The development of large reciprocating generator sets that can run on low Btu (dilute) methane have given us a way to harness waste fuel from landfills, waste treatment plants and coal mines.
Energy issues in recent years have focused our attention on methane as a viable and environmentally advantageous energy source that has vast global potential. Methane represents an abundant natural resource that can economically converted to clean, usable electricity.
In Europe alone, the European Commission estimates that landfills produce upwards of 94 billion cubic meters of methane each year. In the US, the EPA has estimated that landfills could provide more than two quadrillion Btus of energy per year. Currently in the US, there are approximately 400 operational landfill-to-energy projects and another 600 candidate landfills suitable for energy production, according to the EPA’s Landfill Methane Outreach Program.
Methane from coal beds and mines represents another source to be tapped for energy production. In the US alone, estimates of methane production from coal beds amount to 37 billion cubic meters per year.
The vast resources of methane available from landfills, sewage treatment plants and coalmines make a compelling case for “waste to energy” alone. How the energy is efficiently and economically harnessed makes the difference. Reciprocating engine generator systems are far and away the most popular technology being employed today for producing electricity from natural and man- made sources of methane gas. Some of the reasons for this are, the gaseous- fueled reciprocating engine is a mature technology, new low-Btu industrial engine designs are able to operate at full rated horsepower, the technology is significantly less expensive, the generators are more tolerant of impurities and contaminants that are found in methane from landfills and coal seams, and they operate at higher electrical efficiencies than turbines.
Making the case for “waste to energy” depends on engine design technologies that combat many of the typical contaminants found in landfill gas, such as sulfur, siloxanes, ammonia and acids. Cummins Power Generation has developed several technologies that help to minimize maintenance and engine overhauls due to the influence of these contaminants. These technologies include:

• Patented carbon cutting piston ring serves to break up deposits of carbon and silicates, extending the time between major engine overhauls and rendering the engine less prone to siloxane problems than other designs.
• Ferrous cast ductile cast iron pistons are used in its low-Btu engines for extended durability when operating on contaminated landfill gas. They are significantly more durable than aluminum alloy pistons.
• The engine bearings are manufactured from materials that are less susceptible to corrosion from ammonia and acids in the gas stream.
• Charge air cooler. Normally made of copper for the best heat conduction, the vulnerable materials are coated with a phenolic resin to protect them from corrosion.
• Industrial Engine lubricating oil is generally designed to be more alkaline than typical engine oil to extend the time between oil changes.

Waste-to-energy projects that utilize methane from landfills, waste digesters and coal beds are generating a significant amount of electric energy for global customers, eliminating the need for energy that is generated from non- renewable fossil sources that produce carbon dioxide. Cummins Power Generation has been involved in a number of these projects throughout the world. Recent projects include Viridor Waste Management, one of the UK’s largest operators of landfills, Salto del Negro in the Canary Islands and the Moronbah coal seam in Queensland, Australia.
The vast majority of waste-to-energy projects use low-Btu reciprocating engine generators to produce electricity from methane. These engine-generator systems have proven to be environmentally clean, reliable, durable and economical in a wide variety of landfill, garbage digester and coal bed methane projects.
If you need more details, please click here to download our White Paper on The case for waste to energy: Utilizing low-Btu reciprocating gas engine generators written by Keith Packham, Gas and CHP Cogeneration Applications Manager, Energy Solutions Business Unit, Cummins Power Generation, Ramsgate, England.