our waste management system is a key challenge that is currently
engaging Ireland’s citizens and government. A primary goal in accordance
with the EU Landfill Directive is to reduce our dependence on landfill
in favour of more environmentally sound alternatives.
|Biodegradable waste is broadly defined as waste
which is capable of undergoing decomposition either in the presence
of oxygen (aerobically) or in the absence of oxygen (anaerobically).
It is also more commonly known as organic waste and includes
materials such as putrescible food and garden wastes, paper,
cardboard and, to a certain extent, wood and textiles.
Under Council Directive 1999/31/EC
on the landfill of waste, all Member States of the European
Union are required to reduce their landfill of biodegradable
municipal waste and to encourage measures aimed at the separate
collection, recovery and recycling of biodegradable waste.
It is envisaged that such measures will contribute positively
towards the reduction of methane gas produced at landfills and impact
significantly on other adverse effects on the environment arising
from the disposal of biodegradable municipal waste.
Changing Our Ways
The Policy Statement - Changing Our Ways - preceded
the development of the Regional Waste Management Plans, setting
a primary objective of reducing Ireland’s dependence on landfill
in favour of an integrated system of recycling and recovery infrastructure.
Changing Our Ways provided national targets for municipal
waste recycling and biological treatment and set the framework for
regional waste management planning.
Key targets for 2013 -
|Diversion of 50% of overall household waste away
|A minimum 65% reduction in Biodegradable Municipal
Waste (BMW) sent to landfill
|Developing biological treatment capacity of up
to 300,000 tpa
|Recycling of 35% of municipal waste
|Rationalisation of municipal waste landfills to
a network of 20 state-of-the art sites
|Reduction of methane emissions from
landfill by 80%.
Diverting BMW away from landfill will require a high level of source
separation of food and garden waste, followed by biological treatment
- either composting or anaerobic digestion. The aim of biological
treatment is to produce a high quality, marketable product.
Home composting is suitable for garden waste and food waste
of vegetable origin and can divert a maximum of up to 10%
of organic waste. The target set is to treat 7% of all food
waste and 40% of all garden waste by home composting in households
Separate collection will, therefore, be required and the
provision of composting facilities for garden waste and centralised
biological treatment facilities for food waste.
The targets for central biological treatment are - households
- 48% for garden waste and 30% for food waste by 2009 and
commerce – 40% of food waste.
Home composting provides a way of reducing the amount of waste
to be collected, thereby minimising the environmental impacts and
costs associated with managing food and garden waste. Garden waste
and food waste of vegetable origin are suitable for home composting.
Garden waste from public parks and gardens should also preferably
be composted on-site. International experience suggests that up
to 10% of all household organic waste can be home composted and
so diverted from landfill. To reach this level requires widespread
What is composting?
The composting process may be defined as the controlled decomposition
and stabilisation of organic materials such as vegetables, plant,
food waste, garden waste, agricultural waste, etc. - under conditions
that are predominantly aerobic and that allow the development of
thermophilic temperatures as a result of biologically produced heat.
It results in a final product - referred to as compost - that has
been sanitised and sterilised, is high in humic substances and can
have a variety of uses. It is estimated that almost 50% of the total
waste stream could be composted - it is nature's way of recycling
and is an important way to recycle.
Composting is now employed as a treatment process for a wide range
of organic materials such as municipal solid waste, sewage sludge
and agricultural and industrial by-products. The current focus on
composting is primarily due to the expected EU Directive on Biowaste
and Sewage Sludge which, it is hoped, will lead to the diversion
of organic material from landfill. The diversion of organic matter
from landfill is necessary, principally because it can release greenhouse
gases, which are a prime cause of global warming.
Ireland's record in this regard is not particularly good, compared
to other EU countries, as can be seen in the figure below. In this
country, 85% of biological municipal waste is sent to landfill -
compared to 20% in Austria and 10% in the Netherlands. The Department
of Environment, Heritage and Local Government has prepared a draft
report on the National Strategy on Biodegradable waste (click
here to see).
