Page 285 - Materials Chemistry, Second Edition

L1644_C06.fm Page 256 Monday, October 20, 2003 12:06 PM

100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0% EEC after installation
Electricity Transport Ashes treatm. Incineration Eco-ind. after inst.
CaO
Relevant PRs
Scrap-metal rec.
EEC before installation
Eco-ind. before inst.

FIGURE 6.20 Comparison of external environmental cost with eco-indicator 95 for a plant
before and after installation of an advanced acid gas removal system.

6.8.7 ECO-EFFICIENCY
Based on the environmental cost estimations obtained in the previous sections, the
eco-efficiency of the process chain can be calculated. According to the expression
in Figure 6.17, production costs are needed as an additional element. According to
information from SIRUSA (Nadal, 1999), the production costs are:

• Former situation: 32,000 U.S.$/TJ
• Current situation: 37,000 u.S>$/TJ

These costs are based on the yearly total operation costs of the MSWI, including
the financial costs for the investments made. The production costs are higher than
the market price of 0.07 U.S.$/kWh; the deficit is paid by the price for the waste
treatment, which can be considered a service the MSWI is providing to society. By
applying the presented formula, the following eco-efficiency for the process chain
is obtained:

• Former situation: h = 5%
• Current situation: h = 25%

The production of electricity by waste incineration is not very eco-efficient if
avoided environmental charges for the waste treatment are not considered, as is done
in the existing LCA of the MSWI process chain in Tarragona (see Chapter 2 for
further explanations). Nevertheless, installation of an advanced acid gas removal
system increases eco-efficiency significantly.

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