Purification of Biogas for Methane Enrichment Using Biomass Biochar and Biochar–Clay Composite

Biogas is mainly composed of methane (CH₄) and carbon dioxide (CO₂) with trace amounts of hydrogen sulfide (H₂S), of which CO₂ and H₂S are impurities. Scrubbing of these two impurities are crucial for purification and upgradation of biogas, which would simultaneously also increase the calorific value of the treated biogas and address the issue of corrosion. Several studies have used expensive and environmentally harmful chemicals for the purification of biogas. This study reports a simple biogas purification system that utilizes biomass biochar and biochar–clay composites to remove CO₂ and H₂S from biogas by the process of adsorption. The biomass biochar could enrich the methane content of raw biogas from 59.7 to 84.6%, which shows the potentiality and applicability of biomass biochar for the removal of CO₂ and H₂S from biogas. This simultaneously enhanced the calorific value of the biogas and retarded the corrosiveness due to H₂S. The study also indicated that CO₂ adsorption by biomass biochar and biochar–clay composite is transient and has to be reloaded after saturation. Biochar and clay have the added advantage of being environment friendly and require no treatment for disposal. Observed results indicated that similar degree of enrichment, compared to commonly used chemical, could be achieved by application of biomass biochar and biochar–clay at a much lesser cost.