environmental impact statement kilmainhamwood compost facility ...

5361- Kilmainhamwood Compost Facility Extension- EIS
composting process and feedstock to Best Available Techniques (BAT);
Management of fresh biowaste and material composition
Fresh biowaste as delivered to the facility is likely to be partially anaerobic, due to storage at the
location of production and transport. As long as the biowaste is contained in a waste collection/transport
vehicle this will not lead to emissions, since the material is not being handled/disturbed. However,
unloading of the material at the site and further handling may lead to odour emissions. To prevent
emissions to the surroundings, all biowaste is discharged into the facility building which is under
negative pressure with roller shutter doors closed at all times.
The mixing of the biowaste prior to composting is executed in the same enclosed building. The building
is equipped with air ducts on the underside of the roof, which collect the air and transport the air to a
biofilter. As part of the upgrade of the odour abatement system, it is proposed that the composting bays
are enclosed and the process air is treated in an ammonia acid scrubber prior to biofiltration. Since the
building is under negative pressure, the emissions via open doors are minimised when accepting
incoming biowaste.
To prevent delivered biowaste from getting anaerobic and odorous, all biowaste is pre-treated and
placed into the composting bays within one day of arrival and acceptance at the facility.
Appropriate mixing of feedstock and amendment materials (carried out in enclosed building under
negative pressure) prior to composting is required to allow for a proper composting process and for the
production of the desired quality compost. However this mixing is also essential to minimise odour
emissions. The mixing ensures that the composting mass:
• Has the appropriate dry solids content (approximately 45%-35%) and has an adequate porosity,
such as to facilitate the aeration process and prevent the formation of anaerobic zones in the
composting mass during the process. This is achieved by mixing relatively dry and wet feedstock
and if required, the adding of a structure material e.g. wood chips;
For inspection purposes only.
Consent of copyright owner required for any other use.
• Has the appropriate C/N-ratio (approximately 25/30:1) to prevent excessive emissions of Ncontaining
odour components. This is achieved by mixing feedstock which is low in N-content (e.g.
green waste) with feedstock that has a higher N-content (household biowaste);
Aeration of composting material
The first stage of composting is the most critical with respect to odour emissions, since easily
biodegradable components, e.g. sugars, proteins and fats are degraded at a high rate, thus causing
gaseous by-products.
The entire composting process is executed in an enclosed composting building which is maintained
under negative pressure. The interior of the building is coated with an expanded foam membrane
sealing to provide near complete sealing. Applying a high aeration rate, thus ensuring the supply of
sufficient oxygen to the composting mass, prevents occurrence of anaerobic conditions in the first
phase of the composting process in the composting bays. As the composting process proceeds in the
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EPA Export 01-06-2010:03:55:52