environmental impact statement kilmainhamwood compost facility ...

5361- Kilmainhamwood Compost Facility Extension- EIS
maturation area, less easily biodegradable components are degraded (e.g. cellulose and lignin
structures) at a lower rate, reducing the risk of anaerobic conditions. The air supplied to the maturation
area in the later stages of the process is regulated as required. All process air from the composting
bays is collected and treated by the biofilter. It is proposed to include an ammonia acid scrubber as part
of the upgrade to the odour abatement system to further improve odour removal efficiency at the facility.
Monitoring of temperature
If composting temperatures exceed approximately 65°C, odour emissions increase significantly, due to
the changes in process biochemistry. Excessive increases in composting temperatures are especially
relevant in the first stage of composting when, due to the fast degradation, a lot of energy will be
released.
Temperature sensors are used to measure the temperature in the composting bays and subsequently
in the maturation area. The computer control system ensures that the composting temperature does not
exceed 65°C (with the exception of the Animal By-Product treatment stage where a temperature of
greater than 70 o C is only required for one hour), by adding more fresh process air to the biowaste. This
reduces the odour load in the process air, which is transported to the biofilter.
Due to the slow degradation in the maturation stage, temperatures normally do not rise above 60°C. If
this happens incidentally, the variable blowers increase the fresh process airflow to cool the maturating
biomass.
Application of emission reduction techniques
As described earlier, all process air from the composting process is collected and treated in biofilters. It
is proposed to include an acid scrubber to the odour abatement system, to remove ammonia from
process air prior to biofiltration
For inspection purposes only.
Consent of copyright owner required for any other use.
Practical experiences with ammonia acid scrubber and biofilter configurations show that, if properly
designed and operated, an odour removal efficiency of a minimum of 95% can be achieved. To assess
the potential impact of odour emissions from the composting facility due to the proposed increase in
tonnage, odour dispersion calculations have been carried out as detailed in Section 9.2 herein.
Implementation of an effective odour abatement system to Best Available Techniques (BAT)
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 (101,000m3/hr) require
treatment to ensure three air changes per hour in the building. As part of the proposed upgrade of the
odour abatement system, each of the individual composting bays have been enclosed in order to allow
for the capture and treatment of reduced volumes (80,000m 3 /hr) of odourous air. In addition the
odourous air generated by the enclosed composting bays will be treated within an acid scrubber to
minimise ammonia carryover to the biofiltration system. 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 air in an acid scrubber. The building
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EPA Export 01-06-2010:03:55:52