Environmental Engineering Reference
In-Depth Information
heavy-duty engines in commercial trucks do not currently have regulations on fuel economy or GHG
emissions, despite being the second-largest transportation sector oil consumer and GHG emission
producer, accounting for approximately 20% of transportation GHG emissions (U.S. EPA 2010e).
This is changing; the EPA and U.S. Department of Transportation (DOT) recently proposed fuel effi-
ciency and GHG standards to be phased in beginning with model year 2014 for heavy-duty engines
(U.S. EPA 2010f). In addition to CO
2
GHG regulation, two other GHGs, nitrous oxide (N
2
O) and CH
4
,
will also be regulated under this proposed program (U.S. EPA 2010e). Similar to CO
2
, N
2
O and CH
4
are suspected of contributing to global warming, but they have a higher impact than CO
2
for the same
level of emissions concentration (U.S. EPA 2006). It is estimated that these proposed new standards
for heavy-duty engines could reduce GHG emissions by 250 million metric tones, saving approxi-
mately 500 million barrels of oil over the vehicle life, for those sold in 2014-2018 (U.S. EPA 2010e).
10.1.4 E
miSSionS
r
EgulationS
The combustion process inside of an IC engine leads to the production of harmful compounds,
including CO, NO
x
, unburned hydrocarbons (UBHCs or HCs), and PM. These chemicals, com-
monly referred to simply as “emissions”, are harmful to humans and the environment, and as a result
are regulated in the United States by the EPA. The development of advanced engines and aftertreat-
ment systems has reduced emissions to comparatively extremely low levels. For automotive LDVs,
the trends in emissions reduction are shown in Figure 10.5 for U.S. and European standards for
NO
x
and HC (CO has been similarly reduced, but not shown). As can been seen, the emissions have
decreased by more than a factor of 100 over this period. For heavy-duty diesel engine applications,
similar reductions have been mandated. The latest regulations in 2007 and 2010 require a reduction
US emission standards*
European emission standards
1
1
0.9
0.9
EURO 1
(1992-1995)
1980
1980
0.8
0.8
0.7
0.7
0.6
TIER 0
(1981-1993)
0.6
EURO 2
(1996-1999)
0.5
0.5
TIER 1
(1994-1999)
NLEV
(1999-2003)
TIER II LEV
(2004- )
TIER II SULEV
(2004- )
0.4
0.4
EURO 3
(2000-2005)
EURO 4
(2005-2008)
EURO 5
(2009-)
0.3
0.3
0.2
0.2
0.1
0.1
0
0
0
0.1 0.2 0.3 0.4 0.5
HC (g/km)
NLEV = National low emission vehicle
PZEV = SULEV levels with no evaporative emissions
* Standards in g/mi converted to g/km
0.6
0.7
0.8
0.9
1
0
0.1
0.2
0.3
0.4 0.5
HC (g/km)
0.6
0.7
0.8
0.9
1
FIGure 10.5
U.S. and European NO
x
and HC emission standards for LDVs (From NRC,
Evaluating Vehicle
Emissions Inspection and Maintenance Programs,
Board on Energy and Environmental Systems Transportation
Research Board, National Research Council, National Academy Press, Washington, DC, 2001. available at
http://www.nap.edu/openbook.php?record_id=10133&page=R1 (accessed November 11, 2010); U.S. EPA,
Summary of Current and Historical Light-Duty Vehicle Emission Standards,
Office of Transportation and Air
Quality, U.S. Environmental Protection Agency, available at http://www.epa.gov/greenvehicles/detailedchart.
pdf (accessed November 11, 2010), 2007c; U.S. EPA,
Light-Duty Vehicle and
Light-Duty Truck - Tier 0, Tier
1, National Low Emission Vehicle (NLEV), and Clean Fuel Vehicle (CFV) Exhaust Emission Standards
, U.S.
Environmental Protection Agency, available at http://www.epa.gov/oms/standards/light-duty/tiers0-1-ldstds.htm
(accessed November 11, 2010), 2010h; Dieselnet, Emission Standards-European Union-Cars and Light Trucks,
2010. Available at http://www.diesel-net.com/standards/eu/ld.php (accessed November 11, 2010).
