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

handle. The choice of discount rate, as well as changing the sensitivity of the
damages assessed to the time period over which those emissions occur, should
also change the unit damage costs associated with the key climate change gases
and their relative significance since these gases have an effect which occurs over
an extended period, and their residence times in the atmosphere vary.
5) In bottom up studies, the value placed upon the different end-points associated
with the effects of different pollutants will affect the analysis. Different studies
resort, for example, to the use of values based upon the value of a statistical life
(VSL), whereas others use the value of life-years lost approach (VLYL). Similarly, in
top-down studies, the unit damage costs are likely to be high or lower (other things
being equal) depending upon whether the study from which the unit damage costs
are taken made use of VSL or VLYL; 1147
6) Where a study considers the implications of energy recovery, and makes an
assumption that the energy generated ‘displaces’ another source of energy, the
net effects of the energy generation depend critically upon which source of energy
the study assumes to be displaced. The ‘dirtier’ the displaced source, the more
advantageous (in the analysis) the generation of energy appears.
These issues are some of the critical ones in existing studies on the external costs of
waste management. They explain much of the variation between studies.
61.2.2 Landfill
Where landfilling is concerned, the majority of studies concentrate on air emissions.
Of these, methane has, unsurprising, received most attention. Relatively few studies
have sought to look at an expanded range of emissions, or at emissions to other
media. In the external costs literature, it is usually assumed that leachate is well
managed so that there are no relevant problematic emissions to land and water. This
is a contentious (though simplifying) assumption, and it is almost certainly incorrect in
the longer-term. 1148
As regards methane emissions, the quantity of methane released to the atmosphere
depends upon:
937
� The quantity generated in the landfill;
� The quantity collected by gas collection systems;
� The quantity of the uncollected methane which is oxidised as it passes through
the cap, or its leachate; and
� The efficiency of combustion processes in converting methane to carbon
dioxide and carbon monoxide
Each of these variables (with the possible exception of the last) is contested not least
because each of the parameters is likely to vary over time (and space).
1147 Value of Statistical Life or Value of Life Years Lost.
1148 S. Hellweg (2000) Time- and Site-Dependent Life-Cycle Assessment of Thermal Waste Treatment
Processes, Dissertation submitted to the Swiss Federal Institute Of Technology.
International Review of Waste Policy: Annexes