In Indian cities automobile pollution has reached intolerable limits. The vehicular population is continuously increasing and pollution is increasing rapidly. The temperature keeps rising due to the pollution .The presence of carbon dioxide in the atmosphere increases the temperature. The objective of the present study is to investigate the effects of petro diesel and biodiesel blends on the emission characteristics on a four stroke single cylinder diesel engine when biomas additive is added. Biodiesel fuel used in the study was prepared from goat and sheep fats. The fats were collected from meat stalls in and around Hosur town of Krishnagiri District, Tamil Nadu, India. Biodiesel is produced by the transesterification process and subsequently the kamala orange skin additive is blended with the petro diesel - biodiesel blends .The additive is added in varying proportions. The kamala orange skin additive is used to solve some technical problems generated by the use of petro diesel – biodiesel blends. The results showed a reduction of 11.8% NOx, 9.5% HC, 91% smoke and no significant reduction in CO when biomass additive B20 + 30 mL was used as fuel.