EPA Plans to Propose Regulation to Tighten NOx Limit in 2024

This story appears in the Jan. 2 print edition of Transport Topics.

The Environmental Protection Agency is beginning work on a proposed rule that would set new standards to further reduce nitrogen oxide emissions from heavy-duty truck engines beginning in 2024, the same year a provision kicks in for the agency’s heavy-duty Phase 2 greenhouse-gas program.

EPA announced the proposed rule in an agency response to petitions requesting that 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.

In a statement, EPA said the Clean Air Act directs it to revise standards from “time to time” to protect public health. The agency previously tightened its NOx standards for truck engines in 2010, lowering the ceiling to 0.2 gram per brake horsepower-hour.

“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, 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 GHG Phase 2 final rule, issued in June, calls for lowering truck emissions of carbon dioxide and other greenhouse gases in 2021, 2024 and 2027 but had left the NOx limit as is. EPA lowered nitrogen-oxide levels from trucks from 1998 to 2010 but then switched attention to GHGs.

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 a new NOx rule at the same time that caps on CO2 are being lowered.

The two California districts have some of the most stubborn smog problems in the nation, combining large populations with geographical impediments to air flow. They have expressed a desire to see the cap lowered another 90% to 0.02 gram from 0.20 gram.

“The South Coast Air Quality Management District is pleased that U.S. EPA has responded positively to the petition by [the district] and its partners and pledged to begin rulemaking to develop a new, more stringent nationwide emissions standard for new, heavy-duty truck engines,” spokeswoman Tina Cox said. “Such a standard is crucial to [the district’s] ability to meet U.S. EPA deadlines to meet health-based standards for ground-level ozone in 2023 and 2031.”

In a response to the EPA announcement, the Truck and Engine Manufacturers Association said it’s premature to commit to a particular level or form of a future low-NOx standard for heavy-duty vehicles.

“The assessment of whether, to what extent and how to implement additional heavy-duty on-highway NOx controls must be data-driven and must take all current regulations into account,” said Jed Mandel, the association’s president. “It is especially important to ensure that any potential future low-NOx requirements do not compromise compliance with the just-finalized Phase 2 greenhouse-gas standards, which will improve heavy-duty on-highway fuel economy by more than 25% over the next 10 years.”

Historically, limiting NOx and CO2 standards at the same time has been a significant engineering challenge, truck makers have said over the years.

Allen Schaeffer, executive director of the Diesel Technology Forum, said EPA’s announcement signaled further progress.

“Keep in mind where we are today with NOx — near zero — so we’re talking about nearer to zero,” Schaeffer said. “We’d be taking a big step forward in NOx reduction with retirement of pre-2010 vehicles at an accelerated pace.”

American Trucking Associations wants the federal government, not the states, to continue to set NOx standards.

“As an industry that works across state lines, we believe that air quality and emissions regulations should be done exclusively at the federal level and that states should not be allowed to create de facto national standards outside of the federal regulatory process,” said Glen Kedzie, ATA’s energy and environmental counsel.

“ATA has a long track record of improving the environment, from our work with EPA’s SmartWay Transport Partnership to our support of Phases 1 and 2 of EPA’s fuel-efficiency rule for medium- and heavy-duty trucks,” Kedzie added. “That said, the further ramping down of NOx emissions as envisioned by this petition will likely have a deleterious effect on our industry’s overall fuel economy. We believe any tightening of NOx standards for large trucks must consider these impacts, as well as the impact these technologies may have on engine cost and reliability.”