Thermal hydrolysis consists of exposing sewage sludge to high temperature and pressure. As steam explosion destructs the cell walls, more volatile solids in the sludge get transformed into biogas during mesophilic anaerobic digestion. The same volume of sludge, pre-treated via thermal hydrolysis, can yield up to 50% more biogas compared to conventional digestion.
Some of this additional biogas is used for producing the steam needed for thermal hydrolysis, but often there is surplus available for other energy demand. The biogas can be utilised in a gas engine with generator to produce green electricity. Alternatively, it can be cleaned and stripped of CO2 and used to substitute natural gas to grid or used directly for vehicles as renewable fuel.