The Environmental Protection Agency (EPA) has released a new comprehensive technical report of biodiesel emissions data that shows biodiesel use can reduce emissions of particulate matter by 47 percent when compared to petroleum diesel in unmodified diesel engines. The report also verified a 67 percent reduction in unburned hydrocarbons and a 48 percent reduction in carbon monoxide with pure biodiesel (B100). While the technical report, which is a compilation of 39 separate scientific studies, is not an official rulemaking, the release of the report by EPA provides a government-validated reference for federal, state, and local pollution strategies to reduce emissions that are harmful to human health and the environment.
EPA prepared the report because of increasing interest in biodiesel, a domestically produced alternative fuel that can be made from animal fats or vegetable oils. Biodiesel works in any diesel engine with few or no modifications and has achieved a full national standard (ASTM D 6751). More than 250 vehicle fleets use B20, a mixture of 20 percent biodiesel with 80 percent petrodiesel, commercially nationwide. Lower level biodiesel blends, such as B2 or B5, are used in countless pieces of equipment from tractors to over the road semi trucks, and hundreds of fuel distributors are now carrying biodiesel blends.
During the last few years, biodiesel has enjoyed commercial success as one of the most thoroughly tested fuels in the country. “The fact that biodiesel is so well tested actually led to some uncertainty as to which set of emissions data was most accurate,” said Steve Howell, technical director for the National Biodiesel Board and chairman of the American Society of Testing and Materials (ASTM) Biodiesel Standards Taskforce. “The EPA analysis takes any uncertainty out of the equation, and even shows more incremental emissions benefits at the B20 level than for B100. While it remains true that maximum emissions reduction per vehicle can be obtained with B100, for fleets with many vehicles the EPA analysis shows a better value at concentrations lower than B100. Using B20 in 100 vehicles will actually reduce more pollution overall than using B100 in 20 vehicles.”
To provide the comprehensive assessment, EPA analyzed 80 prominent biodiesel emissions studies, including research performed by the U.S. Department of Energy, the U.S. Department of Agriculture, Lovelace Respiratory Research Institute, and Southwest Research Institute. Thirty-nine out of the 80 were used for the actual correlation. The majority of the 39 studies were performed on heavy-duty engines. EPA then developed a set of emissions curves based on the concentration of biodiesel. After peer review and a planned public workshop “…to assure that our correlations represent the best current scientific understanding of the emissions impacts on biodiesel,” the correlations will likely become the industry standard for biodiesel. Due to the sheer volume of studies used by EPA, changes suggested in the peer review and workshop are expected to be minor, if any.
EPA concluded that when compared to petroleum diesel, biodiesel has the following average effect on these regulated emissions:
|
B100 |
B20 |
|
| Total Unburned | ||
| Hydrocarbons |
-67% |
-20% |
| Carbon Monoxide | -47% | -12% |
| Particulate Matter |
-48% |
-12% |
| NOx |
+10% |
+2% |