The main objective of the study is to explore the potential of raw biogas as an alternative and standalone fuel for gasoline fueled spark ignition (SI) engine. In the current investigation, a single cylinder, spark ignition engine is operated both with gasoline and raw biogas at a compression ratio of 10 under wide open and part throttle conditions. The baseline test is performed with gasoline and subsequent experiments are carried out with raw biogas. The engine performance, combustion and emission parameters are measured over a range of speed variations (1450-1700 rpm). Comparative analysis of the result showed 18% of reduction in brake power, 66% of increase in brake specific fuel consumption and 12% of reduction in break thermal efficiency when the engine is fueled with raw biogas. Because of the non uniformity in the amount of supplied air and fuel to the engine in every cycle, the coefficient of variation of indicative mean effective pressure and peak pressure (COVpp and COVIMEP) are seen to be higher for biogas. The emission components such as CO and NOx are significantly reduced by 40% and 81.5%, respectively, while, the unburnt hydrocarbon (UHC) and CO2 emission were increased by 6.8% and 40%, respectively. (C) 2018 Elsevier Ltd. All rights reserved.