Organic materials received at the composting facility require
pre-processing, involving four main activities, namely -
- mixing different feedstocks together to improve homogeneity
and adjust the carbon to nitrogen ratio and/or moisture
- optimising moisture content
- removing very obvious contaminants such as plastics.
Composting is most rapid when certain criteria are present.
The requirements for composting are - a carbon rich material,
a nitrogen source, micro organisms, moisture oxygen and temperature.
Paper, leaves and wood are high in carbon, while grass clippings
and vegetable scraps are high in nitrogen.
During composting, there is a generation of heat and loss
In phase I of the composting process, initial heating takes
place and readily soluble compounds are degraded (mesophilic
During phase II, cellulose and hemicellulase are degraded
under high temperature (thermophilic phase). This is accompanied
by the release of water, carbon dioxide, ammonia and heat.
In phase III, curing and stabilisation takes place - which
results in a drop of temperature and increased humification
of the material.
If, during composting, there is not sufficient aeration,
the composting process will be greatly inhibited and will
result in malodorous material.
In Ireland, composting is still very much in its infancy.
Cré - the Composting Association of Ireland - promotes composting
and compost utilisation in Ireland with a particular emphasis
on research and the development of an information storehouse.
To view current compost facilities in Ireland - Click
Bio Manage: Compost Facility
Enviros Consulting, we provide the ultimate one-stop-shop
for organic waste management. Our aim is to save
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With our leading position in waste treatment technology
appraisal and selection - as well as our role as
Manager of Defra’s New Technologies Supporter Programme
- we ensure that your project is based on selection
of the best available technology to suit your particular
Based in Dublin and Belfast for our Irish clients
- from simple Windrow to complex MBT Plant, from
on-farm Anaerobic Digestion to SRC and Biofuel Projects
- we follow through feasibility, planning, design,
EA, PPC, procurement, construction and commissioning
stages, to deliver our client's expectations.
for more information about our services in Ireland,
or telephone +353 (0)18 13 1020.
Steve Last (Shrewsbury): +44 (0) 1743 284851
Mark Kelly (Belfast): +44 (0) 28 9046 3562
Corporate information - Click
BioManage Composting - Click
BioManage Anaerobic Digestion - Click
Waste Technologies - Click
Composting systems / technologies
There are different types of composting technologies - from a simple
back-yard operation, or home composting - to a more sophisticated
operation using centralised facilities such as windrow or in-vessel
Home composting is becoming more popular as local authorities are
willing to subsidise the cost of the compost bin. It is a system
that is greatly favoured by the EU. However, it is not possible
for everybody to undertake home composting, as not everybody has
space to do so. Home composting can take from a couple of months
- if conditions are optimum - to up to a year or two years - if
conditions are not ideal. It is estimated that up to 10% of all
household organic waste can be home composted and, thereby, diverted
from landfill. However, widespread participation is necessary in
order to reach this level
Composting carried out in the open, is known as windrow composting.
|Windrow composting is the aerobic processing of
organic wastes placed in rows - either actively aerated or turned
to promote aeration - resulting in the decomposition of material
to form compost. It is a technique confined mostly to benign
materials - such as the garden waste element of the municipal
solid waste. The process may take place in static piles aerated
through a sucking or blowing action. This removes the need for
turning to provide aeration. In practice, the majority of windrow
composting is done using some form of mechanical turning.
In-vessel composting encompasses a wide range of techniques for
the composting of organic material in an encapsulating environment.
It is suitable for a wide range of organic waste materials - including
food processing and catering waste. This is due to the enclosed
nature of the process which can be controlled and monitored in order
to develop a high enough temperature throughout the vessel for a
sufficient amount of time to ensure the required level of pathogen
kill. It also prevents vermin infestation.
New requirements in relation to animal by-products
have increased the impetus for in-vessel composting systems and,
therefore, the use of this composting system is likely to increase.
One disadvantage of in-vessel composting is cost
- which is much higher than windrow composting. Another factor which
needs to be considered is that, after a short period in the vessel,
the material has to be cured - and hence, extra space is required
for the curing phase.
