Energy crops in regional biogas systems: An integrative spatial LCA to assess the influence of crop mix and location on cultivation GHG emissions

Abstract

Anaerobic digestion producing biogas is an important decentralized renewable energy technology used to mitigate climate change. It is dependent on local and regional feedstocks, which determine its sustainability. This has led to discussions on how to alter feedstock for biogas plants without compromising their GHG (Greenhouse gas) saving, one particular issue being the use of Maize silage (MS) as the dominant feedstock. To support this discussion, this paper presents an integrated life cycle assessment of energy crop cultivation for 425 biogas catchments in the region of Central Germany (CG). The simulations for the CG region showed that MS as an effective crop to mitigate GHG emissions per kilowatt hour (GHGculti) was context dependent. In some cases, GHGculti reductions were supported due to higher yields, and in other cases, this led to increased GHGculti. We show that the often-proposed strategy of substituting one crop for another needs to be adapted for strategies which take into account the crop mixtures fed into biogas plants and how they perform altogether, under the specific regional and locational conditions. Only in this way can the trade-offs for lower GHGculti be identified and managed.