2 > Methodische Grundlagen

Summary 17
> Summary
According to ISO Standard 14040, the life cycle assessment (LCA) of products,
processes or companies comprises four phases:
> Goal and scope definition
> Inventory analysis
> Impact assessment and
> Interpretation.
The “ecological scarcity” method permits impact assessment of life cycle inventories
according to the “distance to target” principle. Eco-factors, expressed as eco-points per
unit of pollutant emission or resource extraction, are the key parameter used by the
method. With that method, eco-factors are determined by the current emissions
situation and, secondly, by the political targets set by Switzerland or by international
policy and supported by Switzerland.
The eco-factors proposed for various environmental impacts in the first update of the
method (Brand et al. 1998) are used widely. The fresh update presented here became
necessary to reflect new scientific findings, new statutory and political targets, new
international agreements, developments in international standarization and experience
gathered in practice. As a part of this revision, the eco-factor formula has been adjusted
to the structure of the ISO standard (with its elements of charactization, normalization
and weighting). The set of substances assessed has been further enlarged. The data and
information on which the existing eco-factors were based was checked and updated.
The key changes made are as follows:
> The mathematical representation of the ecofactor formula has been slightly modified.
The characterization step is now made explicit. In addition, normalization is
now based on current emissions, as has become common practice. As a consequence
the weighting factor ( ratio of current to critical flow) is squared. With both the old
and new formula representation, the resulting eco-factors remain identical if the data
is the same.
> With regard to CO2 and energy, the long-term target of the Swiss confederation (1
tonne CO2 or 2000 W per capita) was interpolated for the year 2030, which is a
common time horizon of Swiss legislation.
> With regard to air pollutants, new eco-factors were determined for benzene, dioxin
and diesel soot, based on the precautionary principle enshrined in the Swiss
Environmental Protection Act.
> For heavy metal emissions (both to air and to soil), the long-term maintenance of
soil fertility is now used as the new target.
> Eco-factors can now be defined according to regional scarcities, if needed and if
regional data are available. This principle is applied to phosphorus and emissions
to Swiss surface waters.