The results also show, that co-digestion of corn silage with cattle manure (Base SS), will improve the overall environmental performance of single feedstock digestion of corn by over 100% (2.9 pt)
(Figs. 3 and 4). Also, the co-digestion of cattle manure with corn silage, grass silage and whole wheat plant silage significantly enhanced the environmental performance for small (Base SS-1) and large-scale (Base LS-1) biogas plants, respectively, compared to single feedstock digestion of grass silage and whole wheat plant silage. With respect to energy balance (Pöschl et al., 2010), the results indicated that co-digestion of cattle manure with corn silage (Base SS), and MSW with food residues (Base LS) represented the most energy efficient co-digestion scenarios, for small and largescale plants, respectively. Evidence from this study indicates that the environmental performance is the key impedance on feedstocks that could be sustainably used in the mix.