Vermiculture_Composting

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					An Irish Perspective on the Waste Management
    Challenge with Composting as a Viable
            Environment Solution




                          s



             Institute of Technology, Sligo
  Department of Environmental Science and Technology




                         By:
                   Aisling Donegan
                   Ken McNamara
                    Marie Mortell


              Waste Management
                      Lecturer:
                 Dr. Micheal Broaders
Waste Management ,                                      Domestic &                                            Aisling Donegan
Environmental Science,                                  Municipal                                             Ken M c Namara
I. T. Sligo.                                            Composting                                            Marie Mortell




                                                 Table of Contents

1: WASTE FACTS ............................................................................................................. 4
   1:2 Policies and Practices for Waste Management in Ireland......................................... 5
     1:2:1. Reduction of Waste at Source........................................................................... 5
     1:2:2. Reuse and Recycle ............................................................................................ 6
     1:2:4. Disposal of Waste(non-hazardous) ................................................................... 6
   1:2:5 Disposal of Hazardous Waste ................................................................................ 7
2: Changing our Ways ........................................................................................................ 7
   2:1 Waste Management Act, 1996 .................................................................................. 8
   2:2 Waste Management Planning ................................................................................... 9
     2:2:1 From the outset, local authorities were encouraged to - .................................... 9
3:Municipal waste ............................................................................................................. 11
   3:1 Disposal and Recovery Routes ............................................................................... 11
     3:1:1. Waste prevention and minimization ............................................................... 12
     3:1:2. Recovery of municipal wastes ........................................................................ 13
Section 2............................................................................................................................ 14
1: Composting ................................................................................................................... 14
   1:2Biological process .................................................................................................... 17
     1:2:1:Moisture ........................................................................................................... 17
     1:2:2. Carbon and Nitrogen....................................................................................... 18
     1:2:3. Oxygen and Temperature ............................................................................... 19
2: Biological Process Control ........................................................................................... 22
3: Materials Handling ....................................................................................................... 24
   3:1 A. Windrows ........................................................................................................... 24
   3:2 B. Static Piles .......................................................................................................... 25
   3:3 C. Vertical Composting Reactors ........................................................................... 27
   3:4 D. Hroizontal Reactors ........................................................................................... 28
4:Physical Process ............................................................................................................. 32
   4:1 A. Collection .......................................................................................................... 32
   4:2 B. Centralized Separation ....................................................................................... 34
5 C. Size Reduction and Homogenization ........................................................................ 40
Section: 3 .......................................................................................................................... 45
1:Compost Case Studies: .................................................................................................. 45
   1:1 Climate of Areas: .................................................................................................... 45
     1:2 The Main Aims of the Composting Scheme:...................................................... 46
   1:3 The Tralee Area Composting Scheme: ................................................................... 46
     3:1 Communication with householders: ................................................................... 47
     3:2 The Collection: ................................................................................................... 48
     3:3 Composting Platform and Process at North Kerry Landfill: .............................. 49
     3:4 Guidelines for Composting as Provided by Kerry County Council Information
     Pack: .......................................................................................................................... 50


                                                                   2
Waste Management ,                                      Domestic &                                            Aisling Donegan
Environmental Science,                                  Municipal                                             Ken M c Namara
I. T. Sligo.                                            Composting                                            Marie Mortell




      3:5 Finances of Tralee Area Composting Scheme:................................................... 51
   5: Limerick Composting Scheme: ................................................................................ 53
      5:1 The Composting Process at Limerick County Council Landfill: ....................... 53
Section: 5 .......................................................................................................................... 54
1: The Market For Compost:............................................................................................. 54
   1:1Organic Agriculture: ................................................................................................ 55
   1:2 Rural Environment Protection Scheme: ................................................................. 55
   1:3 Large Scale Intensive Agriculture: ......................................................................... 56
      1:3:1 Canadian Study on Benefits of Compost in Potatoes Production: .................. 56
      1:3:2 Overall Findings of Study:............................................................................... 58
   1:4 Landscaping: ........................................................................................................... 59
   Compost Marketing in America: .................................................................................. 59
      1:4:1 The establishment of Xeriscaping: .................................................................. 60
   1:6 Potential for Use of Compost as a Primary Erosion Control Material: .................. 61
      1:6:1 Causes of Erosion: ........................................................................................... 61
      1:6:2 The Use of Compost: ....................................................................................... 62
7: Market Development in Ireland: ................................................................................... 63
Section: 6 .......................................................................................................................... 64
Vermiculture: .................................................................................................................... 64
2:So how is it done? .......................................................................................................... 71
   2:1 The System Elements.............................................................................................. 72
      2:1:1 The Beds .......................................................................................................... 72
      2:1:2 Waste Types..................................................................................................... 72
3: Wastes Managed ........................................................................................................... 74
   3:1 Odour Management ................................................................................................ 74
   3:2 Contaminants Management .................................................................................... 75
      3:2:1 The impact of heavy metals is reduced by two mechanisms. .......................... 75
4: Volume.......................................................................................................................... 76
   4:1 Site Requirements (Civil & Structural) .................................................................. 76
   4:2 Pre Design Requirements........................................................................................ 77
5: Systems and Procedures................................................................................................ 79
   5:1 Benefits of the Vermiculture system ...................................................................... 79
   5:2 Quality Assurance ................................................................................................... 80
   5:3 Destruction of Pathogens ........................................................................................ 82
6: HELMINTHS ............................................................................................................... 83
   6:1 Reduction of Impact of Plant Pathogens................................................................. 85
   7:1 No leachate ............................................................................................................. 85
   7:2 Dust ......................................................................................................................... 85
   7:3 Noise ....................................................................................................................... 86
   7:4: No Odour ............................................................................................................... 86
   7:5: Energy Consumption ............................................................................................. 86
8: Conclusion .................................................................................................................... 87




                                                                   3
Waste Management ,                    Domestic &                         Aisling Donegan
Environmental Science,                Municipal                          Ken M c Namara
I. T. Sligo.                          Composting                         Marie Mortell




Section 1

1: WASTE FACTS


Waste Management remains one of the most challenging areas of modern environmental

management. The latest figures show clearly that waste quantities are continuing to grow

in Ireland. Almost 80 million tones originated from agricultural sources, mainly animal

manures. Over two million tones of municipal waste were generated in the same year. A

comparison of waste collected by or on behalf of local authorities between 1984 and 1998

indicates an increase of over 100% in 14 years. Between 1995 and 1998 there was a 47%

increase in the amount of industrial waste generated, from 6.2 million tones to 9.1 million

tones. Hazardous waste also shows an increase of 13% between 1996 and 1998. The

amount of construction and demolition waste in 1998 was estimated at 2.7 million tones.



Landfill remains the principal waste disposal route in Ireland with 91% of municipal

waste generated in Ireland landfills in 1998. The overall recovery rate for packaging

waste in 1998 was 14.8% and Ireland still has considerable progress to make if it is to

meet international targets set for 2001 and 2005. There has been improved recovery of

industrial wastes from 12.4% in 1995 to 26.6% in 1998 and an increase in overall

recovery within the manufacturing sector from 30% in 1995 to 51.4% in 1998.



There have been major developments affecting the waste sector since the last State of the

Environment report was published. These developments include the enactment of the

Waste Management Act, 1996 and the publication of the following: the National


                                             4
Waste Management ,                    Domestic &                         Aisling Donegan
Environmental Science,                Municipal                          Ken M c Namara
I. T. Sligo.                          Composting                         Marie Mortell




Sustainable Development Strategy (DoE, 1997), a National Waste Policy Statement

“Changing Our Ways” (DELG, 1998), a proposed National Hazardous Waste

Management Plan (EPA, 1999) and standards and guidance on many aspects of land

filling. These policies provide an bases on which to build and to improve the

environmental reputation of Ireland, as an EU state member.




1:2 Policies and Practices for Waste Management in Ireland


1:2:1. Reduction of Waste at Source


This lowers costs in waste disposal, reduces potential for environmental degradation, and

helps to conserve nonrenewable resources. This preventive policy requires a new

approach of 'clean or low waste technology' in industry, involving product design,

materials substitution, less wasteful processes and good housekeeping practices. This is a

priority objective of national and EC policy. Waste can be reduced not only in

manufacturing but in packaging of products and in wrapping and carrying goods at retail

outlets.




                                            5
Waste Management ,                    Domestic &                           Aisling Donegan
Environmental Science,                Municipal                            Ken M c Namara
I. T. Sligo.                          Composting                           Marie Mortell




1:2:2. Reuse and Recycle


Reuse and recycling of materials within industry and after use by the consumer, such as

scrap metal, paper, glass, oil, aluminium cans etc.


3. WASTE COLLECTION BY LOCAL AUTHORITIES


Regular collection of household and commercial waste is provided to 77% of our national

population. In towns the service is almost 100%. The cost of collection service to local

authorities is £23.5 million for 880,000 tones of refuse (1984); disposal costs are £8

million for 1.5 million tones (including material brought by private firms) deposited on

tip-sites. Collection and transport account for 75% of sanitary authority expenditure on

refuse collection and disposal.


1:2:4. Disposal of Waste(non-hazardous)


      Incineration

      Reduction of waste volumes by compaction, high density baling, or pulverisation

      Final disposal of residues by disposal on land or dumping at sea.

      Composting




                                             6
Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




1:2:5 Disposal of Hazardous Waste


The European Commission considers that toxic and dangerous wastes represent one of

the greatest environmental protection problems. In the European Community as a whole

there is a deficiency of 50% an capacity for their safe disposal. It is essential to know of

the presence and movement of hazardous wastes and to ensure they are disposed of in a

controlled way. Our national waste disposal strategy calls for improved arrangements for

the disposal of hazardous wastes which are not suitable for landfilling, plus the controlled

deposit of some hazardous waste at co-disposal sites.


2: Changing our Ways


In October 1998, the Minister for the Environment and Local Government published a

policy statement on waste management, entitled "Changing Our Ways". The statement

set out the following targets to be achieved over a fifteen year timescale -


· a diversion of 50% of overall household waste away from landfill,


· a minimum 65% reduction in biodegradable municipal waste consigned to landfill,


· the development of composting and other feasible biological treatment facilities capable

of treating up to 300,000 tonnes of organic waste annually,


· recycling of 35% of municipal waste,



                                              7
Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




· recycling at least 50% of C&D waste within a five year period, with a progressive

increase to at least 85% over fifteen years, and


· a rationalisation of municipal waste landfills, leading to an integrated network of some

20 or so state-of-the-art facilities incorporating energy recovery and high standards of

environmental protection.




2:1 Waste Management Act, 1996


The enactment of the Waste Management Act, 1996 was a watershed for municipal waste

management in Ireland. Measures initiated under the Act are leading to a radical change

in Irish waste management practice, which will see our current over-reliance on landfill

decline sharply within a relatively short period, in favour of an integrated waste

management approach which utilises a range of waste treatment options to deliver

ambitious recycling and recovery objectives.


Part V of the 1996 Act, and subsequent 1997 Regulations, provide for the operation of a

system of licensing by the EPA of significant waste recovery and disposal activities. All

proposed and existing landfill facilities became licensable on a phased basis between

May, 1997 and March, 1999. This licensing system is intended to ensure that high

standards of environmental protection apply in relation to the operation of relevant waste

facilities.




                                             8
Waste Management ,                      Domestic &                           Aisling Donegan
Environmental Science,                  Municipal                            Ken M c Namara
I. T. Sligo.                            Composting                           Marie Mortell




The greatly increased costs associated with the high environmental standards now being

applied under the Waste Management Act licensing system, as implemented by


2:2 Waste Management Planning


Waste Management planning has also been placed on a new footing under the 1996 Act.

