Several state and local government agencies petitioned the U.S. Environmental Protection Agency (EPA) earlier this year to increase the stringency of the on-highway heavy-duty engine NOx emission standards from 0.2 grams per brake horsepower-hour (g/bhp-hr) to 0.02 g/bhp-hr.
On Dec. 20, 2016, the EPA responded to petitions submitted by 20 of those state and local government agencies and other organizations.
The EPA’s response acknowledges that there is a need for further NOx reductions from heavy-duty on-road trucks, buses and other vehicles to reduce adverse health impacts from ground-level ozone and microscopic airborne particles; that the Clean Air Act directs EPA to revise standards from time-to-time in order to protect public health; and that it has been 16 years since the EPA last revised its NOx standards for heavy-duty highway engines.
The agency says that technical progress has been made in developing technologies and approaches that can reduce NOx emissions beyond the standards put in place in the 2000 rule. As a result, the EPA will initiate the work necessary to issue a Notice of Proposed Rulemaking with the intention of proposing standards that could begin in Model Year 2024.
As reported, this time frame is consistent with the lead-time requirements of the Clean Air Act and is aligned with a milestone implementation year for the EPA heavy-duty Phase 2 GHG program.
The agency’s goal is to develop a program that could be adopted by the EPA and the California Air Resources Board, creating a 50-state program, which would streamline compliance for manufacturers. 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 non-governmental organizations; state and local air quality agencies; truck dealerships; trucking fleets; and truck drivers and owners.