Fundamentals of Modern Biomass Cogeneration

Document Sample
Fundamentals of Modern Biomass Cogeneration Powered By Docstoc
					                                       AFREPREN/FWD
                            Energy, Environment and Development Network for Africa




   BACKGROUND MATERIAL

      Fundamentals of Modern
       Biomass Cogeneration
           Technologies




Financing Cogeneration and Small-Hydro projects in the Sugar and tea
            Industry in East and Southern Africa Training
                        Modern Biomass – Cogeneration1




Module Overview:

Sugarcane Bagasse Energy Cogeneration in Mauritius and its Potential for
Africa

Biomass as a renewable and environment friendly resource for energy cogeneration is
being given increasing importance worldwide, and, in particular, in fossil fuel
importing countries. One such resource of particular significance to a number of
countries in the African continent is sugar cane. This plant, as a commercially grown
crop, is known to have the highest bioconversion efficiency of capture of sunlight
through photosynthesis compared to other crops. Around 55 tonnes of dry matter in
the form of carbohydrate compounds, fibre (lignocelluloses) and soluble sugars are
accumulated in the cane biomass in commercial plots. Of this amount of dry matter,
only 50% in the form of sugars and fibre in the cane are being harvested for sugar
recovery.

In this sugar recovery process, bagasse, the fibrous fraction of the cane stalk
composed of 50% fibre, 48% moisture and 2% sugars, is normally burnt to meet the
heat and electricity requirements of the cane factory. The simultaneous generation of
heat and electricity in a single power plant is known as Cogeneration. In the original
cogeneration setup, the emphasis had been to incinerate all the bagasse, produce
enough steam to drive the prime movers of mills and turbo alternators. Such steam
was generally at low pressure (10-15 bars). Over the years, countries like Mauritius
and Reunion devoid of any fossil fuel came to realize that with adoption of:

 (i).    Energy conservation and efficiency measures in cane processing and
(ii).    Boilers and turbo alternators operating at higher and higher pressures (up to 82
         bars, a significant amount of electricity can be exported to the grid.

In Mauritius, pressures being adopted have evolved from 21 bars to 82 bars through
31 and 44 bars. One constraint of such plant has been the seasonal (5-6 months)

1
  This module was prepared by Dr. Kassiap Deepchand (Mauritius Sugar Authority) for the ADB FINESSE
Training Course on Renewable Energy and Energy Efficiency for Poverty Reduction held in Nairobi, Kenya on
19th – 23rd June 2006

    Financing Cogeneration and Small-Hydro projects in the Sugar and tea
                Industry in East and Southern Africa Training
availability of bagasse and coal is used as complementary fuel to guarantee year
round electricity export to the grid. In Mauritius, 11 cane sugar factories are in
operation and 10 of them export electricity to the grid, 3 of which throughout the year.
Around 44% (or 750 GWh) of electricity are exported from the sugar factory located
plant to the grid of which 300 GWh is from bagasse. This development has enabled
Mauritius to diversify its energy base, to rehabilitate, modernize and centralize cane
milling activities, save on fossil imports and more importantly, reduce greenhouse gas
emissions.




  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
The total potential from bagasse is 600 GWh and there is an additional potential of
around 250 GWh with the exploitation of the other fractions of the cane biomass in
the form of green tops and leaves and the dry trash. This strategy thus offers
opportunities for the sugar industry to increase its revenue or mitigate the impact of
reduction in price of sugar in the EU preferential market.

This strategy can be replicated in other African countries. Around 90 million tonnes
of cane are harvested annually and the total potential for electricity export using state-
of-the-art commercially proven technologies in Mauritius will be around 10,000
GWh. The techniques adopted in successful development of cogeneration in
Mauritius have been highlighted in the module and complementary information on
this development have been provided in the power point presentation. However, not
all countries have a cane production, investment potential and indigenous skill to tap
this potential. Mauritius is well positioned to share its experience on cogeneration
with countries in the region.


Key Aims:
This module aims to introduce the participants to sugarcane-based cogeneration
options, explain the fundamentals and principles of operation, provide the status of
sugarcane-based cogeneration in Africa, discuss its potential, and present a brief
overview of successful implementation of cogeneration in Mauritius.


