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A common practice in the oil industry called flaring is believed to reduce methane emissions by burning waste or excess gas during the oil extraction or processing process. But flaring may not be as effective as previously thought, according to a new study published in the journal Science.
It is a widely held belief that flaring is 98% effective in destroying methane emissions caused by oil and gas operations. However, according to Eric Kort, associate professor in the Department of Climate and Space at the University of Michigan and one of the authors of the paper, this hypothesis has only rarely been tested.
Why burn a potentially useful fuel? “You might have a volume of natural gas, which is mostly methane, that you have nothing to do with. You don’t have the ability to capture it and put it in a pipeline – it’s not economical, the pressure would exceed safety tolerances,” Kort told Ars.
The difference between the supposed flaring efficiency and the efficiency found in the results of Kort and colleagues is a matter of a few percentage points. However, the researcher said this seemingly small difference could be a big deal when extrapolated to the entire fossil fuel industry. Additionally, methane has more than 80 times the global warming impact of carbon dioxide, at least for the first 20 years it’s in the air.
” Burning [the excess gas] and by converting it to CO2, it greatly reduces the impact on the climate,” he said.
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Kort noted that oil and natural gas extraction often happens in the same place, with oil being the main reason for extraction in one place. As such, the gas is something of an afterthought. It may be less profitable to capture natural gas and try to sell it, Kort said. “In that case, you’re just going to set up and flare it,” he said, adding that his study didn’t reflect the natural gas industry, but rather the oil and gas industry. “These wells are there mainly for oil. They just co-produce the gas.
To study this, Kort and his team looked at flaring in three different regions that extract oil in the United States: the Eagle Ford, Permian, and Bakken basins. While that may seem limited, according to the research, these three locations account for more than 80% of the country’s total flaring. To get a better idea of what was going on there, the team flew over the three regions in 2020 and 2021.
Considering both inefficient flaring and gas that is not flared, the true efficiency is around 91%, the team found. Inefficient combustion means that not all of the methane ends up burning during flaring, which could be due to several reasons. The pressure in the pipe could be incorrect, which means the gas exit velocity is not quite correct, or high winds could cause the flame to flicker. Either way, the methane ends up in the atmosphere, Kort said.
They used an aircraft equipped with equipment to measure carbon dioxide and methane. The team visually spotted flares in all three regions and then flew downwind into the flares’ exhaust plumes. The process then involved pumping air from outside the aircraft into the instrument and using an airborne greenhouse gas analyzer to measure its contents.
The craft would pick up a big CO2 spike, which is expected, given that’s what flaring aims to produce from methane. The craft would also pick up either no methane, some methane, or a fair amount of methane, depending on how effectively the flare destroyed it. In all, the team studied 300 flares across the regions.
To measure when natural gas was unburned, the team took an infrared camera, pointed it at the flares (the tall chimney through which natural gas passes before combustion) and determined when a chimney is extinct.
The impact could be “quite significant”
While the difference between 98% and 91% doesn’t seem large, it can add up, Kort noted. “We are talking… relatively small percentages, but there are very large volumes of gas [that] flare out,” Kort said.
He added that reducing these inefficiencies would result in fewer methane emissions reaching the atmosphere and contributing to climate change. This may involve ensuring unlit flares are lit and ensuring optimal conditions for igniting flares. If these inefficiencies can be corrected and we actually achieve 98% combustion, reducing emissions could mean as much as taking 2.9 million cars off the road every year.
“The impacts could be quite significant,” Kort said. “There’s a pretty big climate impact in this inefficiency.”
Science, 2022. DOI: doi/10.1126/science.abq0385 (About DOIs)
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