A Brief Overview of Compressed Biogas

1. A Brief Overview of Compressed Biogas Biogas, obtained from the anaerobic decomposition of organic waste like cattle dung, agriculture residue, municipal solid waste, sugarcane press mud, sewage treatment plant, and other such sources of biomass, is rich in energy. The primary constituents of biogas are methane (60%), carbon dioxide (40%), and particles of hydrogen sulfide. It is possible to use raw biogas as fuel directly or purify and upgrade the gas by eliminating H2S (Hydrogen Sulfide) and CO2 (Carbon Dioxide) while increasing the presence of methane to obtain CBG (Compresses Biogas). CBG, with over 90% methane content, is similar to CNG (Compressed Natural Gas) in terms of energy potential and composition. Biogas Purification Using biogas as renewable natural gas highly depends on the methane concentration of the gas. Thus, purifying raw biogas in a biogas bottling plant is important to eliminate the corrosive impact of hydrogen sulfide and increase the energy per unit volume of CBG. Overall, the process of purification focuses on reducing the concentration of carbon dioxide and other impurities, which can include hydrogen sulfide, siloxanes, moisture, ammonia, and more, while increasing the presence of methane with the ai m of achieving a high calorific value. The methane content in compressed biogas should be over 90%, and it should comply with IS 16087: 2016 specifications of the Bureau of Indian Standards (BIS).

2. Several technologies like Pressure Swing Adsorption (PSA), Water Scrubbing, Vacuum Swing Adsorption (VSA), and Membrane Separation use different pieces of equipment such as carbon dioxide scrubber, water scrubber, adsorption towers, membranes, and more to reduce the presence of carbon dioxide during the purification process. The upgraded or purified biogas with a methane composition of over 90% is compressed at 250 bar and is then transported in cascades (gas cylinders) for final use. Compressed Biogas (CBG) CBG, a popular acronym for compressed biogas, is quite similar to compressed natural gas (CNG) in terms of properties and calorific value, which is why it can replace CNG in several industrial, automotive, and commercial applications as a renewable natural gas (RNG). Moreover, the Indian government has authorized the use of CBG as an alternative to CNG in motor vehicles. Oil marketing companies should retail CBG, produced from the compressed biogas plant, through the dispensing unit established within 25 kilometers. In addition, CBG supplied should meet the BIS’s IS 16087: 2016 specifications mentioned below. IS16087: 2016 Standard Contents Requirement CH4 (Methane) Minimum 90% C02 (Carbon Dioxide) + O2 (Oxygen) + N2 (Nitrogen) Maximum 10% Only CO2 (Carbon Dioxide) Maximum 4% O2 (Oxygen) Maximum 0.5% Moisture Maximum 5 mg/m3 Total sulphur Maximum 20 mg/m3 Wrapping Up CBG (Compressed Biogas) holds great potential to replace CNG in several applications as a renewable source of energy. But, for using CBG to reduce dependence on fossil fuels and contribute towards a greener planet, the purification of biogas to biomethane is essential. Source: https://biogasbottlingplant.blogspot.com/2023/06/a-brief-overview-of-compressed- biogas.html