Biogas plants currently rely on alternative feedstock from food processing and MSWstreams, due to their easy availability, and also high cost of alternative energy crop feedstock. High feedstock demand has led to reduction in gate fees, therefore biogas plants are more attractive for management of organicwaste (Poeschl et al., 2010). The main process in biogas production system is the AD of organic material for biogas production, which, after cleaning and secondary processing, could be used to generate electricity and heat, and in direct applications as substitute for natural gas or as transportation fuel. The functional unit applied in the assessment was the treatment of 1 tonne of organic material (feedstock) in small and large-scale biogas plants. The biogas generated was considered as main product, which contributes to the total environmental load. The by-products were included by system expansion (Börjesson and Tufvesson, 2011), hence, digestate and energy derived from biogas, were considered to substitute other products in the market. The system boundary (Fig. 1) considered the production of chemical fertilizers, electricity generation with Germany’s fuel mix, heat generation using natural gas, as well as imports of natural gas and transportation fuel. Their equivalent environmental loads were subtracted from the scenario’s total environmental impacts.