The use of an engine-generator package, fueled by landfill gas, to produce usable electrical power has generated considerable interest among both landfill operators and engine manufacturers. Landfill gas operation presents some unusual technical challenges that require preparation of the gas prior to engine consumption as well as modifications to the spark-ignited engine. The primary obstacles to landfill gas operation are the low-Btu content of the gas, its poor combustion characteristics, and fluctuations in the heating value of the gas. Even so, the engine was not derated from the standard natural gas generator set rating of 762 kW net electrical output. In addition, the engine performance was optimized to meet the EPA site laws for stationary gas engines while still maintaining very low brake specific fuel consumption (BSFC). Finally, 90 days of continuous operation demonstrated engine durability.