Local authorities are required to make new, detailed, plans for the management of non-

hazardous wastes within their functional areas. Reflecting the waste hierarchy, the

statutory objective of these plans is to -


· prevent and minimise the production of waste and its harmful effects, and encourage

and support the recovery of waste,


· ensure that such waste as cannot be prevented or recovered is safely disposed of, and


· address the need to give effect to the polluter pays principle, in relation to waste

disposal.


There is a strong emphasis on public consultation and engagement in the planning

process.


Detailed requirements in relation to the preparation and content of waste management

plans were set out in the Waste Management (Planning) Regulations, 1997.




2:2:1 From the outset, local authorities were encouraged to -


                                              9
Waste Management ,                      Domestic &                        Aisling Donegan
Environmental Science,                  Municipal                         Ken M c Namara
I. T. Sligo.                            Composting                        Marie Mortell




· adopt a regional approach to this planning process, with a view to the more efficient

provision of services and infrastructure, and


· carry out preliminary waste management strategy studies, to provide a context for

evaluating available options and for identifying the measures, or combination of

measures, most likely to optimise waste management.


Generally, the regional strategy studies assess the scope for, and make appropriate

recommendations regarding the provision of -


· door to door collection of recyclables in urban areas;


· extended bring facilities in rural areas;


· networks of civic amenity sites and transfer stations;


· biological treatment of "green" and organic household waste, involving both

composting and anaerobic digestion;


· materials recovery facilities;


· capacity for recycling of C&D waste, involving fixed and mobile plant;


· thermal treatment; and


· residual landfill.




                                              10
Waste Management ,                    Domestic &                           Aisling Donegan
Environmental Science,                Municipal                            Ken M c Namara
I. T. Sligo.                          Composting                           Marie Mortell




3:Municipal waste




It is estimated that over 2 million tones of municipal waste were generated in Ireland in

1998. This consisted of approximately 1.22 million tones of household waste, 0.755

million tones of commercial waste and 81,000 million tones of street cleansing waste.

This is an increase of 11.3% on the 1995 estimate of 1.85 million tones of municipal

waste generated (1.32 million tones from households, 0.48 million tones from

commercial sector and 47,000 tones of street cleansing wastes).



3:1 Disposal and Recovery Routes



The primary route for the disposal of household and commercial waste in Ireland is

landfill. At present, Ireland, unlike the majority of its European neighbors, has no

incineration capacity for such waste. In the absence of incineration, landfill will continue

to be the primary disposal route for household and commercial waste, despite the fact that

EU policy considers landfill to be the least desirable waste management practice. Of the

1.85 million tones of household and commercial waste collected in Ireland in 1998,

91%was consigned to the landfill with 9% recovered for recycling.




                                             11
Waste Management ,                    Domestic &                           Aisling Donegan
Environmental Science,                Municipal                            Ken M c Namara
I. T. Sligo.                          Composting                           Marie Mortell




The overall recovery rate for municipal waste has increased from 7.8% in 1995 to 9% in

1998. However, the recovery rate for the household waste fraction decreased from 4.3%

to 3.2% over that year. This is mainly due to a decrease in the collection of paper waste

from households. In contrast, recovery of glass from households has improved

considerably, from 7,900 tones in 1995 to 14,100 tones in 1998. There has also been an

increase in batteries.




3:1:1. Waste prevention and minimization




The preferred options in relation to waste are prevention and minimization. They are also

the most challenging options, as their successful implementation requires a change in the

attitude of the waste producers. At the development and manufacturing level, each step in

the chain has to be considered in relation to its waste production potential. At consumer

level, the consumer needs to consider the waste implications of particular purchases.

Planning for waste prevention and minimization requires a knowledge of the sources of

the waste, as realistic targets for individual sectors can only set when it is known what

quantities and types are produced by each sector.



Waste prevention and minimization strategies have a positive impact on the environment.

In many cases, strategies are put in pace either to replace or modify existing processes




                                             12
Waste Management ,                    Domestic &                           Aisling Donegan
Environmental Science,                Municipal                            Ken M c Namara
I. T. Sligo.                          Composting                           Marie Mortell




leading to waste production in order to reduce the volume and toxicity of waste produced.

Waste prevention is an integral aspect of IPC licensing.


3:1:2. Recovery of municipal wastes




After waste prevention and minimization, the next best environmental options in relation

to waste management are re-use and recovery. The main environmental options in

relation to waste management are re-use and recovery, which includes recycling and

energy recovery. The main environmental advantage afforded by waste recovery is the

saving on the use of natural resources. However, when considering the net environmental

impact, this needs to be balanced against the overall cost to the environment in relation to

energy usage and pollution that might arise as a result of the recovery process itself. Once

a waste is produced its management is unlikely to result in negative environmental

impacts whether the waste is recovered or disposed. This lights the importance of waste

prevention and minimization and the integration of waste issues into the

production/consumption cycle so that products are designed to have as little impact as

possible on the environment when they become redundant. The Department of the

Environment and Local Government has also encouraged the development of recycling

and recovery infrastructure. During 1997 and 1998, 65 projects received funding, ranging

from £1, and 5000 to 40,000. The main recovery processes for municipal waste was

composting. The standard means of disposal for most yard and food waste includes

landfill and incineration. These practices are not as environmentally or economically


                                            13
Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




sound as composting. Yard waste which is landfilled breaks down very slowly due to the

lack of oxygen. As it decomposes, it produces methane gas and acidic leachate, which are

both environmental problems


Landfill of organic wastes also takes up landfill space needed for other wastes.

Incinerating moist organic waste is inefficient and results in poor combustion, which

disrupts the energy generation of the facility and increases the pollutants that need to be

removed by the pollution-control devices. Composting these wastes is a more effective

and usually less expensive means of managing organic wastes. It can be done

successfully on either a large or small scale, but the technique and equipment used differ.




Section 2


1: Composting


The process whereby organic matter is broken down by micro-organisms in the presence

of heat and moisture is known as composting. Composting process involves three types

of micro-organisms- bacteria, fungi and actinomyctes. After organic material has been

gathered these micro-organisms rapidly grow in numbers to colonies the waste. As a

result of their biological activity the waste is broken down into compost. The micro-

organisms grow and assimilate the sugars, starch and organic acids. As a result of their

activity the temperature at the centre of the compost heap rises, often to 60C. At this

temperature thermophillic bacteria live in the waste. After, the bacteria have assimilated


                                             14
Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




all the sugars and starch the temperature begins to decrease. At these low temperatures

other micro-organisms, like fungi, become dominant. Now the waste is said to be

stabilizing but the continuing biological activity also the woody elements of the waste to

be broken down.



The benefits of composting are as follows;

   1. the conversion of organic waste into valuable end products

   2.   reduction of the quantity of waste to be disposed by the house holder

   3. reduction of the need for landfill space

   4. recycling of organic materials and nutrients back into the soil

   5. conservation of peat lands and bogs




Composting of organic wastes, such as kitchen waste and garden clippings, provides a

viable alternative to disposal of such wastes. A key component of the Government‟s

waste strategy is 65% reduction in the quantity of biodegradable waste consigned to

landfill and the development of biological treatment facilities, including composting,

capable of treating up to 300,00 tones per annum. It is estimated that in excess of 1

million tones of biodegradable waste, consisting of paper and kitchen/garden wastes,

were consigned to landfill in 1998.




                                             15
Waste Management ,                    Domestic &                         Aisling Donegan
Environmental Science,                Municipal                          Ken M c Namara
I. T. Sligo.                          Composting                         Marie Mortell




The developments of composting as an alternative to landfill have been slow in Ireland.

A number of home composting schemes have been set up by local authorities, eight such

schemes are receiving funding under the Operational Programme for Environmental

Services, and 1994-1999.Centralised composting of municipal waste is under

development in South Dublin, Cork, limerick and Kerry. There will need to be

considerable development in centralized composting, in the short term, if composting is

to contribute significantly to the diversion of biodegradable waste away from landfills.

Given that the decomposing of biodegradable waste is responsible for many of the

environmental problems associated with landfills, such as leachate contamination, landfill

gas and odour nuisance, these should be considered by householders and local authorities.

The recent upsurge of interest in composting the organic fractions of municipal solid

waste (MSW) builds on largely successful efforts with composting yard trimmings,

agricultural wastes, and sewage sludges. While experience with these other materials is

helpful in considering an MSW composting program, there are a number of challenges

unique to MSW, which need to be addressed. MSW contains materials, which vary

widely in size, moisture, and nutrient content, and the organic fractions can be mixed

with varying degrees of non-compostable wastes and possibly hazardous constituents.

Manufacturing a marketable compost product from this material requires a range of

physical processing technologies in addition to the biological process management

common to other types of composting. Section 3 gives a detailed account of these

processes.




                                            16
Waste Management ,                     Domestic &                        Aisling Donegan
Environmental Science,                 Municipal                         Ken M c Namara
I. T. Sligo.                           Composting                        Marie Mortell




1:2Biological process


Composting is in essence a biological process. But proper design and management must

be based on the needs of microorganisms if the process is to be a success. Neglect or

misunderstanding of biological process control can lead to serious problems at

composting facilities, and has contributed to facility closings.


Composting is defined by human intervention into the natural process of decomposition.

With a combination of proper environmental conditions and adequate time,

microorganisms turn raw putrescible organic matter into a stabilized product. Through

composting, readily available nutrient and energy sources are transformed into carbon

dioxide, water, and a complex form of organic matter compost. Process management can

be optimized for a number of criteria, including the rate of decomposition (to reduce

residence time in reactors and thus minimize facility size requirements), pathogen

control, and odor management. The key parameters are the available carbon to nitrogen

(C:N) ratio, moisture, oxygen, and temperature.


1:2:1:Moisture


Moisture management requires a balance between these two functions: microbial activity

and oxygen supply. Moisture is essential to the decomposition process, as most of the

decomposition occurs in thin liquid films on the surfaces of particles. However, mixtures

can be too wet, thereby reducing the oxygen supply. Excess moisture will fill many of the



                                             17
Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




pores between particles with water, limiting oxygen transport. Oxygen diffusion, the

movement of oxygen due to differences in concentration, is 10,000 times slower in water

than in air. If too little oxygen gets to the center of the compost, anaerobic (without

oxygen) decomposition will result. While anaerobic activity normally occurs to a limited

extent in the interior of particles within an otherwise aerobic system, high levels of

anaerobic metabolism can generate a wide range of unpleasant and pervasive odors and

other by-products.


Decomposition slows dramatically in mixtures under 40 to 45 percent moisture, which

can lead facility operators to prematurely assume compost is stabilized and ready to sell.

A minimum moisture content of 50 to 55 percent is usually recommended for high rate

composting of MSW. MSW collection programs which include paper are often drier than

this, and water or sludge should be added to bring moisture into the optimum range. The

heat and airflow generated during composting evaporate significant amounts of water and

tend to dry the material out. During the active composting phase, additional water usually

needs to be added to prevent premature drying and incomplete stabilization. MSW

compost mixtures usually start at about 52 percent moisture and dry to about 37 percent

moisture prior to final screening and marketing.


