Biodiesel NOx Increase Concerns Air Board

By Published On: March 2, 2007

Biodiesel makers must limit nitrogen oxide emissions before the California Air Resources Board will certify their product under the state’s low-carbon fuel standard. A fuel-cycle analysis, expected to be taken up March 2 by the air board and the California Energy Commission, shows that diesel fuel blended with 20 percent biodiesel, commonly known as B20, increases nitrogen oxide tailpipe emissions from trucks and buses by 2 percent. The two agencies are scheduled to meet to work on an alternative fuel plan for the state as required by AB 1007. The agencies are also set to flesh out the details of Governor Arnold Schwarzenegger’s low-carbon fuel standard (Circuit, Jan. 22, 2007). “The standard won’t allow any relaxation on nitrogen oxides,” said Catherine Witherspoon, air board executive officer. Until manufacturers figure out how to reduce nitrogen oxide emissions, she said, biodiesel will not be included under the governor’s low-carbon fuel standard. However, a California biodiesel company claimed that the report to the air board and the Energy Commission may not reflect more current data showing that there is no increase in nitrogen oxide emissions from B20. “What we’d like California to do is use the best data, not work off old data,” said Ryan Lamberg, Community Fuels vice-president. He said that National Renewable Energy Laboratory data released February 7 using chassis emissions tests, as opposed to engine tests, show that B20 does not increase nitrogen oxide emissions. In engine tests, just the emissions from the engine are measured over a variety of operating conditions. In chassis tests, emissions from actual vehicles are tallied over a range of operating conditions designed to simulate actual driving conditions. The Encinitas-based company is building a biodiesel production plant at the Port of Stockton (Circuit, Feb. 9, 2007). The effect of biodiesel on nitrogen oxides is a major issue because the pollutants are prime culprits in forming summertime ozone pollution, which blankets much of the state. They also form fine particulate pollution, which is closely associated with premature deaths from heart and respiratory ailments. Diesel trucks and buses account for 23 percent of statewide nitrogen oxide emissions, air board data show. Off-road diesel equipment adds even more NOx emissions. While there is argument about the effect of biodiesel on nitrogen oxide emissions, there is general agreement that the fuel does reduce carbon dioxide emissions compared to petroleum-based diesel fuel, according to the fuel-cycle analysis prepared by TIAX. It also cuts tailpipe emissions by 10 percent for particulates, 11 percent for carbon monoxide, and 21 percent for hydrocarbons. Air board officials said that they may consider setting a fuel-quality standard for biodiesel to deal with the nitrogen oxide problem and other issues, including the stability of the product after it is manufactured. Problems include potential coagulation during cold weather that can clog fuel lines. Community Fuels claims that the NOx problem can be solved initially by limiting the biodiesel to no more than 5 percent in diesel fuel. Tests have shown that the B5 blends cut nitrogen oxides. In the longer term, the company also points to changing the feedstock used to make biodiesel from soybean oil to other types of materials, including recycled feedstocks. “California biodiesel will be made from multiple feedstocks,” said Lamberg. Yellow grease (used frying oil), for instance, lowers nitrogen oxide emissions. Additives can be useful too, he said.

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