There are many types of equipment available for in-vessel
composting and these are varied. It suffices to say that they all
have their advantages and disadvantages and the choice of technology
will depend on feedstock, scale of operation, location, etc.
This is the process of using worms and micro-organisms to turn waste,
particularly kitchen waste, into compost - a dark humus which is
rich in nutrients with a rich earthy smell. It can be used as a
soil amendment or even as a component of a growing media.
Mechanical Biological Treatment
If the organic matter is largely stabilised - but contaminated and
not suitable for use in agriculture - the final product may be used
for landfill cover, soil conditioning, applications in forestry
- or may be fed into another treatment process, such as incineration
or gasification. The practicing of this process is likely to increase
in the short or medium-term, as source separation is not very common
in Ireland and in order to achieve the landfill directive targets
of biodegradable municipal waste.
When composting is considered to be complete, the compost material
must be analysed. Some of these tests are obligatory - for instance,
the EPA has a set of tests which the composted material must pass
before it can be released. These tests consist of plant nutrient
levels, stability or maturity, levels of heavy metals, foreign materials
such as plastic and glass and microbial tests for human pathogens
- e.g. Salmonella in the compost. However, additional tests
may be carried out - e.g. suitability for proposed use - this often
includes a growing trial with plants.
A number of EU member states - including the UK - have established
their own standards. There is a need for the development of standards
for Irish composts. This should include minimum requirements for
the process of composting, selection of input materials, quality
of composted material and information labelling of the product.
Cré - the Composting Association of Ireland - is presently working
on these standards and, at this stage, compliance by the compost
producer is likely to be voluntary.
Applications of Compost
If there is not enough emphasis placed on the end-use of the product
derived from composting, there is a danger that Ireland will end
up with huge amounts of finished compost material with no ultimate
use. Though there are numerous usages of composted material, the
following are some of the major applications.
Compost as a soil amendment and mulch
In this case, the compost can be mixed into the soil. This will
increase the water holding capacity of sandy soil, improve the aeration
of heavy clay soil and, thus, improve drainage. Compost also inoculates
the soils with a vast number of microbes. These microbes are able
to extract nutrients from the mineral part of the soil as well as
from the organic material.
Leaching losses of nutrients to the groundwater are reduced
relative to chemical fertilisers. However, it is not likely
to completely replace chemical fertilisers.
If a sub-mature greenwaste compost is used, it can soak up
excess nitrogen from the soil and thus prevent groundwater
pollution. This is relevant in relation to the Nitrate Directive.
It has also been found that plants growing in soils which
have been amended with compost are less susceptible to soil-borne
diseases. In this way, compost acts as a disease suppressant.
With the growing public demand to use less and less
agricultural chemicals and an increase in using 'organic' methods
of growing, it would be accurate to say that there will be an increased
demand for composted material.
Other applications of compost as a soil amendment
include the use on road side embankments, golf greens, sports fields,
forestry, the manufacture of topsoil, nursery beds and back-fill
for trees and shrubs. It can also be used as a mulch (ground cover
to keep down weeds and hold moisture).
Due to environmental concerns and the forthcoming EU Biowaste Directive,
there is a big demand to reduce the quantity of peat being used
in horticulture. One of the ways to achieve this is to dilute the
peat with a suitable recycled material.
Research conducted at Bord na Mona Horticulture has shown that
properly processed composted greenwaste can be used to dilute peat
up to 30% without any significant decrease in the quality of the
Composted material, by itself, cannot be used as a growing media
except in very special circumstances.
Compost bioremediation refers to the use of micro-organisms to break
down contaminants in soil. Compost bioremediation has proven effective
in degrading or altering many types of contaminants - such as chlorinated
and non-chlorinated hydrocarbons, pesticides and explosives.
Compost biofilter is one of the most important biological processes
used to treat waste gases and to control odour. The degradation
activity derives from micro-organisms which live and develop in
the media. Undesirable compounds in the gas are absorbed and degraded
by the micro-organisms and high efficiency has been recorded for
the reduction of VOCs.
