Biogas from anaerobic digestion of biological wastes is a renewable energy resource. Typical biogas contains 50-65% methane (CH4), 30-45% carbon dioxide (CO2), moisture and traces of hydrogen sulphide (H2S) and can be used for power generation through internal combustion engine. Reducing CO2 and H2S content will significantly improve engine performance. Different techniques such as water scrubbing system, pressure swing adsorption, chemical absorption method; cryogenic separation & membrane separation available for up gradation of the biogas are compared. The biogas up gradation using the different absorbent solutions such as sodium hydroxide, calcium hydroxide & potassium hydroxide is studied in pilot plant scale. The results showed the up gradation in the methane (3-4%) and decrease in the carbon dioxide (4-5%) & hydrogen sulfide (40-45 ppm) after the chemical absorption method.