Draft PPS18: Renewable Energy
Annex 1 Energy from Waste (Biological Processes) Technology: Gas Collection & Management
C30. Many landfill sites are already equipped with LFG collection and control systems to prevent the gas from dispersing. The gas is piped to an extraction plant on the edge of the landfill site. The plant will typically include:
- gas conditioning equipment;
- extraction pumps;
- a flare stack;
- pipework and valves; and
- control and monitoring equipment.
C31. Gas is drawn from the waste via vertical and/or horizontal wells, each of which is monitored and regulated. It is then conveyed to the extraction plant, usually in polyethylene pipes placed underground. LFG comes out of a landfill site warm and saturated with moisture. As it cools in the extraction pipework, liquid condenses out. The pipework is therefore laid at a gradient and incorporates condensate traps to remove this liquid from the gas flow. The type of gas conditioning equipment required depends on the use to which the gas will be put: gas for heat generation does not need to be purified as much as that used for electricity generation.
C32. At any landfill site a flare stack is required to mitigate emission of methane, which will be generated regardless of whether there is energy recovery or not. Where engines are installed the flare will be used where there is excess production or during servicing. In visual terms, flares can be either open (where a luminous flame will be observable) or closed (where the flame will be shrouded).