Assessing the life cycle greenhouse gas emissions of biorefineries

During the next decades there will be a growing demand for new land for food production due to population and economic growth. Simultaneously, global warming has been recognised as one of the most severe environmental problems of our time, and industrialised countries are negotiating on considerable emission cuts for the next decades. Biorefineries are considered by many as one solution for mitigation of climate change and improvement of the future security of food, chemical, forest and energy industries. Since increased use of biomass in biorefineries also implies increased use of land and auxiliary inputs, many have proposed to use by-products of food and forest industries in biorefineries. When assessing the global warming impacts of biorefineries, the setting of the spatial system boundary to include or exclude indirect impacts may significantly affect the results. In this paper, we discuss the life cycle greenhouse gas impacts of a hypothetical forest-based biorefinery by using two different approaches - attributional and consequential life cycle assessment (LCA) - to set the system boundary. The results imply that for those bio-based side-streams for which there presently exists use, the environmental benefits of diverting them to new uses as bio-fuel or bio-material are not straightforward and should be carefully and comprehensively studied before making decisions.