Carbon dioxide 47.0
Paraffin hydrocarbons 0.1
Aromatic-cyclic hydrocarbons 0.2
Hydrogen sulfide 0.01
Carbon monoxide 0.1
Trace compounds 0.5
Source: Data from R. Ham, 1979, Recovery, processing and utilization of gas from sanitary landfills, EPA 600/2-79-001.
When energy is to be recovered, the gas can be piped directly into a boiler, upgraded to pipeline quality, or cleaned and directed to an onsite electricity engine-generator. The first two options are feasible only if a boiler or gas pipeline is located near the landfill, which is not common.
Because of the explosive and suffocative properties of landfill gases, special safety precautions are recommended (O'Leary and Walsh 1991a):
• No person should enter a vault or trench on a landfill without checking for methane gas or wearing a safety harness with a second person standing by to pull him to safety.
• Anyone installing wells should wear a safety rope to prevent falling into the borehole.
• No smoking is allowed while gas wells or collection systems are being drilled or installed or when gas is venting from the landfill.
• Collected gas from an active system should be cleared to minimize air pollution and a potential explosion and fire hazard.
Personnel entering the landfill through gas collection manholes must carry an air supply.
Gas monitoring wells should be placed around the landfill if methane migration could threaten nearby buildings. Gas wells are used to measure gas pressure and to recover gas from soil pore space. The explosive potential of gases can be measured with portable equipment.
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