Underestimated emissions: Only a few weeks ago, the increased flaring of natural gas in Russian plants made the headlines. Now a study reveals that this “flaring” widespread in the oil and gas industry is even more harmful to the climate than previously thought.
Because such systems burn on average only 91 percent of the methane to carbon dioxide, some of these systems release the potent greenhouse gas even without combustion. In the USA alone, five times more methane is released from flaring than assumed, as the researchers report in Science.
In fact, natural gas has been in short supply worldwide since the start of the Ukraine war at the latest, and the demand for liquid gas and pipeline gas from non-Russian deposits has increased rapidly. Despite this, it is still common practice in the oil and gas industry to flare large quantities of natural gas.
This sometimes happens for safety reasons, to avoid imminent overpressure. But in oil fields, the natural gas that occurs as a by-product is often routinely flared off because it is not worth processing and transporting away.
At the end of August 2022, the increased flaring of natural gas at the Russian Portovaya compressor station also caused a stir. This facility is located at the beginning of the Nord Stream 1 pipeline, but also includes a plant for the production of liquefied natural gas.
According to estimates, Gazprom burned more than four million cubic meters of natural gas there every day – far more than is normal for the so-called “flaring”. According to the World Bank, more than 140 billion cubic meters of methane are flared off globally every year.
The problem: methane is a potent greenhouse gas that is shorter-lived in the atmosphere than CO2, but has a 20 to 30 times greater impact on the climate. In order to at least reduce this climate-damaging effect, the natural gas is burned to form CO2 during flaring. According to the oil and gas industry, the efficiency of this combustion is more than 98 percent – if the flaring is carried out according to regulations.
However, as is now apparent, a significant proportion of the flaring systems are by no means as efficient as the industry makes them out to be. For their study, Genevieve Plant from the University of Michigan and her team examined natural gas flaring using the example of the three largest gas and oil producing regions in the USA – the Permian and Eagle Ford deposits in Texas and the Bakken field in North Carolina. Together they are responsible for a good 80 percent of US flaring.
The scientists conducted measurement flights through more than 300 flares in these areas in 2020 and 2021 and determined the amounts of CO2 and methane released. By comparing the two values, they were able to calculate how much of the methane released is converted into CO2 by flaring.
“If a flare works as it should, then we would have to measure a large carbon dioxide peak and a comparatively low methane value,” explains Plant.
However, the evaluations revealed something else: according to the measurements, a significant proportion of the flaring systems work inefficiently and only burn part of the methane to form CO2. In some plants, the methane removal rate was only 60 percent.
The proportion of methane that escapes unburned is correspondingly high: “We estimate the methane emission rate of the burning flares in these three deposits to be 270,000 tons per year,” report the researchers.
In addition, many such vents do not burn at all at times, releasing the natural gas directly into the atmosphere. In the areas examined, between three and almost five percent of the active flaring chimneys had gone out or had not even been lit, as the measuring flights showed.
As a result, unburned methane escaped from these systems. “If you include these non-burning flares, the methane emissions for these regions rise to 490,000 tons of methane annually,” the team said.
Overall, the efficiency of natural gas flaring is only 91.2 percent, as Plant and her colleagues determined. “That’s considerably less than the 98 percent reported by the gas and oil industry,” they point out.
But that means: In the USA alone, the flaring of natural gas releases five times more methane than previously assumed. Four to ten percent of the total methane emissions in the USA could be attributed to flaring. “This sheds light on a previously underestimated source of methane,” says Plant’s colleague Eric Kort. “Much more methane is being released into the atmosphere than is currently recorded by surveys and estimates.”
According to the researchers, it cannot be ruled out that things will look similar in other countries. Flaring of natural gas occurs in most oil and gas producing regions, even if it is subject to different strict regulations. The International Energy Agency (IEA) is now also assuming that methane emissions from flaring will be higher globally: It estimates that flares released eight million tons of methane worldwide in 2020 alone.
Compared to the total anthropogenic methane emissions of almost 400 million tons a year, this may not seem like much – but it would be avoidable and is also a waste. “This source of methane emissions is easily addressable,” says Plant. On the one hand, the monitoring and maintenance of the systems would have to be improved. On the other hand, the oil industry would have to consistently intercept and continue to use the natural gas instead of simply burning it.
Norway, for example, demonstrates how this works: During oil production there, natural gas is only flared off in emergencies. 99 percent of the natural gas produced with the oil is separated and reused. (Science, 2022; doi:10.1126/science.abq0385)
Quelle: Science, University of Michigan
This article was written by Nadja Podbregar
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The original to this article “Climate effect of flaring underestimated” comes from scinexx.
