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SRP makes methane magic using gas produced at landfill

Arizona's Salt River Project uses methane gas produced by landfill garbage as its latest and least-expensive source of green power. Located on the Salt River Pima-Maricopa Indian Community, the four-megawatt Tri-Cities Generating Facility is the first of its kind in Arizona and the only one in the country located on an Indian reservation. It began operating in July.

The plant converts methane gas into electricity used to power about 2,000 Valley homes. The powerplant sits on an acre of the Tri-Cities landfill, which contains about 10 million tons of garbage. The landfill was closed 10 years ago and produces methane gas as it decomposes.

The gas fuels five internal combustion engines and will generate electricity for 10 to 15 years. A landfill is not the place you would expect to find a source of clean energy, but landfill gas is a reliable, renewable energy source. Capturing the gas and using it to produce electricity also improves the environment.

The gas occurs naturally as waste decomposes in a landfill. Using it in this manner is less polluting than using conventional sources of energy and costs less than other forms of renewable energy.

Landfill gas is about 50 percent methane, a potent greenhouse gas that, if uncollected, might contribute to global warming. SRP's landfill project will reduce problems normally associated with uncollected landfill gas, such as odors, air pollution, and safety hazards, by converting this naturally occurring waste to energy.

In March 1998, SRP began buying landfill gas from three landfills on the SRPMIC. SRP tested the gas to determine if it was feasible to construct energy generation facilities at the landfills. SRPMIC is using collection systems to remove the harmful gases from the atmosphere.

In August 1999, SRP installed a thermal hybrid electric solar dish at the Salt River landfill, located at the SRPMIC. The device is the first of its kind to generate electricity using heat from the sun when available and landfill gas when the sun isn't shining.

Beside landfill gas generation, Salt River Project's portfolio includes funding for other "clean" technologies such as fuel cells.

In principle, a fuel cell operates like a battery. But unlike a battery, a fuel cell does not run down or require recharging. It will produce energy in the form of electricity and heat as long as fuel is supplied. Fuel cells use an electrochemical reaction rather than combustion to generate electricity, so emissions are minimal, making them an environmentally friendly alternative to conventional power sources.

The 4-megawatt Tri-Cities Landfill Gas Generating Facility will produce enough electricity to power about 2,000 homes. Decomposing garbage produces methane, which is used as fuel. Photograph by Mark Durben of SRP.

Web Sites Salt River Project: www.srpnet.com/environment/renewable.asp To access the tour: www.srpnet.com/powertour