Natural gas has long been considered a more climate-friendly alternative to coal, as gas-fired power plants generally release less carbon dioxide into the atmosphere than their coal-fired counterparts. But a new study finds that when the full impact of the industry is taken into account, natural gas could contribute as much as coal to climate change.
Natural gas is primarily composed of methane, a potent greenhouse gas. A new peer-reviewed analysis in the journal Environmental Research Letters finds that when even small amounts of methane escape from natural gas wells, production facilities and pipelines, it can drive up the industry's emissions to equal the effects of coal.
Recent studies have found much higher rates of leakage from natural gas infrastructure than previously known. Researchers wanted to understand the impact of those leaks.
"This analysis compares gas and coal at varying methane leakage rates. We find that very small methane leakage rates from gas systems rival coal's greenhouse gas emissions," said Deborah Gordon, co-author of the analysis and a senior principal at the environmental group RMI, formerly Rocky Mountain Institute. Scientists from NASA, Harvard University and Duke University also contributed to the paper.
That finding holds even if leaks amount to a tiny fraction of the methane in the country's gas production and supply system, as low as 0.2%, according to the researchers. The paper highlights recent surveys that found leak rates far above that, of "0.65% to 66.2%."
The study takes into account all stages of production and uses for both gas and coal in making the comparison. Researchers included in their calculations one counterintuitive effect of burning coal – it releases sulfur dioxide, which produces particles that reflect sunlight and actually reduce warming (sulfur dioxide pollution also can lead to heart and lung problems). Researchers also took into account the fact that coal production leaks methane.
The findings are a challenge to the natural gas industry, which bills itself as part of the solution to addressing climate change. Carbon dioxide emissions from power plants in the U.S. have fallen about 35% since 2005, largely because of the shift from coal to gas.
But the natural gas production and distribution system leaks methane from beginning to end, a problem producers say they are working to address through an industry-sponsored program.
"The U.S. natural gas and oil industry is leading the world in advancing innovative technology to better detect and reduce methane emissions, and U.S. methane emissions intensity are amongst the lowest of any major-producing nation," wrote Dustin Meyer of the American Petroleum Institute, in a statement.
Methane is a more potent greenhouse gas than carbon dioxide, though it doesn't stay in the atmosphere as long. Scientists are clear that the world needs to reduce both to avoid the worst effects of climate change.
The API didn't offer an assessment of this latest research. But to achieve and maintain a climate edge over coal, the natural gas industry may have to nearly eliminate methane leaks. That's difficult, and it comes as critics are working to find more leaks regulators and the industry may be missing.
Environmental groups say the Environmental Protection Agency currently undercounts methane emissions. Several groups have started looking for leaks themselves, using special cameras, aerial surveys, and increasingly powerful satellites. The conservation and advocacy group Environmental Defense Fund plans to launch what it says will be "the most advanced methane-tracking satellite in space" early next year.
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