One way to quantify the magnitude of the methane leakage is to divide the amount of methane emitted each year by the total amount of methane pumped out of the ground each year from natural gas and oil wells. The EPA currently estimates this methane leak rate to be 1.4 percent. That is, for every cubic foot of natural gas drawn from underground reservoirs, 1.4 percent of it is lost into the atmosphere.
This study synthesized the results from a five-year series of 16 studies coordinated by environmental advocacy group Environmental Defense Fund (EDF), which involved more than 140 researchers from over 40 institutions and 50 natural gas companies.
The effort brought together scholars based at universities, think tanks and the industry itself to make the most accurate estimate possible of the total amount of methane emitted from all U.S. oil and gas operations. It integrated data from a multitude of recent studies with measurements made on the ground and from the air.
All told, based on the results of the new study, the U.S. oil and gas industry is leaking 13 million metric tons of methane each year, which means the methane leak rate is 2.3 percent. This 60 percent difference between our new estimate and the EPA’s current one can have profound climate consequences.
Methane is a highly potent greenhouse gas, with more than 80 times the climate warming impact of carbon dioxide over the first 20 years after it is released.
An earlier EDF study showed that a methane leak rate of greater than 3 percent would result in no immediate climate benefits from retiring coal-fired power plants in favor of natural gas power plants.
That means even with a 2.3 percent leakage rate, the growing share of U.S. electricity powered by natural gas is doing something to slow the pace of climate change. However, these climate benefits could be far greater.
Also, at a methane leakage rate of 2.3 percent, many other uses of natural gas besides generating electricity are conclusively detrimental for the climate. For example, EDF found that replacing the diesel used in most trucks or the gasoline consumed by most cars with natural gas would require a leakage rate of less than 1.4 percent before there would be any immediate climate benefit.
What’s more, some scientists believe that the leakage rate could be even higher than this new estimate.