Module Learning Outcomes:
  • Broad appreciation of the fundamentals and principles of operation of
     sugarcane-based cogeneration
  • Take stock of successful sugarcane bagasse energy development and progress
     in Mauritius
  • Broad appreciation of the status and potential of sugarcane-based cogeneration
     in Africa
  • Enhanced understanding of the contribution of sugarcane-based cogeneration
     to Africa’s energy sector and the socio-economic impacts.


Table of Contents

1.0     Modern Biomass - Cogeneration............................................................................... 7
  1.1   Sugarcane Bagasse Energy Cogeneration in Mauritius and its Potential for Africa ..................7
  1.2   Sugar Cane as a Biomass Resource...................................................................................7
  1.3   Sugar Cane Processing and Bagasse Utilisation ..................................................................7
  1.4   The Cogeneration Technology ..........................................................................................8
  1.5   Cogeneration in Mauritius ..............................................................................................13
    1.5.1      The Cogeneration Projects in Mauritius.................................................................................. 13
    1.5.2      Impact of Cogeneration on Power Sector............................................................................... 15
    1.5.3      Impact of Cogeneration on Sugar Sector ............................................................................... 17
    1.5.4      Further Investments in Cogeneration .................................................................................... 17
    1.5.5      Future Potential .................................................................................................................. 17
  1.6   Techniques Adopted in Successful Development of Co-Generation .....................................17
  1.7   Potential for Replication in the African Continent ..............................................................18
  1.8   Opportunities and Challenges .........................................................................................19
  1.9   Environmental Benefits of the Sugar Cane Biomass Energy ...............................................21
  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
  1.10        Concluding Remarks ..................................................................................................21

List of References ...............................................................................................................23




   Financing Cogeneration and Small-Hydro projects in the Sugar and tea
               Industry in East and Southern Africa Training
List of Tables

Table 1:      Bagasse based Power Plants in Mauritius up to year 2000..........................................15
Table 2:      Evolution of Cogeneration (1991 – 2002) .................................................................16
Table 3:      Evolution of Electricity Production from the Sugar Industry (GWh) and
              kWh/tonne cane.....................................................................................................16
Table 4:      Production of Sugar and Sugar Cane and Potential for Cogeneration in Africa
              (2002)...................................................................................................................19




List of Figures

Figure   1:   Sugar Cane Processing .............................................................................................8
Figure   2:   The Co-generation Technology ................................................................................10
Figure   3:   Firm power generation set-up .................................................................................11
Figure   4:   Firm power plant – operation in bagasse mode .........................................................12
Figure   5:   Firm power plant – operation in coal mode ...............................................................12




  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
1.0 Modern Biomass - Cogeneration


1.1    Sugarcane Bagasse Energy Cogeneration in Mauritius and its
       Potential for Africa

Interest in renewable energy resources was aroused in the early seventies as a
consequence of escalating oil prices coupled with the fear that the world’s fossil fuel
reserves were decreasing and may be depleted within the foreseeable future. Interest
was revived in the early 90s with the gulf crisis associated with a threat to oil supply
and, subsequently the Kyoto Protocol – commitment to reduce carbon emission from
fossil fuels combustion by a certain percentage – more particularly in the developed
countries. Significant progress has been made over the years in the development of
renewable energy resources such as water heating and cooling, photovoltaics, wind
power, ocean wave energy, geothermal energy and biomass.

The majority of countries in the African continent and more particularly the small
island states have very limited, or are even devoid of, fossil fuels. On the other hand,
a significant number of them are endowed with agroclimatic conditions which are
conducive for the production of biomass in the form of wood or sugar cane as an
annually renewable resource. The emphasis in this paper is on the production of
energy from sugar cane and more specifically from bagasse derived therefrom.

