environmental impact statement kilmainhamwood compost facility ...

5361- Kilmainhamwood Compost Facility Extension- EIS
Proposed Upgrade to Odour Abatement System
The existing composting system involves material being composted in open bays whereby odourous air
is displaced to the building headspace. Hence large odourous air volumes (101,000m 3 /hr) require
treatment, which is deemed inefficient in regard to power consumption.
The odour abatement system currently in operation at the Kilmainhamwood Compost facility involves
biofiltration. The ventilation system consists of three 37kW extraction fans that extract a total of
101,000m 3 of air per hour. This volume of odourous air is processed by two biofilters. One biofilter
processes the air stream generated by one 37 kW fan (38,000 m 3 /hour) and the other biofilter
processes the air stream generated by two fans (63,000 m 3 /hour). Each biofilter is 23.5m long, 16.5m
wide and 2.1m high. The existing biofilter construction is based on a firm concrete floor and surrounding
concrete walls. The bed media consists of a combination of woodchip and carbon media mix.
Thorntons Recycling has commenced the upgrade of the odour abatement system on site in order to
further reduce the odour emission rate from the facility. Each existing composting bay within the facility
building has been enclosed/roofed (such that the distance from the floor of the composting bay to the
underside of the roof is 6m), thus significantly reducing the volumes of process air that require
treatment. Works on enclosing existing composting bays were completed on site in January 2010. The
displacement of odourous air, from the composting process, to the headspace of the building is now
prevented thereby implementing double containment features and allowing for the specific treatment of
this odourous air.
In addition Thorntons Recycling propose to process the odourous air generated within the enclosed
composting bays in an acid scrubber to minimise ammonia carryover to the biofiltration system. The
enclosing of existing composting bays and treatment in an acid scrubber will ensure the efficient
capture and focused treatment of odours generated by the composting process itself, thereby ensuring
that the maximum allowable odour threshold concentration in the exhaust air of the biofiltration system
is achieved.
Notwithstanding the above, odour abatement at the facility will still involve treating the air within the
building headspace, however as this air will not be a direct product of the composting process, it will be
low in ammonia levels and will only require treatment by biofiltration.
Thorntons Recycling employed the services of an independent odour consultant to design the upgrade
to the odour abatement system as described above. A range of odour abatement technologies were
considered in the design process. The following technologies were examined:
• Thermal Oxidation;
• Chemical Scrubbing and biofiltration;
• Carbon absorption
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EPA Export 01-06-2010:03:55:50