Article: Aerobic vs. Anaerobic Digestion

By Mark Eklund, P.E., Columbian TecTank

The popular choice in the United States among wastewater treatment facilities has been the use of an aerobic digestion process, because of the attractive cost to construct an aerobic digester. The cost of land, depending on geographical region, has been reasonable, and aerobic digesters take up a large footprint. It was considered acceptable that aerobic digestion consumes higher net energy to operate and produces more excess solids than anaerobic digestion.

The anaerobic digestion process has been not nearly as popular in the United States due to the higher upfront expense to install. So land use and energy consumption played a small roll in process decisions. This ended up being a deterrent to using the anaerobic process. However, anaerobic digesters encompass a much smaller footprint in construction and offer a lower net operating cost.