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

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� Optimised biofilter; and
� Thermal filter.
The choice of abatement equipment determines the level of removal of some of the
gases prior to their emission to the atmosphere. It also determines the level of energy
use in the process (especially relevant for the thermal filter option).
We have assumed that MBT facilities operate with optimised biofilters. The
requirement, in Germany, to deploy regenerative thermal oxidation (or other)
processes to crack remaining VOCs from the exhaust gas appears, in our view, to be
unjustifiable when the additional benefits are set against the additional energy
demand implied by the process. 1252
Pollution abatement techniques employed at incineration facilities have been
previously discussed in Section 63.3.2. Again we have assumed two types of facilities
– one which complies with the WID, and a second which has installed additional
abatement equipment and therefore exceeds the requirements of the WID. Our
assumptions for the landfill of pre-treated (stabilised) material have been previously
discussed in Section 63.2.1.5.
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.
The principal air quality impacts are:
1. Energy used within the treatment process, giving rise to damage costs of
€6.42 under high externalities or €2.22 assuming low external costs. Most of
this impact arises from the use of diesel within the facility. 1253
2. Where the SRF is sent to an incinerator, total emissions from direct treatment
processes (including the biodrying and stabilisation components and the
combustion of SRF as well as the landfilling of residues) result in external
damage costs of €10.64 under the higher externalities or €3.69 assuming low
1252 Biofilters themselves are sources of VOCs, though typically of less benign species than the type
one seeks to remove from exhaust gases. To assume that all VOCs are equally detrimental to air
quality and health is to misunderstand the problem, and although RTO deployment will further reduce
VOC emissions, (as we show within this review) it tends to do so at considerable additional cost from
the perspective of climate change.
1253 The additional diesel consumption reflects that used within the incineration of SRF. Assumptions
used here are the same (on a per tonne basis) as for the incineration of untreated wastes.
International Review of Waste Policy: Annexes