United States              Air and Radiation         EPA420-F-00-048
                    Environmental Protection                           November 2000

                    Office of Transportation and Air Quality
&EPA       Program
                    Reducing Air Pollution from
                    Nonroad  Engines
                    In response to environmental and public health concerns, the U.S.
                    Environmental Protection Agency (EPA) has established emission
                    standards for several nonroad engine categories. These engines
                    operate in a wide variety of applications, including farm and
                    construction equipment, lawn and garden equipment, marine vessels,
                    and locomotives. As a whole, these emission control programs
                    significantly reduce the impact of nonroad engines and equipment on
                    the nation's air quality.

                    At EPA, we have set increasingly stringent emission standards for
                    highway cars and trucks since the early 1970s. After making much
                    progress in controlling highway emissions, we turned our attention to the
                    wide variety of nonroad engines, which also contribute significantly to
                    air pollution. These programs reduce harmful  air pollution and help
                    states meet the National Ambient Air Quality  Standards.

                    "Nonroad" is a term that covers a diverse collection of engines,
                    equipment, vehicles, and vessels. Sometimes referred to as "off-road" or
                    "off-highway," the nonroad category includes  outdoor power equipment,
                    recreational vehicles, farm and construction machinery, lawn and garden
                    equipment, marine vessels, locomotives, aircraft, and many other
                    applications. Until the mid-1990s, very few of these engines faced any
                    kind of emission standards.
                                                               I Printed on Recycled Paper

The 1990 amendments to the Clean Air Act
directed us to study the contribution of
nonroad engines to urban air pollution, and
regulate them if they contributed to air
quality problems. In  1991, we published a
report showing that nonroad equipment
emitted large amounts of oxides of nitrogen
(NOx), hydrocarbon  (HC), carbon
monoxide (CO) and paniculate matter
(PM). In general, we found that nonroad
engines had total emissions almost as high
as highway engines. In the case of
particulate matter, nonroad emissions were
significantly higher than  highway
emissions. 1 The following pie charts show
updated emission estimates.
       2000 Nonroad NOx Emissions
     Trains 22%
               Other  Large SI
                  3% 6%
3% Planes
  Marine Cl 18%
                      48% Nonroad Cl
     Total nonroad NOx emissions = 5,461 tons
     Total highway NOx emissions = 7,988 tons
        2000 Nonroad HC Emissions
 Nonroad CI9%
         Other Planes Large SI
             W   5% 3%  16% Recreational SI
 Marine SI 25%
                       40% Small SI
     Total nonroad HC emissions = 3,677 tons
     Total highway HC emissions = 3,772 tons
     1 We refer to the combined set of highway and nonroad
  engines as mobile sources. This does not include stationary
  engines, which are regulated by separate programs, usually
  at the state level.
2000 Nonroad CO Emissions
 Other 0.8%i  rPlanes3%
               Large SI Recreationa| S|
                      Nonroad Cl 4%
                    Marine SI 7%
                                62%Small SI
                        Total nonroad CO emissions = 29,514 tons
                        Total highway CO emissions = 49,701 tons
                    Marine Cl 6'5%
                          2000 Nonroad PM Emissions
                                       Other  small SI
                         Marine SI
                                  55% Nonroad Cl
                                                   Total nonroad PM emissions = 459 tons
                                                   Total highway PM emissions = 240 tons
                   In response, we have initiated regulatory
                   programs for several  categories of nonroad
                   engines. The following sections summarize
                   the status of these programs for the various
                   nonroad equipment categories.
                   Land-Based Diesel Engines
                   Nonroad diesel engines dominate the large
                   nonroad engine market. They currently
                   contribute about 20 percent of NOx
                   emissions and 36 percent of PM emissions
                   from mobile sources.2
                       2 Diesel engines may also be referred to as
                     compression-ignition (or Cl) engines. These engines
                     typically operate on diesel fuel, but other fuels may be also
                     be used. In contrast, spark-ignition (or SI) engines
                     generally operate on gasoline, natural gas, or liquefied
                     petroleum gas.

Examples of applications falling into this
category include agricultural equipment
such as tractors, construction equipment
such as backhoes, material handling
equipment such as heavy forklifts, and
utility equipment such as generators and
      Examples of Nonroad Diesel
In 1994, we issued the first set of emission
standards ("Tier 1") for all nonroad diesel
engines greater than 37 kilowatts (50
horsepower), except those used in
locomotives, marine vessels, and
underground mining equipment.3 The Tier
1 standards were phased in for different
engine sizes between  1996 and 2000,
reducing NOx emissions from these
engines by 30 percent.
    3 The U.S. Mine Safety and Health Administration sets
  requirements related to emissions from underground
  mining equipment.
We have since adopted even more stringent
emission standards for NOx, HC, and PM
from new nonroad diesel engines. This
program includes the first set of standards
for nonroad diesel engines less than 37 kW
(phasing in between 1999 and 2000),
including marine propulsion and auxiliary
engines in this size range. It also phases in
more stringent "Tier 2" emission standards
from 2001 to 2006 for all engine sizes and
adds yet more stringent "Tier 3" standards
for engines between 37 and  560 kW (50
and 750 hp) from 2006 to 2008. These
standards will further reduce nonroad
diesel engine emissions by 60 percent for
NOx and 40 percent for PM from Tier 1
emission levels.

