Beginning in 2014, on-highway trucks will face new greenhouse gas emissions and fuel
economy standards. The new regulations are the first of their kind in the world.
light-duty vehicles. New CO2 and fuel
economy regulations for MY 2012-2016
light-duty vehicles were adopted last
year. These standards, which strengthen in each model year from 2012-2016,
are expected to result in an average
MY 2016 vehicle emissions level of 250
g CO2/mile and 34. 1 mpg CAFE fuel
economy. A new set of standards is
under development for MY 2017-2025.
Under a recent agreement between
the U.S. administration and a group
of major carmakers, the average fuel
economy in cars and light trucks will
increase to 54. 5 mpg, equivalent to
163 g CO2/mile, by MY 2025.
In the nonroad sector, CO2 emissions from diesel engines remain
unregulated and the U.S. EPA is
currently not developing such regulations. It may be noted that mandatory energy-efficiency requirements
have been adopted for ships by the
International Maritime Organization
(IMO). The regulations apply to all
ships of 400 gross tonnage and above
and enter into force from 2013.
The new CO2 emission and fuel-
efficiency standards also have an
effect on the choice of technology
for the control of diesel PM and
NOx emissions. In conventional die-
sel combustion, emissions of PM,
NOx and fuel economy are correlated
— engines calibrated for high NOx
also have high thermal efficiency and
produce low PM emissions, while
engines calibrated for low NOx show
poor efficiency and high PM emis-
sions. Hence, the strategy of high
engine-out NOx in combination with
deNOx aftertreatment can also pro-
vide reductions in CO2 emissions —
in other words deNOx = deCO2.
A range of technol-
ogies are being
used to meet Tier
4 final nonroad
emissions stan-
dards. Engines suchas the
new Cat 1. 5 and 2. 2 L three- and four-
cylinder diesels that meet EPA Tier
4 final/EU Stage 3a/Stage 3b emis-
sions requirements use a diesel
particulate filter that incorporates
active regeneration to periodically
burn away the collected soot.
