1. Introduction
Life cycle assessment (LCA) has been used for many years in
waste management research in order to estimate the life cycle impact
of waste management and to compare and optimise systems
(Bergsdal et al., 2005; Christensen et al., 2009; Iriarte et al., 2009).
The ultimate goal for an LCA is to model the real world system as
accurately as possible. Waste management systems are, however,
complex, and uncertainty in the modelling is unavoidable. Managing
these uncertainties therefore becomes important. Gentil et al.
(2010) made a qualitative comparison of different waste LCA-models
and found the functional unit, system boundaries, waste composition
and energy modelling to have a potentially significant impact
on the results. Large uncertainties were also found by Winkler and
Bilitewski (2007) when applying identical system assumptions in
different LCA-tools. Merrild et al. (2008) found that both technology
choices and system boundaries have a significant impact on the results
when comparing recycling and incineration of paper waste,
and Rigamonti et al. (2009) discussed the importance of choices
in material and energy recovery parameters when assessing integrated
waste management systems. While the importance of technology
choices, system boundaries and energy substitution are
discussed in the literature, much less attention is paid to uncertainty
in the waste composition. Christensen et al. (2009) included
a variation in waste composition when performing sensitivity