We are currently pursuing new emission
standards and measurement  methods that
focus on controlling NOx and PM
emissions from the wide  range of in-use
Land-Based Spark-Ignition
We divide land-based spark-ignition
engines into three broad categories—small
engines typically used for lawn and garden
applications, large engines used in
industrial applications, and specialty
engines used in recreational applications.

Small SI  Engines
Small SI engines at or below 19 kW (25
hp) contribute about 20 percent of HC
emissions  and 23 percent of CO emissions
from mobile sources. These engines, which
usually run on gasoline, are used primarily
in lawn and garden equipment, such as
lawnmowers, string trimmers, leaf blowers,
chain saws, commercial turf equipment,
and lawn and garden tractors.

   Examples of Small SI Equipment:
              brush cutters
              lawn mowers
              lawn tractors
              leaf blowers
Under the Phase 1 regulations, new Small
SI engines have had to meet emission
standards for HC, CO, and NOx since
1997. These standards apply to all nonroad
SI engines at or below 19 kW except those
used for marine propulsion, for recreational
applications (such as motorcycles or
snowmobiles), or for toy boats and
airplanes. The Phase 1 standards have
resulted in a 32 percent reduction in HC
We recently adopted Phase 2 standards for
Small SI engines. For nonhandheld
applications (such as lawn and garden
tractors and lawnmowers), these standards
phase in between 2001 and 2007 and will
result in an additional 60 percent reduction
in HC and NOx emissions beyond Phase 1
levels. For handheld applications (such as
leaf blowers and chainsaws), these
standards phase in between 2002 and 2007
and will result in an additional 70 percent
reduction in HC and NOx emissions
beyond Phase 1 levels.

Large SI  Engines
Nonroad SI engines above 19 kW (25 hp),
which are usually car and truck engines
installed in industrial equipment are used in
a wide variety of applications, including
forklifts, airport ground-service equipment,
generators, compressors, welders, aerial
lifts, and ice grooming machines. These
engines, which may operate on gasoline,
liquefied petroleum gas, or natural gas,
contribute about 2 percent of NOx and HC
emissions, and 3 percent of CO emissions
from mobile sources. Many of them
operate indoors, where high exhaust
concentrations often expose workers to
dangerous levels of CO emissions.

We will propose emission standards for
Large SI engines in 2001. The emission
standards already adopted by the California
Air Resources Board for these engines,
which phase in between 2001 and 2004,
serve as the starting point for this effort.
Application of basic automotive emission
control technologies can reduce CO, NOx,
and HC emissions by about 90 percent.
   Examples of Large SI Equipment:
     airport ground-service equipment
               aerial lifts
              ice machines
Recreational SI Engines
We will propose emission standards in
2001 for engines used in nonroad
recreational applications, such as

motorcycles, all-terrain vehicles, and
snowmobiles. This may also include
motorized scooters, mini-bikes, and some
mopeds. These engines contribute about 8
percent of HC emissions and 5 percent of
CO emissions from mobile sources. This is
especially important in areas where their
concentrated use can cause problems for
local air quality, operators, or bystanders.
Emission control technologies appear to be
available to substantially reduce emission
levels without sacrificing the performance
of these engines.
  Examples of Recreational SI Vehicles:
            all-terrain vehicles
Marine Engines
Marine vessels vary widely in the sizes and
types of engines they use. We have divided
marine engines into three broad categories
for setting emission standards: (1)
gasoline-fueled outboard engines and
personal watercraft; (2) sterndrive and
inboard gasoline engines; and (3) marine
diesel engines. While marine diesel
auxiliary engines are included under these
marine programs, gasoline-fueled auxiliary
engines must meet  emission standards that
apply to land-based engines.

Outboard and Personal Watercraft
These engines, which have typically used
simple two-stroke technology, contribute
about 12 percent of HC emissions from
mobile sources. Emission standards for
outboard and personal watercraft engines
call for manufacturers to meet increasingly
stringent HC levels over a nine-year phase-
in period starting in 1998. By 2006 all
manufacturers will produce engines with
75 percent lower HC emissions. The
gradually decreasing emission standard
allows manufacturers to determine the best
approach to achieving the targeted reduc-
tions over time by allowing them to phase
in the types of control technologies in the
most sensible way, while minimizing the
cost impact to the consumer.

