One of Seneca’s main goals is to ensure we provide renewable energy back to our community from the waste we collect each and every day to reduce the need on the Earth’s natural resources. Seneca accomplishes this by collecting landfill gas (biogas) that is generated as waste decomposes and processing it through our high BTU gas plant to produce renewable energy consisting of 98% methane gas.
Two key components that help us collect and maximize the landfill gas generated are gas wells and temporary/permanent capping systems. In 2017, we installed over 20 gas extraction wells and also installed over 10 acres of temporary cap at the Seneca Landfill. The gas extraction well borings are drilled vertically into the waste mass with a 36-inch diameter auger bucket. The wells are completed by installing a 6-inch diameter PVC perforated pipe along with gravel back into the boring to allow gas to flow out of the waste mass. The vertical gas wells are brought to the ground surface with a solid piece of PVC pipe and a well head assembly that includes a valve to help control the flow of gas out of the landfill. The vertical gas wells are then connected to horizontal gas piping that conveys the gas to our gas processing plant.
The temporary cap consists of a 40 mil high density polyethylene geomembrane liner that is installed over the waste. The cap helps maximize the gas wells’ production and reduces oxygen infiltration into the collection system. Gas wells and temporary caps also play a role in operating a compliant site by reducing potential for offsite odors, reducing water infiltration into the landfill, reducing leachate generation, and eliminating soil erosion on the side slopes.