Biogas is a combustible gas obtained from anaerobic digestion of various organic waste resources. It can be considered as a renewable fuel and can be used in automotive engines as well as for cooking and lighting. In this study, an experimental study on the performances and exhaust emissions of a spark ignition engine of fuelled by mixtures of 65% CH and 35% CO (a typical biogas composition) has been performed at different engine speeds and different air excess ratios. The work has been carried out on a Ford engine. This is a four-stroke four-cylinder spark ignition engine with a compression ratio of 10:1 and with water cooling. The engine performances and emissions are compared between the engine running with biogas and with a conventional fuel. The results are discussed and compared to the literature