Portland, Oregon

Columbia Boulevard Wastewater Treatment Plant (CBWTP), the largest wastewater plant in Oregon, is operated by the Portland Bureau of Environmental Services (BES). The facility is the collection point for about 1,800 miles of wastewater sewer pipes and includes 92 pumping stations. CBWTP treats 80-90 million gallons of sewage and wastewater each day. CBWTP’s wastewater treatment process produces about one million cubic feet of anaerobic digester gas each day and about 55 percent of the gas is methane. Typically, treatment plants like CBWTP flare or burn excess biogas. Using this fuel source to generate power provides the facility with a free, renewable energy source that displaces local utility electricity (likely generated from natural gas or coal fuels).

The plant has investigated several technologies over the years to reclaim this “biogas” for electrical power generation to reduce utility costs and has installed a number of these advanced systems. CBWTP installed a 200 kW anaerobic digester gas fuel cell power generation project in 1999, but it was decommissioned in 2005. In April 2003 four 30kW Capstone microturbines were installed.  Based on its experience re-claiming biogas for electricity generation with other CHP technologies, the City (with assistance from Oregon state renewable incentive funding) made a major CHP investment in June 2008 installing two 850kW I/C Engine-Generators which are operating successfully and have substantially reduced the need to flare biogas.