Page 87 - Materials Chemistry, Second Edition

L1644_C02.fm Page 63 Tuesday, October 21, 2003 3:07 PM

The function of the incineration process is to reduce the volume and toxicity of
the municipal waste treated. The production of electric energy must be seen as an
added value to the incineration process. Because the objective of the study is the
analysis of the electric energy generated in the incineration process, the functional
unity selected is “TJ of produced electricity.”
The study comprises all the processes from the municipal waste disposal in
containers to the landfill of the final waste, as shown in Figure 2.8. Consequently,
the following processes are considered: transport of the municipal waste to the
incinerator, combustion, gas treatment and ashes removal, as well as slag disposal
(including transport to the final localization). The final step, with its emissions
associated to the landfill, is not analyzed. The incineration process has been divided
into subsystems:

1. Waste incineration plant with combustion process and including gas treat-
ment
2. Water treatment (treatment process applied in the ash bath, demineraliza-
tion process applied in the kettles by osmosis and refrigeration process
by means of a tower)
3. Ash treatment (ionic ashes and waste from the gas treatment filters)
4. Scrap treatment (iron waste recycling process)

The latter were analyzed as processes that generate a useful product for the
incineration process. The environmental loads are associated with the consumed
product by the principal process (e.g., water) or the treated product (e.g., municipal
solid waste). Literature values have been used for raw material production and the
transport process (16-t truck).
Due to the study’s objective, the electricity produced is considered to be the
only useful measurable product to which all environmental loads are assigned.

2.7.2 DATA USED IN LIFE-CYCLE INVENTORY

In order to carry out the study, three types of data were used:

• Literature data of environmental loads for the raw material used in the
analyzed processes. The considered source was the report referred to as
ETH 1996 (Frischknecht et al., 1996). The exactness of the report and the
agreement of these data with the particular situation in Spain determine
the data quality.
• Real data of consumption and emissions associated with the incineration
process, average values from 1996 (Scenario 1) and average values for 2
months with the advanced acid gas removal system in operation (Scenario
2). The data quality can be considered reliable because they have been
obtained directly from the process.
• Real data of consumption and emissions associated with the waste treat-
ment processes, obtained by visits and questionnaires answered by the

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