The Swiss Eco-Point (SEP) Method

(Source:  Hertwich et al., Evaluating the environmental impact of products and production processes: a comparison of six methods. Science of the Total Environment, 1996 Vol. 196, Issue 1, 13-29.)

This method determines pollutant loadings based on a source’s contribution to an acceptable total pollution load and an environmental scarcity factor. The impact analysis in the Swiss model of LCA (SEP) is based on the idea of critical pollution loads. It considers the scarcity of environmental absorption capacity by relating a production process’ load to the actual load of that stressor as well as the critical load that can be absorbed by the receiving environment. The sum of ‘points’ from all stressors gives a measure of the total environmental impact:

 SEP score    = [relative emissions][scarcity factor]

                         =

The critical flow or maximum acceptable pollution load E_Acceptable represents the absorption capacity of an environmental compartment for a particular pollutant. A watershed, an airshed, or the area of a nation are chosen as control volumes, depending on the scale of the effect. The critical flow is derived from an ambient pollution standards and the removal rate of the pollutant by advection or decay. The emissions from the investigated process or product are designated E. E_Total is the current pollution load independent of the investigated process or product, in the control volume. 

The concept of SEP is elegant and seems to suggest that valuation can be achieved automatically through the use of scarcity. The valuation, however, implies that we are equally concerned about each pollutant, independent of the effect it causes. A comparison of the SEP score with the effects-based global warming potential shows that SEP overrates methane and nitrous oxide. Nitrous oxide in fact has a higher GWP than methane and the role of carbon dioxide is not as small as SEP would indicate.