Innovative Recycling Solutions
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Recycling Solutions Limited, is an Irish company committed
to providing solutions and alternatives to incineration
and the landfill of waste. Faced with the EU directives
on landfill reduction and pre-treatment of biodegradable
waste prior to landfill, SRS has a solution which
not only meets, but exceeds all of the regulations
- using a proven, tried and tested system.
of the SRS in-vessel composting/bio-drying tunnels
is to accelerate and control the decomposition of
organic wastes by optimising the natural composting
process. It utilises a flow-through tunnel that exhausts
all air through a bio-filter and transforms organic
waste into a soil-like material in 14 days - while
eliminating problems typically associated with composting,
such as odour.
The SRS offering does
not end with the in-vessel composting/bio-drying system,
however. While the tunnels can transform source segregated
organic material into high grade compost, it is not
necessary for waste to be source-segregated prior
to arrival at the waste facility.
SRS can also provide the client with a front-end,
turnkey operation for complete waste separation. SRS
is a market leader and specialises in the supply,
manufacture and installation of bag openers, conveyors
and conveyor systems, ballistic separators, trommels,
shredders, wind shifters, weight systems and air filters.
Recycling Solutions Ltd
Co. Meath, Ireland
Tel: 00353 46
Fax: 00353 948 7199
Email: [email protected]
Contact: Eileen Connolly-Crehan
Organic material such as food and garden waste comprises
40% of biodegradable municipal waste.
A combination of home composting and centralised biological
treatment facilities will be employed to divert approximately
45% of organic waste to biological treatment of source-separated
Meeting these targets can divert 21% of all BMW from landfill
Targets for households for 2009 include -
- Minimum of 30% separate collection and biological treatment
of food waste (from households not involved in home composting)
- 7% home composting of garden waste and food waste of vegetable
origin – targeted in areas where separate collection not
- 88% biological treatment of garden waste – 40% via home
composting and 48% via green waste composting by 2009
- Separate collection and biological treatment of 40% of
food waste from commerce.
Households in both rural and urban areas, where there is
suitable garden space, will be encouraged to compost their
garden waste at home.
Particular emphasis will be placed on home composting of
food waste (of vegetable origin) in rural areas where separate
collection system for organic waste is not feasible.
Targets are based on 25% of urban households and 60% of rural
households participating in home composting of food waste.
All households will be required to separate garden waste and
either compost on site or deliver to a local recycling centre.
Garden waste that is generated by green areas around multi-storey
households should also either be composted on-site or treated
at a central composting facility.
Separate collection of organic waste will be required in
all urban areas, possibly extending to rural areas as part
of an integrated collection system.
Community composting facilities are an emerging system
at European level - where local communities can become involved
in the management of their own wastes, whilst implementing the proximity
principle and increasing awareness of waste recycling practices
within their own community.
In Ireland a number of initiatives have been undertaken
- for example at an urban apartment complex and as part of the Ballymun
redevelopment project in Dublin. Other examples of where community
composting might be applied include -
- in relation to tidy-towns schemes
- local composting of green waste from public open spaces
- in residential housing estates - or
- in industrial estates where groups of companies pool their
Interaction with farming in relation to green waste composting
and vermi-composting schemes may also be considered.
Capturing organic waste from commerce is required
in order to meet the target for 2009. Food waste from larger enterprises
should be collected in separate containers. The following commercial
enterprises are particularly relevant:
- Hospitality Sector – Hotels, Restaurants, B&B;’s, etc.
- Canteen Kitchens – in major companies and institutions
- Retail Sector - Supermarkets, Fruit and Vegetable Shops, Food
Sector retails outlets
- Businesses and Offices with kitchen/ canteen facilities.
|Requiring separate container collection of food
waste from commerce where food waste production is > 50 Kg/week
will be considered. The penetration of separate collections
into the commercial sector should be progressively widened to
capture greater quantities of organic waste.
The overall capacity to treat source-separated food and garden
waste must increase substantially to meet the targets set out.
The current operational capacity must increase to approximately
350,000 tonnes/ annum in 2009.
The Environmental Protection Agency essentially has already adopted
the treatment standards being promoted in the technical working
documents associated with the proposed European Community Initiative
on the Biological Treatment of Biodegradable Waste.
