Diesel Tech Drastically Cut Emissions in Real-World Conditions

New research from North Carolina State University shows that federal
requirements governing diesel engines of new tractor trailer trucks
have resulted in major cuts in emissions of particulate matter (PM)
and nitrogen oxides (NOx) – pollutants that have significant human
health and environmental impacts.

Clean machine?
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"These requirements for new emission control technologies have
increased costs for truck owners and operators, and we wanted to know
whether there was any real benefit," says Dr. Chris Frey, professor of
civil, construction and environmental engineering at NC State and
co-author of a paper describing the research. "We found that there is
a huge reduction in both PM and NOx emissions."

Frey and Ph.D. student Gurdas Sandhu used a portable emissions
measurement system to sample exhaust from diesel trucks while the
trucks were in use on roads and highways. The emission requirements
apply to new trucks, meaning that trucks purchased in 2010 and trucks
purchased in 1999 were subject to different emission requirements.

Frey and Sandhu found that a truck in compliance with 1999 standards
emitted 110 grams of NOx per gallon of fuel used, and 0.22 grams of PM
per gallon of fuel used. NOx is a significant contributor to low-level
ozone, which adversely impacts respiratory health. PM also adversely
impacts respiratory health and, because it is largely made up of black
carbon, also contributes to global climate change.

Trucks in compliance with newer standards had far lower emissions. For
example, a 2010 truck emitted 2 grams of NOx per gallon of fuel – a
decrease of 98 percent. The PM emissions were 95 percent lower.

The NOx reductions stem from the implementation of exhaust gas
recirculation and selective catalytic reduction technologies. The PM
reductions are the result of installing diesel particulate filters
into the tail pipes of diesel trucks.

"While these technologies are a significant investment for truck
owners, this study shows that they are achieving a remarkable drop in
emissions of contaminants that have meaningful health and
environmental consequences," Frey says.

The paper, "Real-World Measurement and Evaluation of Heavy Duty Truck
Duty Cycles, Fuels, and Emission Control Technologies," is forthcoming
from Transportation Research Record, the journal of the Transportation
Research Board (TRB). Sandhu is lead author of the paper. The research
was supported by the North Carolina Department of Transportation and
the National Science Foundation.