Page 342 - Materials Chemistry, Second Edition

L1644_C08.fm Page 310 Tuesday, October 21, 2003 3:03 PM

Operation (per month) — sand: 350 t, electricity: 2250 kWh; diesel: 4500 l; oil 100 l
Biogas — free discharge: 50%; combusted in flare: 50%
Leachate — total production: 55 l/t; free discharge: 20%; biologically treated: 80%
Final capping — clay: 13,500 t; top soil: 6000 t; diesel: 13,500 l

After introducing the previously presented input data in the software model
(WISARD), the eco-balance or inventory of the landfilling activity studied (50,000
t of MHSW) has been automatically calculated. The complete inventory was inte-
grated by 307 environmental loads (inputs and outputs): energy and raw materials
consumed and emissions to air, water and soil. The main inputs and outputs of the
system that contribute more than 5% in any of the environmental impact indicators
subsequently considered are shown in Table 8.5.

8.2.2.4 Impact Assessment

To carry out this phase of the LCA case study, the following nine impact categories
have been considered: water eutrophication (WE), depletion of nonrenewable
resources (DNRR), air acidification (AA), greenhouse effect (GE), aquatic eco-
toxicity (AE), human toxicity (HT), terrestrial eco-toxicity (TE), depletion of the
ozone layer (DOL) and photochemical oxidant formation (POF). The specific envi-
ronmental impact indicators used in each of the environmental impact categories
mentioned are shown in Table 8.6.
The environmental loads (inputs and outputs) previously inventoried have been
classified under their corresponding environmental impact indicator, following the
classification criteria specified in these indicators. Characterization factors have then
been used to prioritize the environmental loads or, in other words, to quantify the
potential contribution of each environmental load in the different impact indicators.
These characterization factors are pre-established for each impact indicator. Finally,
the corresponding potential contributions have been determined by multiplying the
mass of the environmental loads in the inventory by these factors (for example,
54,533 g trichloroethane × 1200 g equiv. of 1-4-dichlorobenzene/g trichloroethane
= 65,439,600 g equiv. of 1-4-dichlorobenzene).
The inventoried environmental loads are classified under their corresponding
impact indicators with their respective characterization factors in Table 8.7. The total
potential contribution of each environmental load in each impact category, as well
as its corresponding contribution percentage for the four stages of the landfilling
activity (containers, collection, transport and landfilling), are presented.

8.2.2.5 Interpretation

As can be seen in Table 8.8 and Figure 8.3, landfilling is the stage that contributes
more to WE, AA, GE, AE, HT, DOL and POF, indicators being the transport of
wastes to the landfill, the main contributor to DNRR and TE indicators.
Direct and indirect consumption of scarce natural nonrenewable resources con-
tributes significantly to DNRR indicator. During the construction of vehicle bodies
for collecting and transporting wastes to the landfill, these scarce raw materials are

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