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

It should be noted that bioaerosols from the composting process contain the same
micro-organisms as ones to which citizens are routinely exposed. They are present
naturally and are essential to the recycling of nutrients in our gardens, parks and
countryside.
We have not been able to incorporate the impacts of bioaerosol emissions into our
model as no dose-response functions have yet been developed to quantify the
impacts associated with this type of pollutant. However the preceding discussion
suggests the environmental and health impacts of these emissions should be
minimised with the adoption of appropriate operational management techniques.
63.8.4 Benefits Associated with the Use of Compost
The use of compost is associated with monetised benefits, extending beyond the
realm of air pollution to include, amongst others, reductions in water pollution and
improvements to soil quality.
We include within our model the slow release of CO2 from the soil after the compost is
added. After 50 years, approximately 13% of the initial carbon contained within the
compost remains in the soil.
65% of the compost produced is assumed to be used in agriculture. Our model
considers the following benefits associated with the use of compost in this way: 1269
1023
� The displacement of alternative nutrient sources otherwise applied through
the use of synthetic fertiliser, including the avoided external costs of fertiliser
manufacture and the avoided energy use associated with this;
� The greenhouse gases avoided from nitrogenous fertiliser applications (i.e.
N2O emissions) and the external costs associated with this;
� Avoided external costs from a reduction in the leaching of nitrate (from
nitrogenous fertilisers) into groundwater;
� Avoided external costs associated with process wastewater and
phosphogypsum disposal during the manufacture of phosphate fertiliser;
� Avoided energy requirement associated with the mining of phosphate rock for
phosphate fertiliser, and the avoided external costs associated with this;
� Avoided external costs through a reduction in the use of pesticides; and
� Avoided external costs through a reduction in the use of water.
The remaining 35% of the compost is assumed to displace the use of peat in
horticulture and hobby gardening applications. Here the avoided impacts are the slow
release of CO2 from the aerobic degradation of peat after its removal from the peat-
1269 For a detailed description of the methodology used to calculate these estimates see: Eunomia (2007)
Managing Biowastes from Households in the UK: Applying Life-cycle Thinking in the Framework of Cost-benefit
Analysis, Appendices to the Main Report, Report for WRAP, May 2007
International Review of Waste Policy: Annexes