United States Air and Radiation EPA420-F-03-016
Environmental Protection June 2003
Agency
Office of Transportation and Air Quality
and on a
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The pollution emitted by diesel engines contributes greatly to our
nation's air quality problems. Even with more stringent heavy-duty
highway engine standards set to take effect in 2004 and 2007, existing
trucks and buses will continue to emit large amounts of nitrogen oxides
(NOx) and particulate matter (PM), both of which contribute to serious
public health problems in the United States. Fortunately, there are
several techniques and technologies designed to reduce diesel
pollution from existing trucks and buses. Using pollution control
devices such as a diesel oxidation catalyst (DOC) is one way existing
engines can be upgraded (or "retrofitted") to pollute less. This fact
sheet discusses diesel oxidation catalysts.
What are the health and environmental of
exhaust?
Heavy-duty trucks and buses account for about one-third of NOx emis-
sions and one-quarter of PM emissions from mobile sources. In some
urban areas, the contribution is even greater. The fine particles in diesel
exhaust (known as particulate matter) can penetrate deep into the lungs
and pose serious health risks including aggravated asthma, lung damage,
and other serious health problems. In addition, diesel exhaust is a likely
human carcinogen. Children are more susceptible to air pollution than
healthy adults because their respiratory systems are still developing and
they have a faster breathing rate.
> Printed on Recycled Paper
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Diesel exhaust also has environmental impacts. PM from diesel engines
contribute to haze, which restricts visibility. In addition, diesel exhaust
contributes to ozone formation (a component of smog), acid rain, and
global climate change.
What is a Oxidation Catalyst?
A DOC is a device that uses a chemical process to break down pollutants
in the exhaust stream into less harmful components. More specifically, it
is a physical device with a porous ceramic honeycomb-like structure that
is coated with a material that catalyzes a chemical reaction to reduce
pollution.
What are the of a DOC retrofit?
DOCs reduce emissions of particulate matter by at least 20 percent.
DOCs also reduce emissions of hydrocarbons by 50 percent and carbon
monoxide by 40 percent.
the EPA verify emission reductions?
Yes, EPA evaluates the emission reduction performance of retrofit tech-
nologies such as DOCs, including their durability, and identifies engine
operating criteria and conditions that must exist for these technologies to
achieve those reductions. For a list of DOCs and other technologies that
EPA has verified, visit: www.epa.gov/otaq/retrofit/retroverifiedlist.htm.
For more information about EPAs verification process, visit:
www.epa.gov/otaq/retrofit/retrofittech.htm.
How much a DOC cost?
DOCs for school buses cost about $1,000 - $2,000. Field experience
suggests DOCs take about 1-3 hours to install.
What type of fuel a DOC require?
DOCs can be used with regular diesel fuel, but the effectiveness of a
DOC may be increased with the use of ultra low sulfur diesel (ULSD -
15 parts per million sulfur). Currently, ULSD costs between 8 and 25
cents per gallon more than regular diesel. ULSD is available in many
parts of the country now and will be available nationwide beginning in
June 2006.
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Can a DOC be on any engine?
Yes. DOCs have been used for years on a variety of diesel vehicles
including trucks, buses and construction equipment.
Are there maintenance requirements for a
DOC?
No. Much like a catalytic converter on a car, once a DOC is installed, it
rarely requires maintenance.
How long a DOC
Most DOCs come with a 100,000 to 150,000 mile warranty, and can last
7 to 15 years.
Where can I get a DOC?
For more information about manufacturers of DOCs or other retrofit
equipment visit our Web site at: www.epa.gov/otaq/retrofit/
cont retromfrs.htm.
Where can I find more information?
For more information on these topics, please visit these EPA Web sites:
• Voluntary Diesel Retrofit Program: www.epa.gov/otaq/retrofit
* Clean School Bus USA - Basic Information on Retrofit Options:
www.epa.gov/otaq/schoolbus/retrofit.htm
• Clean Diesel Independent Review Panel: www.epa.gov/air/caaac/
clean_diesel.html
* Health Assessment Document for Diesel Engine Exhaust: http://
cfpub. epa. gov/ncea/cfm/recordi splay. cfm?deid=29060
You can also contact the Office of Transportation and Air Quality library
for document information at:
U.S. Environmental Protection Agency
OTAQ Library
2000 Traverwood Drive
Ann Arbor, MI 48105
Phone: 734-214-4311
Email: GroupAALibrary@epa.gov
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