Improving Bioenergy Recovery from Anaerobic Digestion of Sewage Sludge

Water utilities generate enormous amounts of sewage sludge globally each year. This chapter introduces the characteristics of sewage sludge and anaerobic sludge digestion. The state-of-the-art technologies for enhancing methane and hydrogen productions from sewage sludge are also elucidated, including physical, chemical, and biological pretreatment. Emphasis is put on their effect on methane and hydrogen production performance, with an increase of 10–340% in methane production and an increase of 20–1300% in hydrogen production. In general, thermal pretreatment, free nitrous acid pretreatment, free ammonia pretreatment, and temperature-phased anaerobic digestion show advantages over the other pretreatment technologies. In addition, ultrasonic pretreatment (<4400 kJ/kg total solids) will also be promising if pathogen destruction is not a main concern. In the future, various pretreatment technologies should be implemented to the same sludge source in order to avoid the bias imposed by the different sludge sources.