Mesophilic digestion is the most commonly used process for anaerobic digestion, in particular waste sludge treatment. Digestion takes place over a period of 15 to 40 days at a temperature of 30 to 40oC
It is usually more robust than the thermophilic process, but the biogas production tends to be less, and additional sanitisation such as pasteurisation is usually required.
Thermophilic digestion is less common and not as mature a technology as mesophilic digestion. The reactor is heated to 55oC and held for a period of 12 to 14 days.
Thermophilic digestion systems provide higher biogas production, faster throughput and an improved pathogen and virus ‘kill’, but the technology is more expensive, more energy is needed and it is necessary to have more sophisticated control & instrumentation.