Biological desulfurisation utilizes the microbial process where microbes remove hydrogen sulfide (H2S) and convert it into sulfur.

 With farm material and substrates low in protein desulfurization is handled by air injection into the gasholder. Microbes take the oxygen and convert hydrogen sulfide (H2S) into sulfur.

2  H2S  + O2 -> S2 + 2 H2O

Sulfur oxidizing bacteria perform that task. Being autothrophic these species oxidize hydrogen sulfide as a source of energy.

Air is normally injected into the biogas digester with a controlled compressor. The total air going into the digester should not exceed 2-5% of the biogas (volume) produced at any one time. Higher levels can lead to incendive and explosive gas mixtures.Warning: Methane can form a highly incendive and explosive gas mixture in connection with air.

How biological desulfurization of biogas works?. Available from: https://www.researchgate.net/post/How_biological_desulfurization_of_biogas_works [accessed May 4, 2017].

Thank you, Mushtaq Ahmad!

Biological desulfurization for biodigesters is a highly inefficient process and very slow process. I recommend using desulfurization using Ca(OH)2 solution or CaO powder injection in the flow stream from the biodigesters. If you use Ca(OH)2 solution to absorb SO2, the efficiency of removal could be up to 95% for this wet process. If you use the dry process by injecting CaO in the gas stream, the removal efficiency of sulfur removal could be up to 80%.

Hope this helps answer your question.

Professor Yehia Khalil, Yale University, USA

Fellow of the University of Oxford, UK

Thank You, Professor Yehia Khalil.

Hellow, Professor Yehia Khalil. I’m part of an environmental engineering team in Brazil and we are attempt to build a biodigester to a big project, but we still having problems with the biological desulphurization. I saw your comment about the Ca(OH)2 solution to absorb SO2. Could you send me some paper or scientific article in order to get more details. I would appreciate that. Thanks for your attention.

Hello Freddo,

Sure, I'll upload my lecture notes on sulfur removal technologies. This lecture note is part of the course I teach at Yale University on Air Pollution Control.

Best wishes,

Prof. Khalil