A proposal for using process-based soil models for land use Life cycle impact assessment: Application to Alentejo, Portugal

Human occupation and transformation of land are a root cause of ecosystem services degradation. For example, land use (LU) and land use change (LUC) are drivers of soil organic carbon (SOC) change, decreasing the biotic production potential of soils. In Life Cycle Assessment (LCA) there is a growing trend towards accurate and regionalized impact assessment of LU?LUC. Available impact assessment models apply statistical procedures to a simplified static characterization framework, including a limited set of aggregated LU classes. In this paper we propose process-based modelling as the basis for LU/LUC Life Cycle Impact Assessment (LCIA) and calculate midpoint process-based characterization factors (CFs) using SOC depletion as the impact indicator. This forecast or scenario-based approach included climate change scenarios for the study region. Temperature and precipitation changes are likely to affect the role of LU in SOC accumulation, which should influence LUC choices today. As proof of concept we used the region of Alentejo, Portugal, which was divided in more than 1500 unique homogeneous territorial units (UHTU). We used the process-based model RothC to establish the likely dynamic SOC evolution after LUC in each UHTU. Our work suggests that process-based models are necessary to move beyond the calculation of CFs for generic LU classes. We provide CFs for individual crops and discriminated LU classes and management practices. We additionally provide insights and indication for future work leading up to the production of global CFs using similar soil models and an updated procedure for CF calculation.