Underestimated Methane Leak Severity in the US

Roughly one-third of all global warming thus far is attributed to methane emissions. Despite natural contributors such as wetlands, human activities such as agriculture and fossil-fuel production have added millions of additional metric tons of the gas to the atmosphere. The concentration of methane has seen a twofold growth over the last two centuries, but it remains unclear where these emissions are primarily originating from.

Resolving this data deficit is challenging yet essential in order to effectively reduce emissions and manage climate change. In their research, scientists employ a variety of tools, from satellites like MethaneSAT to ground and aerial surveys.

According to estimates by the US Environmental Protection Agency, roughly 1% of all oil and gas produced ultimately leaks into the atmosphere as methane pollution. However, recurrent surveys imply that the actual extent of the methane issue may be greater than the official figures suggest.

For the sites analyzed in a new study, “methane emissions seem to exceed government estimates, on average”, notes Evan Sherwin, a research scientist associated with Lawrence Berkeley National Laboratory. Sherwin’s research was based on an extensive survey of US fossil-fuel production sites. Initiated in 2018 by Kairos Aerospace and the Carbon Mapper Project, this survey covered six major oil- and gas-producing regions that together contribute to about 50% of onshore oil production and around 30% of gas production. The data comprising nearly 1 million measurements of well sites was collected by planes equipped with spectrometers that sense methane through specific light wavelengths.

Methane sources in oil and gas production vary in size, making tracking complex. Some smaller wells steadily leak gas at a rate of roughly a kilogram of methane per hour, whereas larger sources intermittently emit hundreds or even thousands of kilograms per hour. The planes primarily detect the larger leaks of above roughly 100 kilograms per hour, but sometimes register smaller ones as well. Using these measurements, researchers calculate that these large leaks contribute disproportionately to total emissions. In some cases, approximately 1% of the well sites may account for over half the total methane emissions.

Some experts suggest that existing studies might still be constrained by the measurement tools at hand. Ritesh Gautam, a lead senior scientist at the Environmental Defense Fund, argues that the findings demonstrate the limitations of current technology.