1:2:2. Carbon and Nitrogen


Carbon and nitrogen are the two most important elements in the composting process, as

one or the other is normally a limiting factor. Carbon serves primarily as an energy

source for the microorganisms, while a small fraction of the carbon is incorporated in


                                             18
Waste Management ,                      Domestic &                           Aisling Donegan
Environmental Science,                  Municipal                            Ken M c Namara
I. T. Sligo.                            Composting                           Marie Mortell




their cells. Nitrogen is critical for microbial population growth, as it is a constituent of

protein which forms over 50 percent of dry bacterial cell mass. If nitrogen is limiting,

microbial populations will remain small and it will take longer to decompose the

available carbon. Excess nitrogen, beyond the microbial requirements, is often lost from

the system as ammonia gas or other mobile nitrogen compounds and can cause odors or

other environmental problems. While the typically recommended C:N ratios for

composting MSW are 25:1 to 40:1 by weight, these ratios may need to be altered to

compensate for varying degrees of biological availability. While wood chips have a high

C:N ratio, most of the carbon in a large wood chip will not be available to

microorganisms during the time frame of typical composting processes. Increasing the

surface area of wood and other organic particles through size reduction (grinding or

shredding), can increase carbon availability and accelerate decomposition if adequate

nitrogen is available. Nitrogen is usually the limiting element in MSW, and additives

such as manure, clean sewage sludge (biosolids), septage and urea can be used as a

supplemental nitrogen source.


1:2:3. Oxygen and Temperature


The remaining key environmental parameters, oxygen and temperature, are linked by the

decomposition process. Both fluctuate in response to microbial activity, which consumes

oxygen and generates heat. Oxygen and temperature are also linked by a common

mechanism of control: aeration. Aeration both re-supplies oxygen as it is depleted and




                                              19
Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




carries away excess heat. This dual purpose makes aeration management a central feature

of biological processing, as it controls these two parameters.


Inadequate oxygen levels lead to the growth of anaerobic microorganisms which can

produce odorous compounds. While adequate oxygen can minimize these odors, it is

important to note that anaerobic pockets will exist in a heterogeneous material like MSW,

and some odors including ammonia and some organic compounds can be generated even

under generally aerobic conditions. Thus, while proper oxygen supply can minimize

odors, it may not completely eliminate them. And since some of the odors causing

problems at MSW composting facilities originate at the tipping floor with raw waste prior

to composting and aeration, most MSW composting facilities are likely to require odor

treatment to maintain good neighbor relations. Odor treatment options include biological,

chemical, and thermal technologies.


Just a few of the many pre-processing steps described in Fact Sheet 1 are normally

adequate to provide reasonably aerobic conditions as the feedstock enters the composting

system, but additional oxygen must quickly be supplied. Rapidly decomposing wastes

can use up the oxygen introduced by turning within a matter of minutes. Oxygen

concentrations in the large pores must normally be at least 12-14 percent (ideally 16-17

percent) to allow adequate diffusion into large particles and water filled pores. Most

MSW composting systems used a forced aeration system with blowers and distribution

pipes to supply oxygen during the initial phases of active composting. Passive diffusion

and natural convection help supply oxygen to windrow systems between turning events.



                                            20
Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




Heat is a by-product of decomposition, and is important in raising and maintaining

temperatures for efficient decomposition. There are several trade-offs related to

optimizing temperature control. Temperatures of 45 to 59°C (113-138°F) provide the

highest rate of decomposition, with temperatures above 59°C (138°F) reducing the rate of

decomposition due to a reduction in microbial diversity. Since temperatures in excess of

55°C (131°F) for several days are usually required for pathogen control, the ideal

temperature operating range is relatively narrow. Temperature also can affect odor, with

odor generation rates for many compounds peaking between 56 and 70°C (132-158°F).




                                            21
Waste Management ,                    Domestic &                         Aisling Donegan
Environmental Science,                Municipal                          Ken M c Namara
I. T. Sligo.                          Composting                         Marie Mortell




2: Biological Process Control


Most composting systems reconcile these trade-offs between reaction rate, pathogen

reduction, and odor generation by an attempt to control temperatures to a narrow range

near 55 to 60°C (131-140°F). To maintain this temperature range, heat gains from

microbial activity need to be balanced against heat losses, which occur primarily through

evaporation of moisture and heating the aeration air. Temperature, like oxygen supply, is

usually managed by an aeration system: the same air which supplies oxygen can carry

away excess heat. During most of the active composting stage, several times as much air

is needed to remove heat as to supply oxygen, so maintaining proper temperatures will

usually also keep oxygen levels in the proper range. Forced aeration systems are

commonly used during this stage of composting, using temperature sensors to control

blowers. Eventually, as readily available compounds are decomposed, the rate of

composting slows, with less oxygen required and less heat generated. This slower stage is

called curing, and while it requires less management than active composting, it is

important to compost quality,


Windrow composting usually relies on natural convection and diffusion for oxygen

supply. Pile size and turning frequency are used to balance heat loss in managing

temperature control (Figure 1).




                                            22
Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




Figure 1. Natural Air Circulation in a Compost Windrow




The effectiveness and penetration of oxygen supply in a windrow system varies with the

rate of microbial activity and porosity of the pile. Anaerobic zones can be minimized by

decreasing pile size or increasing its porosity, although in practice fully aerobic

conditions are difficult to achieve in windrows during the active composting phase. Pile

size may be increased in extremely cold weather or when decomposition slows as

compost matures. Mechanically turning the pile releases heat and moisture and can

temporarily increase the porosity. Agitation can also help break up clumps of material

and thereby increase oxygen transfer. Management of convection and diffusion through

pile size and turning frequency can be a cost-effective strategy, although decomposition

is generally not as rapid as with forced aeration systems.




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Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




3: Materials Handling


The process control strategies described above regulate temperature and oxygen to

encourage microbial decomposition. Much of the scientific literature on composting

focuses on these options for process control, but in the practical world of industry and

government the emphasis, expense and hotly debated differences among systems have

more to do with materials handling. Materials handling technologies mix, macerate, and

move the compost through the facility. A variety of technologies have been adapted for

use with MSW, which can be roughly divided into four groups: A.windrows, B.static

piles, and C.vertical and D.horizontal reactors. Each of these composting materials

handling technologies is described below.


3:1 A. Windrows


Windrows (Figure 2) are defined as regularly turned elongated piles, shaped like a

haystack in cross section and up to a hundred meters (yards) or more in length. Process

control is normally through pile management as described above, although forced

aeration can also be used. The cross-sectional dimensions vary with feedstock and

turning equipment, but most MSW windrows are 1.5 to 3 meters (yards) high and 3 to 6



                                            24
Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




meters (yards) wide. Windrows composed of MSW are usually required to be located on

an impermeable surface, which greatly improves equipment handling under inclement

weather conditions. Windrows can be formed with a front-end loader, dump truck, or

conveyor. A variety of specialized turning machines are available, although front-end

loaders can also be used if operators are adequately trained. Windrow turners should

perform several functions: 1.increase porosity of the pile, 2.redistribute material to

enhance process uniformity, 3.and break up clumps to improve product consistency.

Some machines also perform a shredding or macerating function, which may partially

substitute for other processing steps and can accelerate decomposition.


Figure 2. Windrow




3:2 B. Static Piles



Static piles can be shaped much like windrows or in an elongated pile or bed (Figure 3).

The essential difference is in the name; static piles are not mechanically agitated. Once



                                             25
Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




constructed by conveyor, loader or truck, the piles remain in place until the

decomposition slows. The lack of agitation requires the maintenance of adequate porosity

over an extended period of time. When composting fine materials like sludge, a coarse

stable substrate such as wood chips is often incorporated in the mix. Inert materials or

slowly degrading cellulosic substrates like cardboard or leaves may help supply that

stable porous structure in MSW, but this needs to be considered in the preprocessing

system design. Process control is normally through pressure and/or vacuum-induced

aeration, with either temperature or oxygen as the control variable. Blower piping can be

temporary plastic or metal in a bed of coarse material at the base of the pile, or recessed

into the composting pad under perforated plates. Piles are often covered with a layer of

wood chips or mature compost to insulate the active compost from ambient temperatures

and/or provide some odor treatment. Both windrows and static piles are often outside and

exposed to weather, but can be covered with a roof to minimize the impacts of weather

and provide an opportunity for odor capture and treatment.



                                 Figure 3. Aerated Static Pile




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Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




3:3 C. Vertical Composting Reactors



Vertical composting reactors (Figure 4) are generally over 4 meters (yards) high, and can

be housed in silos or other large structures. Organic material is typically fed into the

reactor at the top through a distribution mechanism, and flows by gravity to an unloading

mechanism at the bottom. Process control is usually by pressure-induced aeration, where

the airflow is opposite to the downward materials flow. The height of these reactors

makes process control difficult due to the high rates of airflow required per unit of

distribution surface area. Neither temperature nor oxygen can be maintained at optimal

levels throughout the reactors, leading to zones of non-optimal activity. Some

manufacturers have minimized these difficulties by enhanced air distribution and

collection systems, including changing the airflow direction from vertical to horizontal

between alternating sets of inflow and exhaust pipes. As with static pile composting, a

stable porous structure is important in vertical reactors which usually lack internal

mixing. Tall vertical reactors have been successfully used in the sludge composting

industry where uniform feedstocks and porous amendments can minimize these

difficulties in process control, but are rarely used for heterogeneous materials like MSW.




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Waste Management ,                    Domestic &                         Aisling Donegan
Environmental Science,                Municipal                          Ken M c Namara
I. T. Sligo.                          Composting                         Marie Mortell




Figure 4. Vertical Reactor




3:4 D. Hroizontal Reactors




Horizontal reactors avoid the high temperature, oxygen, and moisture gradients of

vertical reactors by maintaining a short airflow pathway (Figure 5). They come in a wide

range of configurations, including static and agitated, pressure and/or vacuum-induced

aeration. Agitated systems usually use the turning process to move material through the

system in a continuous mode, while static systems require a loading and unloading

mechanism. Materials handling equipment may also shred to a certain degree, exposing

new surfaces for decomposition, but excessive shredding may also reduce porosity.

Aeration systems are usually set in the floor of the reactor, and may use temperature



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Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




and/or oxygen as control variables. Systems with agitation and bed depths less than two

to three meters (yards) appear effective in dealing with the heterogeneity of MSW.



Figure 5. Horizontal Bed Reactor




Horizontal and vertical reactors are commonly referred to as in-vessel systems as

differentiated from open systems such as windrows and static piles. Because of the higher

capital and operation costs associated with these contained systems, residence time in the

reactors is rarely adequate for the production of mature compost. Instead, in-vessel

composting technologies are often used to help get the material through the early stages

of composting when odors and process control are most critical, and the material is then

moved into a windrow or static pile system for the later stages of decomposition and

curing.


Rotating drum reactors take the trade-off between reactor cost and compost residence

time to an even further extreme than the horizontal or vertical in-vessel systems (Figure

6). These reactors (sometimes called digestors) retain the material for only a few hours or

days. While the tumbling action can help homogenize and shred materials, the short




                                            29
Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




residence time usually means the processing is more physical than biological. While

rotating drums can play an important role in MSW composting, they are normally

followed by other biological processing, which may include in-vessel, static pile, and/or

windrow systems.


Figure 6. Rotating Drum




The materials handling systems described above must be combined with a process control

strategy to produce a workable composting system.



All these examples of composting systems can be used for a variety of feedstocks, and

may require modifications for the biological processing of MSW. Some important

characteristics of MSW which may be different from other composting feedstocks

include high carbon levels (mostly cellulose), low levels of moisture, and a weak porous

structure. The high cellulose levels require longer curing than many other materials, so

that it may take six months to achieve the degree of stability found after only two or three

months in sewage sludge composting. Mixing can provide a way to add moisture and to


                                            30
Waste Management ,                    Domestic &                           Aisling Donegan
Environmental Science,                Municipal                            Ken M c Namara
I. T. Sligo.                          Composting                           Marie Mortell




renew porosity, as well as increase the compost uniformity. Whatever technology is

utilized, operator skill is required in adapting to changes in the waste stream. Seasonal

fluctuations in yard waste constituents (i.e. grass clippings) and even load-to-load

variability with commercial or industrial wastes require competent and flexible

management.




