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Report n°4: How Much to Spend for the Protection of Health and Environment

Assumptions

Since the comparison necessitates an LCA, the work begins by choosing the boundaries of the analysis. The most appropriate choice is to start at the point where the waste has been collected and sorted. From here the waste must be transported to the landfill or incinerator; we have included the emissions due to possible differences in transport distance by showing a hypothetical distance of 100 km, for the purpose of illustration. In addition to the emission of pollutants from the landfill or incinerator, the emissions avoided by recovery of energy and materials are also taken into account, based on the LCA data of ADEME [2000]. The assumptions of the analysis are summarized in Table 5.

The principal emissions from landfill are CH4 and CO2. Fig.6 shows the total greenhouse gas emissions of a municipal solid waste landfill versus time. CH4 is expressed as equivalent CO2, using a GWP (global warming potential) of 20. Note that a modern landfill is divided into a large number of individual compartments; they are filled one after another and sealed when full. The time in Fig.6 is measured from the date that a compartment is sealed.

There may also be emissions to soil and to water. Emissions to soil can occur from slag, from leaking liners under the landfill, and from the storage site of incinerator fly ash. Emissions to water arise from certain types of flue gas treatment and from the extraction of leachates under a landfill. Emissions to soil are difficult to estimate because they depend on integrity of the liners in the future. If the landfill is operated according to regulations and if there are no mishaps, there are no such impacts during the foreseeable future because the operator has the obligation to maintain and safeguard the facility for 30 years after closure. In any case their impacts would remain limited to the immediate vicinity of the landfill, with the possible exception of sites with sufficient ground water movement. In the present version impacts of emissions of leachates to soil or water have not been considered.

The damage costs and the comparison between landfill and incineration turn out to be extremely sensitive to assumptions about energy recovery. For that reason we consider a fairly large number of options (indicated in the figures by labels such as E=c+o):

for incineration:

  • recovery of heat and electricity, for typical installations in France, according to ADEME [2000] (E=..., H=...),
  • recovery of electricity (E=...),
  • recovery of heat (H=...);

for landfill:

  • no energy recovery,
  • recovery of electricity, by motor (reciprocating engine) (E=...),
  • recovery of electricity, by turbine (E=...),
  • recovery of heat (H=...).

For recovery of electricity we assume a year-round demand, so all the electricity is used. Likewise for recovery of heat we assume a year-round demand (industrial process heat loads or certain district heating systems with year-round demand, e.g. Paris and Vienna), so none of the heat is wasted. Year-round demand is essential for good recovery rates because the supply of waste tends to be fairly constant.

For each of these options we consider several suboptions (indicated by the labels in the captions):

  • the recovered electricity displaces coal and oil fired power plants, 50% each (E=c+o),
  • the recovered electricity displaces nuclear power plants (E=n),
  • the recovered heat displaces gas and oil fired heating systems, 50% each (H=g+o),
  • the recovered heat displaces only oil fired heating systems (H=o).

H indicates the fuels displaced by recovery of heat, E those replaced by recovery of electricity, c indicating coal, o oil, g natural gas and n nuclear. For example, (E=c+o, H=c+o) designates a system where heat and electricity are produced, each displacing a fuel mixture of 50% coal and 50% oil. Note that for the purpose of this analysis the benefit of recovered electricity is essentially zero if it displaces nuclear because the damage costs of nuclear are very small compared to those of oil or coal; thus this option is essentially equivalent to no electricity production at all as far as damage costs are concerned.