In a multi-part series about biodiesel, this is one of several articles in an attempt to dispel the myths about biodiesel and it’s use in commercial and private diesel engines.
Myth #8 – Biodiesel Emissions Are No Better Than Regular Diesel
Biodiesel is the only alternative fuel that has completed all the testing requirements of the Clean Air Act. Biodiesel contains oxygen and it burns more completely than diesel fuel, resulting in reduced emissions. All major pollutants are reduced dramatically in biodiesel exhaust (most of them at least 50% for B100), except one—nitrogen oxides (NOx)—and that’s only for blends over B20 (see my post on the subject). In fact, NOx emissions from biodiesel increase or decrease depending on the engine family and testing procedures. NOx emissions (a contributing factor in the localized formation of smog and ozone) from pure (100%) biodiesel increase on average by 10 percent. However, biodiesel’s lack of sulfur allows the use of NOx control technologies that cannot be used with conventional diesel. Additionally, some companies have successfully developed additives to reduce NOx emissions in biodiesel blends. In fact, in certain independent studies using more modern engines than the EPA study have shown that biodiesel use actually reduced NOx emissions.
The most common report when users switch to biodiesel is the noticeable decrease in diesel smoke (the black, sooty clouds). B20 reduces air toxics (the most damaging pollutants for human health) by 20-40%, while B100 reduces them by as much as 90%. Sulfur oxides and sulfates (major contributors to acid rain) are almost completely eliminated. The only caveat is that nitrogen oxide (NOx) emissions can increase up to 10% with B100. If you would like to evaluate this for yourself, see the National Biodiesel Board’s emissions fact sheet.
New diesel technology like the Mercedes BlueTec and the 2009 Jetta TDI eliminate this problem by reducing NOx emissions by 80-90%.
All-in-all, biodiesel offers such a substantial reduction in emissions that it’s frequently used in sensitive areas like national parks and marine habitats. School districts all over the country have also turned to biodiesel as a way to reduce children’s’ exposure to toxic diesel exhaust.