Report to Congress Details Progress Made in Cleaning Up Dirty Diesel

Emissions from the tailpipe of a school bus.
Soot emanates from a school bus tailpipe.

School buses remain the largest transportation segment to receive funding as a result of the Diesel Emissions Reduction Act (DERA), the U.S. Environmental Protection Agency reported to Congress last month.

The EPA released its fourth annual state of DERA on July 25 to provide final results from fiscal years 2008-2013, plus final and estimated results from fiscal years 2014-2016. Enacted as part of the Energy Policy Act of 2005, the U.S. EPA passed on-highway emissions standard two years later and began providing funding in 2008 with its National Clean Diesel Campaign (NCDC).

The report indicated that over 40 percent of all DERA projects awarded between 2008 and 2016 have benefitted school buses. Prior to the development of the NCDC, the EPA awarded over $31 million in school bus grants through its Clean School Bus Program, which existed from 2003 to 2007.

From 2008 to 2016, the EPA said DERA awarded $629 million to retrofit or replace 67,300 total commercial vehicle engines, for a reduction of:

  • 472,700 tons of nitrogen oxides (NOx)
  • 15,940 tons of particulate matter (PM)
  • 17,700 tons of hydrocarbons (HC)
  • 61,550 tons of carbon monoxide (CO)
  • Nearly 5.09 million tons of carbon dioxide (CO2)

These reductions are estimated to result in up to $19 billion in monetized health benefits and 2,300 fewer premature deaths. Nearly three-quarters of all projects serve areas with air quality challenges.

However, EPA officials also pointed out that nearly 10 million older diesel engines of all types continue to operate across the U.S. without modern emissions controls. “While some of these will be retired over time, many will remain in use, polluting America’s air for the next 20 years,” EPA wrote. “The DERA program provides rebates and grant funding to replace these vehicles and engines with equipment that meets or exceeds current emissions standards.”

DERA funding appropriations more than doubled from fiscal year 2014 to 2016, from $20 million to $49.5 million. Over that same period, the EPA estimated that the grants reduced NOx by 14,275 tons, PM by 890 tons, and CO2 by 120,794 tons over the lifetime of the new engines.

Overall, EPA said DERA grants have saved 454 million gallons of fuel, with 10.6 million gallons saved during 2014-2016.

While EPA wrote that the DERA program has seen a greater interest in vehicle replacements compared to aftermarket tailpipe technologies, or retrofits, idling reduction technologies were still the leading benefactor of funds through the 2016 fiscal year, followed by retrofits of diesel oxidation catalysts (DOCs).

The NCDC also funds additional retrofits, such as adding vehicle aerodynamics, DOCs and closed crankcase ventilation (CCV) filters, diesel particulate filters (DPFs), and engine and vehicle replacements. EPA said that the technologies purchased with DERA grants can reduce particulate matter, the ultra-fine emissions particles that are most hazardous to young children, by 95 percent, as well as oxides of nitrogen (a significant contributor to smog), by 90 percent.

An EPA spokesperson told School Transportation News that fiscal year 2008-2016 DERA funds were used to scrap and replace approximately 2,500 older diesel school buses with new school buses.

The EPA report also said DERA funds resulted in the school bus installation of nearly 13,000 DOCs or DOCs plus CCVs, as well as approximately 1,400 diesel particulate filters (DPFs).

DOCs have resulted in an up to 20 percent reduction in PM, an 81 percent reduction in HC and a 66 percent reduction in CO. DPFs have cut PM by as much as 99 percent, HC by as much as 92 percent and CO by as much as 77 percent.

The EPA said it anticipates awarding about $40 million in competitive grant funding for the Diesel Emissions Reductions Act (DERA) Clean Diesel Funding Assistance Program this year. The 2020 request for applications is planned to open in December.

Additionally, the NCDC has funded a total of $35 million in rebates since 2012 for the purchase of new school buses that replace or retrofit diesel vehicles with engine model years of 2006 or older. Over 500 school districts nationwide have benefited to date.

The EPA also provided 13 tribal grants between 2014 and 2016 that totaled $3.7 million. These funds mostly replaced older diesel engines, but also replaced a handful of diesel vehicles. School buses represented a small fraction, about 5 percent, of the funded projects.

The EPA also makes available 30 percent of its annual DERA appropriation to allow states, the District of Columbia, Puerto Rico, Virgin Islands, Guam, America Samoa, and the Northern Mariana Islands, to implement their own clean diesel programs. From 2014 to 2016, EPA said it awarded $23.2 million in funds.

Over the lifetime of the affected engines, these state and territory projects are estimated to have reduced 3,670 tons of NOx, 200 tons of PM, 360 tons of hydrocarbons, 1,015 tons of carbon monoxide, and 110,115 tons of CO2. The EPA said these projects also saved nearly 10 million gallons of fuel, and retrofitted or replaced 1,520 engines or pieces of equipment.

The EPA also noted that starting in fiscal year 2017, states and territories have had the option to use their allocation of the Volkswagen Environmental Trust funds to match these state grants.


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Congress last reauthorized DERA in 2010 and has passed continuing resolutions since then to fund the program.

There are 10 members of the U.S. Senate Committee on Environment and Public Works who introduced a bill in March 2019 to reauthorize DERA through 2024, at $100 million a year. Previously, Congress appropriated $87 million to DERA for fiscal year 2019, which was a 16 percent increase from the previous year.

Gabe Rozsa, a managing director for National School Transportation Association lobbyist Prime Policy Group in Washington, D.C., said a House committee provided $55 million for fiscal year 2020. The Senate is expected to mark-up (edit/update/reconcile) its version after returning from recess.

Meanwhile, Senate Bill 747, the Diesel Emissions Reduction Act of 2019, was reported favorably out of the Committee on Environment and Public Works this spring. Rozsa added that its language is also included in the Committee on Environmental and Public Work’s highway bill, Senate Bill 2302, which was marked-up and reported last week.