The oil industry’s practice of burning unwanted methane is less effective than previously assumed, scientists said Thursday, leading to new estimates of U.S. greenhouse gas emissions nearly five times higher than previous ones.
In a study of the three largest oil and gas basins in the United States, researchers found that this practice, known as flaring, often does not completely burn methane, a powerful heat-trapping gas that is often a byproduct of oil production. . In many cases, they discovered, the flames were extinguished and not ignited again, so all the methane was escaping into the atmosphere.
Scientists said improving efficiency and ensuring all flares stay lit will lead to annual emissions reductions in the United States equivalent to taking nearly 3 million cars off the roads each year.
One of the researchers, Eric A. Kurt, atmospheric scientist at University of Michigan. “But they’re actually more important to the climate than we realized.”
“If we clean up our work with these flares, we will actually have a much more positive impact on the climate than we initially realized,” Dr. Kurt said.
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Because methane is a stronger, albeit shorter-lived, greenhouse gas than carbon dioxide, efforts to quantify and reduce methane emissions have intensified in recent years.
Methane is the primary component of natural gas, also known as fossil gas, which can leach into the atmosphere from wells, pipelines and other infrastructure, and is also intentionally released for maintenance or other reasons.
But huge quantities are burning.
Oil-fired gas is often produced in wells around the world, or at other industrial facilities. There may be no pipeline or other means to market it economically, and because it is flammable, it poses safety issues. In such cases, the gas is sent through a vertical tube with an igniter on top, and then burned.
The International Energy Agency estimated that in 2021, more than 140 million cubic meters of methane were burned in this way globally, which is equivalent to the amount imported by Germany, France and the Netherlands that year.
If the combustion is efficient, nearly all of the methane is destroyed, turning it into carbon dioxide, which has a less direct impact on the climate. The Environmental Protection Agency calculated, in studies in the 1980s, that burners destroyed 98 percent of the methane sent through them.
But the new research found that the ignition was actually much less effective, especially when unlit flares were taken into account. Scientists said emissions from improper burning account for up to 10 percent of all methane emissions in the oil and gas industry. The results were published in the journal Science.
The researchers studied the processes in the Permian and Eagle Ford Basins in Texas and the Bakken in North Dakota, which together account for about 80 percent of the fires in the United States. “The idea was that if we could do a nice, representative sample in those areas, we would get a good picture of what it looks like across the United States,” Dr. Kurt said. They sampled gas columns from torches by flying through them in a small plane.
They found that smoldering flames destroyed only about 95 percent of the methane, not 98 percent. They found that in some ponds up to 5 percent of the flame torches were unlit. This reduced the overall efficiency to about 91 percent.
Flares can be affected by winds, which can allow some unburned methane to escape, or by the presence of other gases. Wind, changes in gas pressure, or problems with the igniter can cause the flames to extinguish, and if there is no routine monitoring, flares can remain unlit for a long time.
Riley Doreen, CEO of carbon diagram A nonprofit group that will launch satellites next year that will detect and monitor sources of greenhouse gas emissions, said the results were not surprising to those who have studied emissions from these oil and gas basins and know how much flaring is being done.
But the researchers’ comprehensive survey shows that ineffective burning “is a more systematic issue,” said Dr. Dorin, who was not involved in the study.
Elsewhere in the world, Dr. Doreen said, there is little direct observational evidence for efficient combustion. But globally, he said, “combustion and combustion are likely to be less efficient than assumed.”