1.2    Sugar Cane as a Biomass Resource

Sugar cane biomass is the organic matter composed mainly of carbohydrate
compounds originally derived from the process of photosynthesis. Sugar cane, as a
commercially grown crop, is known to have a photosynthesis bioconversion
efficiency of capture of sunlight of around 4% and this efficiency is much higher than
the 1-2% achieved by most other crops. Under the prevailing agroclimatic conditions,
cane biomass yield reaches up to 130 t per hectare in commercial plots of land. A
breakdown of this biomass by fraction reveals the following:

Cane biomass Fraction                 Dry Matter (tonnes/ha)
Cane Stalk Fibre                      14
Absolute Juice                        16   30
Cane Tops and Leaves                  9
Trash                                 9
Roots                                 6    24
Total                                      54



1.3    Sugar Cane Processing and Bagasse Utilisation

In almost the totality of cane sugar producing countries, only the cane stalk is
harvested for sugar recovery. In this process outlined in Figure 1, the fibrous fraction
of the cane leaves the cane milling department of the sugar factory in the form of
bagasse. The bagasse is normally composed of 50% fibre, 48% moisture and around
  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
2% sugars. It has a gross calorific value of 9,950 kJ/kg. The bagasse is burnt to
generate steam and electricity which are used to process the cane into sugar and its
by-products. In a properly designed factory, the totality of energy required for the
process is normally met from the bagasse.




Figure 1:      Sugar Cane Processing

However, in a number of cane sugar producing countries, energy conservation
measures have been adopted which have resulted in the generation of significant
amounts of surplus bagasse. The surplus bagasse is being used for pulp and paper or
particle board. Alternatively, surplus electricity is also generated for export to the
public grid through a process known as cogeneration.



1.4    The Cogeneration Technology



  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
Cogeneration is defined as a process during which electricity and heat are generated
simultaneously in a single power plant. In order to maximise energy output per unit
of steam of high pressure, the topping cycle cogeneration is used. In this process,
primary heat at the higher temperature of the Rankine cycle is used to generate
exhaust or process steam and electricity. The process steam at a low temperature and
pressure to match with that required for cane juice heating and evaporation is
extracted from the steam turbine. This cycle thus brings about significant savings in
the primary energy.




  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
In the traditional cane sugar factory, all the operations – cane processing and energy
generation – are carried out within the same premises. Bagasse, by virtue its low
density, high risks of inflammability and fermentation and loss in calorific value, is
normally burnt in situ normally at low pressures or at most stored for very short
periods. However, this combustion of the bagasse in low pressure boilers is
inefficient. The steam so obtained is used to drive the mills using back pressure steam
turbines and to generate electricity in similar turbines. In such a set-up, almost no
electricity is exported to the grid.

In an improved system wherein investments are made in:

       (i)     Energy conservation measures in juice heating and evaporation as well
               as adopting quintuple effect evaporation and continuous/automated
               processes for sugar boiling and crystallisation; and

       (ii)    Boilers and turboalternators, preferably of condensing-extraction types,
               operating at pressures varying between 25 and 31 bars,

It has been possible to export surplus electricity to the public grid. The kWh exported
per tonne of cane in such a system has reached up to 55 and have required a moderate
investment of around US$4 million in cane sugar factories processing 3,000-3,500
tonnes cane daily. These plants export electricity to the grid during the crop season
from bagasse only. This concept is termed continuous power. This system of
electricity generation is given in Figure 2.




Figure 2:      The Co-generation Technology

Electricity export to the grid has been improved through retrofitting the conventional
sugar factory with boilers and condensing-extraction turboalternators operating a
higher pressure (44 bars) and temperature (4300C) with provision to extract steam for
process from the steam turbine. In order to maximise the use of the installed capacity,
these plants are equipped to burn coal as a complementary fuel in particular during the
  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
off-season when bagasse is no longer available. This is termed firm power. Such
power plants are part of the factory but managed as a workstation of the factory. The
kWh/tonne cane for these plants operated in a factory with a TCD of 6,000 has been
around 70 and has required an investment of around US$ 20-25 million. This process
is outlined in Figure 3.




Figure 3:      Firm power generation set-up

The most recent development on the issue of export to the public grid of electricity
generated from bagasse has been in the investment and the commercial operation of a
power plant as a separate entity distinct from cane milling activity. In this set-up, the
power plant is located next to a sugar factory which supplies all its bagasse (at an
agreed moisture content) and condensed water in exchange of process steam and
electricity from the power plant. The characteristics and the amount of each of these
items are normally defined in an agreement and it includes bonus or penalty elements
linked to either efficiency or default by either of the two parties. This firm power
plant and the utility are bound in a power purchase agreement which defines in very
extensive details the obligations of either of the two parties as well as the
remuneration packages including bonus and penalty elements linked to performance.
The set-up for this system is outlined in Figure 4 and 5.




