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NREL: Rethinking Biodiesel and NOx

Martin Tobias, a venture partner at Ignition Partners, private investor and consultant who has a strong affinity for biodiesel and biodiesel projects, posts a report that a current NREL research project indicates that biodiesel may not increase NOx emissions compared to petroleum diesel.

On a technical session panel at the Society of Automotive Engineers’ (SAE) recent Government/Industry Meeting,  Wendy Clark, Manager of the Fuels Performance Group at NREL’s ReFUEL Laboratory, reported that after extended dynamometer testing,  NOx emissions from two 40-foot urban transit buses burning B20 were comparable to the buses’ NOx emissions when burning conventional diesel.

The tests on two different buses burning B-20 were repeated because the initial results were so surprising, Clark told the SAE conference participants.

According to Clark, the research team hasn’t concluded the research program yet. A formal report on the findings should be out later this fall.

There has been some reluctance to embrace biodiesel in some sectors due to what up to now has been the understanding that biodiesel combustion increases NOx emissions. The contradictory findings from NREL, if verified through this and other testing, could accelerate policy-driven adoption of the biofuel.



It's always been my understanding that because of biodiesel's different viscocity or lubricity that a simple timing adjustment to engines running biodiesel brings NOx emissions inline with that of conventional diesel fuel.

Nicholas M. Irving

FAME’s Deceptive Carbon Footprint and Carbon Credits

Take a close look at a typical biodiesel molecule represented by a Fatty Acid Methyl Ester (FAME) structure, where R stands for a general oleaginous hydrocarbon section:


If the formula is rewritten using parentheses you realize how much real CO2 is actually hiding in each molecule of FAME:


In the above formula there is only one useful type of carbon, meaning the hydrocarbon found in “R” and “CH3”, while the rest is plain POLLUTING DEAD WEIGHT.

R-(OC-O)-CH3 = R-CH3 + CO2

This pollutant, one whole CO2 molecule, is already built into your FAME molecules, and you are stuck with it! In a typical FAME blend you carry between 14 to 20% of CO2 BALLAST, all going straight into the environment without giving you any returns in heat, useful work, or in mileage. For example, if you get 25 miles per gallon with petroleum diesel, with FAME you can get 21 mpg. The CO2 in FAME is practically pre-formed and has no energy value, yet it certainly pollutes the environment giving you plenty of carbon redundancy. It amounts to you buying 14 to 20% less fuel for your dollar. All the CO2 that is released to the atmosphere, arising from energy-depleted carbon amounts to REDUNDANT EMISSIONS. By the same token, this (OC-O) part of FAME biodiesel should not be taken into account when figuring CARBON CREDITS. In other words, carbon credits should not be given to any energy-depleted carbon. Carbon credits should not take redundant emissions into account. In FAME the dead weight should be subtracted, and carbon credit adjusted so that benefit is given only to those carbons contributing to the true heat value of the biofuel.

Nicholas M. Irving
May 2007
Western Biofuels, Inc.

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