Sterndrive and  Inboard Gasoline
Sterndrive and inboard gasoline engines
typically use four-stroke automotive
engines that have been modified for sport
boats. Emissions from recreational marine
diesel engines account for about 0.5
percent  of NOx emissions and about 0.2
percent  of PM emissions from mobile
sources. However, because of the nature of
their operation, the contribution of these
engines to total emissions in and around
marinas and harbors is higher. Also, CO
emissions from these engines pose an
ongoing safety threat to boaters.
Uncontrolled emission levels from these
engines are usually considerably lower than
from outboard engines, but there is still an
opportunity to significantly reduce NOx,
HC, and CO emissions. We are developing
emission standards that would require
manufacturers to use available emission
control technology on their new engines.

Marine Diesel Engines
Marine diesel engines are a diverse
nonroad category that includes small
auxiliary and propulsion engines, medium-
sized propulsion engines on coastal and
harbor vessels, and very large propulsion
engines on ocean-going vessels. These
engines contribute about 7 percent of NOx
emissions and 6 percent of PM emissions
from mobile sources, though the
contribution is much greater in areas with
commercial ports.
At the international level, emissions from
marine diesel engines are controlled by
Annex VI of the International Convention
on the Prevention of Pollution from Ships
(commonly known as the MARPOL
convention). The NOx limits, contained in
Regulation 13, apply to marine diesel
engines rated above 175 hp. The standards
target a 30 percent reduction from
uncontrolled levels. The standards apply to
engines installed on vessels whose
construction starts on or after January  1,
2000, even if they will operate only within
the U.S. The standards also apply when
someone substantially modifies one of
these engines on or after January 1, 2000,
regardless of the engine's age.

On the national level, we have adopted
emission standards that go  beyond the
MARPOL Annex VI levels for commercial
marine diesel engines that will be installed
on U.S.-flagged vessels. These standards
apply to new commercial marine diesel
engines produced in 2004 or later. For very
large engines, these standards begin in
2007. Manufacturers will likely use
technologies from highway and land-based
nonroad engines to reduce emissions from
the similar marine engines. These standards
will reduce NOx emissions by 24 percent
and PM emissions by 12 percent.

Recreational marine diesel engines are
usually calibrated for greater power output
and are used much differently than
counterpart commercial engine models. We
are considering these and other factors in a
current effort to set emission standards for
these engines. We expect that
manufacturers will use the same kind of
emission control technologies they are
developing for the commercial engines.
Locomotives contribute about 9 percent of
NOx emissions and 4 percent of PM
emissions from mobile sources. These
engines are generally larger and last longer
than any land-based nonroad diesel
engines. New emission standards will
reduce NOx emissions by two-thirds, while
HC and PM emissions from these engines
will decrease by 50 percent.

Three separate sets of emission standards
have been adopted, with applicability of the
standards dependent on the date a
locomotive is first manufactured. The first
set of standards (Tier 0) apply to
locomotives and locomotive engines
originally manufactured from 1973 through
2001 any time they are manufactured or
remanufactured. This is a unique feature of
the locomotive program, which is critical
because locomotives are generally
remanufactured 5 to 10 times during their
total service lives of 40 years or more.

The second set of standards (Tier 1) apply
to locomotives and locomotive engines
originally manufactured from 2002 through
2004. These locomotives and locomotive
engines will be required to meet the Tier 1
standards at the time of original
manufacture and at each subsequent

The final set of standards (Tier 2) apply to
locomotives and locomotive engines
originally manufactured in 2005 and later.
Tier 2 locomotives and locomotive engines
will be required to meet the applicable
standards at the time of original
manufacture and at each subsequent
Aircraft emissions contribute about 1
percent of NOx emissions and 6 percent of
PM emissions nationwide from mobile
sources. Some cities with a lot of airport
traffic see a more pronounced impact from
these engines. In addition, commercial
aircraft emissions are a fast-growing
segment in the transportation sector. An
EPA report, "Evaluation of Air Pollutant
Emissions from Subsonic Commercial
Aircraft," estimates that commercial
aircraft will contribute as much as 10
percent of 2010 mobile source NOx
emissions in at least two cities studied (see
below). Aircraft emissions also contribute
significantly to global climate change and
the depletion of the stratospheric ozone

Emission standards for gas turbine engines
that power civil aircraft have been in place
for about 20 years. These engines are used
in virtually all commercial aircraft,
including both scheduled and freight
airlines. The standards do not apply to
military or general aviation aircraft.
Controls on engine smoke and prohibitions
on fuel venting were instituted in 1974 and
have been revised several times since then.
Beginning in 1984, gas turbine  engines
must comply with limits on hydrocarbon
emissions per landing and takeoff cycle.
Due to the international nature of the
aviation industry, the International Civil
Aviation Organization (ICAO) plays an
important role in defining uniform
emission standards that can be adopted by
individual nations. In May 1997, we
adopted ICAO's NOx and CO emission
standards for gas turbine engines. In
addition we plan to adopt a second round
of more stringent ICAO NOx standards for
gas turbine engines for implementation in

