Another layer of garbage and more soil is added, and so on until the landfill section is deemed full. The area is then topped with special low permeability soil, an HDPE membrane, more soil and vegetation cover. Holes are bored and piping collects the potentially hazardous methane gas. The quantity of vent pipes is determined based on many factors including the rate of decomposition, climate, thickness, the number of layers, and more. A multistage centrifugal blower/exhauster forces the gas mixture, mostly methane gas and carbon dioxide, to leave the landfill and send it to the landfill gas vent flare.
This process can use one or multiple multistage centrifugal blowers/exhausters. A single blower/exhauster could draw from twenty or fifty vent pipes; however, the vent pipes must be engineered to draw an even vacuum. Multiple blowers/exhausters can address this potential issue.