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CARB Approves Low-NOx Requirements for Medium and Heavy Duty Trucks

Last Friday, the California Air Resources Board (CARB) approved the Omnibus Low-NOx Rule, requiring new engines and trucks to meet more demanding NOx standards – 75% lower in 2024 and 90% lower in 2027. The rules also lower the standard for particulate matter by 50 percent and include new tougher in-use testing protocols, extended deterioration requirements, and extended warranty provisions, among other things. CARB also approved changes to the optional low-NOx certification program under which most natural gas engines are currently certified. The new rules will require optional low-NOx engines and trucks to be certified to a level of no more than 0.02 g/bhp-hr in 2024 and 0.01 in 2027. PM levels would have to be no more than 0.005 g/bhp-hr to be considered an optional low-NOx engine.

NGV advocates including NGVAmerica provided written comments in advance of the Board’s approval, principally to point out that the Board in addition to adopting these rules must take more decisive steps to encourage greater adoption of currently available low-NOx trucks like those powered by natural gas. The comments coordinated by the California Natural Gas Vehicle Coalition indicated that moving more quickly to encourage greater uptake of available low-NOx trucks is critical to satisfying federal clean air standards and more importantly to more quickly delivering better air quality to affected communities. NGV advocates also urged CARB to ensure that currently available low-NOx engines continue to earn credits under the regulatory program until the 0.02 NOx standard becomes mandatory in 2027.

California’s decision to approve the new engine standards comes despite the request by engine manufacturers and trucking representatives like the American Trucking Association that the state work with the U.S. EPA to develop one national standard for trucks and engines. The U.S. EPA in January of this year issued an advanced proposed rulemaking inviting comment on new emission requirements for trucks as part of the Cleaner Trucks Initiative. NGVAmerica commented on that proposal in February, also urging the EPA to provide enhanced credits for natural gas engines and trucks, which already deliver much lower emissions than required by existing federal rules. EPA, however, has not issued a notice of proposed rulemaking and the effort appears to be sidelined for now according to news reports.

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