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Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




4:Physical Process


Four tasks are central to the design of a modern MSW composting system: A. collection,

B. contaminant separation, C. sizing and mixing, D. and biological decomposition.


The first of the preprocessing tasks, collection, largely determines the processing

requirements of the remaining tasks because they must be tailored to the characteristics of

the incoming waste. Separation processes at the composting facility generate recyclable

and reject streams, usually at several places in the process. Size reduction increases the

surface area of the organic wastes, enhancing opportunities for biological activity, while

mixing ensures that nutrients, moisture and oxygen are adequate throughout the material.

Options for accomplishing these first three tasks are described below.


4:1 A. Collection


If we take the perspective that composting is a manufacturing process, the ideal input

material for a compost product is a consistent and clean organic waste. This ideal is rarely

reached, and even leaf composting facilities receive tennis balls, plastic bags, and street

sweepings, which can contain a variety of contaminants such as motor oil and asbestos.

Moving across the collection spectrum from leaves and grass to "biowaste" (such as food

scraps, yard trimmings, and selected other organics like soiled paper) to totally mixed

MSW, the types and volumes of non-compostable contaminants increase. These include

visible materials such as plastic and glass, and chemical contaminants, such as Household

Hazardous Wastes (HHW). Both physical and chemical contaminants can have a negative


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Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




impact on the marketability of the finished product, and their removal forms a large part

of the expense of modern MSW composting facilities.


Some composting programs require source separation of organic compostables by

participating residents and businesses, while others accept a mixed stream and separate

non-compostables at a centralized facility. Separate collection of compostable materials

programs can include everything from yard and food waste to soiled paper products, and

in some cases has recovered 45 to 50 percent of the entire solid waste stream for

composting. However, even when organic compostables are separately collected, a small

fraction of non-compostable wastes will need to be removed at the composting facility.

Educational programs are a critical aspect of source separated composting systems, since

such programs depend on residents to accomplish much of the separation.


Composting programs, which accept a mixed waste stream, accept material more or less

as it is currently collected, relying on the facility separation techniques described below.

One important modification to traditional collection techniques is the establishment of a

HHW collection program. To be effective at reducing the contaminants of concern in

MSW compost, such programs must emphasize heavy metal sources such as batteries and

consumer electronics. The remaining mixed waste (less any separately collected

recyclables and HHW) then serves as feedstock for the composting facility, where

centralized separation of non-compostable materials will occur. With this approach, 60 to

70 percent of the solid waste stream is typically processed into compost. The remaining




                                             33
Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




30 to 40 percent includes recyclables as well as rejects destined for the landfill or an

incinerator and landfill.


There are several trade-offs between source separation and centralized separation of

compostables. It is clear that source separation can produce a higher quality, less

contaminated compost, as well as maximize the recycling of glass and paper. And while

source separation is generally less convenient for the waste generator, pilot programs are

finding that many generators like to do it. However, two other important factors, the

overall system cost and the quantities of materials recovered for recycling and

composting, have not yet been adequately researched or evaluated.


4:2 B. Centralized Separation


In composting systems there are three objectives for materials separation: 1) recover

recyclable or combustible materials as marketable by-products, 2) reduce the levels of

visible inert materials (e.g., plastics and glass), and 3) reduce the levels of chemical

contaminants (e.g., heavy metals and HHW). Many of the separation technologies now

applied to MSW composting were originally developed to recover recyclable or

combustible materials from solid waste. While some of these technologies have been

adapted for reduction of inerts, they have rarely been optimized for reducing chemical

contaminant levels.


A wide range of technologies are available (see Table 1), and many facilities use

asequence of steps employing different processes. Facility designers can select among



                                              34
Waste Management ,                    Domestic &                           Aisling Donegan
Environmental Science,                Municipal                            Ken M c Namara
I. T. Sligo.                          Composting                           Marie Mortell




them based on expected feedstock characteristics, finished product quality specifications,

and the options for marketing separated by-products.


                                 Table 1. MSW Composting - Centralized Separation

                                 Technologies




While machines can do a reasonably good job of separating by size, density, or

electromagnetic characteristics, we have yet to invent a pattern recognition device as

good as the human brain. Manual separation can occur at several points in the process,

starting at the tipping floor where large bulky items such as mattresses, carpets,

appliances and hazardous materials such as propane cannisters are removed.


4:3 Screening: Most MSW composting facilities first convey the waste into a bag-

opener and screen or trommel to separate different sizes of waste (Figure 1). Fine

materials, including soil, grit, and much of the organic wastes, fall through the screen as

"unders". Plastic films and large paper products are retained on the screen as "overs" and

may possibly be recycled or marketed as a refuse derived fuel (RDF), which is burned for

energy recovery. But the main purpose of size segregation in a composting plant is to



                                             35
Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




facilitate further separation. It is much easier for either people or machines to further

separate materials of a similar size, as small items are not buried under large ones. Size

fractionation also takes advantage of the size distribution properties of different waste

components, generating streams in which certain recyclables or contaminants are

concentrated.


Figure 1. Trommel




4:4 Manual Separation: With materials segregated to a relatively uniform size, it

becomes much more practical to hand separate recyclables and contaminants as they

move along conveyor lines. As manual separation of MSW can be an unpleasant task,

worker comfort and safety are very important. Ergonomic design can help workers

function at their best, and issues such as conveyor speed, reach, placement of containers,

flooring material, lighting, ventilation and dust control should all be considered.




                                             36
Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




Conveyors and other materials handling machinery are critical to the operation of a plant.

While this equipment may seem mundane, proper materials handling can minimize

downtime and cleanup, and contribute to the overall efficiency of the facility.


4:5 Magnetic Separation: As materials are conveyed from one separation system to

another, the conveyors can utilize magnetic belts, rollers or overhead magnets to separate

the ferrous metals from the rest of the stream. Magnetic separation efficiency is sensitive

to the depth of waste, as small ferrous items will not stick to the magnet if they are buried

in non-ferrous materials, while larger ferrous items can drag non-ferrous items like paper

and plastic along. Air classification to remove the light paper and plastic fractions prior to

magnetic separation minimizes the contaminants in the scrap ferrous. Pre-shredding and

screening can also enhance ferrous recovery. Because magnetic separation is relatively

inexpensive, it can sometimes be found at several locations in the composting facility. A

minimum of two stages of magnetic separation are usually needed to achieve efficient

ferrous recovery. Magnetic separation is effective with iron and most steel, but does not

separate aluminum, copper, and other non-ferrous metals.


4:5 Eddy current separation systems have been developed to separate non-ferrous

metals. This technology works by exerting repulsive forces on electrically conductive

materials. These systems should be located after magnetic separation to minimize

contamination by ferrous materials. Aluminum is the primary metal recovered from

MSW, although some copper and brass will also be separated. Cans literally jump off the




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Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




conveyor into a waiting bin (Figure 2). Eddy separators, while they do not achieve perfect

removal of aluminum, do produce a relatively marketable aluminum by-product.




Figure 2. Eddy Current Separator




Air classification is an additional separation technology used in some MSW composting

facilities, and is commonly used to generate a marketable RDF. The heart of an air

classification system is an air column or "throat", into which the waste stream is fed at a

gradual rate. The air column is usually oriented vertically. A large blower sucks air up

through the throat, carrying light materials such as paper and plastic, which then enter a

cyclone separator where they loose velocity and drop out of the air stream. Heavier

materials, such as metal, glass, and food waste, fall directly out of the throat (Figure 3).

These two streams tend to be different sizes as well as densities, facilitating further



                                              38
Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




separation. Glass and metal can be sorted out of the heavy fraction by systems such as the

wet separator described below.




Figure 3. Air Classification




Wet separation technologies, while taking advantage of the same sorts of density

differences as air classifiers, use water rather than air as the floating medium. These units

are usually used to separate particles of glass, sand, and other heavy particles from

organic materials prior to composting. A hammermill or other size reducer is needed

prior to wet separation to minimize the potential for air pockets in the heavy fraction.

After entrainment in a circulating water stream, the heavy fraction drops into a sloped

(and sometimes vibrating) tank where it moves to a removal zone. The less dense organic




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Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




matter floats and is removed from the recirculating water using screening systems similar

to those employed by wastewater treatment facilities. Wet separation is particularly

effective at removing glass fragments and other sharp objects, which tend to be heavier

than organic materials.


Ballistic separation takes advantage of both density and elasticity differences to separate

inert and organic constituents. This method can be used in either initial processing or in

the refinement of the final compost product. Compost is dropped on a rotating drum or

spinning cone, and the resulting trajectory differences bounce glass, metal and stones

away from the compost.




5 C. Size Reduction and Homogenization


Even after the removal of much of the non-compostable material, municipal solid waste

needs further processing before composting. Large pieces of paper, cardboard, food and

yard waste will break down slowly if not reduced to a smaller size. Reducing particle size

increases surface area, enhancing composting rates because the optimum conditions for

decomposition occur on the surfaces of organic materials. However, reducing particle

size also reduces the pore size, limiting the movement of oxygen required for

composting. Thus for any composting system and material there is an optimum range of

particle sizes, and for MSW this is usually between 0.5 and two inch diameters (1.2 - 5

cm).



                                             40
Waste Management ,                    Domestic &                         Aisling Donegan
Environmental Science,                Municipal                          Ken M c Namara
I. T. Sligo.                          Composting                         Marie Mortell




Size reduction and mixing processes usually occur after initial separation and removal of

non-compostables. However, some separation processes, including wet separation, air

classification and magnetic separation can achieve greater levels of removal after size

reduction. Proper sequencing of these materials preparation processes can have a

significant impact on system performance.


There are three major types of size reducing devices available for municipal waste

processing: 1. hammermills, 2.shear shredders, and 3. rotating drums.




5: 1. Hammermills consist of rotating sets of swinging steel hammers through which the

waste is fed (Figure 4). Tub grinders use a rotating tub to feed a horizontal hammermill,

and is a common item at large yard waste composting facilities. Hammermills are energy

and maintenance intensive, with hammers requiring frequent resurfacing or replacement.

In MSW processing applications they must be housed in specially designed chambers as

propane tanks and other flammable materials can cause serious explosions.


                                Figure 4. Hammermill




                                            41
Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




5:2. Shear shredders usually consist of a pair of counter-rotating knives or hooks (each

of which is several centimeters thick), which rotate at a slow speed with high torque. The

shearing action tears or cuts most materials, although thin flexible items like film plastic

may slip through the gaps between the knives. This tearing may help open up the internal

structure of the particles, enhancing opportunities for decomposition. Shear shredders

consume less energy and are less destructive than hammermills, but still can break apart

contaminants and make subsequent recovery difficult.


5: 3. Rotating drums mix materials by tumbling them in a rotating cylinder (Figure 5).

Internal flights or vanes lift material up the sides of the rotating drum where they fall to

the base by gravity. Drums may be set on a slight incline from horizontal, although this is

not always necessary to carry the material through the drum from the feed end to the

outlet. While some of these drums can also function as biological reactors, typical

residence times of less than 36 hours allow only the beginnings of microbial

decomposition. To the extent that decomposition does occur in a rotating drum, it is

important that aeration is adequate. Excessive anaerobic activity can lead to low pH

(<5.0), which may result in ammonia volatilization, corrosion of the drum, and leaching

of metal contaminants.




