Page 352 - Materials Chemistry, Second Edition

L1644_C08.fm Page 316 Tuesday, October 21, 2003 3:03 PM

The combustion in a flare of the biogas collected (estimated at 50% of the total
generated) and the consequent air emissions of nitrogen and sulfur oxides are the
main contributors to the AA indicator. Also, significant nitrogen and sulfur emissions
are produced during collection and transport of wastes to the landfill.
The potential risk of leachate free discharges into soil (estimated at 20% of the
total generated) significantly increases the risk of WE; ammonia is the main con-
taminant contributor to this indicator. In the TE indicator, the main contributors are
cadmium and zinc air emissions generated primarily during the construction of
vehicle bodies but also during diesel oil production and its combustion during
collection and transport of wastes. Mercury in water, generated during the container
manufacturing process, is also an important contaminant contributor to this indicator.
As a final comment, it should be mentioned that impact assessment interpretation
is a particularly difficult task in a landfilling activity, mainly because of the temporary
dependence of its environmental consequences. In landfilling, the chemical life of
wastes can be estimated approximately 30 years before being considered an inert
waste, which implies that biogas and leachate emissions will vary in quantity and
composition during this period. In this case study, any emission to air, water and
soil produced along the chemical life of wastes (30 years) has been directly assigned
to the functional unit considered (50,000 t of MHSW).

8.2.3 SELECTION OF POLLUTANT FOR SITE-SPECIFIC IMPACT
ASSESSMENT IN LANDFILLING EXAMPLE
As pointed out in the introduction to this example, a dominance analysis is to be
carried out for the human toxicity indicator. Table 8.7 indicates that the air emissions
of 1,1,1-trichloroethane (C H Cl ) contribute most to the human toxicity indicator.
2
2
3
Therefore, the next section presents an exposure risk assessment for 1,1,1-tricholoro-
ethane from landfilling of MHSW.
8.2.4 RISK ASSESSMENT OF THE 1,1,1-TRICHLOROETHANE EMISSIONS
FROM LANDFILLING OF MIXED HOUSEHOLD SOLID WASTE

8.2.4.1 Introduction

Pollutants emitted to the atmosphere are transported through it and may subsequently
impact environmental media (i.e., soil, water and vegetation) near the plant, resulting
in a number of potential sources for human exposure. Because the landfill’s emissions
of trichloroethane were the main contaminant contribution to the human toxicity
indicator according to the LCA applied in Example 1.1(Table 8.7 and Section 8.2.3),
the aim of this exercise is to calculate the incremental lifetime risk due to the 1,1,1-
trichloroethane (C H Cl ) emission of the landfill of MHSW for the residents living
2
3
3
in the surroundings of the plant. In order to obtain this, the air 1,1,1-trichloroethane
concentrations in the vicinity of the landfill were quantified by application of a
Gaussian dispersion model (ISCST-3). Then, human health risks due to 1,1,1-trichlo-
roethane emissions from the landfill were calculated by application of a multimedia
exposure model (CalTOX).
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