This numerical investigation aimed at studying the effects of varying biogas composition, equivalence ratio and intake charge temperature on combustion phasing of a biogas powered homogeneous charge compression ignition (HCCI) engine. Initially, the numerical model is validated against the experimental results. The present numerical investigations on a biogas powered HCCI engine indicates that the combustion phasing is advanced with increase in the methane concentration present in biogas. While, higher concentration of carbon dioxide is resulted in delayed onset of combustion. It was noticed that above 50% of biogas composition shows significant improvement in combustion phasing. Low concentration of methane helps in avoiding the knock combustion and it needs high intake charge temperature of 475 K to sustain the combustion. With increase in methane concentration, the combustion phasing was advanced for a constant equivalence ratio of 0.2 and 0.3 respectively. Combustion noise was attenuated at high concentration of carbon dioxide for a fixed value of equivalence ratio. © IAEME Publication