Important Correction
I just got a great response from Susan Petty (see the last blog entitled “Latter Day”, with Susan’s comment at the bottom) in which she made me aware of the fact that biodiesel totally does contribute to smog. Here’s an exerpt about B20 from the EPA’s 2002 report entitled “A Comprehensive Analysis of Biodiesel Impacts on Exhaust Emissions”:
“One of the most common blends of biodiesel contains 20 volume percent biodiesel and
80 volume percent conventional diesel. For soybean-based biodiesel at this concentration, the
estimated emission impacts for the current fleet are shown in Table ES-A.
Table ES-A
Emission impacts of 20 vol% biodiesel for soybean-based
biodiesel added to an average base fuel
Percent change in emissions
NOx +2.0%
PM -10.1%
HC -21.1%
CO -11.0%
Biodiesel is also predicted to reduce fuel economy by 1-2 percent for a 20 volume percent
biodiesel blend. Aggregate toxics are predicted to be reduced, but the impacts differ from one toxic compound to another. We were not able to identify an unambiguous difference in exhaust CO2 emissions between biodiesel and conventional diesel. However, it should be noted that the CO2 benefits commonly attributed to biodiesel are the result of the renewability of the biodiesel itself, not the comparative exhaust CO2 emissions. An investigation into the renewability of biodiesel was beyond the scope of this report.”
For a complete copy of the report, and other studies, please see EPA’s Biodiesel Emissions Analysis Program. And check out the Union of Concerned Scientists’ Clean Vehicles page for a comprehensive discussion of Biodiesel and even greener fuel/energy solutions.
And Susan, in answer to your question: because I was uninformed and sloppy! Thank you for keeping it honest.
–Refined gOil