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Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




Figure 5. Rotating Drum




Drums take advantage of gravity to tumble, mix, and homogenize the wastes. Dense,

abrasive items such as glass or metal will pulp the softer materials, resulting in

considerable size reduction of paper and other cellulosic materials. Rotating drums are

the least destructive size reduction technology, and many solid contaminants can more

readily be separated after passing through the drum..


The last stage of processing before the active composting stage is usually the

incorporation of water. If it includes a large paper fraction (with a high carbon to nitrogen

ratio), MSW also benefits from mixing with nitrogen-rich materials such as sewage

sludge. Size reduction and blending homogenizes the compostable materials, achieving

greater uniformity of moisture and nutrients. Thorough mixing is important for rapid

decomposition, and a variety of devices are available. The drum-type wet pulverizer

described above commonly serve as a mixing and blending device. Some mixers have

been adapted from agricultural feed mixer designs, and may contain counter-rotating




                                             43
Waste Management ,                    Domestic &                           Aisling Donegan
Environmental Science,                Municipal                            Ken M c Namara
I. T. Sligo.                          Composting                           Marie Mortell




augers or a reel. Pug mills can also be used, which blend by means of slowly counter-

rotating hammers.


Note


Separation, size reduction and mixing/homogenization are all prerequisites to the

biological process of composting. The individual physical processes described above

must be selected and linked together with biological processing technology to form a

complete composting system. In evaluating a system design, several criteria stand out as

particularly important to these physical processing steps, including cost (capital,

operations and maintenance), market specifications for compost and recyclable by-

products, and the flexibility of the system to respond to a changing MSW feedstock.




                                             44
Waste Management ,                    Domestic &                         Aisling Donegan
Environmental Science,                Municipal                          Ken M c Namara
I. T. Sligo.                          Composting                         Marie Mortell




Section: 3


1:Compost Case Studies:


1:1 Climate of Areas:

The two composting schemes chosen for this case study are in the west of Ireland. Tralee

and Limerick both experience a moderate climate with an average rainfall of 1,000 to

1,500mm per year and an average temperature of 5ºC in January and 16ºC in July. This

climate is present in most of the first world and so any conclusions from the study can be

applied to a much larger international as well as national population. However other

countries such as Canada have developed proven methods of large scale composting

scheme.




In the western world each person produces 12 tonnes of rubbish per year and there is

constant pressure to reduce reuse and recycle the production of waste. Composting is one

of the most useful methods of waste reuse.




                                             45
Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




1:2 The Main Aims of the Composting Scheme:


The initial motivation for this scheme came from the 1999 European Directive on Waste

which requires all EU members to reduce their waste production. To implement this

directive the Irish government published a national waste-management policy document

which sets a target of minimum reduction of 65% of biodegradable waste reaching

landfill over the next fifteen years. In County Kerry as in most of Ireland biodegradable

waste accounts for 30% of all household waste. There is also an economic motive for the

scheme. The high engineering costs of acceptable quality landfills which take account of

ground, surface waters, odor, air emissions and pest control as well as leachate

production makes any scheme that prolongs the life of such a landfill site viable.



1:3 The Tralee Area Composting Scheme:


Kerry County Council was one of the first in Ireland to actively reduce the county‟s

waste production by Composting. The Tralee Composting Scheme was launched March

29th 1999 and the first bin collection date was April 12th 1999. A figure of 1,766

householders in the Manor, Oakpark and Caherslee areas in Tralee participated and were

given a second brown wheelie bin for their organic waste only. The County Council also

provided a small kitchen caddy, an information pack and stickers for householders bin

showing what can and cannot go into the bin and a calendar showing the compost bin

collection weeks.




                                            46
Waste Management ,                    Domestic &                         Aisling Donegan
Environmental Science,                Municipal                          Ken M c Namara
I. T. Sligo.                          Composting                         Marie Mortell




3:1 Communication with householders:



Resident associations of the Manor, Oakpark and Caherslee areas in Tralee were invited

to a presentation on the scheme at Kerry County Councils headquarters in advance of the

launch. They were informed of what to expect and were asked for their suggestions. Two

weeks before the bins were delivered, the participants were provided with an information

leaflet introducing them to the scheme and informing them of what to expect and why it

was necessary to begin this scheme. Participants were also asked to complete a short

questionnaire requesting details such as name and address and their comments on the

scheme. Also included in this introductory information pack was an invitation to the

launch of the composting scheme in Siamsa Tire on March 29th. The launch involved a

display of all Environmental Services activities with particular emphasis on the

composting Scheme. Those attending were given a presentation on the composting

scheme. The evening was very successful with over 200 people attending. The

participants an information booklet which details everything from how the bin collection

system would change, to the composting process itself and why this program was

introduced. For those who had any further queries a freephone number was set up to

allow them a free and direct access to the environment section of Kerry County council.

Follow up contact with the public is important and was provided in the form of a survey

which currently being conducted of the participants and at present approximately 350

householders being visited by staff from the Environmental Services Section. The

objective of the survey is to determine how the participants found the service and other



                                            47
Waste Management ,                    Domestic &                         Aisling Donegan
Environmental Science,                Municipal                          Ken M c Namara
I. T. Sligo.                          Composting                         Marie Mortell




details that indicate the performance to date and how the public perceive the operation

and necessity of the project. The survey has so far revealed a very positive reaction from

the participants to the composting scheme. To keep residents informed of progress and of

any changes in the scheme a number of newsletters have been distributed. The

„ECOSENSE‟ keeping you informed newsletter, of which to date there have been four,

has been an important line of communication between the participants and the

Environmental Services Section. A database has been established to record the results of

the survey, the participants whose bins have been rejected due to contamination and the

number of their bin.




3:2 The Collection:


The brown wheelie bins provided are designed to minimize odours from the

food waste. These bins have a false bottom and ventilation holes at the top and

bottom allowing air to move freely through the contents of the bin. The county

Council employed a consultancy firm Ramboll for the scheme. It was advised in the first

week only to accept vegetable waste once the nature of the organic waste was established

it was found that newspaper and garden waste could also be collected. The

brown wheelie bins are collected every second week along with the regular

weekly black wheelie bin. It was planned for the black and brown bins to be

collected in alternate weeks but the need to keep public support required a




                                            48
Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




weekly black bin collection. The organic waste was brought to the composting platform

at the north Kerry Landfill.




3:3 Composting Platform and Process at North Kerry Landfill:


Before each collection run a load of wood chips is added to the truck. The woodchips are

necessary for composting to provide carbon and a texture to the waste that aids free

movement of air and moisture through the material. The truck used for collection is a

Roto- press. This type of collection vehicle is ideally suited to organic waste collection as

it mixes the wood chips and organic waste thoroughly together. On arrival at the

composting platform at the North Kerry Landfill, the organic waste is shredded and

stacked for composting. The waste is then covered with „Toptext‟ which allows air into

the compost heap and vapor out but keeping the rain from the organic material as an

excess of rainwater upsets the composting process.




There are five piles of organic material composting and two piles for maturing. Every

two weeks each composting pile is mixed and moved up in the composting platform.

After 10 weeks the compost is sieved and then added to the first maturing pile. After 38



                                             49
Waste Management ,                      Domestic &                           Aisling Donegan
Environmental Science,                  Municipal                            Ken M c Namara
I. T. Sligo.                            Composting                           Marie Mortell




weeks the compost is ready for use. When the compost is mature it is available to the

public free of charge. It will also be used for council landscaping activities. The average

tonnage collected is 18 tonnes per fortnight with 60% participation rate by the public

participating.




3:4 Guidelines for Composting as Provided by Kerry County Council Information Pack:




         WHAT’S IN from the House               WHAT’S IN from the Garden
         Fruit and vegetable scraps             Leaves
         Baked goods including bread            Grass cuttings
         Rice and other grains                  Weeds
         Pasta Paper towels and serviettes      Plants and plant cutting (non
         Tea leaves and bags                    diseased) Twigs etc (break into
         Coffee grounds and filters             smaller pieces).
         Egg shells (important source of
         calcium for the compost)
         Shredded paper (newspaper, cereal
         boxes, paper packaging etc.).




         WHAT’S OUT from the House              WHAT’S OUT from the Garden
         All meat including chicken             Weeds that have gone to seed
         Fish and shell fish                    Diseased plants
         Bones                                  Large branches and roots
         Fat, grease, oils                      Dog and cat waste
         All dairy products including cheese    Plants previously sprayed with non-
         Vacuum cleaner bags                    degradable pesticides.
         Textiles
         Glossy print material




                                               50
Waste Management ,                         Domestic &                       Aisling Donegan
Environmental Science,                     Municipal                        Ken M c Namara
I. T. Sligo.                               Composting                       Marie Mortell




3:5 Finances of Tralee Area Composting Scheme:




The financial support for the scheme was provided by a grant from the operational

program for environmental services under the Irish Structural Funds program 1994-1999.

On a broad scale the costs are as shown below.

                  Table: Cost Details


                               Set-up Costs             €193,000/tonne

                               Operating Costs          €209/tonne

                               Publicity Costs          €32/tonne

                               Avoided Disposal Costs   €18.3/tonne




Any financial shortfall will be reduced by charging for the compost product for which

there is an increasing market for or by increasing the gate fee for the landfill. There is

also the possibility of increasing the tonnage of raw material which will increase its

profitability. The Tralee scheme has a capacity for 1,000 tonnes per annum. The potential

to make profit from this enterprise is there for the longterm as the compost becomes a

viable product.




                                                 51
Waste Management ,                   Domestic &                          Aisling Donegan
Environmental Science,               Municipal                           Ken M c Namara
I. T. Sligo.                         Composting                          Marie Mortell




4: Research into Compost as a Product:


The Composting Association of Ireland cré has supported Kerry County Council in their

composting scheme. The association provided for research into the nitrogen release from

composted green waste by Bord na Móna horticulture Ltd. and Teagasc Kinsealy. The

research is not yet complete but early indications show no adverse effects to plants grown

in compost. The high potassium levels accelerate early plant growth but later

development may be limited by nitrogen content. Research was also carried out on a 20-

50% mix of composted green waste and peat compost.




The research is ongoing but with interest from companies such as Bord na Móna with its

very large horticulture export market compost production could become a very profitable

industry. Kerry County Council uses the compost in landscaping projects such as the

„Tralee Urban District Council Landscaping‟ and by park department.




                                           52
Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




5: Limerick Composting Scheme:

Limerick Corporation implemented a similar scheme to the Tralee Area Composting

Scheme. Limerick put the project up for tender in 1996 but the first bin collection did not

take place until 1999. The Limerick scheme was within a higher density area of Limerick

City and collected from 2,800 households more one and a half times that of the Tralee

scheme. The collections were also collected every second week. There were problems

with waste sticking to the bottom of the bin and developing into a mal odour source. To

deal with this biodegradable plastic bags were provided and proved to be successful. The

plastic takes longer to decompose and are removed by sieving the compost after three

months. Unlike the Tralee scheme the public were informed through press releases,

leaflets and radio announcements only and not through an open meeting. As a result

contamination due to poor segregation occurred. These contaminations were removed

before loading into the shredder.


5:1 The Composting Process at Limerick County Council Landfill:

The compost at Limerick landfill was not covered as at Tralee the compost was

developed in windrows using a loader. The loader was equipped with a grab on the front

bucket to ease of handling tree cuttings and a telescopic extension for placing material

into the shredder. The windrows were turned once the temperature reached 60ºC to keep

decomposition rate and temperature constant throughout the windrow. After three months

the compost is removed to Limerick Corporation Parks Department depot where it

matures for a further eight to ten weeks. This compost was used for tree planting in the

parks.


