Being a renewable fuel, biogas can be produced either through anaerobic digestion from animal manure, inedible seed residue, food waste, agricultural waste, domestic waste and sewage sludge or through thermo-chemical processes. Along with thermal applications, by means of combustion inside an engine, biogas can produce both mechanical and electric energy. Depending on the inertia forces of the active parts and the characteristics of the in-cylinder combustion of the engine, vibration can be quite a big problem because it leads to rapid breakdown of engine parts, noisy operation and decreased performance and power output. The CO2 in biogas is an important compound that affects its lower heating value (LHV), burning characteristics and exhaust emissions. There are a limited number of studies in the literature on the effect of biogas CO2 content on engine vibration.