The principal treatment methods to be developed and controlled
under the initiative are -
|Green Waste Composting
|Centralised Composting (‘Biowaste’ composting)
Biological treatment of BMW can be successfully carried out in
tandem with other waste streams, such as agricultural wastes, organic
industrial wastes, fisheries residues, etc. Co-treatment can provide
economies of scale and encourage investment in the development of
modern recovery plants.
Other local opportunities for biological treatment in a ‘cross-sectoral’
approach are also emerging - such as the composting or digestion
of food waste on farms, or the development of composting plants
close to sources of fish waste.
Such avenues can provide a sustainable solution - but regard
should be had that the scale of facility and environmental
controls are adequate to ensure full compliance with legislation.
Health effects of composting
There are minimal effects on the health of people working at compost
plants - or to the general public near composting plants - if certain
precautions are taken. However, one area of concern is bioaerosols.
Gaseous emissions from composting piles can include bioaerosols
(fungi, bacteria, actinomycetes) and fine dust.
At present, there are few studies on the health effects of composting
from which any quantitative indication of risk can be derived. A
report has been prepared by Cré - partly funded by the EPA -which
deals with the risks associated with bioaerosols. Odour from compost
plants can sometimes be a nuisance if the composting is not done
properly - but if the pile is well aerated, it should not be a problem.
A Report entitled - “Assessments and Evaluation of Outlets of Compost
Produced from Municipal Waste” (click
here) - was published in 2002 by the EPA (ERTDI programme, under
the 2000-2006 National Development Plan). This report contains a
series of strategic recommendations in support of sustainable markets
for compost. The Report recommends adopting a ‘Hierarchy’ for compost
utilisation, aiming for high quality product linked to a high revenue
market. It also identifies a range of potential market outlets for
compost and outlines a possible scenario for what quantity of waste
could be sold to each market.
|The Department of Environment, Heritage and Local
Government (DOEHLG) will seek to enter dialogue with the Peat
Industry (and the Retail Sector) towards a voluntary industry
initiative that will introduce peat extenders into horticultural
compost products. Such a voluntary approach has been industry
led in the United Kingdom where public pressure to reduce peat
extraction was the motivating force. Inclusion of compost as
a peat extender will require a very consistent and high quality
compost to be produced from municipal green waste and biowaste.
Development of Horticultural, Agricultural and Forestry Markets
Use of compost in conventional agriculture is a vast potential market,
where even a small degree of penetration will create a significant
and stable demand for compost. Developing farmer confidence and
know-how in relation to compost is, therefore, essential.
A Quality Assurance Scheme is a market-oriented step that goes
beyond the adoption of National Compost Quality Standards. The aim
is to prove to potential buyers that the product has been independently
verified as coming from a process that has produced a bona-fide
and high quality material that will deliver the purpose it is intended
for. Experience shows that market-driven quality schemes can have
a positive impact on collection and treatment of organic waste as
well as the end-product itself.
The EPA report identified a need for market plan preparation
by existing and new composting facility operators. A guidance note
in this regard would be a useful tool for the industry and it is
recommended that the industry should lead the implementation of
this initiative which is essentially designed for its members.
High levels of awareness and motivation towards composting
will benefit source separation schemes and, ultimately, lead to
better quality compost products in greater volumes. Better awareness
will also help expand the market for compost. Responsibility for
improving public awareness in relation to compost and composting
is a shared responsibility.
Composting is a very economical way of treating organic
waste. Not only is the volume decreased by up to half of the original
volume, but also, a range of products can be developed. Public authorities
and the public sector should encourage the use of compost. Public
funds should be made available to develop new products from composts.
In addition, the environmental standards should be similar to an
'average' European country - rather than being unrealistically stringent
- which would impede composting in the Irish context.
Part of this article has been written by - and reproduced
with the kind permission of Dr. Munoo Prasad.
Dr. Prasad is recognised as one of the leading authorities
on composting and is Chief Scientist with Bord na Mona Horticulture,
Chairman of the Technical Committee, Compost Association
Ireland (Cré) - and national Representative at the European