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

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1. Energy used within the treatment process, giving rise to damage costs of
€3.08 under the high externalities (mostly from the use of diesel);
2. Total direct emissions from the stabilisation process and the landfilling of the
residues result in external damage costs of €0.47 under the high externalities
(emissions of NMVOCs from stabilisation account for most of this impact).
63.5 MBT Aerobic Biodrying Systems
63.5.1 Climate Change Impacts of MBT Aerobic Biodrying Systems
Biodrying systems involve the application of intensive heat to the waste to ensure the
removal of moisture prior to it being used as fuel. During this process degradation of
some of the carbon fractions will occur as a result of the increase in temperature but
the amount of degradation is relatively limited in comparison that occurring during
aerobic decomposition (stabilisation) processes.
Emissions of CO2 are calculated from the carbon loss estimated over a two week
period. The figures for carbon loss are estimated by ourselves for each of the
components of the waste stream. We have been able to correlate these estimates
over several years using an analysis of data from technology suppliers.
The central aim of biodrying processes is to produce a fuel. A reject stream is also
produced, which is assumed to be stabilised before being sent to landfill, using the
process previously described in Section 0.
Table 63-15 outlines key assumptions used to model the biodrying phase.
Our assumptions regarding the nature of the SRF produced are detailed in Table
63-16.
Our analysis considers two uses for the output from the biodrying process:
1. The SRF is combusted at a dedicated incineration facility generating electricity
as has been previously described in Section 63.3.
2. The SRF is combusted at a cement kiln where it is assumed to displace the
use of coal. We assume a 90% substitution ratio for the fuel displacement,
and that the coal would otherwise emit 0.37 kg CO2 equivalent per kWh of
energy generated.
Our assumptions for the landfill of pre-treated (stabilised) material have been
previously discussed in Section 63.2.1.5.
International Review of Waste Policy: Annexes