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 NOx 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 NOx than B20, but still within the range of control with existing technology. Change-air cooling and a fuel additive were tested as NOx 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 Caterpiller 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 40ÀC reduction in the temperature of the intake air charge to the engine. A comparison of the NOx, CO, and Total Particulate Matter emissions for D2 at 90ÀC charge air temperature and B20 at 50ÀC charge air temperature is a realistic scenario. Average NOx 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 NOx and PM when compared to emissions from petroleum D2 fuel that is normally used, with appropriate engine modifications.