The City of San Leandro, California, is to be the site of a 330 kW cogeneration facility at the town’s Water Pollution Control Plant (WPCP).

The installation, to be built by Siemens Building Technologies Inc, will run on methane produced by the water treatment process.

The WPCP treats an average of 6 million gallons (22 million litres) per day of municipal and industrial wastewater and is the largest single city-owned electricity consumer. It also produces some 96,000 cubic feet (2680 cubic metres) of methane a day, most of which is currently flared. The new cogeneration facility will use this gas in reciprocating engines and is expected to produce around 60% of the plant’s energy use, currently supplied by local utility Pacific Gas & Electric (PG&E).

The heat produced by the engines will be used in the water treatment process.

The proposed facility includes three 110 kW gas engine generators that produce 285 kWe, a gas conditioning facility that cleans and cools the methane from the digester – making it suitable for the reciprocating engines – and a grease receiving station that will accept additional waste grease from commercial waste haulers to enhance the digester process and increase methane gas production. The use of grease from companies not only improves the performance and efficiency of the system, it also generates revenue from waste disposal fees, the company says.

The US$5.6 million agreement with Siemens includes design, construction and maintenance for the cogeneration system. Project costs will be covered by WPCP enterprise funds, which are collected annually from city sewer service fees and will be used for maintaining the plant. The new facility will also take advantage of applicable rebates, including a $255,000 Self-Generation Incentive Program (SGIP) rebate from PG&E.

San Leandro mayor Tony Santos commented: ‘We are cutting the city’s energy costs, reducing the city’s impact on global warming; re-using a waste product, namely, grease; and using only funding that is specifically dedicated for this purpose.’