The U.S. Environmental Protection Agency (EPA) needs to improve air emissions data for the oil and natural gas production sector, according to a report issued by the agency’s Inspector General.

“EPA has limited directly-measured air emissions data on criteria and toxic air pollutants for several important oil and gas production processes,” said the report. “This limited data, coupled with poor quality and insufficient emission factors and incomplete NEI [National Emissions Inventory] data, hamper EPA’s ability to assess air quality impacts from selected oil and gas production activities.”

Limitations in EPA’s air emissions data for some oil and gas production pollutants “have contributed to emission factors of questionable quality,” said the report, and, because insufficient data is used in the agency’s NEI — only nine states submitted criteria pollutant emissions data for small stationary sources, for example — “we believe the NEI likely underestimates oil and gas emissions.”

The Office of Inspector General recommended that EPA develop and implement a comprehensive strategy for improving air emissions data, prioritize which emission factors need to be improved, develop additional emission factors as appropriate, and ensure that NEI data for the oil and gas industry sector are complete. EPA has concurred with most of the recommendations but does not agree with recommendations to ensure that states submit required data and develop default calculation guidance. “These recommendations are unresolved pending the agency’s final report response,” said the report.

The oil and gas industry has been critical of EPA’s estimates of methane emissions from oil and gas wells since they were released last year (see Shale Daily, Aug. 20, 2012). The standards “are based on emissions estimates that are overstated by as much as 1,400%,” said Lee Fuller, vice president of government relations for the Independent Petroleum Association of America. A coalition of seven states, led by New York Attorney General Eric Schneiderman, has said it will sue EPA for failing to address methane emissions from oil and gas operations in violation of the Clean Air Act.

In its recently released annual update on greenhouse gas emissions from stationary sources, the EPA said petroleum and natural gas systems produced about 6.8% of stationary source emissions, far less than the 67% contributed by power plants.