EPA Proposes Reducing Nitrogen Oxide Emissions by 2024

The U.S. Environmental Protection Agency said on December 20 it is beginning work on a proposed rule that would set new standards to reduce nitrogen oxides (NOx) for heavy-duty engines, beginning model year 2024—the same year a provision kicks in for the agency’s heavy-duty Phase 2 greenhouse gas program.

The announcement came in an EPA response to petitions requesting the agency take action to reduce NOx emissions from heavy-duty trucks.

The petitioners include the states of Connecticut, Massachusetts, New York, Rhode Island, Vermont, and Washington as well as local air-quality agencies from California, New York, and Ohio.

The EPA said the Clean Air Act directs it to revise standards from “time to time” in order to protect public health. It has been 16 years since the EPA last revised its NOx standards for heavy-duty highway engines, the statement said.

“The agency’s goal is to develop a program that could be adopted by EPA and the California Air Resources Board, creating a 50-state program, which would streamline compliance for manufacturers,” EPA said. “In developing the proposal, the EPA will work with a broad range of stakeholders, including heavy-duty vehicle and engine manufacturers; the California Air Resources Board; labor groups; technology suppliers; environmental nongovernmental organizations; state and local air quality agencies; truck dealerships; trucking fleets; and truck drivers and owners.”

The proposed version of Phase 2, which came out in June 2015, calls for lowering truck greenhouse gas emissions in 2021, 2024, and 2027 but had left the NOx limit at 0.2 gram throughout. The EPA did lower nitrogen oxide levels from trucks from 1998 to 2010, but then switched attention to greenhouse gases.

The South Coast Air Quality Management District in metropolitan Los Angeles and the San Joaquin Valley Air Pollution Control District around Bakersfield, Fresno, and Modesto were the main petitioners calling for the NOx rule at the same time that caps on carbon dioxide and other greenhouse gases are lowered.

NGWA impact: The impact is difficult to determine because the rule has not yet been proposed. Prior rules have exempted drilling rigs and other vehicles classified as mobile machinery from more stringent regulations.