Choice of land reference situation in life cycle impact assessment

Purpose Land use life cycle impact assessment is calculated as a distance to target value-the target being a desirable situation defined as a reference situation in Mila i Canals et al.'s (Int J Life Cycle Assess 12(1):2-4, 2007) widely accepted framework. There are several reference situations. This work aims to demonstrate the effect of the choice of reference situation on land impact indicators. Methods Various reference situations are reported from the perspective of the object of assessment in land in life cycle assessment (LCA) studies and the modeling choices used in life cycle land impact indicators. They are analyzed and classified according to additional LCA modeling requirements: the type of LCA approach (attributional or consequential), cultural perspectives (egalitarian, hierarchist or individualist), and temporal preference. Sets of characterization factors (CF) by impact pathway, land cover, and region are calculated for different reference situations. These sets of CFs by reference situation are all compared with a baseline set. A case study on different crop types is used to calculate impact scores from different sets of CFs and compare them. Results and discussion Comparing the rankings of the CFs from two different sets present inversions from 5% to 35% worldwide. Impact scores of the case study present inversions of 10% worldwide. These inversions demonstrate that the choice of a reference situation may reverse the LCA conclusions for the land use impact category. Moreover, these reference situations must be consistent with the different modeling requirements of an LCA study (approach, cultural perspective, and time preference), as defined in the goal and scope. Conclusions A decision tree is proposed to guide the selection of a consistent and suitable choice of reference situation when setting other LCA modeling requirements.