International Review of Waste Management Policy - Department of ...

Eunomia. 1263 The principal climate change impacts are associated with release of
biogenic CO2 emissions which are not reported in the majority of studies that use a
life-cycle assessment approach to analyse the emissions of greenhouse gases. Some
impacts are different depending on the feedstock used within the composting
process. N2O emissions are higher when food waste is composted due to the higher
nitrogen content of the feedstock.
Table 63-24: Assumptions Used to Model Composting Processes
Parameter Parameter
Assumption
Assumption
CH4 emissions from process 0.816 kg / t input
N2O emissions from process
In vessel (garden waste)
In vessel (food waste)
Windrow
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International Review of Waste Policy: Annexes
0.361 kg / t input
0.477 kg / t input
0.117 kg / t input
Non-degraded carbon (retained in biomass) 30%
Electricity requirement
In vessel
Windrow
Diesel use by process
In vessel
Windrow
40 kWh / t input
0 kWh / t input
0.3 l / t input
1.0 l / t input
Mineralisation rate of readily available organic matter 20%
Mineralisation rate of stable humus 1%
% of organic matter from compost becoming humus 25%
Notes:
1. No action of biofilter is assumed for windrow facilities.
2. A further 0.4 litres of diesel is used to spread the compost onto land.
3. The mineralisation rate is the rate at which carbon contained within the organic
matter (or humus) is assumed to become atmospheric CO2.
63.8.3 Air Quality Impacts of Composting Processes
Other than the greenhouse gases, the principal emissions to air from composting
processes are:
1. NH3;
2. VOCs;
1263 Eunomia (2006) Managing Biowastes from Households in the UK: Applying Life-cycle Thinking in
the Framework of Cost-benefit Analysis, Final report for WRAP, May 2006