Methane could be a bigger climate problem than previously thought, study says

The oil industry’s practice of burning off unwanted methane is less effective than previously assumed, scientists said Thursday, resulting in new estimates for greenhouse gas emissions in the United States that are about five times higher than the previous ones.

In a study of the three largest oil and gas basins in the United States, researchers found that the practice, known as flaring, often doesn’t fully burn methane, a potent heat-trapping gas that is often a by-product of oil production. . And in many cases, they found, the flares die down and don’t reignite, so all the methane escapes into the atmosphere.

Improving efficiency and ensuring all the flares stay lit would result in annual emission reductions in the United States equivalent to taking nearly 3 million cars off the road each year, the scientists said.

“Flares have been kind of ‘out of sight, out of mind,'” said one of the researchers, Eric A. Kort, an atmospheric scientist at the University of Michigan. “But they are actually more important for the climate than we realised.”

“So if we cleaned up our act with these flares, we would actually have a much more positive climate impact than we would have initially realized,” Dr. Kort said.

Because methane is a stronger but shorter-lived greenhouse gas than carbon dioxide, efforts to identify and reduce methane emissions have intensified in recent years.

Methane is the main component of natural gas, also known as fossil gas, which can leak into the atmosphere from wells, pipelines, and other infrastructure, and is also deliberately released for maintenance or other reasons.

But large quantities are burned.

The gas that is flared is often produced with oil in wells around the world or in other industrial facilities. There may not be a pipeline or other means to market it economically, and because it is flammable, it poses safety concerns. In such cases, the gas is sent through a vertical pipe with an igniter at the top and is burned.

The International Energy Agency estimated that worldwide in 2021 more than 140 million cubic meters of methane were burned in this way, equivalent to the amount imported that year by Germany, France and the Netherlands.

If combustion is efficient, almost all of the methane is destroyed and converted to carbon dioxide, which has less immediate climate impact. The Environmental Protection Agency, in studies done in the 1980s, calculated that flares destroyed 98 percent of the methane sent through them.

But the new research found that flares were actually much less effective, especially when unlit flares were taken into account. Emissions from improper flaring accounted for up to 10 percent of all methane emissions in the oil and gas industry, the scientists said. The findings were published in the journal Science.

The researchers looked at operations in the Permian and Eagle Ford basins in Texas and the Bakken basin in North Dakota, which together account for about 80 percent of burning in the United States. “The idea was that if we can do a good cross-section in those domains, we would get a good picture of what it looks like in the US,” Dr. Kort said. They sampled the gas plumes from the flares by flying through them in a small plane.

They found that burning flares destroyed only about 95 percent of the methane, not 98 percent. And they found that in some basins as many as 5 percent of flares were out. That dropped the overall efficiency to about 91 percent.

Flares can be affected by wind, which can allow some unburned methane to escape, or by the presence of other gases. Wind, gas pressure changes, or igniter problems can cause the flame to blow out, and without routine checking, sparklers can stay out for a long time.

Riley Duren, CEO of carbon Mapper, a nonprofit group that will launch satellites next year that will detect and monitor sources of greenhouse gas emissions, said the findings did not surprise those who have studied emissions from these oil and gas basins and know the amount of burning which is done.

But the researchers’ extensive survey shows that inefficient burning “is a more systemic problem,” said Dr. Duren, who was not involved in the study.

In other parts of the world, there is little direct observational evidence for burning efficiency, Dr. Duren said. But globally, he said, “combustion and burning are likely to be less efficient than assumed.”