Improving Air Quality by Using Biodiesel in Generators

A biodiesel / petroleum fuel blend and practical low-cost methods of emission control were sought to obtain reductions in emissions from diesel generators. Little direct testing of biodiesel in diesel-powered electric generators has been done. Laboratory and field evaluations were conducted to determine the influence of using biodiesel on diesel exhaust emissions. B20 (20% biodiesel / 80% petroleum diesel) was chosen because of previously successful studies with this blend level, and there is evidence that the NO_x emissions increase that result from using B20 can be controlled using existing technology. B85 was selected because it is a “high blend,” which promised to give a large decrease in PM at the expense of a larger increase in NO_x than B20, but still within the range of control with existing technology. Charge-air cooling and a fuel additive were tested as NO_x controls. For PM, CO, and HC reduction, a diesel oxidation catalyst (DOC) was evaluated. The laboratory tests were conducted on a Cummins ISM heavy-duty engine. Field tests were conducted on a Caterpillar model 3406 B, turbocharged and aftercooled engine. A B20 fuel blend with additional charge air-cooling was evaluated at the field demonstration site. A supplemental cooling circuit was designed and installed to enable a 40°C reduction in the temperature of the intake air charge to the engine. A comparison of NO_x , CO, and Total Particulate Matter emissions for D2 at 90°C charge air temperature and B20 at 50°C charge air temperature is a realistic scenario. Average NO_x emissions are reduced 15-18 percent, CO is reduced 35-37 percent, and TPM was reduced significantly. The successful field tests demonstrated that a renewable fuel, such as B20, can be effectively used in gensets to achieve significant reductions in NO_x and PM when compared to emissions from petroleum D2 fuel that is normally used, with appropriate engine modifications.