Currently, fossil fuels such as petroleum, natural gas and coal meet most of the world's energy demand. However, combustion products of these fossil fuels, such as carbon monoxide (CO), carbon dioxide (CO2), oxides of sulfur (SOx), and oxides of nitrogen (NOx), hydrocarbon (HC), toxic metals and ashes cause many environmental problems and posing hazardous effect for the world. The limited fossil fuel resources and toxic emissions exhausted from internal combustion (IC) engines have pushed research to focus on alternative fuels. In this study, combustion and emission performance characteristics of an IC engine were experimentally investigated for different mixtures comprising of 7080-100% biogas (65% CH4 and 35% CO2) and 3020-0% H-2 by volumetric. The fuel mixtures consisted of 15% H-2 and 85% biogas content of 65% CH4+35% CO2, 60% CH4+40% CO2 and 55% CH4+45% CO2, were also investigated to determine its effect on performance and emissions. Experimental studies were carried out in Ford 1.8 L, four strokes, four cylinders, water cooled SI engine. Experimental studies were performed at different engine speeds (1500, 2000, 2500 and 3000 rpm) for different excess air ratios in the range of 1.0 to 1.4 with 0.1 increments. For all mixtures, it has been found that CO and CO2 emissions and maximum pressure decrease with the increase of excess air ratios. The highest torque and power values were obtained at 15% H2-85% biogas content of 65% CH4+35% CO2 mixtures. It can be concluded that the addition of biogas could result in an improvement in the combustion parameters.