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April 07, 2017   |   Diesel Technology Forum

Policy Insider

One of the Smallest Chemical Plants Responsible for One of Biggest Clean Air Success Stories

Near-zero emission reduction is achieved with Selective Catalytic Reduction – a technology very similar to a tiny chemical plant attached to the emissions system of a commercial truck.

According to the U.S. Environmental Protection Agency (EPA), the largest sources of emissions of oxides of nitrogen – or NOx, a smog forming compound – are attributable to large heavy-duty commercial vehicles. However, over the next 20 years, the largest reduction in emissions of oxides of nitrogen is attributable to commercial vehicles. The greater adoption of a clean diesel technology called Selective Catalytic Reduction is largely the contributing factor to this emission reduction success.

After decades of research and investment in new technologies, a new generation of clean diesel technologies is available to meet near-zero NOx emissions standards established by U.S. EPA required of commercial  vehicles. Beginning in model year 2010, new heavy-duty vehicles must come with technologies that achieve these near-zero emissions standards. Relative to a truck manufactured in 1988, a clean diesel truck results in a 98 percent reduction in NOx emissions. In fact, a single Class 8 tractor on the road for, on average 120,000 miles a year, can reduce NOx emissions by over 1 ton each year relative to a truck deployed with an older generation of technology.

This near-zero emission reduction is achieved largely through the development of Selective Catalytic Reduction – a technology very much similar to a tiny chemical plant attached to the emissions system of a commercial truck. Today, one-in-three commercial vehicles on the road is of a generation that is deployed with this technology designed to meet this near zero NOx standard.

SCR system

The California Air Resources Board projects that in looking at NOx emission reduction across all sources of emissions, the largest contributor to declining NOx emissions by 2035 are from commercial vehicles. This significant reduction in emissions relates to the greater adoption of diesel trucks that meet the near-zero NOx emissions requirement through the use of Selective Catalytic Reduction. More great things are expected as even more of these clean diesel trucks enter into the vehicle population. Similar emission reduction achievements are also expected in other states and communities across the country thanks to the greater adoption of the latest proven and available clean diesel technology at work.

 SCR Chart



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Ezra Finkin
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