Land use and land use change in agricultural life cycle assessments and carbon footprints - the case for regionally specific land use change versus other methods

摘要

The supply chain of a product is essential for understanding its environmental impacts. As parts of agricultural product supply chains, land use (LU) and land use change (LUC) are considered to be major contributors to global CO_2 emissions. Nevertheless, LU and LUC (LULUC) are rarely included in GHG estimations for food and feedstuffs. Here we propose a method which can be used to derive emissions from LU and LUC on a regional level. Emissions are distributed over an accounting period chosen to match the physically occurring carbon fluxes. As fluxes from soil organic carbon persist for years or even for decades after a LUC episode, depending on the climatic conditions of the region, we apply 10 and 20 years as suitable accounting periods for tropical and temperate climate zones, respectively. We compare the proposed method with two other methods proposed in the literature. Using two types of feedstuffs (Brazilian soybean-meal and Austrian barley) as examples, we find that the other two methods produce mostly lower emission estimates in the case of Brazilian soybeans, and higher estimates for Austrian barley. We conclude that these differences are caused mainly by different accounting periods and by a (non)consideration of regional specificities. While analysing life cycles necessarily entails a well supported - but still arbitrary - setting of such system boundaries, we argue that the methodology presented here better reflects actually occurring carbon fluxes that we understand to be the foundation of any environmental product assessment.