use a range of
         techniques to achieve the objectives – incentives, executive orders, contract
         conditions, rebates or directs funding.

         The report sets out the current (at the time of the report) equipment certified to the
         urban bus requirements. It also sets out some information on the performance of
         oxidation catalysts.


                 Equipment Certified & Status of Notifications of Intent
                           to Certify Urban Bus Equipment
                                     March 18, 1999
                                    Air Docket A-93-42

           Certifier                         Equipment Description                        Federal Register Notice:
                                                                                         Effective Certification Date
1.   Engelhard 1                  Exhaust catalyst (CMX) for 2 stroke/cycle             60 FR 28402, 05-31-95
2.   Engelhard 2                  Exhaust catalyst (CMX) and ceramatized engine parts   60 FR 47170, 09-11-95
3.   Detroit Diesel Corp. (DDC)   Engine upgrade kit for DDC 6V92TA MUIs                60 FR 51472, 10-02-95
                                  Life Cycle Cost Evaluation                            EPA Ltr, 06-24-96
                                                                                        61 FR 37734, 07-19-96




                                                         72
 4.   Cummins                           Engine upgrade for Cummins L10                          60 FR 64046, 12-13-95
                                        4 stroke/cycle
 5.   Twin Rivers Technologies          Biodiesel, exh cat (CMX) & timing retard:               EPA Ltr, 09-20-96
                                        2 stroke/cycle engines                                  61 FR 54790, 10-22-96
 6.   Johnson Matthey 1                 Exhaust catalyst (CEM 1) for 2 stroke/cycle             EPA Ltr, 03-28-96
                                                                                                61 FR 16733, 04-17-96
 7.   DDC 2                             Engine upgrade kit for DDC 6V92TZ DDECIIs               61 Fr 37738, 07-19-96
 8.   Engelhard 3                       ETX 2002 kit: Exhaust catalyst, ceramitized parts, &    EPA Ltr, 02-38-97
                                        engine upgrade parts for DDC 6V92TZ MUI (0.10)          62 FR 12166, 03-14-97
 9.   Engine Control Systems (ECS)      Exhaust catalyst (OCM) for 2 stroke/cycle               EPA Ltr, 12-02-96
                                                                                                62 FR 746, 01-06-97
10.   Johnson Matthey 2                 Exhaust catalyst (CEM) & engine mods for DDC            EPA Ltr, 09-08-97
                                        6V92TA MUI (0.10)                                       62 FR 60079, 11-06-97
11.   ECS 2                             Exhaust catalyst (OCM) for 4 stroke/cycle               63 FR 4445; 01-29-98
12.   Engelhard 4                       Exhaust catalyst (CMX) for 1992 – 1993 Cummins          EPA Ltr, 02-12-98 63 FR 13660; 03-
                                        L10 EC                                                  20-98
13.   Nelson Industries                 Exhaust catalyst for 2 stroke/cycle                     EPA Ltr, 10-14-97, 62 FR 63159; 11-
                                                                                                26-97
14.   DDC 3                             TurboPac, exhaust catalyst (OCM), and engine            EPA Ltr, 04-06-98 63 FR 26798; 05-
                                        upgrade for DDC 6V92TA MUI (0.10)                       14-98
15.   Johnson Matthey 3                 Exhaust catalyst (CEM) & engine mods for DDC            EPA Ltr, 10-21-98 63 FR 66798; 12-
                                        6V92TA MUI (0.10)                                       03-98
16.   Engelhard 5                       ETX 2002 kit: Exhaust catalyst, ceramitized parts and   EPA Ltr, 07-01-98 63 FR 50225; 09-
                                        engine upgrade parts for DDC 6V92TZ DDEC 2              21-98
                                        (0.10)
17.   Turbodyne Systems, Inc.           TurboPac & exhaust catalyst (OCM) 6V92TA MUI            Under review
                                        (0.10)
18.   DDC 4                             TurboPac, exh cat (OCM, and engine upgrade for          EPA Ltr, 10-02-98
                                        6V92TA DDEC (0.10)
19.   Engelhard 6                       ETX Plus Technology for DDEC II engines (.1)            Under review
20.   Johnson Matthey                   CEM Cat Muffler for 4 s/c engines                       Under review




