Natural gas is often seen as a bridge to a more sustainable energy future since it emits less carbon dioxide during combustion than other fossil fuels. But according to a recent study published in the journal Science, the total impact of switching to natural gas depends heavily on methane leakage during the natural gas life cycle, which is consistently underestimated. This suggests that more can be done to reduce methane emissions and to improve measurement tools which help inform policy choices.
The study, “Methane Leaks from North American Natural Gas Systems,” presents a first effort to systematically compare North American emissions estimates at scales ranging from device-level to continental atmospheric studies.
“Recent life cycle assessments generally agree that replacing coal with natural gas has climate benefits,” said Garvin Heath, a senior scientist at the National Renewable Energy Laboratory and a lead author of the report. “Our findings show that natural gas can be a bridge to a sustainable energy future, but that bridge must be traversed carefully. Current evidence suggests leakages may be larger than official estimates, so diligence will be required to ensure that leakage rates are actually low enough to achieve sustainability goals.”
Among other key findings of the research:
- 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 policy making.
“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.
For the full report, visit Science.