Cathodes in microbial electrolysis cells are exposed to poisoning in particular when using activated sludge as substrate. In this work, it was examined how well hydrogen generation is possible and what kind of membrane protection is sufficient to produce hydrogen from activated sludge. Also model microbial electrolysis was performed to simulate hydrogen evolution in a mimic biological environment at pH = 7. With activated sludge, it was found that electrodeposition of calcium, iron and phosphor and other impurities inhibited the hydrogen evolution reaction. Applying 2.0 V, the biogas productivity increased notably as if it induced rather chemical hydrolysis than hydrogenation and favored methanisation. This MEC generated methane in up to highest purity, 67-97%. In addition, this room-temperature methanisation consumed far less energy than with comparable mesophile conditions. (C) 2017 Elsevier B. V. All rights reserved.