Landfills: Using Recovered Methane Fuel as a Sustainable Power Source

Landfill gas-to-energy projects use generator sets to turn waste into economically viable electricity. Caterpillar continually researches, develops and delivers products specifically designed to be operated on landfill gas fuels. In fact, over 1,500 MW of electricity is produced from Cat® landfill generator sets - enough power for more than one million homes.

Cat landfill gas generator sets are designed to:

• Extend equipment life and maintenance intervals for landfill applications
• Deliver improved performance and reliability
• Offer lower operating and maintenance costs
• Reduce environmental impact

Cat Switchgear with PLC-based controls is supplied to parallel the generators to the local electrical grid to export renewable power at a premium to the local electric utility.

How It Works

Landfill gas is produced naturally as organic waste decomposes in landfills. It is composed primarily of methane and carbon dioxide. It also contains small amounts of nitrogen, oxygen, ammonia, sulfides and non-methane organic compounds. As an important and growing application within the world's power generation mix, landfill gas-to-energy systems collect, process and treat this gas for use in generating electricity. Two common approaches to landfill gas collection include vertical well extraction and horizontal collectors or trenches.

Municipalities generally use blowers or vacuums to direct the gas from a collection site through a network of pipes to a central facility. At most developed municipal solid-waste landfills, the methane and carbon dioxide are destroyed in a gas collection and control system, or utility flare. The sustainable alternative is to divert the landfill gas from the flare to an electricity-producing Cat generator set.

The diverted fuel is dried and sometimes refined to remove impurities such as:

• Hydrogen sulfide
• Halides
• Siloxanes (silica)

After fuel treatment, the methane is introduced into a gas generator set as fuel. Cat® Dealers offer sets specifically designed for operation at landfills. These generator sets feature:

• Crankcase ventilation pump to eject potentially acidic blow-by gases
• Specially designed aftercooler cores, cylinder heads, main bearings and connecting rod bearings that are hardened against corrosive elements
• Differentiated cooling systems to operate at elevated jacket water temperatures to prevent condensation of contaminants