Scientists collaborating with the Environmental Defense Fund (EDF) have found that methane emissions from the U.S. oil and natural gas supply chain exceed the Environmental Protection Agency's estimates by nearly 60%. The findings were published today in the journal Science.
Carnegie Mellon University's Professor Allen L. Robinson, head of the Department of Mechanical Engineering, was one of the researchers involved with the study. Although the findings reveal important gaps in the federal government's Greenhouse Gas Reporting Program, he believes it offers an opportunity.
"With some modest adjustments, we can really improve the effectiveness of these [reporting] programs to ensure that companies provide the most valuable and accurate data to guide future decision making,” he said.
Methane is a powerful greenhouse gas that traps heat in Earth's atmosphere. The main component of natural gas, it can escape from multiple points in the oil and natural gas supply chain. Once in the atmosphere, it has over 80 times the warming impact of carbon dioxide over the first 20 years after its release.
According to the study, the current methane leak rate represents a loss of $2 billion worth of natural gas—enough to fuel 10 million homes.
With the advent of hydraulic fracturing and horizontal drilling to access natural gas pockets trapped in shale formations, the U.S. experienced a sharp increase in gas production over the last decade. This has increased the opportunities for methane leakage.
The good news is that our new understanding provides a cost-effective path forward to eliminate the wastage of this valuable resource.Allen L. Robinson, Professor and Department Head, Mechanical Engineering, Carnegie Mellon University
Robinson's team focused on the midstream portion of the supply chain that connects the gas well to the city gate. It is comprised of a network of thousands of miles of interstate pipeline, compressor stations, and gas processing plants.
Robinson and his collaborators measured emissions at hundreds of midstream facilities located throughout the United States. They discovered that midstream emissions are often dominated by a relatively small number of super emitters with abnormally high emissions. Together, these super emitters contribute around half the total amount of all leaked methane. Super-emitters are typically caused by an abnormal operating condition.
Previous investigations had identified anomalies in the EPA's methane reporting data but could not explain them. These new findings confirm the important role of super emitters. The new data provide direction for regulators and the industry to address the issue.
“Although we confirmed that methane emissions are substantially higher than previously thought, the good news is that our new understanding provides a cost-effective path forward to eliminate the wastage of this valuable resource,” said Robinson.
Robinson directs Carnegie Mellon University's Center for Air, Climate and Energy Solutions (CACES).