Methane enrichment of biogas by carbon dioxide fixation with calcium hydroxide and activated carbon

• Biogas was generated from anaerobic co-digestion cafeteria, fruit and vegetable wastes.
• The CH4 and CO2 content in raw biogas was 62 and 34%, respectively.
• Solid-CaO, CaO-solution and activated-carbon were employed to remove CO2 from the raw biogas.
• The highest percentage of CH4 achieved by solid-CaO (89%), CaO-solution (90%) and activated-carbon (91%).
• The removal efficiency trends as CaO-solution ˃ activated-carbon ˃ solid-CaO.

Although, Biogas generated from anaerobic digestion process is a clean, carbon neutral and environmental friendly energy alternative, raw biogas needs to be purified necessarily before using. The removal of CO2 from raw biogas ensures its better applications in engines, heating purposes and electricity generation. Reduction of CO2 content also enhances the calorific value. Biogas generated from vegetable, fruit and cafeteria wastes for duration of 30 days with the average concentration for CH4 and CO2 as 62 and 34%, respectively have been observed. The CO2 content was possible to reduce significantly by treating the raw biogas with purifying agents as: solid CaO, CaO solution and activated carbon. Purifying agent's mass and concentration and treatment time dependent biogas upgradation profile reveals that these novel purification processes are effective and affordable.

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