Everything is relative and nothing is certain. Toward a theory and practice of comparative probabilistic LCA

Introduction It is widely recognized that LCA is in most cases relative and contains uncertainties due to choices and data. This paper analyses the combination of the two comparative uncertainties. Basic concepts We carefully define the idea of relativity and uncertainty within LCA. We finish off by giving an example of case where inappropriate handling of comparative uncertainties will lead to a misleading result for a decision-maker. Correlations We develop a generic framework for probabilistic comparative LCA and analyse at which places correlations may be present. We also discuss the most convenient approaches for handling such correlated uncertainties. Conclusion We put the elements discussed in a structure that provides a research agenda for dealing with comparative uncertainties in LCA.