US EPA issues ANPR for Cleaner Trucks Initiative
6 January 2020
Today, the US Environmental Protection Agency (EPA) released an Advance Notice of Proposed Rule (ANPR) soliciting pre-proposal comments on a rulemaking effort known as the Cleaner Trucks Initiative (CTI). The ANPR describes the EPA’s plans for new emission standards for NOx and other pollutants for highway heavy-duty engines. It also proposes to streamline engine certification procedures.
The EPA is considering implementation of new standards beginning in model year 2027, which is also the implementation year for the final set of Heavy-Duty Phase 2 GHG emission standards. The ANPR outlines several areas where regulatory changes are expected, however, it does not specify the emission limit values under consideration or other particulars of the future regulation.
The intended regulatory changes focus on the control of in-use emissions under real world operating conditions. The current heavy-duty engine emission standards reduced PM and NOx tailpipe emissions by over 90% for emissions measured using the specified test procedures, but their impact on in-use emissions during real-world operation is less clear, the EPA said. There are engine operating modes where SCR systems commonly used to reduce NOx are much less effective. For example, NOx emissions can be significantly higher during engine warm-up, idling, and certain other types of operation that result in low load on the engine or transitioning from low to high loads. Moreover, deterioration of emission controls in-use, along with tampering and mal-maintenance, can result in additional NOx emissions.
The main technologies and emission reduction strategies considered for the CTI include thermal management technologies that can be used to better achieve and maintain adequate catalyst temperatures, and next generation catalyst configurations and formulations to improve catalyst performance across a broader range of engine operating conditions.
The EPA intends to develop a heavy-duty engine emission program applicable to all 50 states. The agency said it is closely following the technical work initiated by the California Air Resources Board (CARB) to update their heavy-duty vehicle and engine programs under the CARB Heavy-Duty NOx Omnibus proposal.
Some noteworthy components of the ANPR include:
- Providing Important NOx Emission Reductions—Reductions in NOx emissions will help areas attain and maintain the ozone and PM2.5 NAAQS and help prevent future nonattainment. While the ANPR does not specify NOx emission limits, CARB has been considering an FTP/RMC NOx limit between 0.015 and 0.030 g/bhp-hr, down from today’s 0.2 g/bhp-hr.
- Updating Laboratory Test Cycles for Heavy-Duty Vehicles—The EPA is considering changes to the weighting factors for the FTP cycle for heavy-duty engines, by increasing the weight of the cold start run. Furthermore, the EPA intends to introduce an additional low-load test cycle and standard that would require diesel engine manufacturers to maintain the emission control system’s functionality during operation where the catalyst temperatures have historically been below their operational temperature.
- Improving Real-World Emissions Testing—To improve in-use performance, the EPA is considering a broader range of engine operation when evaluating in-use compliance. The agency is considering a moving average window (MAW) approach consisting of time-based windows. Instead of basing window size on an amount of work, the EPA is evaluating window sizes ranging from 180 to 300 seconds. For the MAW-based standards, the EPA could design their certification and in-use programs to include corresponding laboratory-based cycles and in-use bins with emission standards that relate by a scaling factor.
- Extended Useful Life and Emissions Warranty Provisions—The useful life values with respect to years would remain unchanged. However, the EPA intends to propose new, extended useful life mileage values for all categories of heavy-duty engines to be more reflective of real-world usage. The EPA would also propose longer emissions warranty periods.
- Diesel Aftertreatment Rapid Aging Protocol—The EPA is developing a protocol for demonstrating aftertreatment durability through an accelerated catalyst aging procedure. The objective of this protocol is to artificially recreate the three primary catalytic deterioration processes observed in field-aged components: thermal aging based on time at high temperature, chemical aging that accounts for poisoning due to fuel and oil contamination, and deposits. This work to develop a diesel aftertreatment rapid-aging protocol (DARAP) builds on an existing rapid-aging protocol designed for light-duty gasoline vehicles.
The CTI program focuses on engine-certified products—the proposed changes to the standards or test procedures are not applicable to chassis-certified heavy-duty vehicles.
Comments on the ANPR can be submitted at regulations.gov, docket ID #EPA-HQ-OAR-2019-0055. The EPA intends to publish a proposed CTI rule in early 2020.
Source: US EPA