Where that emissions went? Characterising the uncertainty of characterisation factors of underspecified emissions.

Life cycle impact assessment (LCIA) methods use unspecified archetypes to model situations of imperfect knowledge. There is an inherent uncertainty in characterisation factors to unspecified archetypes, and this study proposes an estimation of this uncertainty using continuous and discrete probability distributions. The extent of “archetype uncertainty” is analysed for several methods and the impact on LCIA scores is quantified for all activities in the database ecoinvent. Results indicate that this source of uncertainty can be very large, introducing systematic as well as random errors in LCIA scores. Based on this research we recommend using undefined archetypes only when needed and quantify this source of uncertainty by default. The continuous and discrete approaches to model uncertainty give similar results, but the continuous approach is easier to implement.