Fourth, results on eco-efficiency are presented per impact
category; eight eco-efficiency indicators are calculated and shown
for each system. Such profusion is difficult to communicate for
decision- and policy-making purposes, especially when ambiguous
results or interpretation occur or when EE indicators on a given
system show contradicting results. Trade-offs and possibly
weighting and normalisation of the impacts are needed. Further
research should investigate the development of a single EE index
per system for synoptic information of decision-makers, local
communities and the general public, following the model of Eco
Indicator 99 for single-score environmental impacts (ecopoints).
Choices have to be discussed and negotiated with these stakeholders
in terms of the selection and weighting of impacts and
normalisation.