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Let’s set the record straight. According to the data results posted in the EPA report for Emission comparisons1, the use of biodiesel in a conventional diesel engine not equipped with the new diesel after-treatment, show to have a substantial reduction of unburned hydrocarbons, carbon monoxide, and particulate matter when compared to those of petro-diesel emissions. Furthermore, the data shows that Biodiesel sulfur oxides and sulfates – which are major contributors to acid rain – to be virtually eliminated when compared to the sulfur levels of traditional diesel.

What does that mean exactly? Biodiesel showed a significant amount in the reduction of unburned hydrocarbons which along with nitrogen oxides are the leading causes for ozone and smog forming. When considering the data pertaining to carbon monoxide (CO) emissions, Biodiesel (B20) reduced emissions by over 11% compared to diesel with increased reductions gained by a higher mixture of biodiesel in the fuel blend.

Nitrogen Oxides (NOx) emission levels demonstrated approximately a 2% rise in some instances but fluctuated on the duty cycle of the engine and testing methods employed in the study. An examination of all of the published data suggests that there is no discrepancy between engine and vehicle testing and that for B20 on average there is no net impact on NOx. However, the reasons for the variability in NOx with engine model are not understood and are worthy of further study. It is possible that the variation is caused by differences in how engine fuel injection systems and electronic controls respond to the lower energy content or other properties of B20.1

Furthermore, the study demonstrated that even blended diesels, those consisting in part of Biodiesel mixed with petroleum diesel, proved beneficial in moving the dial towards lessening greenhouse gases. You can find the complete report here. Click to enlarge the charts below.


1: National Renewable Energy Laboratory, Milestone Report -