            Summary of Available Data for Oxidation Catalyst Use in HDD

        Study/Report               Number and             PM Reductions HC Reductions                         CO
                                 Types of Engines                                                          Reductions
      Urban Bus and             19 four stroke and        38% avg. for            51% avg. for                n/a
      Engelhard data            10 two stroke             two stroke              two stroke avg.
                                                          27% avg. for            64% avg. for
                                                          four stroke             four stroke
      SAE 960134i               5 four stroke and 2       32.8% avg. for          75.9% avg. for         67.1% avg. for
                                two stroke                all vehicles            all vehicles           all vehicles
      SAE 970186i               5 four stroke and 5       24% avg. for all        50-90% for all         45-93% for all
                                two stroke                vehicles                vehicles               vehicles
      SAE 932982i               4 four stroke             44-60% avg. for                n/a                   n/a
                                                          all vehicles
      SAE 950155i               two stroke buses               32-41%                 60-70%                    90%
      London Busi               6 four stroke                     45%                   86%                     92%
      Report MBK
      961165
      Engelhard                 1 four stroke             49% avg. for            93% avg. for                  98%
      Report                                              three catalysts         three catalysts
      #980342i


                                                                73
APTA paperi      two stroke                  19-44%            50-90%          45-93%



  The report notes that oxidation catalysts are the only exhaust treatment technology
  currently certified under the urban bus program. This presumably reflects the effect
  of the SIP calculations and is similar to European retrofit programs where the costs of
  particulate trap technology have favoured the use of oxidation catalysts. The report
  also notes that studies suggest that 2-way catalytic converters have no effect on fine
  particulates.

  The report canvasses the need to screen fleets on the basis of engines to eliminate
  engines not suited to retrofit. This may include extreme wear and very old engines –
  soon due for replacement or very little used. The report also notes that it is necessary
  to be careful that installations are properly designed and appropriate to the engine.

  Given the nature of the program, and the incentives for states, it is necessary to put in
  place good record keeping to monitor the program. The record keeping needs in an
  Australian program might be quite different.

  Issues of equipment warranty and labelling of equipment are also discussed.

  The report then discusses extensively the issue of third party verification. This is an
  issue for the program because of the nature of the air quality management program
  and the claiming of credits. This should not be an issue in Australia, but should give
  some confidence in the certified equipment performance.

  Testing and monitoring programs are discussed extensively. The interesting aspect is
  the significant responsibilities put on the equipment manufacturer for testing and in-
  service monitoring.

  Model State policies are then discussed in two categories:
         Highway vehicles
         Non-road vehicles including Marine engines.

  The highway vehicles program is discussed in terms of opportunities and incentives.
  The fleets are known to government -–they are registered – and governments own or
  contract large numbers of these vehicles. The report notes that while mandatory
  programs are an option, voluntary programs probably provide the best near term
  option.

  The report mentions – almost in passing- that there are technologies that give better
  performance than the 2-way catalytic converter (e.g. the continuously regenerating
  particulate traps), and credits should reflect this.

  An example strategy is set out for school buses. In the US, the school bus fleet is a
  separate and identifiable fleet, either owned by or contracted to school authorities.
  There are a small number of engine types (4 ) offering program economies. There is
  also the public relations aspect – reducing the exposure of children to emissions.


                                              74
The issue of market incentives is then canvassed. The view is put that “command and
control” approaches may not achieve the best outcomes. A flexible approach offers
benefits in that incentives can be tailored to focus on the most effective arrangements
for all the stakeholders. It also allows the program to focus on the most effective
target vehicles.

The incentives suggested include preferential parking, "green" contracts, differential
tolls, access to high occupancy vehicle lanes, tax credits and rebates and inspection
rebates. To this can be added restricted access zones used in some European cities.

The report then discusses issues related to inspection and testing, and the need for
relatively simple roadside tests, including smoke tests.

The issues of program phasing is canvassed and the issue of compliance and
enforcement. The discussions are naturally in the US context, and while of general
interest, they may not be particularly relevant to Australia.

The nonroad retrofit strategies are not relevant to this project. The final section of the
report addresses funding options, again in the US context.


