From a case study of the Eau Claire Waste Water Treatment Plant:
The City of Eau Claire generates methane gas from its Waste Water Treatment Plant to help copower the facility. The following is a summary of computed savings at the plant using the methane gas produced during the Anaerobic Digestion of biosolids, and the generators to unitize this gas. The volume of the plant’s gas production is 24,000 kWh or as indicated . . . .
Thus, an estimate of $203,868 of annual savings occurs at the Waste Water Treatment Plant using a by‐product of the anaerobic digestion process. However, because of the higher price of energy, the City has been running the generators typically from 18‐24hours per day, so the savings have been greater. The City has been using this gas in generators for over 27 years, so the savings have been very significant.