A new study in the Proceedings of the National Academy of Sciences sheds light on a question that continues to vex industry executives and policymakers alike: How significant are fugitive methane emissions from oil and gas production?
The study claims that U.S. methane emissions may be as much as 50 percent higher than estimates in the Environmental Protection Agency’s (EPA) annual Inventory – the equivalent to adding 2.3 million cars to the road. Most significantly, the study’s authors assert that methane that is leaked or vented during oil and gas production—aka “fugitive methane”—may be up to five times greater than current estimates. If these results are correct and applicable to oil and gas development nationwide, it would fundamentally alter the scale of the fugitive methane problem and seriously undermine any climate advantage natural gas possesses over coal.
Here, we seek to address some of the biggest questions this new study raises.
What Does the Study Say?
The study’s authors, led by researchers from Harvard University, used atmospheric measurements of methane – a greenhouse gas at least 25 times as powerful at trapping heat as CO2 – from aircraft and stationary towers. Overall, the study found that methane emissions from all U.S. sources—including agriculture, oil and gas development, landfills, and coal mining—are 50 percent greater than estimates from the EPA Inventory, which recently lowered its estimate of methane emissions from oil and gas systems. The study found evidence of even greater discrepancies in individual sectors; methane emissions from livestock, for example, were estimated at twice the level estimated by EPA. But it was the oil and gas sector – the largest source of methane emissions in the United States – where the variance was greatest, and which is the greatest cause for concern.
Measurements of methane were taken in 2007 and 2008 in Texas and Oklahoma, the locus of U.S. oil and gas extraction during that time period. The authors estimated that the region’s methane emissions were 3.7 million metric tons of CO2 equivalent, almost five times greater than the 0.75 million metric tons previously estimated (according to the study, methane emissions from oil and gas operations are 2.3-7.5 times greater than earlier estimates). Furthermore, the methane was highly correlated with propane, a byproduct of oil and gas extraction and refining, which strengthens the researchers’ contention that these methane emissions are coming from oil and gas production.
What Are the Implications of this Study? And What Are the Caveats?
If fugitive methane emissions from oil and gas systems are indeed five times greater than previously estimated, that would imply a leakage rate in the range of 5-15 percent of total production. Not only is this a substantial quantity of product vanishing into the air (natural gas is primarily methane), it is also significantly higher than most previous estimates – including from industry – and would reduce or eliminate any advantage natural gas has over coal from a climate standpoint. While natural gas emits roughly half the CO2 of coal at the point of combustion, because methane is such a powerful greenhouse gas, any fugitive methane that escapes during the drilling, processing, or transmission of natural gas serves to lessen that benefit.
However, it’s important to note that much has changed since Harvard researchers took their measurements in 2007 and 2008. The boom in natural gas development due to hydraulic fracturing had not yet begun in earnest; there are now hundreds of thousands of hydraulically fractured wells across the United States. How their emissions compare to those of conventional wells is still an open question. The industry has also changed in important ways in the last five years. We know a lot more about where fugitive methane emissions come from and how to address them. While it’s clear that some companies are taking advantage of best practices to reduce these emissions, there are also now many more companies operating in this space—it’s impossible to determine how many of them are actively reigning in fugitive methane. And while the Harvard researchers plan to repeat their measurements with data from 2012, even these updated estimates may overstate current emissions. EPA rules affecting some of the larger sources of U.S. methane emissions went into effect just this year.
Despite these caveats, this is nonetheless a valuable and important study—one that sheds light on an issue that remains all too murky. The EPA Inventory uses bottom-up estimates and engineering calculations in determining emissions levels. While this data is still the definitive source for all U.S. greenhouse gas emissions, it’s far from perfect. Any direct measurement data helps bring clarity to the confusing world of fugitive methane emissions.
How Does this Study Compare to Other Recent Studies?
Another recent study, led by researchers at the University of Texas at Austin, measured methane emissions from natural gas development. However, the two studies are not entirely comparable for a number of reasons. The most significant is that the UT Austin study looked only at the production stage of natural gas, while the Harvard study used atmospheric measurements to estimate methane emissions from all sources. The UT Austin measurements were also more recent and demonstrate the impact that the aforementioned EPA rules are having on fugitive methane emissions during the production stage. It is worth repeating that, despite widespread reports to the contrary, the UT Austin study does not confirm that EPA estimates of methane emissions from natural gas systems are correct and accurate. Although the study’s estimated leakage rate for production operations was in line with EPA’s estimate, several processes leaked more than previously thought, while another (well completions) emitted much less due to the effectiveness of recent EPA rules.
What More Can Be Done?
Ultimately, more direct measurements are needed to get a better handle on the size and scale of the fugitive methane problem. We do, however, know enough on how to reduce fugitive methane now—for the good of the environment and human health.
In addition to the EPA rules, many states have taken a lead role in addressing air and water pollution from natural gas development. Colorado, for example, has proposed rules that would require companies to monitor new and existing oil and gas infrastructure for leaks, and to repair those leaks within 15 days. While Colorado could still strengthen its rules – for example, by requiring the immediate repair of leaking equipment – the state is demonstrating to both the federal government and other states that natural gas development can be improved without economic harm. With the litany of policies and cost-effective technologies available to governments and industry, we can reduce fugitive methane emissions and take a step toward preventing the worsening impacts of climate change.
- LEARN MORE: Download WRI's publication, Clearing the Air: Reducing Upstream Greenhouse Gas Emissions from U.S. Natural Gas Systems