The EPA’s recently released draft annual GHG emissions inventory report includes new, lower estimates for the amount of methane (CH4) emitted during natural gas production. The new estimates are the result of a change in the way the agency calculates the amount of CH4 released during liquids unloading, or the process of flushing excess water from a well. The agency has incorporated data gathered by API and ANGA on liquids unloading, determining that the industry data was far superior because it covered more wells, was more recent, and included more information on plunger lifts and control technologies.

There were further changes made to the estimate of the number of active wells, and the methodologies for estimating emissions from hydraulic fracturing and refracturing well completions. In totality, the changes resulted in an annual average decrease in CH4 emissions of 41.3 teragrams of carbon dioxide equivalents. The agency’s estimation of GHG data has long been controversial, with industry regularly asserting that the agency’s overestimation of CH4 emissions from natural gas production is harming the fuel’s potential to displace more carbon-intensive fuel sources such as coal.

Even as EPA improves its GHG data set through the utilization of industry data, EPA’s Inspector General (IG) is calling for further data improvements. A Feb. 20 report from the IG calls for a broad strategy for improving emissions data from the oil and gas sector, prioritizing updated or first-time emissions factors for production processes for which data is scarce, such as hybrid wells, wastewater ponds, hydraulic fracturing of oil wells, and liquids unloading.

However, the agency is pushing back on some of the IG’s recommendations, specifically those intended to increase states’ participation in the National Emissions Inventory (NEI). The IG states that the rate of data submission by states is low, which the IG believes may lead EPA to underestimate oil and gas emissions. The IG recommends that the agency verify the NEI data by “ensuring that states submit point and nonpoint source data,” and craft guidance for states to use in estimating nonpoint source emissions. The agency, however, contends that states are doing their best to comply with reporting requirements, but are contending with limited resources and a lack of available data. Rather than “ensuring” states submit the data, the agency suggests it is more important to provide assistance to the states. The EPA further contends that the guidance it is currently crafting for calculating nonpoint source emissions is sufficient for states, and that additional state guidance would potentially add confusion if it is not in harmony with the forthcoming guidance.