                                            53
Waste Management ,                                 Domestic &                     Aisling Donegan
Environmental Science,                             Municipal                      Ken M c Namara
I. T. Sligo.                                       Composting                     Marie Mortell




Section: 5

1: The Market For Compost:

Biotec is a company which manufactures equipment for large scale compost production.

The company has identified markets for compost as shown in the table below with the

potential volume and price range per tonnage shown.



                                                                  POTENTIAL
   MARKET SEGMENT                                                             PRICE RANGE/TON
                                                                  SIZE/YEAR


   Retail markets (Home, landscaping, lawn care and                  4.4          $15-150
   maintenance, and gardening)


   Nurseries (Seeding starters, partial peat moss replacement)       0.5           $10-60


   Sports turf markets (Golf courses and athletic fields)            0.5           $16-40


   Industrial and commercial landscaping                             1.4           $8-40


   Topsoil blending                                                  0.8           $6-20


   Field agriculture including intensive vegetable production        445           $4-15


   Sod productions, roadside and reclamation (Strip-mining, re-      13.0          $4-12
   vegetation and restoration, highway and road construction


   Public property (Parks, recreational areas)                       1.0           $4-12


   Silviculture (The care and cultivation of forest trees)           55             $0-5




                                                             54
Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




1:1Organic Agriculture:


Organic farming is the most obvious market for composed waste as few other fertilizers

are available to this industry. Organic growers keep land fertile by crop rotation and the

use of organic fertilizer. While seaweed and manure are options to this market both fall

short of providing all that is required for maximum fertility. There are problems with

runoff from manure and the possibility of freshwater contamination. The consumer may

not accept food grown in animal waste and there are strict laws on when manure

application can take place. Compost provides all the nutrients required for plant growth

and in a slow release form easily available to plants and over a long period of time.

Composted waste also has other advantages in its texture which improves the air and

water movement in the soil. The organic industry is growing in this country as a result of

consumer pressure and the negative publicity that intensive farming has received from

BSE and „Foot and Mouth‟ disease.

1:2 Rural Environment Protection Scheme:


The Rural Environment Protection Scheme (REPS) which was established by the

department of agriculture places fertilizer restrictions on participants. There are limits

placed on the amount of inorganic fertilizer applied to land and organic fertilizer has to

be used. The main advantage of compost in this area is weed control. Animal manure

often contains seeds of plants eaten by the animal and in many cases these are pest

species such as Dock leafs. To control these plants herbicides are often used. Compost

also prevents certain diseases to develop reducing the amount of pesticide required.


                                             55
Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




Herbicide and pesticide application are also restricted within this scheme. This shows

composted waste to be a useful product to this industry and with government backing

there is an opening in this market.

1:3 Large Scale Intensive Agriculture:


While these too sections of agriculture are potential markets for composted waste large

scale intensive agriculture is a much bigger market. Research into the viability of this

market in this country is slow but other countries such as Canada have been researching

this market for some time. Canada is often used as an example in waste management as

the country reduced its landfill waste by 70% through recycling and composting without

resorting to incineration. The Composting Council of Canada has carried out detailed

research into compost use in agriculture.


1:3:1 Canadian Study on Benefits of Compost in Potatoes Production:


Composted waste may be an efficient way to improve the nutrient status and biochemical

and physical properties of coarse-textured soils devoted to intensive potato production. A

study was initiated to assess the impact of addition of compost and pig manure, used

alone or in combination with inorganic fertilizers, on soil quality and potato (Solanurn

Tuberosum L. Hilite Russet) yields on a Bevin sandy loam (Orthic Humo-Ferric Podzol)

located in St-Ubalde, Québec, Canada. The compost was applied in spring on a wet basis,

and was supplemented or not. The compost was incorporated in the top 10 cm of soil.

The inorganic fertilizers were fractionated at planting and hilling.




                                             56
Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




The addition of compost produced the highest marketable tuber yields independently of

the inorganic fertilizer supplement. Compost reduced the degree of potato scab coverage

on the tubers. Compost addition significantly influenced the soil Kcl extractable nitrogen

days after planting and the extractable P and K contents at potato harvest. Enzyme

activities were maximum early in the season. Compost addition resulted in the highest

enzymatic activity, Nitrobacter sp. counts and C-CO2 evolution. Compost addition also

influenced the synthesis of particular microbial phospholipid patterns. Addition of

inorganic fertilizers to compost resulted in higher enzyme activity than compost alone but

had little effect on C mineralization or microbial biomass C. It was found that addition of

120 Mg compost ha-1 was excessive. Compost, when added at a reasonable rate (40 Mg

ha-1), is a good way to increase the inorganic fertilizer efficiency by increasing potato

tuber yields and soil quality.


Soils used for potato production in Eastern Canada are normally of coarse texture and are

subject to degradation when crop rotations are not frequently used. Loss of organic matter

is the main form of degradation which results in loss of aggregate stability and increased

water or wind erosion. Loss of organic matter and erosion result in diminished water

retention capacity, resistance to compaction and cation exchange capacity (Saini and

Grant 1980). The nitrogen mineralization potential from soil humus will also be

decreased since it is closely related to the soil organic matter content (Simard and

N'dayegamiye 1993). All of this may result in yield losses and increased fertilizer and

irrigation cost.




                                             57
Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




1:3:2 Overall Findings of Study:


Rotations involving crops with large amounts of residues are certainly a good alternative

in organic matter management. Large inputs of exogenous organic materials would be

preferable if a rapid increase in organic matter content is targeted. There is over one

million tonnes of organic waste produced every year. Although excellent results in term

of improvement of soil quality and crop yields have been obtained in crop production

with the raw sludge materials these materials have the disadvantages of generating bad

odors and potential biohazard, composting may be the solution. Also, land spreading of

the raw material is only possible in a part of the year. Using of composted materials may

have a longer impact on organic matter content than raw materials on these coarse

textured soils. Composted waste was previously shown to result in improved soil quality,

nutrient efficiencies and crops yields in winter cabbage and dry bean production.




                                             58
Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




1:4 Landscaping:


Domestic gardening is an industry which has grown extensively in Ireland over the past

five years. There are garden centers and nurseries in every part of the country. The

interest of companies such as Bord na Móna horticulture Ltd. in waste composting

projects indicates a real potential in this market. As yet landscaping is an undeveloped

market in this country. This is related to the small scale of composted waste production.

California in America has been producing composted waste on a large scale for over ten

years and has marketed the product well.

Compost Marketing in America:

The California Integrated Waste Management Board conducts compost and mulch

outreach activities throughout the state. These activities include exhibiting at agricultural

and landscaping industry show and workshops. They also include the sponsorship of

demonstration projects and partnerships to demonstrate the effectiveness and benefits of

compost and mulch.




                                             59
Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




1:4:1 The establishment of Xeriscaping:




California State is limited in by the availability of water. Irrigation of gardens and public

landscaped areas is a strain on this resource. California has a dry and warm climate with

high evaporation and irrigation is a large cost for any landscape. It from this background

that xeriscaping was developed as a market developed for composted waste.

Xeriscaping is the practice of landscaping which requires the least resource input and

produces the least waste in the form of plant trimmings and leaves. The plants used are

generally slow growing with a low consumption of nutrients. Few trees are planted and

plants that are drought tolerant are used.

Xeriscaping is a market for compost as its high moisture holding capacity reduces the

need for irrigation especially if covered with mulch to reduce evaporation. Compost

reduces the cost of fertilizers as it provides slow release nutrients which are required by

plants used in xeriscaping. Compost also increases the activity of Nitrobacter sp in the

soil which increases the nitrogen available to the plants without the addition of fertilizers.

Compost use is known to reduce the risk of many plant diseases reducing the use of

pesticides and further reducing the costs of landscaping.



                                             60
Waste Management ,                      Domestic &                            Aisling Donegan
Environmental Science,                  Municipal                             Ken M c Namara
I. T. Sligo.                            Composting                            Marie Mortell




The texture of compost is particularly encouraging for the growth of root systems. The

high survival rate of young plants in compost is of great advantage as most landscaping

projects experience their greatest loss of plants during the root development stage.



1:5 Compost Pellet

An Australian municipal waste compost trial has developed a niche export market to the

Middle East. A South Australian stock feed manufacturer have exported pellets made out

of cereal straw and composted vegetable waste. Similar composts applied to agricultural

land in Australia have increased horticultural crop yields by as much as five times and

reduced water use by 25 percent. This again shows the value of compost in a water

restricted climate while this is not an issue in Ireland it does give export potential to the

market.

1:6 Potential for Use of Compost as a Primary Erosion Control Material:


1:6:1 Causes of Erosion:



A primary limiting factor in the revegetation of degraded soils is the loss of the erosion-

resistant plant litter layer and soil nutrients during and after disturbance of the soil

resource (Bradshaw and Chadwick, 1980). Loss of plant litter and mulch material results

from erosion or physical removal during construction. The first soil horizons to be

removed are typically deposited at the bottom during fill slope construction. The

remaining soil surface is exposed and the nutrients in the previous topsoil horizons are

buried beyond the reach of plant roots. Revegetation of drastically disturbed sites often


                                              61
Waste Management ,                      Domestic &                         Aisling Donegan
Environmental Science,                  Municipal                          Ken M c Namara
I. T. Sligo.                            Composting                         Marie Mortell




requires protection of the bare soil surface from erosion. The bare soil particles are

vulnerable to raindrop impact, which detaches or close-packs the fine particles. When the

surface of the soil seals and becomes resistant to percolation of precipitation, overland

flow is increased, resulting in sheet and rill erosion.


1:6:2 The Use of Compost:



Composts are shown to reduce these types of erosion. Loss of topsoil during disturbance

also reduces the ability of the vegetative community to regrow because the soil‟s nutrient

reserves are depleted. Inadequate pools of plant-available nitrogen (N) can restrict

growth on the site for extended periods of time because nitrogen is needed in relatively

large amounts for regeneration of the shoots, roots, litter layers, and for microbial

biomass. Because soluble fertilizer nitrogen is easily depleted from the soil by leaching

or plant uptake, the regeneration of the plant community is expected to be improved by

the application of larger, stabilized pools of nitrogen that mimic the organic matter lost

during topsoil removal. Recent work in the Tahoe Basin suggests that these long-term,

slowly available pools are better correlated with the soil‟s ability to support plant growth,

than are soluble nitrogen levels. While many organic or chemically based soil

amendments can provide nitrogen for early phases of plant establishment, few provide

nitrogen for a long-term, multi-year period of community development. Composted green

material on the other hand, may provide this type of nitrogen release because the

composting process converts readily degradable organic materials into stabilized,




                                              62
Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




partially humified materials. Compost is used in orchards and roadsides to prevent

erosion in many parts of America.




7: Market Development in Ireland:




The market for compost in Ireland has not been developed in any way. This is due to the

low production of the product but from observation of the American, Australian and

Canadian markets there is great potential for development. Compost is initially a solution

to a waste management problem but a shift in perception of compost, as waste to quality

product will change the future of composting. Not only are there massive savings to be

gained by the government through reductions in landfill costs there is also a raw material

source that is virtually free. Most production costs place raw material as one of the

highest expenses and with compost it is possible for individuals to pay for the collection

of the raw material. It is important that a diverse market is developed now to avoid

flooding any single market later.




