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Engine makers are developing new technologies that further reduce both NOx and CO2 emissions. Cummins’ under-development concept emissions control system combines turbocharged air management with exhaust aftertreatment as a single close-coupled system, together with a new rotary turbine control. (Cummins)

Cleaner Trucks Initiative starts NOx-reduction journey

The U.S. Environmental Protection Agency (EPA) is in the beginning stages of establishing new NOx regulations for heavy-duty on-highway trucks. The agency is spurred by advances in technology and a desire to streamline the certification process.

The EPA last revised NOx standards for on-road heavy-duty trucks and buses in January 2001. The process that culminated in those standards actually started in the late 1990s. Rulemaking takes time, both to understand technology trends and incorporate a wide group of stakeholders. It will take no less time to update those NOx standards under the program called the Cleaner Trucks Initiative (CTI), announced by the EPA in November 2018.

Why update the regulations now? Three reasons, according to William Charmley, director of Assessment & Standards Division, Office of Transportation and Air Quality at the U.S. EPA. Emissions control technology has improved; EPA and the industry better understand emissions science; and there is a desire by all parties to streamline the certification process, easing the regulatory burden for all.

“Both we and the industry as well as other stakeholders have ideas about how we can make our regulations better, using what we have learned in the last 10 to 20 years,” he told Truck & Off-Highway Engineering. Some of these stakeholders include the California Air Resources Board (CARB), who have sponsored testing that also shows new technologies are now available to reduce NOx.

“The last time the standards got more stringent was in 2010,” said Charmley, who is responsible for developing vehicle, engine, and fuel environmental air quality regulatory standards for all transportation sources in the U.S., as well as the development and ongoing improvements to EPA’s official air pollution emissions inventory forecasting model for highway and nonroad transportation sources. “In these last nine years we learned that even though heavy-duty engines have become much cleaner, under some conditions new technology can reduce NOx emissions even more.”

He notes that the current EPA program for on-road emissions was probably the first in the world to emphasize real-world testing, where engine and truck makers would test vehicles selected from fleets with portable emissions testing equipment and report the results, in addition to running test cycles on an engine dynamometer.

The data from such testing found that NOx emissions is higher under idle conditions, low-load, start and stop, or creep/crawl operations for trucks, according to Charmley. “These emissions are a lot higher than we think we could meet with [today’s] new technology,” he said. “They meet today’s in-use testing regulations, which were designed for line-haul operations. But one of the goals of the Cleaner Trucks Initiative is to reduce NOx emissions under the majority, or even all, of the in-use operating cases.”

Technology improvements he points to include improved catalysts, better understanding of how to calibrate engines, and even some new technologies used in light-duty today, like cylinder de-activation. These should reduce NOx under a wider set of operating conditions.

Another key element of the program is streamlining the regulatory process.

“Whenever we have asked the regulated industry about this, they have answered that they want EPA to do the Cleaner Trucks Initiative,” said Charmley. In fact, the Truck & Engine Manufacturers Association (EMA) issued a press release on November 13, 2018, supporting the Cleaner Trucks Initiative. The EMA press release emphasizes it supports a move from a prescriptive-based compliance program to one that is performance-based.

Charmley was quick to point out that engine makers also have to meet other regulations, most notably the Phase 2 greenhouse gas (GHG) emissions standards that have regulatory deadlines in 2021, 2024, and 2027.

“My engineering staff and I know it takes time to develop heavy-duty engines,” he said. “We are sensitive to the fact that those same companies affected by the Cleaner Trucks Initiative are working hard to meet this existing Phase 2 program.”

He emphasized that EPA desires both to meet the goals for NOx under Cleaner Trucks Initiative and that it harmonizes with the Phase 2 GHG program. “We want to give the companies enough time to develop technology to meet [GHG and NOx] emissions requirements and all the requirements for their customers,” he said.

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