Process Landfill Gas

Landfill Gas Process

"Landfill gas" is not the same thing as "natural gas" or "methane." They are three separate terms which mean different things. They should not be used interchangeably. The term "landfill methane" is deceiving as it's usually used to imply that landfill gas is simply methane.

Landfill gas is about 40-60% methane, with the remainder being mostly carbon dioxide (CO2). Landfill gas also contains varying amounts of nitrogen, oxygen, water vapor, sulfur and a hundreds of other contaminants most of which are known as "non-methane organic compounds" or NMOCs. Inorganic contaminants like mercury are also known to be present in landfill gas. Sometimes, even radioactive contaminants such as tritium (radioactive hydrogen) have been found in landfill gas.

Burning landfill gas is dirtier than burning natural gas. Whether using an internal combustion engine or a gas turbine, burning landfill gas to produce energy emits more pollution per kilowatt hour than natural gas does.

Landfills should install gas collection systems to prevent the problems with gas migration. Once collected, landfills can do any of the other options. These options are focused around handling the methane (usually by burning it) and are not focused around addressing the toxics issues.

Landfill Gas Plant

Regardless of what is ultimately done with the gas, the gas should be filtered so that the halogenated compounds are segregated. Once filtered out, these compounds should not be combusted (as that doesn't tend to improve the situation, but may make it worse).

They should be handled as hazardous waste and isolated from the environment as best as is possible until there is a proven technology which can neutralize the toxics by converting the halogens to relatively harmless chemicals like salts.

The general options for dealing with landfill gas (once collected) are as follows:

flare it

boiler - makes heat

internal combustion engine - makes electricity

gas turbine - makes electricity

fuel cell - makes electricity

convert the methane to methyl alcohol

clean it up enough to pipe it to other industries or into the natural gas lines