California City To Turn Waste Into Energy - Facility Executive Magazine - Creating Intelligent Buildings

Plant will recycle methane produced by waste water treatment facilities.
Plant will recycle methane produced by waste water treatment facilities.

California City To Turn Waste Into Energy

California City To Turn Waste Into Energy - Facility Executive Magazine - Creating Intelligent Buildings

To help reduce energy use and help the environment the City of San Leandro, CA recently approved a contract with Siemens Building Technologies, to build a 330 kilowatt cogeneration facility at the city’s water pollution control plant (WPCP). Expected to save 60% in plant energy use, the new power plant has the potential to reduce CO2 emissions by 1,500 tons per year, or the equivalent of planting 1,500 new trees. The new facility represents a major step in helping the city meet its goal of reducing San Leandro’s greenhouse gas emissions by 25% below 2005 levels by 2020.

“Any way you look at this project is a win-win,” says San Leandro mayor Tony Santos. “We are cutting the city’s energy costs and reducing the city’s impact on global warming; reusing a waste product, namely, grease; and using only funding that is specifically dedicated for this purpose, preserving our general fund monies for critical city programs. It is exciting to be at the forefront of cities taking on this type of project and look forward to all the benefits it will bring.”

The $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 according to San Leandro officials are collected annually from city sewer service fees and will be used for maintaining and improving the plant. The new facility will also take advantage of applicable rebates, including a $255,000 self-generation incentive program (SGIP) rebate from local utility Pacific Gas & Electric (PG&E).

“The city of San Leandro has put themselves at the forefront of municipal sustainability and energy efficiency by embarking on this innovative renewable energy project,” says Mike Kearney, sr. director, U.S. energy & environmental solutions for Siemens Building Technologies. “Through the conversion of waste to energy, this new cogeneration plant not only takes advantage of local resources, it is kinder to the environment—through reduced greenhouse gas emissions—and will operate at a lower cost.”

The WPCP treats an average of 6 million gallons per day of municipal and industrial wastewater and is the largest single consumer of electrical energy of all city facilities. Currently, the plant uses PG&E supplied energy to run wastewater treatment operations. The plant also produces some 96,000 cubic feet per day of methane gas (a greenhouse gas shown to be 21 times more potent than CO2), most of which is burned off and not reused. The new co-generation facility will now use all the methane gas to fuel specially designed reciprocating engines (large internal combustion motors) to spin generators that will produce the electricity needed to power the plant and treat the wastewater. 

In addition, the heat produced by the reciprocating engines will be recycled in effect and used to raise the temperature of the water needed in the treatment process. This system is efficient because it uses normally discarded methane to create both electrical energy and heat; hence, the term cogeneration.

The proposed facility features three major components: three 110 kilowatt generators that produce 285 kilowatts of continuous electrical energy needed to power the plant; a gas conditioning facility that cleans and cools the methane from the WPCP’s digester (making it suitable to fuel 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. With the new system, not only will the city be recycling grease from companies throughout the local area, it will improve the performance and efficiency of the generators while generating revenue from grease disposal fees.

Prior to construction, the project will require review and approval by the city’s Community Development Department and permits from the Bay Area Air Quality Management District. Construction on the facility should begin in late summer 2009, after the necessary permits and reviews have been completed.

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