Life Cycle Assessments of Energy From Solid Waste (PDF)

other product system boundaries leads to so called allocation problems, which are further
discussed below.
Finally, the inputs and outputs from all processes are adjusted to relate to the functional unit.
Aggregation of all data, through addition, then results in an inventory table. In the inventory
table all economic inputs and outputs will have been translated into environmental inputs and
outputs, in terms of resource extraction and emissions.
2.1.4 Life cycle impact assessment
As the inventory table often contains a vast number of figures, that are difficult to interpret
intuitively, the need for a more formalised evaluation arises. The inventory table constitutes
the input to the life cycle impact assessment (LCIA). According to the ISO-standard (ISO
1999), the LCIA is a phase of the LCA aimed at understanding and evaluating the magnitude
and significance of the potential environmental impacts of a product system. It is divided into
several elements; some are described as mandatory in an LCIA and some as optional.
The first mandatory element is a selection of a manageable number of impact categories of
resource use and environmental impacts, indicators for the categories and models to quantify
the contributions of different inputs and emissions to the impact categories. As an example of
impact categories that may be discussed in an LCIA, Table 2.1 presents a default list
suggested by the SETAC-Europe working group on LCIA (Udo de Haes 1996). In practice
however, a shorter list of impacts are normally included in current LCAs (Finnveden 2000a).
The second mandatory element (classification) is an assignment of the inventory data to the
impact categories. The third mandatory element (characterisation) is a quantification of the
contributions to the chosen impacts from the product system.
Table 2.1. Default list of impact categories for life cycle impact assessment (Udo de Haes 1996).
Input related categories
1. Abiotic resources (deposits, funds, flows)*
2. Biotic resources (funds)
3. Land
Output related categories
4. Global warming
5. Depletion of stratospheric ozone
6. Human toxicological impacts
7. Ecotoxicological impacts
8. Photo-oxidant formation
9. Acidification
10. Eutrophication (incl. BOD and heat)
11. Odour
12. Noise
13. Radiation
14. Casualties
Pro memoria: Flows not followed to the system boundary
Input related
Output related
*Deposits are resources which can only be depleted, with no renewability within the timeframe considered
(examples include mineral ores and fossil fuels). Funds are resources which are intrinsically renewable but
which can be depleted (examples include wood and fish). Flows are resources which can be deflected and used
but not depleted (examples include wind and solar radiation).
There are also several optional elements which can be used depending on the goal and scope
of the LCA (ISO 1999). Normalisation relates the magnitude of the impacts in the different
categories to reference values; an example of a reference value is the total contribution to an
impact category by a nation. Grouping includes sorting and possibly ranking of the
indicators. Weighting aims at converting and possibly aggregating results across impact
categories resulting in a single result, sometimes with a monetary measure. The final element
is a data quality analysis, which is described as mandatory in comparative assertions.
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