ATTACHMENT 3

UK CLEANER VEHICLES TASK FORCE
FINAL REPORT – “The Way Forward”,
Department of the Environment, Transport and the Regions, June 2000

The “Cleaner Vehicles Task Force” was a high level group from government and
industry, set up to “develop a package of practical solutions to put cleaner vehicles on
the road now and in the future”. The work on diesel emissions focuses on PM as the
main issue, and the evaluations are in terms of reductions in PM.

While the ambit of the work is quite broad, the Task Force did address the area of
retrofit to reduce emissions from pre-Euro 1 vehicles. This is set out in the report
from the “Technology and Testing” Group of the Task Force. The report notes that
particulate traps and oxidation catalysts are considered to be cost effective, giving
significant reductions in emissions. The report also concludes that retrofitting petrol
cars with catalysts is likely to be cost effective in reducing NOx emissions.

The report includes a range of cost estimates for diesel retrofit technology:
                                      2000                    2005
       Particulate traps              $7,700-11,000           $5,500
       Oxidation catalysts            $1,650-4,400            $1,650-4,400

The performance assumptions used in the analysis are:
                                   PM reduction
       Particulate traps                  95%



                                            75
       Oxidation catalysts            50% for pre Euro, 40% for Euro 1, 30% for
                                      Euro2 engines

Particulate traps and oxidation catalysts are assumed to be reliable and last the
remaining life of the vehicle after installation.

A 1% fuel economy penalty is assumed for particulate traps and a 0.5% penalty for
oxidation catalysts.

The analysis concludes that, for cost structures applying at that time, oxidation
catalysts are generally more cost effective than particulate traps. The report goes on
to note that this will change as the cost of particulate traps falls.

The Testing group Report also addresses the following issues:
       Alternative fuel options
       The role of in-service testing
       Identification and removal of gross emitters
       Reliability of petrol emission control devices
       Pollution avoidance.


The Final Report of the Task Force addresses a number of areas:
        Encouraging a market transformation
        Helping fleets reduce their impact on the environment
        Cleaner fuels and Technologies
        Low emission zones
        Making sure everyone plays their part.

The first section of the report addresses the role of incentives and the role of
technology, as well as the role of consumer information. The second section is
largely focussed on improving fuel economy to reduce CO2 emissions.

The cleaner fuels and technologies section draws on the report of the Testing Group,
and recommends further development of retrofit programs, with a focus on cost
effectiveness. The report recommends that technology developments be continually
monitored both in alternative fuels and retrofit technology.

The report notes the potential role of low emission zones and sets out some guidance.
The report recommends that government support local authorities in developing
model programs.

“Making sure everyone plays their part” addresses the problem of gross polluters and
difficulties in testing and enforcement. It recommends further research and
development in these areas as well as the possibility of extending the power to stop
vehicles beyond the police.




                                           76
It is understood that the UK government has set up a “Cleaner Vehicles Program”. To
take the recommendations further, focussing on vehicles that make major
contributions to pollution in urban areas – taxis, buses and heavy vehicles.



ATTACHMENT 4
LONDON TRANSPORT BUSES
“BUSES: a cleaner future
Bus emissions and air quality in London”

Summary of Relevant Key Points:
 London transport purchases bus services from private companies. Bus services
   comprise 20% of vehicle trips and 13.5 % of passenger km travelled in Greater
   London.

   Since 1996, all new buses have Euro 2 engines. Tests have shown that the oldest
    buses operating in London can be improved to a point where only particulate and
    NOx emissions remain worse than a Euro 2 engine. This is achieved by the use of
    ultra low sulphur fuel and oxidising catalysts (CATs).

   Euro 2 engines fitted with a continuously regenerating particulate trap (CRT)
    generate emissions broadly similar to those achieved by modern CNG and LPG
    engines for all emissions other than NOx.

   London Transport Buses will consider Euro 3 engines when they are available.

   80% of London buses scheduled travel is now on ultra low sulphur fuel and 20%
    with exhaust after treatment.

   London Transport Buses emissions program has:
        Reduced SO2 by 37%
        Reduced PM by 17%
        Reduced HC and CO by some 10%
        Visible smoke virtually eliminated.

   London Transport Buses is committed to further reducing emissions by:
        Encouraging the use of ultra low sulphur fuel
        Fitting exhaust after treatment as funding allows
        Consideration of particulate traps where ultra low emission vehicles are
          essential to meet air quality standards: further buses will be fitted with
          particulate traps in 1999/2000
        Constantly reviewing emerging technologies and policy.

