Landfill gas is collected through a series of vertical and horizontal wells drilled into the landfill. The wells are constructed of plastic pipe, perforated at depth, similar to a water well. The pipe extends to the surface as solid pipe and is connected to a valve, to control flow, and a flexible connection to gathering pipes to accommodate differential settlement in the landfill surface. The gathering pipes are typically buried at least one metre below the surface. The gathering pipes come together in a main header pipe that terminates at the gas plant.
The gas is collected in the pipe system by applying a vacuum in the wells using a blower or compressor. The vacuum draws the gas out from around the wells and brings it to the plant, compressing it to a pressure appropriate for the end user. Just prior to injecting the gas into a boiler, engine or turbine, the gas is cooled to the dew point to allow the moisture, typical of landfill gas, to condense and drop out of the gas. The gas is then filtered and reheated.
Finally, the gas is fed into a boiler where it is combusted to generate steam, or for use as a fuel in an engine or turbine connected to a generator to create electricity. This power is then fed through control equipment and ultimately out to the grid.