Sequestration of hydrogen sulfide and carbon dioxide from biogas

Anaerobic Digestion (AD) of wastes is one of the best treatment methods in the arena of waste management. Biogas, the end product of AD, comprises of 40%-75% CH4 and 25%-55% CO2, with other minor components such as H2S and SO2. Increased concentration of minor gases will cause the corrosion of the pipe lines which are being used in bio-energy generation. Hence, the present study is undertaken to develop a low-cost scrubbing mechanism for toxic gas removal. A biogas purification system with multi scrubbing apparatus (Phase I and Phase II) was designed and utilized for the study. The principle of chemical absorption was employed and the efficiency of the different caustic solutions at saturated concentration was investigated. Scrubbing at Phase I reported a 5% increase in methane and a 5.8% removal of CO2. The removal rate of 43% and 37% was observed for H2S and NH3 respectively. Carbon dioxide was removed at a rate of 34.9% for KOH, followed by NaOH and Ca(OH)(2) at a rate of 34.1% and 33.9% respectively, in a time duration of three minutes. It has been found that the absorption capacity of caustic solution was dropping 'within' a short time period. Hence, it is necessary to replace the caustic solution in order to uphold the chemical at saturation point.