  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
Figure 4:     Firm power plant – operation in bagasse mode




Figure 5:     Firm power plant – operation in coal mode

Such power plants operate at very high pressure and temperature (around 82 bars,
5250C) and are exporting more than 110 kWh of electricity per tonne cane to the

  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
grid1. The investment required for plant with a total installed capacity of 70 MW
comprising of 2 units of 35 MW each is around US$100 million.

1.5    Cogeneration in Mauritius

Mauritius, as a Small Island Developing State forming part of the African continent,
is devoid of any fossil fuel and depends heavily on imported energy for use in the
various sectors of the economy. Hydro power and sugar cane bagasse are the two
renewable resources that can potentially be used for electricity generation. Hydro
power is limited to availability of rain water, seasonal in nature, and this resource is
fully exploited in Mauritius. Interest in the use of bagasse for electricity generation
and export to the grid intermittently in Mauritius started in 1957 from one sugar
factory and since then more and more of these factories joined in. But the most
significant developments occurred in 1980 when a 10 MW continuous power plant
was commissioned to export electricity to the grid during the crop only and in 1984
when another factory invested in a firm power plant (21.7 MW) to export electricity
year round to the grid.

With the success achieved in those plants and pressed by events in the gulf area in
1991, Government in collaboration with the private sector worked out a Bagasse
Energy Development Programme2. The objective of the programme were to displace
investments to be effected by the utility, to reduce the reliance of the country on
petroleum products and diversify its energy base, to allow foe the modernization and
rehabilitation of the sugar industry and improve its viability, to save on foreign
exchange through reduction in imports of fossil fuel and finally to contribute in the
mitigation of the enhanced greenhouse effect by displacing fossil fuel.

A number of factors contributed in the eventual success in bagasse energy
development. A clear policy on bagasse use for electricity was defined by
Government and agreed by all stakeholders. A number of plans, policies, actions and
legislations to facilitate bagasse energy development were put in place. Constraints
identified all along the implementation of these plans were attended to in consultation
with all stakeholders including Government agencies and the utility with the
Mauritius Sugar Authority acting as the focal point/facilitator.

While providing incentives to the entrepreneurs to invest in the power plants as
independent power producers, the interest of the small cane growers and the workers
had not been ignored. Government through legislation and creation of a Sugar
Investment Trust ensured that this vulnerable group in the sugar industry shares in the
profit generated in that sugar related activity as well.

1.5.1 The Cogeneration Projects in Mauritius

The sugar industry future is at stake. In the local context, the cost of production is
increasing and in the international scene, sugar prices are decreasing. These factors
will impact negatively on the industry if measures are not taken to mitigate these
effects. Factory modernisation, centralisation and exploitation of the by-products for
more value added products are measures that will ensure long-term viability of the


  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
industry. Energy from bagasse was one option which was given top priority in this
context.

With the centralisation of cane milling activities, investments were made in 7
continuous power plants and 7 firm power plants. Some characteristics of these
power plants are given in Table 1.




  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
Table 1:           Bagasse based Power Plants in Mauritius up to year 2000

                               Tonnes                               Units from   Units       Total Units
Factory                        cane per     Power      Start Date   Bagasse      from Coal   from Bagasse
                               hour                                 (GWh)        (GWh)       & Coal
                                                                                             (GWh)
FUEL                           270          F          Oct 1998     60           115         175
Deep River Beau Champ          270          F          April 1998   70           85          155

Belle Vue                      210          F          April 2000   105          220         325
Médine                         190          C          1980         20           -           20
Mon Tresor Mon Desert          105          C          July 1998    14           -           14
Union St Aubin                 150          C          July 1997    16           -           16

Riche en Eau                   130          C          July 1998    17           -           17
Savannah                       135          C          July 1998    20           -           20
Mon Loisir                     165          C          July 1998    20           -           20
Mon Desert Alma                170          C          Nov 1997     18           -           18

Total                                       3F                      360 GWh      420 GWh     780 GWh
                                            7C                      235 GWh F
                                                                    125 GWh C

