Burning landfill gas has environmental and economic benefits

Ben Armstrong, Exelon Corp.

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Exelon Power's Fairless Hills Generating Station (Figure 1) is a two-unit, 60-MW power plant purchased in 1997 from USX Corp. (then known as U.S. Steel). It recently was reconfigured to burn captured landfill gas, rather than its design fuels—oil, natural gas, and waste gases from an adjacent USX steel plant. Each of the plant's boilers supplies 300,000 lb/hr of steam at 850 psi and 900F to its turbine-generator (Figure 2).

1. Old dog, new tricks. The 60-MW Fairless Hills Generating Station was recently repowered to burn landfill gas. Courtesy: Exelon Corp.

2. Aging gracefully. The plant's two 30-MW steam turbines were originally installed in the 1950s. Courtesy: Exelon Corp.

Waste not, want not

Soon after purchasing the plant, Exelon (PECO at the time) retrofitted both of the plant's boilers to burn landfill gas by replacing their burners and burner management systems. The methane-rich gas comes from the nearby Grows and Tulleytown landfills, which are owned and operated by Waste Management Inc.

Exelon is reducing its overall greenhouse gas emissions by using more landfill gas to generate electricity (see box). Burning it produces less emissions than burning fossil fuels while making use of an energy source that otherwise would have gone to waste. The carbon dioxide (CO₂) in landfill gas is considered biogenic, or part of the natural carbon cycle.

Electricity production with environmental protection

Although Exelon deserves credit for repowering Fairless Hills Generating Station to extend its life by enabling it to fire landfill gas, the project is only one of the company's ongoing efforts to reduce its overall greenhouse gas emissions.

In addition to operating the 6-MW, landfill gas–fueled Pennsbury Power Plant, six years ago Exelon Power signed an agreement to purchase the output of Green Knight Energy Center, a similarly fueled 10-MW plant in Pen Argyl, Pa. In addition, Commonwealth Edison, another unit of Exelon Corp., purchases 118 MW of landfill gas generation from 21 projects across northern Illinois.

To date, Exelon landfill gas initiatives have avoided over 35 million CO₂-equivalent tons of emissions.

In addition to methane and CO₂, uncontrolled municipal solid waste (MSW) landfills also emit nonmethane organic compounds (NMOCs). Among them are hazardous air pollutants and volatile organic compounds that contribute to ozone formation. Burning the landfill gas to extract its energy significantly reduces emissions of methane and NMOCs. Nearly 400 MSW landfills in the U.S. recover and combust landfill gas to generate heat or electricity. More than 450 other MSW landfills flare the gas.

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