As part of its climate policy, Germany promotes the production of biogas via its so-called Renewable-Energy-Act (EEG). The resulting boost in biogas output went along with a significant increase in production of green maize, the dominant feedstock. Existing studies of the EEG have analysed its impacts on German agriculture sector without considering market feedback. We thus expand existing quantitative analysis by also considering impacts on European and global agricultural markets, land use and the environment by combining a detailed location model for biogas plants, the Regionalised Location Information System – Maize (ReSi-M2012), with a global Partial Equilibrium model for agriculture, the Common Agricultural Policy Regional Impact (CAPRI) model. Our results indicate that the German biogas production is large enough to have sizeable impacts on global agricultural markets in prices and quantities, causing significant land use change outside of Germany. While profits in the agricultural sector increase, food consumer face higher prices and subsidies for biogas production are passed on to electricity consumers. The German biogas program, as long as it is almost entirely based on non-waste feedstocks, is probably not a promising avenue towards a GHG-saving renewable energy production, but a rather expensive one.