Major oil and gas-producing regions in the US are leaking much more methane than current estimates suggest, according to nearly a million aerial measurements of the potent greenhouse gas.
鈥淥ur study used the largest such dataset that鈥檚 ever been assembled,鈥� says at Lawrence Berkeley National Laboratory in California, who conducted the research while at Stanford University.
He and his colleagues combined data from numerous aerial surveys that used infrared sensors to measure methane leaking from wells, pipelines and other infrastructure in the oil and gas-producing regions of the US. Together, these surveys covered 52 per cent of all US onshore oil production and 29 per cent of natural gas production.
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To estimate methane emissions too diffuse to be detected from the air, the researchers also extrapolated from a few ground-based measurements to simulate total emissions.
On average across the regions surveyed, they found methane leaking at a rate of 2.95 per cent of total natural gas production, a number nearly three times what the US Environmental Protection Agency鈥檚 estimates. The number is also about 50 per greater than the , says Sherwin.
The estimated 6.2 million tonnes of annual methane emissions from these sites represent about $1 billion in annual losses due to the value of the gas, which is the main constituent of natural gas fuel. It also represents more than $9 billion in damages from the associated climate effects. The leakage rates could affect the price of US oil and gas as the climate impacts of production are increasingly scrutinised. 鈥淚t鈥檚 important to get this right,鈥� says Sherwin.
However, not all regions were emitting equally. In part of the Permian basin in New Mexico, methane was found to be leaking at the extraordinary rate of about 9 per cent of total gas production, while a basin in Colorado had a leakage rate of about 1 per cent. That variability means it isn鈥檛 possible with this data to extrapolate overall US oil and gas methane emissions, says Sherwin.
High-emitting sources large enough to be measured were responsible for the majority of emissions in the new assessment. But at the Environmental Defense Fund, a US advocacy group, says emissions from more diffuse sources could be even greater than these estimates.
鈥淭o get a complete picture, these data need to be combined with direct measurement of total methane emissions from these same regions,鈥� he says. That could soon be possible thanks to a growing constellation of methane-sensing satellites聽keeping watch on oil and gas fields.
Nature
