environmental impact statement kilmainhamwood compost facility ...

5361- Kilmainhamwood Compost Facility Extension- EIS
Residual treatments include thermal treatment and Mechanical Biological Treatment (MBT) and are the
least preferred treatment options. The residual treatment of organic waste is considered undesirable for
many reasons including the following:
• Organic material recovered by MBT typically emerges as a low quality material (stabilised
biowaste) that has limited applications outside of landfill. On the other hand, compost generated
by the biological treatment of the source separated collection biowaste is recognised as a
sustainable product which can be utilised for beneficial landscaping and agricultural purposes;
• Organic waste is high in moisture content (>50%) and hence has low calorific value in
comparison to waste paper and plastic. Therefore, the use of organic waste as a feedstock in a
thermal treatment plant results in minimal energy recovery and the loss of a sustainable natural
resource (high quality compost) for the improvement of agricultural land;
Alternative Biological Treatment Processes:
The existing Kilmainhamwood Compost facility biologically treats a range of biodegradable wastes to
produce a high quality product for agricultural and landscaping applications. The biological process,
which has been operated successfully at the facility since September 2006, is composting. Composting
is defined as the biodegradation of organic waste into stable humus like product. Nonetheless, for the
purpose of completeness of this document, alternatives biological treatment processes are explored
herein.
Alternative biological treatment processes to composting include:
• Anaerobic digestion;
• Vermiculture;
• Ethanol production.
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Anaerobic digestion
Anaerobic digestion has been used to treat sewage since the late 19 th Century and has also in more
recent times been widely applied in European countries for the treatment of agricultural and municipal
biodegradable wastes. The process is therefore proven at full-scale. The process is undertaken within
sophisticated enclosed facilities, which have been carefully designed to optimise the conditions for
decomposition. This is especially the case for solid waste digesters, which operate at dry solids
contents > 10-20% (as opposed to slurry digesters with lower dry solids content).
As a result, the capital and operational cost of an anaerobic digestion facility for the envisaged solid
waste streams are significantly higher than for a conventional composting facility. A composting
process is therefore preferred to anaerobic digestion for the proposed extension of the
Kilmainhamwood Compost facility.
Vermicomposting
Vermicomposting is a method of composting biodegradable waste that utilises earthworms (Vermes) to
speed up the composting process and produce a richer end product. Since the earthworms used in
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