Abstract
Ecological evaluation becomes a valuable tool for process engineering as environmental concerns must more and more be seen as defining boundary conditions for process design. Currently we see a wide portfolio of different measures that may be used to support process engineers in their design decisions. They offer however conflicting advice in many practical applications.
The primary reason for the spread in results for the same process when evaluated by different measures lays in their normative assumption. They influence what is measured and how different impacts are weighed.
The paper dissects the normative assumptions of single issue measures (e.g. Carbon Footprint and Global Warming Potential), efficiency measures (e.g. Material Input per Service Unit), thermodynamic measures (e.g. Emergy) and complex, highly aggregated measures like Ecological Footprint and the Sustainable Process Index. It can be shown that they differ widely in their normative base and consequently lead to quite different evaluation results. The paper will provide guidelines for the choice of environmental measures as well as for interpretation of the often divergent results.