   London Transport Buses program for emissions (excluding the particulate trap
    program) will improve emissions in 2000 below the level they would otherwise be
    by:
         SO2 down 98%


                                          77
          CO and PM down 50%
          HC down 39%.


The following key points were extracted from the statement of the London Transport
Buses policy:
       LT Buses is committed to emission reductions through the following policies:
               Extend the use of ultra low sulphur fuel throughout London.
               Move towards fitting all buses operating in London with exhaust
                 after treatment.
               Noting the high cost of particulate traps, London Transport Buses
                 will nonetheless move to fit more traps to buses as part of a move
                 to monitor developments in this rapidly evolving area.
               London Transport Buses will monitor developments to ensure that
                 the program is optimally matched to the new technology as it
                 evolves.

In Table 2 of the report, London Transport Buses notes the following improvements
in bus emissions from technology (base is the emissions from an untreated engine
using pre 1996 diesel):

     Fuel                Retrofit   CO          HC      NOx    SOx      PM10
     Pre 1996 diesel     None       100%        100%    100%   100%     100%
     0.05% Sulphur       None       100%        100%    100%   425      87%
     0.05%Sulphur        CAT        59%         54%     98%    42%      44%
     ULSD                None       83%         91%     91%    1%       54%
     ULSD                CAT        16%         25%     88%    1%       30%
     ULSD                CRT        16%         22%     84%    1%       11%




The report also includes the following data from bus emission tests at the Millbrook
Proving Ground (Appendix 2, page 36):


                              POLLUTANT (gms/km)
       Vehicle Details
                              CO2        CO            HC      NOx       PM10


       Fleet average          1200       4.60          2.75    21.00     1.90
       pre treatment may      100%%      100%          100%    100%      100%
                96
       Pre E2 engine with     1074       0.31          0.29    15.69     0.53
        ULSD and CAT          89.5%      6.75          10.6%   74.7%     27.9%




                                          78
        E2 engine, standard     1323        1.29       0.61       14.27       0.18
         Diesel, 0.05 S         110.35      19.1%      5.8%       19.1%       0.7%
        no retrofit
        E2 engine with          1288        0.27       0.33       13.41       0.08
        ULSD and CAT            107.3%      5.9%       12.0%      63.95       4.2%

        E2 engine with          1282        0.20       0.14       11.93       0.02
        ULSD and CRT            106.8%      4.35%      5.1%       56.8%       !1%

        CNG with                1344        0.66       3.01       9.92        0.05
        OXYCAT                  112%        14.4%      109,5%     47.2%       2.6%

        LPG with 3-way          1309        0.01       0.03       5.40        0.02
        CAT                     109%        .22%       1.1%       25.71%      1.05%


In summary, the report presents an overview of the challenges facing London
Transport Buses in meeting air quality targets for Greater London. The report
identifies oxidation catalysts as the most cost effective technology (at 1997 prices) but
notes a strong interest in particulate trap technology.



ATTACHMENT 5

BASIC MODEL

The basic model for the option calculations is set out below.

Emission/vehicle/year           = (emission rate) x (annual vehicle km)

Emissions/fleet/year            = (emission rate) x (annual vehicle km)
                                  x (fleet numbers) x (fleet suitability)
                                  x (fleet penetration)

Emission reduction**            = (emissions/fleet/year) x (emission reduction factor)

Equivalent annual capital cost = (vehicles fitted) x (unit cost) / (unit life yrs)

Cost effectiveness of equipment
($/Kg emissions reduction) = (equivalent annual capital cost)
                                  / (Kg emission reduction per year)

** Where there is phased implementation, the emission reduction will need to be
adjusted in the early years of the implementation period to reflect the number of
vehicles retrofitted each year. The calculations in the option sets do not reflect
phasing.




                                             79
To account for fuel efficiency penalties from retrofit, the following relationships were
used:

Annual fuel cost               = (annual vehicle km) x (fuel price)

Fuel cost penalty              = (annual fuel cost) x (fuel efficiency penalty)

Cost effectiveness fuel penalty = (fuel cost penalty)/(Kg PM emission reduction)
($/Kg PM emission reduction)

The overall cost effectiveness would then be given by “cost effectiveness of
equipment “+ “cost effectiveness (fuel penalty”).




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