• Biogas usually contains around 1 vol. % of H₂S.
• Natural gas can contain till 15 vol. % of H₂S
• Conventional technologies for treating such gases based on chemical reactions in a liquid phase, physical absorption and direct chemical conversion have several evident drawbacks - high reagent consumtion, equipment corrosion, application of high temperature and pressure etc. resulted in high process costs.
• Substantially cheaper alternative is biocatalytical reagentless technology

• In the scrubber, the H₂S containing gas comes into contact with a slightly alcaline (pH 8.0-8.5) scrubbing solution where absorption of H₂S takes place.
• Scrubbing liquor then passes to the microaerobic bioreactor containing immobilised bacteria from genus Thiobacillus where a soft oxidation of sulphide into elemental sulphur accompanied by regeneration of alcalinity proceeds.
• Solid sulphur is removed & the liquid is returned to the scrubber for absorption of the next portion of H₂S.

• practically reagentless character (some salts are necessary for bacteria)
• cheapness
• practically closed cycle and minimum of wastewater
• sole process product (sulphur) can be readily re-used (for sulphuric acid production)
• ambient temperature and pressure for the process making it safe.

Dr. S.V.Kalyuzhnyi, Dept. of Chemical Enzymology, Chemistry Faculty, Moscow State University, 119899 Moscow, Russia
Phone: 7-(095)-9395083 Fax: 7-(095)-9395417 or 9393589
Email: svk@enz.chem.msu.ru