NOx reductions shown in NREL study

By | November 01, 2005
A recent study from the Department of Energy's National Renewable Energy Laboratory (NREL) shows that nitrogen oxide (NOx) was reduced in chassis dynamometer tests using B20 fuel versus conventional diesel fuel.

The tests were done in two in-use buses with Cummins ISM 2000 engines in a city suburban heavy vehicle cycle. The engines were not equipped with exhaust gas recirculation (EGR) technology that is available on some Cummins models.

NOx reductions, which were not anticipated, were shown at a 5 percent level with a statistical confidence of 99 percent. Expected reductions in other emissions were found but at higher levels than most previous testing, with particulate matter reduced by 24 percent, hydrocarbons by 40 percent and carbon monoxide by 32 percent.

NREL scientists who conducted this research say this study was not on a large enough scale to determine whether NOx is always reduced, but it does bring into question the largely held belief that NOx increases slightly with B20 in unmodified diesel engines. Since chassis dynamometer emissions are those from an actual vehicle, some scientists believe emissions from chassis dynamometers are more representative of the 'real world' than those from engine-only dynamometers in a test cell.

NOx reductions have also been found in studies with biodiesel blends of home heating oil done through Brookhaven National Laboratory in New York, because NOx with open flame combustion is dependent on different factors than NOx with diesel combustion.
The bus tests were done by NREL at its new ReFUEL facility, which was previously the engine test lab of the Colorado School of Mines.
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