The City of Pittsfield investigated the feasibility of reusing anaerobic digester gas in a combined heat and power (CHP) system to reduce power consumption at its Wastewater Treatment Plant (WWTP). Kleinfelder served as the City’s engineer and designer in developing a system to transform the plant’s digester gas waste into heat and power.
To proceed with the project, the City needed to determine if the plant’s digester gas contained enough energy to operate a digester/biogas handling system. A CHP system would reduce peak energy demand and operation costs, while decreasing greenhouse gas emissions produced by flaring. In addition to funds from the American Recovery and Reinvestment Act (ARRA), the City sought funding from various government and private entities.
After completing a feasibility study that determined the digester gas had enough energy to power a CHP system, Kleinfelder and the City evaluated the cost-effectiveness of the project. Kleinfelder suggested automating the digester mixing system and increasing the sludge heat-exchanger capacity. Recommendations to optimize the CHP system design included installing three 65-kW microturbines, developing a gas conditions system to remove contaminants, and using CHP system recoverable heat for the hot-water loop. Analysis of the proposed method showed that a microbine system offered a potential payback period as low as five to eight years.
Through careful facility planning, leveraging energy audits, and securing additional funding opportunities, Kleinfelder helped the City implement this cost- and energy-saving CHP system. The new system reduces the City’s annual electric utility bill by approximately 30% and provides an estimated annual savings of $206,000.
City of Pittsfield