Biogas production from supernatant of hydrothermally treated municipal sludge by upflow anaerobic sludge blanket reactor

► Biogas recovery from a hydrothermally treated sludge supernatant was tested by a 550 days running UASB reactor. ► The UASB reactor could achieve a high methane production rate and show a stable performance. ► Granular sludge could grow with the supernatant substrate. ► The methane-produced energy was higher than the energy consumed.