Biological desulfurisation of biogas and sour gas instead of chemical scrubbing

Replaces: caustic scrubbing and chemical scavengers · Scope: biogas, landfill gas, some sour gas · Evidence: moderate

The chemical problem#

• Biogas and landfill gas contain hydrogen sulfide (hundreds to thousands of ppm) that corrodes engines and boilers and must be removed before use or grid injection.
• Conventional removal uses caustic soda scrubbing, iron-oxide or iron-chelate scavengers, or liquid-redox processes — continuous chemical purchases and spent-chemical waste.

Product overview#

Biological desulfurisation uses sulfide-oxidising bacteria (Thiobacillus, Thioalkalivibrio and others):

• Bioscrubbers (e.g. Thiopaq): H₂S is absorbed in a mildly alkaline solution and bacteria oxidise it to elemental sulfur, regenerating the alkali — so caustic use falls sharply; the sulfur can be sold as a fertilizer or fungicide raw material.
• Biotrickling filters: gas passes through packing colonised by bacteria that oxidise H₂S to sulfate.
• Micro-aeration inside the digester for low H₂S levels.

Active ingredient / Composition#

• Sulfide-oxidising bacterial biofilms or suspended cultures; nutrients and a little air or oxygen.
• Product: elemental biosulfur (bioscrubbers) or dilute sulfate (biotrickling).

Key facts#

Advantages#

• Far less chemical: alkali is regenerated biologically instead of consumed.
• Produces saleable sulfur instead of spent chemical waste.
• Low operating cost at small and medium gas flows — fits farm and municipal biogas plants (EN01, LE02).

Mode of action#

Bacteria oxidise sulfide with limited oxygen: at low oxygen they stop at elemental sulfur (S⁰), which forms hydrophilic particles that settle; with more oxygen they go to sulfate. Controlling oxygen sets the product.

Application#

Limitations#

• Large sour-gas and refinery streams still use the Claus process; biology suits low-to-medium sulfur loads.
• Needs stable operation (pH, oxygen, temperature); start-up takes days to weeks.
• Polishing (activated carbon) is often still needed for grid-quality biomethane.

Evidence of displacement — D2: measurable displacement (minority share)#

Assessment (hand-reviewed): Count only: >200 Thiopaq biogas desulfurisation units and ~15 oil-and-gas units since the 1990s (peer-reviewed); no market share found.

Verified figures (the number is in the quoted sentence and the sentence is on the source page):

• displacement — Since the 1990s, more than 200 installations of Thiopaq for biodesulfurization of biogas have been under commissioning or startup. (global, 1990s-2025; peer-reviewed: sciencedirect.com)
• displacement — As of the first quarter of 2026, the total number of biological desulfurization units in operation globally has exceeded 2,400. (global, 2026 Q1; weak: iim.net.cn)
• displacement — The Danish company BioGasclean has supplied more than 100 BiogasCleaner desulfurization plants. (global, not specified; weak: teknologisk.dk)

Suppliers — real products and services (from the vendor index)#

Companies below are active vendors in the vendor index whose own card (profile / official website) shows this product or service — matched 2026-10-06 by keyword and checked by hand against the card text. Being listed is not an endorsement; open each card for evidence, contacts and status.

Paques (Thiopaq) and BioGasclean are not in the index.

Government funding signals#

Scanned 2026-10-06.

China, Brazil, India — national research grants acknowledged in publications#

Papers since 2015 whose title matches “biological desulfurization” and that acknowledge national government funders (Crossref funder metadata; conservative lower bounds). Signal bands used here: Strong ≥30 · Moderate 5–29 · Weak 1–4 · None 0.

Scientific evidence#

• Pokorna D, Zabranska J (2015). Sulfur-oxidizing bacteria in environmental technology. Biotechnology Advances 33: 1246–1259.
• Note: journal references are checked against Crossref.

Bioeconomy value#

Bacteria regenerate the alkali that chemical scrubbers throw away and turn a toxic gas into saleable sulfur — now standard in hundreds of biogas plants, though no global share has been measured.

Sixth article of water (added 2026-10-06, evidence-first: grade D2).