F = Firm or Bagasse during crop and Coal during intercrop
C = Continuous or Bagasse during crop season only



1.5.2 Impact of Cogeneration on Power Sector

Over the 10-year period (1993-2002), the installed capacity of the sugar industry
located power plants increased from 43 MW to 242 MW with the concurrent increase
in electricity export to the grid (Table 2). In 1996, 119 GWh of electricity were
exported from bagasse. This was achieved through investment mostly by private sugar
mills implementing cogeneration technology with their own private fund. By the year
2002, cogenerated energy increased significantly with investment in more efficient
bagasse-to-electricity processes and in a greater number of units so much so that the
electricity exported to the grid from bagasse increased to 300 GWh from the 160 MW
installed (or 33%) firm installed capacity, 10 out of the 11 sugar factories operating
bagasse units and contributing to the total. With coal burnt in 3 firm power plants the
total electricity export from the sugar industry reach 746 GWh in 2002. This
represented 43.5% of the total electricity exported to the grid for the island.




   Financing Cogeneration and Small-Hydro projects in the Sugar and tea
               Industry in East and Southern Africa Training
Table 2:                   Evolution of Cogeneration (1991 – 2002)

Year                       Cogeneration                        Island Total                           Bagasse               Bagasse +
                                                                                                        %                   Coal %
                      Bagasse             Coal

               IC             GWh         GWh           IC             GWh               IC                  GWh            GWh

1993           43             71          40            308            870               14.0                8,2            12,8

1994           43             77          46            308            945               14.0                8,1            13,0

1995           43             84          41            332            1047              13.0                8,0            11,9

1996           43             119         -             332            1151              13.0                10,3           10,3

1997           53             125         23            370            1252              14.3                10,0           11,8

1998           90             225         62            397            1365              22.7                14,2           18,7

1999           90             184         155           425            1424              21.2                12,9           23,8

2000           160            274         327           478            1527              33.5                17,0           39,4

2001           246            300         411           660            1657              37.3                18,1           42,9

2002           242            299         447           656            1715              36.9                17,4           43,5


The kWh/tonne cane processed in 1991 was 12 and even after implementation of the
projects in the year 2002, the value has reached only 61 kWh per tonne of cane (Table
3). This is well below the 110 kWh/tonne cane obtained in Réunion where only two
factories are in operation, each processing around 900,000 tonnes of cane annually.
Each factory is equipped with 2 x 30 - 35 MW power plants operating at around 82
bars. Only the CTBV is operating with this efficiency in Mauritius and has reached a
conversion efficiency of 130 kWh/tonne cane.

Table 3:                   Evolution of Electricity Production from the Sugar Industry (GWh)
                           and kWh/tonne cane

                               YEAR

POWER               Fuel       1991   1992       1993   1994      1995        1996   1997       1998     1999       2000    2001   2002
                    Source
Firm                Bagasse    39     50         39     44        46          70     66         81       111        167     186    171

                    Coal       54     43         40     46        41          10     23         62       155        327     411    447

Continuous          Bagasse    21     28         27     28        30          33     53         109      78         107     114    128

Intermittent        Bagasse    10     6          4      4         5           7      6          4        1          0.5     0      0

Total GWh (bagasse)            70     84         70     76        81          110    125        194      190        274.5   300    299

Total GWh (bagasse &           124    127        110    122       122         120    148        256      345        601.5   711    746
Coal)

Total Tonne Cane x 106         5.62   5.78       5.40   4.81      5.16        5.26   5.79       5.78     3.88       5.1     5.78   4.87

kWh/tc                         12     15         13     16        16          21     22         34       49         54      52     61




    Financing Cogeneration and Small-Hydro projects in the Sugar and tea
                Industry in East and Southern Africa Training
1.5.3 Impact of Cogeneration on Sugar Sector

Bagasse energy projects are linked with sugar factory modernization in that boilers,
turbo alternators and other energy efficient equipment represent a major proportion
(up to 50%) of the cost of a sugar factory. Investing in an energy project ensures that
this part of the investment (useful life of 25 years) crucial to sugar processing, is
financed independently of sugar activities. In addition, the sale electricity adds to the
revenue of sugar companies. Furthermore, linking energy projects to centralization
brings about reduction in cost of production. In 1985, 21 sugar factories were in
operation and the number has decreased to 11 in year 2005. 10 of these factories
export energy to the grid and only 3 of them are firm power plants. It has been
projected that by year 2010, only 4 sugar factories will be in operation through the
process of centralization and it is envisaged that each one of them will be equipped
with a firm power plant which are generally more efficient in energy cogeneration and
export to the grid.

