Researchers: Cross natural-gas bridge carefully

Political pressure has mounted to replace coal generation with natural gas to ease climate strain with the cleaner-burning fuel, but a new report published in the journal Science indicates methane leakage during gas extraction could nullify some benefits.

“Recent life cycle assessments generally agree that replacing coal with natural gas has climate benefits,´ said Garvin Heath, lead author of the report who is also a senior scientist at the National Renewable Energy Laboratory in Golden, Colo. “Our findings show that natural gas can be a bridge to a sustainable energy future, but that bridge must be traversed carefully.”

Heath said there is evidence suggesting methane leakage from extraction operations of natural gas may be larger than official estimates, meaning extra diligence will be required to ensure sustainability goals are actually achieved by switching from coal-fired to gas-fired generation.

According to the release from the Joint Institute for Strategic Energy Analysis, an entity under the NREL umbrella, the study suggests that more can be done to reduce methane emissions and improve measurement tools. The study systematically compared North American emissions estimates at scales ranging from device-level to continental atmospheric studies.

“[Natural gas] emits less carbon dioxide during combustion than other fossil fuels and can be used in many industries,” a summary of the study reads. “However, because of the high global warming potential of methane (CH4, the major component of natural gas), climate benefits from natural gas use depend on system leakage rates.”

Even with higher-than-recorded methane leakage, though, one of the researchers said it would still probably be worth the switch.

“While we found that official inventories tend to under-estimate total methane leakage, leakage rates are unlikely to be high enough to undermine the climate benefits of gas versus coal,´ said Doug Arent, executive director of the Joint Institute for Strategic Energy Analysis and a co-author to the study.

Other key findings as detailed in the release follow:

• Official inventories of methane leakage consistently underestimate actual leakage.
• Evidence at multiple scales suggests that the natural gas and oil sectors are important contributors.
• Independent experiments suggest that a small number of “super-emitters” could be responsible for a large fraction of leakage.
• Recent regional atmospheric studies with very high emissions rates are unlikely to be representative of typical natural gas system leakage rates.
• Hydraulic fracturing is not likely to be a substantial emissions source, relative to current national totals.
• Abandoned oil and gas wells appear to be a significant source of current emissions.
• Emissions inventories can be improved in ways that make them a more essential tool for policymaking.

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