                                            63
Waste Management ,                     Domestic &                            Aisling Donegan
Environmental Science,                 Municipal                             Ken M c Namara
I. T. Sligo.                           Composting                            Marie Mortell




Section: 6 Vermiculture:




                                                                              1881


Segmented worms make up the Phylum Annelida. The phylum includes earthworms and

their relatives, leeches, and a large number of mostly marine worms known as

polychaetes. Various species of polychaete are known as lugworms, clam worms,

bristleworms and fire worms.

Earthworms are one of the most important groups of organisms that live in the soil, since

as they burrow their way through the soil they also help to improve the soil structure and

the soil fertility. They create holes which help with root growth and allow air, water and

fertilisers to enter the soil. Their activities can also reduce erosion, increase plant growth

and help to provide food for important micro-organisms.




                                              64
Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




Their main requirement is a good supply of organic matter in the soil which acts as their

main food source. Some species prefer to feed on dead plant roots, dead leaves, dead

herbage or animal dung which gets partially broken down as it passes through their guts.

Other species preferentially graze upon the soil particles themselves, while still others are

said to feed upon fungi and small microorganisms present in the soil.


After the soil has passed through an earthworm's gut some of the soil nutrients become

more available to plants and the structure of the soil also becomes more stable. Some

earthworms are more suited to living in the soil while others are prefer to live in compost.




                                             65
Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




Soil dwelling earthworms will not survive in compost and likewise compost dwelling

worms will usually not survive for very long in soil. In general, earthworms will be

encouraged to survive and multiply where there is a plentiful food supply, sufficient (but

not too much) moisture and where the temperatures do not get either very hot or very

cold. Addition of lime has been shown to encourage earthworms, as most of them prefer

more alkaline conditions.


For soil dwelling earthworms, soil management practices which increase the amount of

organic matter in the soil, usually encourage earthworm activity due to the increase in the

amount of food available to the earthworms. Consequently, as the addition of mulches,

farmyard manure or crop residues to the soil increases the amount of organic matter in




                                            66
Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




the soil, such practices also cause earthworm numbers to increase. Similarly, where the

addition of fertilisers to soil results in an increase in plant production, a simultaneous

increase in earthworm numbers has been found, since the fertiliser indirectly increases

the soil organic matter, the food source for the earthworms, by increasing the plant

production.


The night crawler, Lumbricus terrestis, is the largest and likes soils that are heavy in

organic matter like lawns and meadows. When the soil becomes poorer, the common

field worm, Allolobophora caliginosa, and all its variants become more common. This is

a smaller worm with a pronounced raised band, called the clitellum, about 1/4 of the way

down its body. Both these worms are quite active and feed by bringing down organic

debris in to their borrows from the surface, their holes aerate the soil and their execrate,

called casts, improves the friability of the soil. The last common worm is called the green

worm, Allolobophora chlorotica, which is a stout greenish colored worm that is quite

dormant and does little to improve the soil.




                                               67
Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




From top to bottom: Night crawler, Field Worm, manure worm, and green worm.

The very active red wriggler, or manure worm, can be found in compost piles. The true

red wiggler, Eisenia foetida, has alternating bands of yellow and maroon down the length

of its body. A similar worm, Lumbricus rubellus, is a deep maroon color without the

yellow bands.These manure worms need extremely high organic matter, such as manure

or rich kitchen scraps to survive.


Incorporating modern requirements for the processing of municipal sewage and the

associated sludges with the ability of earthworms to stabilize organic matter has resulted

in the application of vermiculture to this disposal problem and has created a relatively

new industry. As with all utilization of new technologies designed to deal with ever

growing environmental difficulties, the technology should be based on similar values as

follows;


Chapter 34 of the United Nations Agenda 21 document explains, Environmentally Sound

Technologies are not just "individual technologies, but total systems which include know-

how, procedures, goods and services, and equipment as well as organizational and

managerial procedures".


"Consequently, when considering technology transfer, one needs to adopt an approach

which incorporates both the human resource and local capacity building aspects of

technology choices....and to recognize the need to ensure that Environmentally Sound

Technologies are compatible with nationally determined socio-economic, cultural and

environmental priorities and development goals."


                                            68
Waste Management ,                      Domestic &                        Aisling Donegan
Environmental Science,                  Municipal                         Ken M c Namara
I. T. Sligo.                            Composting                        Marie Mortell




The basic scientific definition of Vermiculture is: "the process by which organic material

is fed to a variety of worm species with the purpose of converting the digested organic

material into increased biological mass and vermicast". Vermiculture is in fact a highly

complex mechanical, chemical and biological transformation of waste material into a

potent and proven soil conditioner.




Sites are odour free, as is the end product. The processes create no leachate problems

with ecologies, river systems or underground water tables. Systems are designed to allow

material to be processed on site (reducing the need for cartage and hence limiting

transportation pollution). The process reduces odorous green house gases generated,

(compared with alternate methods of processing such as composting, lime stabilisation or

incineration).




A wide variety of waste can be processed with vemiculture. These include digested,

undigested, and low age extended aeration biosolids. The system can handle total solid

concentrations ranging from as low 12%, and can also handle other organic wastes

(mixed in particular proportions with the biosolid material). The design of the system

allows customization of needs and also allows increases in plant capacity.


It is   widely known that worms have the ability to convert a wide range of organic matter

to vermicast. Many worm species are amongst natures most efficient waste purifiers.




                                              69
Waste Management ,                      Domestic &                        Aisling Donegan
Environmental Science,                  Municipal                         Ken M c Namara
I. T. Sligo.                            Composting                        Marie Mortell




Since there has been life form on earth and organic waste, worms have been a crucial part

of the ecological biocycle.




The body of published knowledge on the conversion by Vermiculture of organic sludge is

quite small although several laboratory scale experiments have been carried out and some

small scale operations do exist.




With a never ending source of waste material and having found answers to many of the

public health, community based, and political issues confronting the waste industry,


vermiculture has shown effective sustainable organic waste management.


Vermiculture yields a pathogen free Grade A stabilised environmental agency approved

soil conditioner - an end product with such soil conditioning and restoration properties

that it is amazing agriculturalists on a international basis.




                                              70
Waste Management ,       Domestic &   Aisling Donegan
Environmental Science,   Municipal    Ken M c Namara
I. T. Sligo.             Composting   Marie Mortell




2:So how is it done?




                              71
Waste Management ,                    Domestic &                        Aisling Donegan
Environmental Science,                Municipal                         Ken M c Namara
I. T. Sligo.                          Composting                        Marie Mortell




2:1 The System Elements


Vermiculture systems comprise three core elements - the beds, the equipment and

processes for mixing and feeding of waste and the equipment for harvesting of end

product.


2:1:1 The Beds


The core of the technology is an open top, steel cage in which the worms are housed. The

beds in the systems are 3.6 meters wide and 70 meters long, though length is variable.


Mixing and feeding equipment and processes


Preparing the waste, to make it worm accessible has required the development of mix

formulae, mixing systems and mechanisms for spreading the material onto the surface of

the bed. Waste is fed to the surface of the bed on a daily basis. The worms consume the

waste in the top region producing the soil conditioner.


2:1:2 Waste Types


Organic waste can be divided into seven categories:


   1. Human Sewage

   2. Animal Manure

   3. Food Processing Waste

   4. Food Distribution (markets)



                                            72
Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




   5. Domestic Wet Waste (household garbage)

   6. Vegetation from parks and gardens

   7. Paper & Cardboard


This system can be used to process all categories of organic waste provided they can be

blended into a "worm acceptable" mix. Variability in input quality, or contamination with

glass, plastic and inorganic material, reduces the attractiveness of many potential waste

streams. Human sewage and animal manure are prime wastes for vermiculture. Paper and

vegetation waste streams can only be incorporated as a blend with the primary nitrogen

rich "food sources", such as sewage or manures. Key to suitability are the carbon nitrogen

ratio, pH and oxygen demand of the final blend. Bench tests on all new waste streams can

be carried out to develop the appropriate formula .




                                            73
Waste Management ,                    Domestic &                           Aisling Donegan
Environmental Science,                Municipal                            Ken M c Namara
I. T. Sligo.                          Composting                           Marie Mortell




3: Wastes Managed


      PAPER

      SEWAGE

      CARDBOARD

      FOOD WASTE

      GREEN WASTE

      ANIMAL MANURE


The primary materials utilised in vermiculture systems are human sewage and animal

manures.


Given that worms are the driving biological consumptive force behind vermiculture

technologies, introduction of other organic waste to the processing plants has included

fruit & vegetable streams, feedlot waste, dairy manures, pulp and paper.


3:1 Odour Management


Management of gases is critical in maintaining the environment for the worms as most of

the gases associated with odour are toxic to worms. Traditional vermiculture has required

the pre-composting of ageing materials to immobilise, or drive off the volatiles before

material could be fed to the worms.




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Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




Recent research, processes and formulae for mixing and blending have been developed

whereby the volatile materials associated with odour such as ammonia and sulphides are

bound. Even undigested municipal sludge can be rendered relatively odourless.


In Australia at Redland, Queensland one particular site contains 2,500 tonnes of work in

progress in the beds (partly stabilised biosolids), 80 tonne of fresh sludge is added daily

and approximately 4,000 tonnes of cast are stored awaiting despatch. Local residents

have noted that the vermiculture facility was not a source of odour.


The lack of odour allows the vermiculture system to be installed adjacent to any sewage

plant. On site processing eliminates the cost of transport and removes the impact of

transporting large quantities of sludge to reprocessing facilities.


3:2 Contaminants Management


Inconclusive evidence has suggested that vermiculture will reduce heavy metals through

the accumulation of the metals in the worm biomass. But research on this area of a new

technological application is unproven and ongoing. Reductions of 10 to 20% have been

identified, but not uniformly across all metals.


3:2:1 The impact of heavy metals is reduced by two mechanisms.


Firstly through dilution. The relatively clean additives provide a 20 to 30% reduction in

concentration. Secondly, the end product is used at relatively low application rates

compared with traditional biosolids and compost application rates.



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Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




The maximum recommended application rate is 5 tonnes per hectare compared with over

40 tons per hectare for biosolids. This reduces the potential soil metals loading by over

80%.


Models for determining soil loading levels of different metals with varying concentration

levels and application rates have been developed and are being refined as the knowledge

base grows.


4: Volume


The technology can be scaled to any size. The modular nature of the bed design can

accommodate capacities from 1 tonne to thousands of tonne per week. As with any

technology, vermiculture benefits from economies of scale. Capital costs and operations

costs can be sensitive to volume. The volume to be processed will also influence the

systems design and supporting equipment to be supplied.


4:1 Site Requirements (Civil & Structural)


       The area requires Bitumen sealing and graded (less than 3% fall to a central

       sump).

      The site needs to be fully external bunded with truck access over drain or hump.

      Complete worm bed area needs to be covered in a shed like structure, totally

       secure from the elements.

      Galvanised steel raised cage worm beds set in rows and tiers. A typical bed is 60-

       100m long x 3.8m wide.


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Waste Management ,                     Domestic &                           Aisling Donegan
Environmental Science,                 Municipal                            Ken M c Namara
I. T. Sligo.                           Composting                           Marie Mortell




      A computer controlled watering system is also required.

      A storage shed for the end product and other site sheds for office, plant storage

       and amenities are required.

      Ideally the site should be in close proximity to the source of the waste, and will be

      Access to the public road network.

      Access to established electricity lines, water supplies and telephony services.

      Access to reticulated waste water as this can be used in the place of freshwater if

       the quality is adequate (pathogen free, silt levels, salt levels).


