Methane emissions higher than previously assumed


Methane gas emissions are becoming more and more important. American scientists and their Dutch colleagues have now discovered in a study that flaring natural gas during oil production causes significantly more methane to be released into the atmosphere than previously thought. Aircraft measurements and calculations based on them show that the amount of greenhouse gases in the US is about five times higher than previously thought.

The study comes from a group led by Genevieve Plant of the University of Michigan in Ann Arbor, Michigan. The basic situation: Natural gas is a by-product in oil extraction. It consists largely of methane that is particularly climate-damaging. At many manufacturing sites, the escaping gas is deliberately flared – a practice known as flaring. Combustion releases carbon dioxide – also a greenhouse gas. However, the greenhouse effect of methane in 100 years is 28 times that of CO2. Therefore, it is actually more environmentally friendly to flare natural gas, which contains methane as the main component, than to release it into the atmosphere unburned.

Efficiency value must be corrected downwards
“Industry and governments generally assume that flares will continue to burn, destroying the main component of natural gas at 98 percent efficiency,” the study authors write. This information is based on a small study by the United States Environmental Protection Agency from the 1980s. However, the Plant researchers question the decades-old value of 98 percent efficiency in the combustion of methane. In the summer months of 2020 and 2021, the scientists therefore flew measurement planes over three major oil and gas fields in the US: Bakken in North Dakota and Eagle Ford and Permian in Texas. More than 80 percent of the natural gas flared annually in the United States comes from these three areas. Flaring is allowed when no distribution line, such as a pipeline, is available.

The measurements of more than 300 exhaust plumes from natural gas flares showed that the methane is burned with an average efficiency of only 95.2 percent. In addition, an average of 4.1 percent of the torches do not burn because they have gone out or have never been properly lit. There, methane escapes unburned into the air. As a result, the overall efficiency with which flares destroy the methane in natural gas is only 91.1 percent.

Experts see “solid methodology” in study
“The research methodology is sound; It is very good that we get clear measurement data from the US,” says Lena Höglund Isaksson of the International Institute for Applied Systems Analysis (IIASA) in Laxenburg. Martin Heimann of the Max Planck Institute for Biogeochemistry in Jena emphasizes that the data cannot necessarily be be transferred to global flaring practice, however, he believes global flaring efficiency is no higher than in the U.S. “The International Energy Agency (IEA) has already reduced the methane combustion efficiency in flaring to 92 percent when calculating are emission inventories independent of this new empirical study,” the SMC quotes Heimann as saying.

To prevent or reduce the release of climate-damaging gases during flaring, the best strategy would be to stop using oil and gas, Isaksson says. “But the next best thing that’s relevant for years to come would be to maximize the associated gas recovery. Norway is recovering about 99 percent, so it is possible.”

Source: Krone


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