1.5.4 Further Investments in Cogeneration

The outcome of the bagasse energy projects has been satisfactory in that its key
strategy was to set up an investment plan, the institutional framework and the policies
to encourage private investment in bagasse/coal power plants. This was successfully
achieved under the Plan and more bagasse units have been projected. As at the year
2002, the bagasse cum coal power plants accounted for 242 MW installed or more
than 37% of the total (660 MW) installed capacity in the island. Three additional firm
power plant projects have already been formulated, one of which located in the South
(2 x 41.5 MW) already under construction and to come in operation in 2007, one in
the East (2 x 41.5 MW) and one in the West (1 x 35 MW).

With the investments in the new plants each of the 4 sugar cane sub clusters will have
a firm power plant and concurrently the continuous power plant will be phased out.
The electricity export from the sugar factory located power plants will reach 1700
GWh of which 600 GWh will originate from bagasse. This development will occur
with centralization of cane milling activities, reduction in exhaust steam in cane
processing, upgrading the efficiency of the power plants by adopting operating
pressures of 82 bars.

1.5.5 Future Potential

With the use of cane field residues as supplementary fuel4, around 800 GWh of
electricity can potentially be exported to the grid from sugarcane biomass. This is
more than twice the current amount. There is a significant potential for additional
power generation and export to the grid if current R and D efforts on biomass
gasifier/gas turbine combined cycle become a commercial reality.



1.6    Techniques Adopted in Successful Development of Co-
       Generation



  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
   1. Clearly spelt out policy on sugar cane bagasse for cogenerated electricity and
      provision for appropriate incentives to induce investment in sugar factory
      modernization and investment in power plants.

   2. Adoption of energy efficiency and conservation measures in cane juice heating
      and evaporation and sugar boiling and crystalisation to bring down process
      steam consumption.

   3. Electrification of drive of all prime movers in cane milling.

   4. Targeting towards a cane crushing capacity of around 200 tonnes cane per
      hour to match with one module of 35-40 MW installed capacity power plant
      operating at steam pressure of around 82 bars. This is a commercially proven
      technology.

   5. Use coal as complementary fuel in case of shortage of cane to enable year
      round power export to grid.
   6. Undertaking centralization of cane milling to ensure bagasse availability on
      site rather than saving bagasse in a cluster and transporting it to a central
      power plant.

   7. Working out and establishing the kWh price independently of the utility and
      the IPP or alternatively inviting request for proposal with set guidelines in a
      competitive bidding process.

   8. Make provision for participation of small planters and workers in the equity
      portion of investment.

   9. Negotiating and presenting a power purchase agreement describing in details
      the obligations of the IPP towards the utility and vice versa, including in
      particular payment obligations by the utility. This PPA is used inter alia in
      negotiating a loan from the bank.



1.7    Potential for Replication in the African Continent

The success achieved on bagasse energy cogeneration in Mauritius can be replicated
in almost all of the cane sugar producing countries in the African continent. Sharing
of experiences and opportunities for training can be offered given the variety of power
plants in terms of capacities, operating pressures and degrees of sophistication linked
with plant efficiency.

Table 4 gives the statistics production of sugar5 and cane in countries in the African
continent. The potential amount of electricity that can be exported to the grid using
two commercially proven technologies (steam pressures of 44 and 82 bars
respectively) have also been worked out on the basis of results obtained in Mauritius.
It must be outright highlighted that such plants require a minimum cane crushing
capacity of 200 to 300 tonnes cane per hour and many of the African countries at
present have cane production well below these capacities. However, it has been

  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
observed that the cane sugar industry in a number of these countries are being
rehabilitated and modernised and there is merit in coupling these plants with a
cogeneration facility. All the cane sugar factories in Mauritius and Réunion have
successfully integrated sugar and electricity production. The total potential in the
countries in Africa is around 9,600 GWh on the basis of present cane production and
only Mauritius and Réunion are exploiting in a significant manner the sugar cane
bagasse for energy.

