Landfills and methane
Among the many human-related sources of methane gas, landfills are by far the biggest producers. Landfills account for roughly 34% of all human-related methane emissions in the United States. The gas is released when organic materials buried beneath the soil of the landfill decompose, thereby releasing a number of greenhouse gases, among them methane.
Landfill gas comprises approximately 50% methane and 50% carbon dioxide. Emission amounts vary from landfill to landfill, and are impacted by the composition and quantity of the buried waste. Natural elements such as moisture and temperature also play a role.
Recent federal laws require larger landfills to capture methane gas emissions before they are released and to flare the gas, converting the methane molecule into water and small quantities of carbon dioxide. The gas is captured through a system of pipes placed beneath the surface and throughout the landfill. The collected gas is then sequestered, treated to remove impurities and then flared.
While the flaring process eliminates the methane emissions, it does not typically harvest the energy potential of the combustion process itself. But developments in landfill gas to energy technologies provide new potentials for turning the environmental liability of methane into a potentially abundant, cleaner source of electricity and heat.
The first landfill gas projects in the United States began in the 1970s and have grown from a few sites 30 years ago to more than 375 projects nationwide. These projects supply nine billion kilowatt-hours of electricity and 74 billion cubic feet of landfill gas annually to companies and municipalities. North Carolina has about a dozen current landfill gas to energy projects in operation, including the recent addition of the Buncombe County Landfill Gas Project as a producer to the NC GreenPower program.
The U.S. Environmental Protection Agency’s Landfill Methane Outreach Program has recognized 38 candidate landfills in the state with potential for methane gas to energy projects. North Carolina ranks third nationally, behind Texas and California, in the number of candidate landfills for such projects. This number translates into a major potential for landfill gas development across the state that may one day provide cleaner electrical and heating alternatives for thousands of homes and businesses.
Converting landfill gas to energy involves collecting the methane from the landfill using wells that draw the gas from the ground. Once the gas is collected in a central storage area, it can be treated to prepare it for various purposes including electrical generation. The vast majority of landfill gas electrical generation utilizes internal combustion engines, with a smaller number making use of micro-turbines or other emerging technologies.
A promising resource
Generating electricity from landfill gas provides multiple benefits to North Carolina’s environment and energy supply. Flaring the methane gas prevents a potent greenhouse gas from otherwise entering the atmosphere. Also, methane is a much cleaner resource to use for electrical generation than coal and other fossil fuels.
In addition, the added electricity being placed into the state’s power supply reduces the amount of energy that must be generated from fossil fuel sources to meet electrical demands. The result is a positive environmental impact on multiple levels that also helps to diversify the state’s energy supply for years to come.
And generating electricity from landfill methane gas can help the economy as well. Purchases of methane generation can help to offset operating costs of landfills, many of which are owned by county and municipal governments. Installing and maintaining landfill gas technologies creates jobs and provides revenue for suppliers of those technologies.
These projects provide an attractive option for industry and business to locate adjacent to the landfill and utilize on-site electrical generation and direct use methane for heating and gas processes. These opportunities can help reduce operating costs and reduce overall demand for utility generated electricity. Providing economic benefits to the community can help keep energy dollars in state and encourage growth of business while reducing the impact on the state’s power supply.
Landfill methane gas is a promising technology that has great potential for North Carolina’s future. The abundance of landfill gas sources throughout the state, the existence of methods to capture and process methane onsite, the availability of practical generation technologies, and the support of electric utilities, businesses, environmental groups as well as the
NC GreenPower program help to make that potential a reality. Today, landfill methane gas to energy projects are taking the realities of waste, and converting them into a cleaner energy future for everyone.