Methane gas (CH4) may be produced in two ways. Thermogenic methane, the source of most natural gas reserves, is produced by the effects of heat and pressure on the deeply buried remains of marine microorganisms, and usually occurs with oil. Biogenic methane is produced by microbes in the stomachs of cows, sheep, goats, and other ruminant animals (known as enteric fermentation), and in manure, shallow coal and oil deposits, and wetlands.
Methane can be a useful fuel, but it is a powerful greenhouse gas when released into the atmosphere. Natural gas, whose main component is methane, is more abundant than petroleum or coal but is nevertheless a non-renewable resource. CO2 emissions from burning natural gas are roughly equivalent to half those of coal. Methane escaping unburned into the atmosphere aggravates climate change while wasting a resource.
Where do methane leaks come from?
Although atmospheric methane levels can be measured very accurately, there is a great deal of uncertainty in the overall proportion of emissions coming from various sources.
Recent research at Cornell University (USA) suggests that hydraulic fracturing (“fracking”) for shale gas in the US and Canada is largely responsible for a dramatic spike in atmospheric methane levels since 2008.
Another Cornell study found that methane emissions from the US industrial sector have been vastly underestimated. Driving a Google Street View car equipped with a methane sensor, the researchers found that methane emissions from ammonia fertilizer plants were 100 times higher than the industry’s self-reported estimate, and substantially higher than the EPA estimate for all industrial processes in the United States.
Methane leaks from homes, businesses, and gas distribution infrastructure could be an even bigger problem than leaks from fossil fuel extraction. New investigations have uncovered leaks of incompletely burned methane from home appliances such as gas stoves, furnaces, and hot water heaters; leaking pipelines, pumps, and valves; water treatment systems; and equipment in power plants fueled by natural gas.
Improvements in remote sensing technologies are allowing increasingly high-precision measurements of regional methane emissions. Pictured here, an artist’s impression of MethaneSAT, funded by the Environmental Defense Fund, which will measure methane emissions from fifty major oil- and gas-producing regions around the world.