You got me wondering about the overall benefits of this technology so I went agoogling for some info. I found that generally Methane is a more damaging greenhouse gas in the atmosphere. 33x more damaging than CO2, so capture seems like a fine idea. Then I looked into the effects of the burning of the captured gas to compare against the effects of methane escape. I found this nightmare:
"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.
-snip-
Natural gas is approximately 80-99% methane, with the remainder being mostly other hydrocarbons (ethane, propane, butane, etc.) as well as some nitrogen, oxygen, water, CO2, sulfur and various contaminants.1
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.
NMOCs usually make up less than 1% of landfill gas. EPA identifies 94 NMOCs in their 1991 report, "Air Emissions from Municipal Solid Waste Landfills - Background Information for Proposed Standards and Guidelines." Many of these are toxic chemicals like benzene, toluene, chloroform, vinyl chloride, carbon tetrachloride, and 1,1,1 trichloroethane. At least 41 of these are halogenated compounds. Many others are non-halogenated toxic chemicals. 2, 3 More exhaustive test for contaminants in landfill gas have found hundreds of different NMOC contaminants.<**NJ**>
When halogenated chemicals (chemicals containing halogens - typically chlorine, fluorine, or bromine) are combusted in the presence of hydrocarbons, they can recombine into highly toxic compounds such as dioxins and furans, the most toxic chemicals ever studied. Burning at high temperatures doesn't solve the problem as dioxins are formed at low temperatures and can be formed as the gases are cooling down after the combustion process.
-continued at link:
http://www.energyjustice.net/lfg/