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MECA report finds additional NOx emission reductions from new heavy-duty trucks achievable and cost-effective (corrected)

[In the earlier version of this post, I mistakenly linked to and used the 2019 report rather than the current 2020 report. I apologize for the error. —Ed]

The Manufacturers of Emission Controls Association (MECA) released a new report—“Technology Feasibility for Heavy-Duty Diesel Trucks in Achieving 90% Lower NOx Standards in 2027”—that presents test results from emission-control and fuel-efficiency technologies installed on heavy-duty diesel on-road engines that offer several cost-effective compliance pathways to reduce NOx emissions by 90% below today’s certification levels with simultaneous CO2 emission reductions in the 2027 timeframe.

The new report is a companion to a report released by MECA in June 2019 that provides an assessment of market-ready technologies for heavy-duty diesel vehicles to meet lower intermediate NOx standards by 2024 (“Technology Feasibility for Model Year 2024 Heavy-Duty Diesel Vehicles in Meeting Lower NOx Standards”). (Earlier post.)


Fully-aged aftertreatment combined with improved engine calibration and catalysts can achieve a 0.05 g/bhp-hr NOx limit with no major hardware changes. By 2027, a twin SCR design with cylinder deactivation can achieve a limit of 0.02 g/bhp-hr NOx, which is 90% below today’s standards, with better fuel economy. Source: MECA, “Technology Feasibility for Heavy-Duty Diesel Trucks in Achieving 90% Lower NOx Standards in 2027”

The main conclusions in the 2020 report include:

  • Engine and powertrain emission control technologies can enable simultaneous reductions in CO2 and NOx by 2027.

    Penetration of fuel saving technologies into the heavy-duty fleet has been spurred by EPA’s Heavy-Duty Greenhouse Gas Phase 1 Standards, and EPA envisions further penetration of these technologies in order for trucks to meet future Phase 2 requirements. At the same time, research undertaken by multiple teams as part of the Department of Energy’s SuperTruck I program has demonstrated how these technologies can be combined to achieve a 16% boost in fuel economy and improved freight efficiency.

    Participants in the SuperTruck II program are in the process of demonstrating even greater gains in fuel and freight efficiency. Component suppliers have continued to innovate, and a number of technologies that were not even considered as compliance options in the Phase 2 rule are now likely to be deployed on limited engine families in 2024 and more broadly in 2027.

    Furthermore, engine efficiency technologies such as cylinder deactivation, advanced turbochargers, and hybridization have also been demonstrated in combination with advanced aftertreatment technologies on heavy-duty diesel engines. Testing has shown the ability of several advanced engine technologies to be optimized to improve fuel efficiency while increasing exhaust temperature in diesel engine exhaust, which improves NOx reduction performance. It has now been widely demonstrated that the traditional trade-off relationship between CO2 and NOx emissions at the tailpipe has been overcome and reductions of both pollutants can be achieved simultaneously through the use of commercially available technologies.

  • Commercially available engine efficiency technologies and advanced aftertreatment system designs can achieve a certification emission limit of 0.02 g/bhp-hr NOx and a low-load cycle (LLC) limit below 0.075 g/bhp-hr NOx by 2027.

    New aftertreatment architectures that employ a close-coupled SCR catalyst before the DOC+DPF in a twin SCR system with dual-urea dosing can meet future NOx limits that phase in from 2024 to 2027. The approaches discussed for meeting these proposed 2027 NOx limits utilize commercially available engine technologies, improved thermal management, and advanced aftertreatment system designs based on high-efficiency catalysts and coating strategies.


    System configurations tested to demonstrate the feasibility of MY 2027 engine emissions. The first system is based on MY 2019 engines in production today. The second system employs a twin SCR arrangement that could be implemented in 2024. The third system adds a close-coupled SCR to a 2019-type underfloor system containing a DOC, DPF, and second SCR. Source: MECA, “Technology Feasibility for Heavy-Duty Diesel Trucks in Achieving 90% Lower NOx Standards in 2027”

  • The estimated cost of engine efficiency and emission controls for a Class 8 tractor meeting these future NOx limits is estimated to add $1,500 to $2,000, or about 1%, to the cost of a model year 2027 truck.

    MECA estimated the cost of emission control hardware, including engine efficiency improvements like those being demonstrated in a California ARB-funded test program, to meet an FTP tailpipe certification NOx value of 0.02 g/bhp-hr and a future LLC certification requirement. For a Class 8 tractor, these incremental improvements were estimated to add about 1% to the cost of a model year 2027 truck.

This new MECA white paper, along with our June 2019 companion report, shows that additional NOx emission reductions from new heavy-duty trucks beyond the current requirements are achievable and cost-effective by combining the improvements made to engines, emission control technologies, and fuels over the past twenty years.

The aftertreatment systems that will deliver ultra-low NOx emissions in 2027 will not look much different than they do today, incorporating advancements in substrates, catalysts, and calibrations. Furthermore, these advanced NOx emission controls are compatible with powertrain efficiency technologies to optimize vehicle fuel economy. As the US EPA and California ARB move forward to strengthen the current heavy-duty emission standards, MECA members are committed to delivering the technology solutions to achieve real on-the-road emission reductions in NOx and CO2 from this sector.

—MECA’s Executive Director, Rasto Brezny

Founded in 1976, MECA is a nonprofit trade association of the world’s leading manufacturers of clean technology solutions for all mobile sources.


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