CARB Staff Current Assessment of the Technical Feasibility of Lower NOx Standards

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April 18, 2019

CARB Staff's Current Assessment of the Technical Feasibility of Lower NOx Standards and Associated Test Procedures for 2022 and Subsequent Model Year Medium-Duty and Heavy-Duty Diesel Engines

White Paper Posted

The California Air Resources Board (CARB) staff has posted a White Paper that discusses staff’s assessment of the technical feasibility of lower oxides of nitrogen (NOx) standards and associated test procedures for 2022 and subsequent model year medium-duty and heavy-duty engines.

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In March 2017, the Board approved the 2016 State Strategy for the State Implementation Plan (SIP). One of the key measures in the SIP is the establishment of on-road heavy-duty low-NOx engine emission requirements that would provide a 90 percent reduction in NOx emissions compared to today’s engines (Heavy-duty Low NOx Omnibus Rulemaking). To complement this measure, the SIP also included a “Lower In-Use Emission Performance Level” measure that would ensure that heavy-duty vehicles remain “clean” in-use, as they were originally certified when new. These two measures are critical for attaining federal health-based air quality standards for ozone in 2031 in the South Coast and San Joaquin Valley air basins, as well as fine particulate matter (PM2.5) standards in the next decade.

In addition to a new lower NOx standard, staff also plans to develop a new low load certification cycle, to strengthen engine and emission control system durability requirements, to improve reporting and corrective action of failing emission control parts covered under warranty, and to improve the in-use testing program. CARB’s overall low-NOx emission standard package, which will include the amendments discussed above, is tentatively scheduled for Board consideration in first quarter of 2020.

Because about 60 percent of total heavy-duty vehicle miles traveled in the South Coast on any given day is accrued by trucks that were newly purchased outside of California, U.S. Environmental Protection Agency (U.S. EPA) action to establish a new national low-NOx standard for heavy-duty trucks is critical. In response to petitions for a low-NOx rulemaking from over 20 organizations including state and local air agencies from across the country, on November 13, 2018, U.S. EPA announced the “Cleaner Truck Initiative” to develop regulations to further reduce NOx emissions from on-road heavy-duty trucks and engines. U.S. EPA intends to publish a proposed rule in 2020. CARB plans on coordinating its regulatory efforts with U.S. EPA.

During recent meetings with CARB staff, many engine manufacturers stated to staff that they are in the process of settling on engine development plans to meet the 2024 model year Phase 2 greenhouse gas (GHG) requirements. They further stated that, in order to accommodate NOx reductions in their 2024 model year engine designs, they need to know as soon as possible what requirements CARB staff is considering to propose for 2024 model year engines. They described their need for sufficient product development time to incorporate NOx requirements together with the Phase 2 GHG requirements. Thus, in response, CARB staff has prepared this White Paper that describes staff's current assessment of what it believes is achievable for 2022 through 2026 model year engines and an assessment of additional requirements for 2027 and subsequent model year engines.

The main objective of this White Paper is to outline staff’s assessment regarding technical feasibility and cost effectiveness of possible NOx reduction programs for 2022 and subsequent model year diesel medium-duty and heavy-duty engines. Although some elements of the Heavy-duty Low NOx Omnibus Rulemaking will affect medium-duty and heavy-duty Otto cycle engines as well, this White Paper focuses solely on an assessment for diesel engines.

It is important to emphasize that this White Paper is strictly staff's current assessment of what is currently considered as technically achievable and cost effective for 2022 and subsequent model years. As additional and/or updated technical information becomes available between now and the Board hearing date, and because the Board has the ultimate authority to accept, reject, or change staff’s proposal as it sees fit, this White Paper cannot predict with certainty what CARB will ultimately adopt in its Heavy-duty Low NOx Omnibus Rulemaking.

For questions regarding the workshop, you may contact Mr. Daniel Hawelti or by phone at (626) 450-6149.

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