Last week, Energy Innovation released its latest paper, “The Mystery of the Missing Methane,” which urges the Environmental Protection Agency (EPA) to improve its data collection and analysis of methane emissions. The paper’s author, Energy Innovation’s Director of Research Chris Busch, describes the significant gap in information on both the amount and sources of U.S. methane emissions. An op-ed article about Busch’s analysis was posted on LiveScience last month as well. Both pieces conclude that better data is necessary to guide climate policy and regulate methane-emitting activities, namely natural gas systems, more efficiently.

Historically, emissions have been measured in two ways. “Bottom-up” studies measure emissions from the source using component-level sampling. Emissions factors are applied to various sources of methane to calculate activity-specific emissions, which are then summed to estimate total system-wide emissions. This is how the EPA calculates methane emissions in its greenhouse gas emissions inventory. Alternatively, “top-down” studies measure total emissions based on atmospheric sampling. While this type of study is less helpful in determining the contribution of various sources to overall emissions, it is much more accurate at reporting overall system-wide emissions levels. A new study by Brandt et al. uses this approach to measure methane emissions. Their study argues that EPA’s source-based data substantially undercounts U.S. methane emissions.

So who is responsible for this ‘missing methane’? Given that approximately one-quarter of methane emissions measured by the EPA emissions inventory come from the natural gas system, it would be reasonable to assume that some of the missing methane is emitted from this source as well. The actual amount that comes from natural gas activities, however, is highly uncertain due to the system’s complex, heterogeneous conditions. In Busch’s paper, he presents four scenarios with different methane emissions rates from the natural gas system to estimate the potential environmental impacts that could be caused by natural gas methane leakage. His analysis reveals that undercounted methane emissions from the natural gas system could be equivalent to the emissions from as many as 249 additional coal plants over a 20-year time period, due to methane’s short atmospheric lifetime and high global warming potential (relative to carbon dioxide). This would make substituting natural gas for coal-combustion actually worse for resolving climate change in the short-term.

This analysis demonstrates the importance of proper data collection to find the missing methane, as there is enormous potential to reduce emissions once the right sources can be targeted. In the short-term, the EPA should increase efforts to improve its methodologies for calculating the inventory of emissions from the natural gas sector. In the long-term, the agency should develop a plan to integrate top-down analysis to provide evidence of overall emissions across large areas and with greater accuracy. EPA should also aim to adopt new technologies that better measure ground level emissions to improve its continued bottom-up analysis. Technologies, such as infrared cameras and stationary detectors, help link emissions back to their original source, where emissions regulations can be directly enforced. Both short-term and long-term actions are necessary by EPA to ensure proper practices by industries and establish the pathway to a sustainable, clean, and healthy future.