Table 4:          Production of Sugar and Sugar Cane and Potential for Cogeneration
                  in Africa (2002)

African              Sugar           Sugar Cane(a)     @31       Cogeneration Potential (GWh)
                          3
Countries            (x 10 t)        (x 103t)          bars(b)   @ 44 bars(c)       @ 82 bars (d)
Angola               31              282               14        20                 31
Benin                5               45                2         3                  5
Burkina Faso         40              364               18        25                 40
Burundi              21              191               10        13                 21
Cameroon             113             1,027             50        72                 113
Chad                 33              300               15        21                 33
Congo                55              500               25        35                 55
Côte d’Ivoire        158             1,436             71        101                158
Egypt                1,397           12,700            635       889                1,397
Ethiopia             294             2,672             131       187                294
Gabon                18              164               8         11                 18
Guinea               26              236               12        17                 26
Kenya                423             3,845             192       269                423
Madagascar           32              291               15        20                 32
Malawi               257             2,336             117       164                257
Mali                 34              309               15        22                 34
Mauritius            552             5,018             250       351                552
Morocco              156             1,418             71        99                 156
Mozambique           242             2,200             110       154                242
Nigeria              20              182               9         13                 20
Réunion              210             1,909             95        134                210
Senegal              93              845               42        59                 93
Sierra Leone         6               55                3         4                  6
Somalia              21              191               10        13                 21
South Africa         2,755           25,045            1252      1,753              2,755
Sudan                792             7,200             360       504                792
Swaziland            520             4,727             236       331                520
Tanzania             190             1,727             86        121                190
Togo                 3               27                1         2                  3
Uganda               244             2,218             111       155                244
Zaire                75              682               34        48                 75
Zambia               231             2,100             105       147                231
Zimbabwe             565             5,136             257       360                565
Total                9,612           87,378            4362      6,117              9,612
(a)       Estimated at sugar recovered % cane of 11%
(b)       Based on 50 kWh/tonne cane
(c)       Based on 70 kWh/tonne cane
(d)       Based on 110 kWh/tonne cane




1.8      Opportunities and Challenges

Implementation of cogeneration will bring additional revenue to the sugar cane
industry which is facing a price cut of 36% in the preferential markets in the context
of trade liberalisation. Besides, cogeneration is a climate friendly technology that can
attract GEF funding as well as financing under EU Energy Fund and carbon emission

   Financing Cogeneration and Small-Hydro projects in the Sugar and tea
               Industry in East and Southern Africa Training
credit for sale under schemes such as Activities Implemented Jointly and the
Prototype Carbon Fund. Most of the cane producing countries in the African
continent could benefit from such funding or schemes.

The on-going power sector reforms in the region have enhanced the prospects of
cogeneration in the continent. However the cogeneration industry has to face a
number of policy and institutional challenges in a reformed power sector. The
national utility generally operates in a monopolistic situation in that generation,
transmission and distribution are undertaken as one bundle of activities. In the
reform, it has been envisaged that generation can also be undertaken by Independent
Power Producers but the issue of open access to the grid has to be properly addressed
in power purchase agreements.

The kWh price of cogenerated electricity is around 6-7 US cents and in many cases
this price is not competitive with that of hydroelectricity which is priced at around 3
US cents/kWh. Furthermore bagasse energy cogeneration is only possible during the
cane harvest season which lasts between 6-9 months and there is need for a
complementary fuel such as coal for 3-6 months.

Another issue likely to pose significant challenges to cogeneration development is the
deterioration in the management of the sugar industry which has led to its near
collapse in many countries and led to closure of a number of sugar factories. This
implies that if a sugar factory is not able to produce sugar, its primary output, it is
unlikely to be a good cogenerator.

Unless there is an integrated policy of cogeneration linking sugar and electricity
exports to the grid as a significant source of income to the industry, it is unlikely that
cogeneration can be realised. In addition, most of the sugar factories need to be
completely overhauled and modernised and these activities have to link with energy
cogeneration which will enhance the financial viability of the facilities. The
Mauritian sugar industry had to face similar situation and sharing of experience
gathered on these issues will prove beneficial to the cane sugar industries in the
region.




