A sanitary landfill's primary purpose is to provide for the disposal of society's waste material. As it decomposes, however, this waste material produces methane, considered a greenhouse gas. To prevent the release of this gas into the atmosphere, the U.S. Environmental Protection Agency has for decades required that landfills be equipped with gas collection systems to capture and destroy this gas. Traditionally, the methane has been destroyed by burning the collected gas in flare stations. While doing so reduces greenhouse gas emissions from the landfill, the potential energy available from the methane combustion is lost. Until recently, this was the case at the Los Angeles County Sanitation Districts' Calabasas landfill, where the amount of energy consumed by the flares was enough to power more than 5,000 households.
In 2004, the District became aware of Solar Turbines' low emissions Mercury™ 50 and approached Solar Turbines with the idea of operating this turbine on landfill gas. With assistance from the U.S. Department of Energy, the Mercury 50 had been developed to advance the sustainability of gas turbine technology in terms of both efficiency and emissions of nitrogen oxides and carbon monoxide. However, it had not been initially designed to operate on landfill gas. The challenge Solar Turbines faced was formidable: modify the Mercury 50's combustion system to operate on the diluted landfill gas produced at the Calabasas landfill while still meeting the strict emissions limits imposed by southern California regulatory authorities.
Solar Turbines took on and successfully completed the necessary development program and in June 2010, three Mercury 50 gas turbines began operating at the Calabasas Landfill Gas-to-Energy Facility. The turbines deliver about seven megawatts of electrical power to the local grid and have also demonstrated exceptional emissions performance, reducing emissions of both nitrogen oxides and carbon monoxide substantially below previously established limits in southern California.
The Mercury 50 has enabled the Los Angeles County Sanitation Districts to productively utilize the low-quality gas produced at the Calabasas landfill while meeting some of the strictest air pollution limits in the world, providing an attractive option for other landfill gas-to-energy developers. The Solar Turbines Mercury 50 has earned its place among Caterpillar's sustainable products.