4:2 Pre Design Requirements


      An acceptable geo-technical report proving that the site is suitable to support a

       pavement and large metal shed structure and has no ground water that would

       require the installation of subsoil drainage.

      An acceptable survey of the site to a scale not smaller than 1:500 showing

       contours (minimum 0.25m contours) and cross sections at minimum intervals of

       20m.

      The site should have an established fence enclosing the site on its perimeter with

       lockable access gates.


      A wash down facility for cleaning and maintenance of biosolid bins, trucks,

       tractors and other equipment.




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Waste Management ,       Domestic &   Aisling Donegan
Environmental Science,   Municipal    Ken M c Namara
I. T. Sligo.             Composting   Marie Mortell




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Waste Management ,                    Domestic &                       Aisling Donegan
Environmental Science,                Municipal                        Ken M c Namara
I. T. Sligo.                          Composting                       Marie Mortell




5: Systems and Procedures


In order to ensure performance, procedures have been established which have provided

sophisticated management systems and operations practices including:


      Worm management

      Mixing formulae for different wastes

      Data base for the analysis and monitoring all aspects of operations

      Established sampling and testing practices

      Comprehensive quality assurance program


5:1 Benefits of the Vermiculture system


      No odour

      Cost competitive

      No process pollution

      Valuable end product

      Destruction of pathogens

      Low green house emissions

      Established on site - low carriage costs

      Scalable to suit any waste volume

      Environmentally sustainable processes

      Environmentally superior end product


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Waste Management ,                     Domestic &                          Aisling Donegan
Environmental Science,                 Municipal                           Ken M c Namara
I. T. Sligo.                           Composting                          Marie Mortell




5:2 Quality Assurance


Leading companies in vermiculture have developed integrated operations and quality

assurance processes which focus on product quality and public health. Quality assurance

is a critical factor in differentiating vermiculture from "worm farmers". Credibility in the

market is based on demonstrating not only the reliability of the systems, but commitment

to and attainment of the environmental and public health standards as prescribed in

legislation. Public health is an overriding concern. This has demonstrated that this

vermiculture system destroys human pathogens present in sewage, resulting in a Grade A

product as defined by the various Environment Protection Agencies.


The bio-solid produced in controlled environments at waste processing facilities is

vermicast which is in fact worm excreta or castings. The castings are produced by the

worms through the consumption of organic material and mineral. There are two products

produced by this tecnology - one sourced from animal waste, the other from human

waste.


The great influencing factor on the NPK of casting is, of course, the food ingested by the

worms themselves. Worms can't manufacture nutrients, only liberate them. If food is

nitrogen rich, then, so too will be the castings.


The technology blends wastes in order to optimise nutrient and mineral input to the

worms, rather than simply blending vermicasts after conversion.


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Waste Management ,                     Domestic &                        Aisling Donegan
Environmental Science,                 Municipal                         Ken M c Namara
I. T. Sligo.                           Composting                        Marie Mortell




The endproduct range is categorised according to the source of waste. Each of the

products may be sold in a variety of packages from truck loads (bulk supply) to 40 litre

bags.


A piggery product has been certified as Grade A Organic by Biological Farmers

Association, a premium high value organic product. market where they have limited input

choices. In America, the organic market is now a multi-billion dollar industry.


Considerable anecdotal information exists on the value of vermicast. The largest users of

vermicast are in Cuba and India where over 160,000 tonnes per year are used on a variety

of crops.


Anecdotal results are being verified by scientific research confirming that vermicast

increases both yield and quality in a range of crops.


One of the primary benefits of remediating organic waste through the vermiculture

system is that all the material passes through the worm gut and upon excretion is already

extremely well broken down into a particle size which plants can readily absorb the

nutrients from. The material is also coated with millions of beneficial microorganisms

and interstitial fluid which readily hasten plant and soil health.




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Waste Management ,                         Domestic &                        Aisling Donegan
Environmental Science,                     Municipal                         Ken M c Namara
I. T. Sligo.                               Composting                        Marie Mortell




5:3 Destruction of Pathogens


Biosolid waste in general and vermicast are tested by external accredited laboratories to

ensure product compliance with regulatory pathogen reduction requirements. Biosolids

contain a range of bacterial, viral and parasitic organisms that have been positively linked

with infection and severe illness in humans. The destruction of pathogens occurs

naturally, but the die off rate varies. Of most concern is Helminth.


Mean Pathogen Level of Casts Through the Vermitech Process

Pathogen (measure)            Fresh Biosolids       Work in     Final Processed        Grade A Soil
                                                    Progress    Product                Conditioner
Faecal Coliform (cfu/g)            >310,000            270            180                <1,000
E coli (cfu/g)                     >110,000             18              4                 <100
Salmonella                       Not detectable,   Not detected   Not detected         Not detected
                                   masked by
                                   Faecal and
                                      Ecoli
Enteric Viruses (pfu/g)            Not tested           <1             <1                  <1
Helminth Ova (ova/g)---            Sludge not           N/d            N/d
--- ---------------------------      tested
-Ascari ---------------------                           <1             <1                  <1
--- Taenia                       Trial seeded to
                                     23/gm
Stabilisation Grade             ..                      A              A          ..

The combination of the strictest Quality Assurance regimen and maintenance of a healthy

active Biomass ensure a quality end product. In ongoing research no regrowth has been

detected in any resampled material over 30 months of operations at established sites.

Regrowth is highly unlikely for two reasons. Firstly a high degree of stabilisation occurs.




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Waste Management ,                        Domestic &                       Aisling Donegan
Environmental Science,                    Municipal                        Ken M c Namara
I. T. Sligo.                              Composting                       Marie Mortell




Secondly the end product is microbially active containing over 70 million beneficial soil

cfu‟s / gram on harvest and over 10 million at point of use after 12 months.




Survival Times of Pathogens in Soil and on Plant Surfaces (US EPA, 1992a)

Pathogen                           Soil                                  Plants
                     Absolute              Common            Absolute             Common
                                                                                  Maximum
                    Maximum               Maximum           Maximum*
Bacteria              1 year              2 months           6 months             1 month
Viruses               1 year              3 months           2 months             1 month
Protozoan cysts      10 days               2 days             5 days               2 days
b

Helminth ova             7 years            2 years          5 months             1 month

(US EPA, 1992a)


a. Greater survival time is possible under unusual conditions such as consistently low

temperatures or highly sheltered conditions


b. Little if any data are available on the survival times of Giardia cysts and

Cryptosporidium cysts


6: HELMINTHS


The helminths of concern are nematodes (roundworm) and cestodes (tapeworm). The

most common pathogenic helminths likely to be found in biosolids are Ascaris

lumbricoides (human roundworm), Ascaris suum (pig roundworm), Trichuris trichiura




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Waste Management ,                    Domestic &                          Aisling Donegan
Environmental Science,                Municipal                           Ken M c Namara
I. T. Sligo.                          Composting                          Marie Mortell




(human whipworm), Taenia saginata (beef tapeworm), Taenia solum (pork tapeworm)

and Toxacara canis (dog roundworm) (US EPA, 1992b).


For helminths, single eggs are infective and hence exposure should be minimised. (US

EPA, 1992b) Because Helminth may not be present in biosolids, a trial was




commissioned by companies involved in th industry to determine Helminth Ova

destruction by the action of earthworms (Luke, 1999 ). A suspension of parasitic

Helminth Ova containing 70,000 ova in a 1:3 ratio of Ascaris lumbricoides to Trichuris

trichiura was poured over a 3L earthworm/biosolids culture system, left for 28 days and

then sampled up until 85 days. The initial concentration of ova in the culture was

approximately 23 ova/gram.


The sampling area was randomly selected from a 16 square grid on the surface of the

culture and a total of forty eight 4 gram samples were removed from depths of 0, 2, 4 and

6 cm in either a straight or diagonal line across the grid. The sample was then repeatedly

centrifuged and decanted before the surface film was sampled using a wire loop (Stewart,

1985, cited in Luke). The sample was then examined microscopically for parasitic

helminth ova. The technique used to sample the worm culture has a sensitivity of 1

ovum/gram.




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Waste Management ,                     Domestic &                         Aisling Donegan
Environmental Science,                 Municipal                          Ken M c Namara
I. T. Sligo.                           Composting                         Marie Mortell




The results of the trial were no detection of Helminth Ova in any of the samples. Luke

suggests that the principal element of the culture was worms and therefore worm activity

must have contributed significantly to the destruction of the Helminth Ova.


6:1 Reduction of Impact of Plant Pathogens


One of the most significant benefits of vermicast endproducts may be in its ability to

suppress the impact of plant pathogens. Grower trials have identified the reduction in the

impact of sclerotinia, downy mildew, club root and various nematode infections. Very

little has been done on a reported scientific basis.


7:1 No leachate

This vermiculture system is a "dry" process with a high moisture zone only in the surface

100mm. The work areas and catchment areas are all hard paved with bitumen asphalt

forming an impervious barrier to protect the soil. The system has a first flush to catch any

run off from percipitation. Run off from the dam is regularly tested. All tests must meet

the nutrient, BOD, COD and pathogen levels set by environmental agencies to allow

release of water to any surface waters near the site. The enclosed nature of the systems

reduces the possibility of rain generated run off.



7:2 Dust

Levels are minimized and processes are designed to comply with any of the statutary

guidelines and steps are taken to continually reduce dust levels through enclosure of

potential dust sources.


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Waste Management ,                    Domestic &                         Aisling Donegan
Environmental Science,                Municipal                          Ken M c Namara
I. T. Sligo.                          Composting                         Marie Mortell




7:3 Noise

Noise is minimised by selection of machinery and proper maintenance of noise

suppression systems.



7:4: No Odour

Vermiculture is a low temperature mesophyllic 10 - 35 C reaction. Worms are sensitive

to most toxic and odourous gases. The neutralisation and immobilisation of gases is an

integral part of the system. No system is emission free, but there are minimal noxious

odours due to the highly aerobic processes. The natural processes involve the production

of CO2. Current ongoing research to determine the exact emission profiles is being

carried out and this data will be made available soon. Indicative results and mass balance

data suggests that the vermiculture produces minimal amounts of Greenhouse gases and

may be entitled to claim green house credits.



7:5: Energy Consumption

Diesel usage is estimated atapproximately 2 litres per tonne of waste processed. A small

amount of energy is consumed by office and maintenance personnel.




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Waste Management ,                    Domestic &                           Aisling Donegan
Environmental Science,                Municipal                            Ken M c Namara
I. T. Sligo.                          Composting                           Marie Mortell




8: Conclusion


If these criteria are used to compare vermiculture with other technologies such as

composting, incineration and landfill, vermiculture will be seen to offer significant

advantages. The technical ability to convert a range of wastes has been established. It

meets the most stringent conditions of environmental sustainability - no process

pollution, low energy consumption. There is almost 100% capture of organic material and

nutrients. The capital and operating costs are competitive and there is a high value added

end product.

There is more to the evaluation, particularly where technologies are developed in one

country and are to be exported around the world.


The next challenge for vermiculture is to develop a process for effective technical

transfer that takes into account the socio-economic, cultural and structural issues for

adaptation and use of the technology on an international basis. Requirements to move to

this next step to ensure that when questioned..."Is this appropriate technology? The

answer will be, "Yes."




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Waste Management ,               Domestic &                      Aisling Donegan
Environmental Science,           Municipal                       Ken M c Namara
I. T. Sligo.                     Composting                      Marie Mortell




References


Home Page URL: http://www.mertus.org/gardening/worms.html

Home Page URL: http://www.mastercomposter.com/search/netlinks.html

Home Page URL: http://www.mastercomposter.com




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