Complex waste streams originating from extraction processes containing residual organic solvents and increased C/N ratios have not yet been considered as feedstock for biogas production to a great extent. In this study, spent rosehip (Rosa canina L.) solid residue (64% VS, 22 MJ/kg HHV, 30(C)/1(N)) was obtained from an industrial ethanol aided extraction process, and extensively examined in an automated batch bioreactor system for biogas production. Fraction separation of the compact lignocellulosic seeds increased the available sugar and ethanol content, resulting in high biogas potential of the sieved residue (516 NL/kg VS'). In co-digestion of spent rosehip substrate with non-deactivated nitrogen rich microbial co-substrates, methanogenesis was favored (Y-m > 68%(CH4)). In individual digestion of microbial co-substrates, this was not the case, as biogas with 28 vol.% N-2 was produced from activated sludge supplement. Therefore, effective inhibition of exogenous microbiota was achieved in the presence of carbonaceous spent rose hip. (C) 2014 Elsevier Ltd. All rights reserved.