  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
1.9    Environmental Benefits of the Sugar Cane Biomass Energy

From an environmental life cycle perspective, sugar cane bagasse energy is associated
with a net positive global benefit in that sugar cane is an annually renewable crop and
contributes to a reduction in Green house gas emissions from energy which would
have otherwise been generated from fossil fuels. The carbon dioxide released from
combustion of bagasse is re-absorbed in the ensuing crop and hence is carbon neutral.
With use of cane field residues for energy, more electricity can be generated,
otherwise the residues decay and release methane, another green house gas.

With the export of around 300 GWh of cogenerated electricity to the grid around
200,000 tonnes of coal are avoided to alleviate the burden on foreign exchange for
such imports. In addition the projects also generate carbon emission credits which are
potentially tradable under the Kyoto Protocol Clean Development Mechanism. The
value of such credits could be as much as US $20 per tonne of carbon dioxide. The
revenue derived therefrom would enhance the financial viability of this renewable
energy project.

Besides, the environment control technology adopted in the power plants is associated
with improved thermal efficiency (that is, less heat rejected compared to older
systems, less particulate matter emissions (< 100 mg/Nm3), Sulphur dioxide emission
is insignificant (bagasse contains no sulphur) and NOx is also reduced due to use of
spreader stoker technology.



1.10 Concluding Remarks

The sugar cane plant is an agricultural crop which is known to have a high
bioconversion efficiency of capture of sunlight as a result of which a high amount of
atmospheric carbon is fixed into biomass. The main interest until recently is to
recover only sugar from this biomass and, in the light of successful experiences in
cogeneration, it can now be considered as a major renewable energy resource in cane
sugar producing countries. The majority of the countries in the African continent are
endowed with agroclimatic conditions which are conducive to sugar cane production
and, with proper investment and management of resources, high yields are potentially
obtainable.

Amongst other energy carriers, electricity from the fibrous fraction of cane known as
bagasse is the one which has been shown to be commercially viable in island states
like Mauritius and Réunion which are devoid of any fossil fuel. In the African
continent, around 10,000 GWh of electricity is potentially exportable to the grid on
the basis of current amount of cane production and using state-of-the-art technology
for conversion of bagasse into electricity. Power sector reforms in the African
countries should take on board this option of cogeneration through inclusion of
independent power producers to undertake power generation.

Opportunities for replication of the success achieved to other countries in the region
should be looked into, the more so that this technology is environment friendly and it
can attract funds from international agencies like the GEF, the Prototype Carbon Fund
  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
and Activities Implemented Jointly under the Clean Development Mechanism of the
Kyoto Protocol.




  Financing Cogeneration and Small-Hydro projects in the Sugar and tea
              Industry in East and Southern Africa Training
List of References
1.       AFREPREN (2003) AFREPREN Occasional Paper No. 21: Opportunities for
         Cogeneration in a Reforming African Power Sector - Proceedings of an
         Energy Training Course, Nairobi, AFREPREN

2.       Ministry of Agriculture and Natural Resources (1991). Report of the High
         Powered Committee on Bagasse Energy Development Programme.

3.       Deepchand, K. (1986). ‘Economics of Electricity Production from Sugar
         Cane Tops and Leaves, a preliminary study’, International Sugar Journal 88
         (1055):210-216.

4.       Deepchand, K. (2000). ‘Cogeneration of Bagasse Energy in Mauritius’,
         Energy for Sustainable Development, V(I): 15 – 22, Bangalore, International
         Energy Initiative

5.       Lichts, F.O. (2004). World Sugar Statistics. 65th Edn

6.       Quevauvilliers, J M (2001) Advanced Cogeneration Plant: The Case of CTBV.
         AFREPREN Energy Training Course’, AFREPREN Occasional Paper No. 21:
         Opportunities for Cogeneration in a Reforming African Power Sector -
         Proceedings of an Energy Training Course, Nairobi, AFREPREN




     Financing Cogeneration and Small-Hydro projects in the Sugar and tea
                 Industry in East and Southern Africa Training