Energy recovery from sewage sludge offers an opportunity for sustainable management of sewage sludge and energy. Anaerobic digestion and pyrolysis are among the most promising processes applicable for sewage sludge-to-energy conversion. Anaerobic digestion of sewage sludge forms methane-rich biogas, which can be utilized as fuel to offset heat and electricity consumption of the wastewater treatment sector. However, the digestion process has the efficiency limitation since it cannot sufficiently extract the energy from sewage sludge. The digested sludge is still energy profitable and it contains considerable organic matter, but poor in biodegradability. This paper presents a brief overview of anaerobic digestion, pyrolysis, and the combination of other processes with anaerobic digestion in the application to bio energy production from sewage sludge. An assessment of energy conversion of five sludge to energy pathways is also presented. The pathways via pyrolysis and the combination of anaerobic digestion, thermal hydrolysis, and thermal drying could achieve higher energy efficiency compared to other pathways.
Dry semi-continuous anaerobic digestion of food waste in the mesophilic and thermophilic modes: New aspects of sustainable management and energy recovery in South Korea
