Throughout the oil extraction and refining process, methane is produced as a by-product. When there’s no economic incentive to capture that methane, oil companies usually opt to burn off the gas at the wellhead. This purpose of this practice, called flaring, converts the methane into carbon dioxide. Because of CO2’s lower global warming potential, this conversion ends up having less of a climate impact than if these companies vented methane directly.
However, a new study suggests that the efficiency of flaring might be lower than previously thought (Science 2022, DOI: 10.1126/science.abq0385). Instead of the 98% conversion rate generally assumed by theUS Environmental Protection Agency, the study’s authors found that that number might actually be closer to 91% because of a combination of poor combustion and unlit flares.
The finding is based on measurements collected in three regions that account for the vast majority of gas volume flared in the country. As such, “one could posit that this is probably pretty representative” of flares found across the US, says Eric Kort, a climate scientist at the University of Michigan who worked on the project.
A 7% percentage drop might not seem particularly noteworthy. But Kort emphasizes that this small difference is still impactful because of the sheer amount of flaring that happens in the US. This lower efficiency could mean that methane emissions from flares could be up to five times as great as what current estimates suggest, equivalent to adding 3 million cars to the road every year, Kort notes.
But steps can be taken to reduce these emissions, says Robert Kleinberg, an energy policy researcher at Columbia University and Boston University who was not affiliated with this study. “In view of this work, the EPA should pay more attention to the problem of inefficient and unlit flares in the new methane-control rules that are expected to roll out by the end of the year,” he wrote in an email.
Kort adds that “reducing the flare volumes is an even simpler fix.” Because of the lower flare efficiency, “any reduction in the volume of gas that’s flared, will have a much larger climate benefit than we had previously realized,” he says.