Biogas purification processes: review and prospects

Biogas is generated by controlled anaerobic digestion from animal manure, wastewater, landfills, industry, agroindustry, or other organic residues. Biogas is mainly composed of 60-70% methane, 30-40% carbon dioxide, and hydrogen sulfide <1%. Pure CH4 generates approximately 30.67 to 36.68 MJ m(-3) or 10 Kw m(-3) of energy, being able to compete with conventional fuels. The carbon dioxide and hydrogen sulfide from biogas decrease the energy potential of methane and damage equipment. The biogas purified could be a competitive biofuel with conventional fuels. Currently, there are many physical, chemical, and biological biogas upgrading methods; efficient, promising, and yield greater than 90% of recovered CH4. The biogas upgrading requires expensive infrastructure and chemical reagents and generates by-products that can cause long-term environmental problems. For this reason, purification methods must be comprehensive and should contribute to improving the purity of CH4 from biogas. This study reviewed the most relevant methods, the operating conditions to remove CO2 and H2S, as well as the advantages and disadvantages of biogas purification processes.