Most experts believe that an energy system based on fossil fuels cannot be sustained for another century; the reason is that they are going to be exhausted soon. Even if additional reserves are discovered, many scientists say that continued reliance on fossil fuels as a primary energy source over the coming decades could release into the atmosphere billions of metric tons of carbon dioxide and other heat-trapping gases. For all these reasons there is need to rely on Alternative Fuel Technology. It is estimated to increase the use of alternative and reproducible fuels to 30% and 50% of fuel requirement by the years 2030 and 2050 respectively. At present, biodiesel is commercially produced from the vegetable oils by esterification process. This process is not suitable for production of biodiesel from many vegetable oils because of their high acid value. Hence supercharging is done by means of an electrically driven two stage reciprocating air compressor and Straight Rice bran oil is implemented as fuel by means of two tank SVO system with heating arrangement. In the present investigation, tests were carried out to determine the performance and the emission characteristics of the CI engine under Natural aspirated and supercharged conditions with petroleum Diesel and Pure Rice bran oil and the results were compared. . BSFC is increased with supercharging pressure in both diesel and RBO operations and BSFC is more in RBO operation than in Diesel operation. The CO emissions tend to increase with supercharging pressure in both diesel and RBO operations. Unburnt HC emissions are lesser in RBO operation than in diesel operation. CO₂ levels tend to increase with supercharging pressure in both diesel and RBO operations with loads near to rated load of the engine. The NO_x emissions are lowered with RBO than diesel with supercharging.