We are also exploring other ways to reduce
air pollution from air transportation. Since
1998, EPA and the Federal Aviation
Administration have jointly chaired a
national stakeholder process to reduce
emissions from aircraft, ground service
equipment, aircraft auxiliary power units,
and other related equipment through a
voluntary program. Stakeholders, which
include airlines, aircraft engine
manufacturers, airports, state and local air
pollution control officials, and
environmental organizations, are
cooperating to accomplish three tasks:

  «  Assess existing and projected
     emissions from each type of aviation-
     related source category at various
     types of airports.

  •  Evaluate a wide range of potential
     control measures, considering the
     effectiveness of control, cost, timing,
     enforceabiliry, SIP and conformity
     implications, and many other issues.

  *  Develop a framework for reaching
     consensus on the goals or targets of a
     voluntary program.

These three tasks and a resulting agreement
should be completed in 2001. A successful
agreement will be a big step toward
establishing a comprehensive national
program for reducing aviation-related
You can access additional documents on
nonroad engine programs on the Office of
Transportation and Air Quality (OTAQ)
Web site at:

You can also contact the OTAQ library for
document information at:

    U. S.EPA
    OTAQ Library
    2000 Traverwood Drive
    Ann Arbor, Michigan 48105

Additional fact sheets go into more detail
on these nonroad engine control programs:

  • Emission Standards Reference Guide
    for Heavy-Duty and Nonroad Engines,
    'October 1997: map format (EPA420- '
    F-97-014); poster (EPA420-H-97-

  * Rebuilding Diesel Engines (EPA420-
    F-99-045), December 1999.

  • Voluntary Emission Standards for
    Blue Sky Series Engines (EPA420-F-
    99-048), December 1999.

  • New Emission Standards for Nonroad,
    Diesel Engines (EPA420-F-98-034),
    August 1998.

Land-Based Spark-Ignition Engines:
  * Final Phase 2 Standards for Small
    Spark-Ignition Handheld Engines
    (EPA420-F-00-007), March 2000

  • New Phase 2 Standards for Small
    Spark-Ignition Nonhandheld, Engines
    (EPA420-F-99-008), March 1999

  « Small Engine Emission Standards—
    Answers to Commonly Asked
    Questions from Dealers and
    Distributors (EPA420-F-98-025),
    September 1998.

    Be a Grower, Not a Mower (EPA420-
    F-96-018), April 1997.
  « Emission Standards for Marine Diesel
    Engines: Scope of Application
    (EPA420-F-00-006), February 2000.

  * Organization of Gasoline and Diesel
    Marine Engine Emission Standards
    (EPA420-F-99-046), December 1999.

  • Responsibilities for Marine Vessel
    Operators with EPA-Certified Engines
    (EPA420-F-99-044), December 1999.

  * Emission Standards for New
    Commercial Marine Diesel Engines
    (EPA420-F-99-043), November 1999.

  • MARPOL 73/78 Annex VIMarine
    Diesel Engine Requirements
    (EPA420-F-99-038), October 1999.

  • Emission Standards for New Gasoline
    Marine Engines (EPA420-F-96-012),
    August 1996.

  • Emission Standards for New Spark-
    Ignition Marine Engines: Information
    for the Marine Industry! (EPA420-F-
    '96-013), August 1996.

  * Boating Pollution Prevention Tips
    (EPA420-F-96-003), July 1996.

  • Reducing Marine  Vessel and Port
    Emissions in the South Coast
    (EPA420-F-96-011), July 1996.
  * Requirements for Railroads Regarding
    Locomotive Exhaust Emission
    Standards (EPA420-F-99036),
    September 1999.

  • Final Emission Standards for
    Locomotives (EPA420-F-97-048),
    December 1997.

  « Federal Preemption of State and
    Local Control of Locomotives
    (EPA420-F-97-050), December 1997.

  * Environmental Benefits of Emission
    Standards for Locomotives (EPA420-
    F-97-049)', December  1997.

  * Emission Factors of Locomotives
    (EPA420-F-97-051), December 1997.

  « Aircraft Contrails Factsheet (EPA430-
    F-00-005), September 2000.

  * Evaluation of Air Pollutant Emissions
    from Subsonic Commercial Aircraft
    '(EPA420-R-99-013), April  1999.

  * Adopted Aircraft Engine Emission
    Standards (EPA420-F-97-010), April

  * Reducing Aircraft and Airport
    Emissions in the South Coast
    (EPA420-F-96-010), July 1996.
  « Applicability of Locomotive Emission
    Standards (EPA420-F-99-037),
    September 1999.