Varec Biogas + BioGasclean A/S. A Partnership in H2S Removal Systems

Varec Biogas is pleased to announce a partnership with BioGasclean A/S, a Danish private corporation located in Odense, Denmark. BioGasclean develops, manufactures and markets biological H2S  scrubbers.

The partnership will allow Varec  Biogas to provide a complete package for digester gas cleaning in municipal wastewater or industrial wastewater. H2S removal is one of the key steps in cleaning when biogas is recovered and used to run engine generators. The biogas typically goes through:


  • Removing the H2S – either  with the BiogasCleaner or our Model 235 or Model 236 Gas Purifiers .
  • Chilling and drying the gas – See our Model 237 Gas Chiller Drying System.
  • Siloxane removal – as a final step when and if required.

The biological H2S removal process will enhance our ability to handle higher flow rates and higher concentrations of H2S. The media used is more cost effective than iron sponge providing for  a  longer bed life resulting in an overall lower operating cost. The only residual product from the biological process is a liquid sulfate solution. This is normally mixed with the treated effluent or biomass from the biogas digesters and recycled to the fields as valuable S-fertilizer.

BioGasclean has a worldwide installation base which complements that of Varec Biogas. The partnership will enhance Varec Biogas product offering to include the products  necessary  to  address the ever growing demands for gas cleaning for efficient biogas recovery and use.



The hydrogen sulfur (H2S) is removed from the biogas in a 100% biological process. The sulfur oxidation bacteria lives and multiplies on a packed media inside a closed acid-proof tank.

It requires sulfur from the H2S, carbon from the CO2, oxygen from atmospheric air, water and nutrients (nitrogen, phosphorus and potassium) from the treated effluent and a temperature between 86-130°F (30-55°C).

The sulfate is discharged with the effluent from the gas cleaner which contains up to 8% SO4. The chemical composition of the effluent will depend on the water or treated digester effluent added to the process.


Injection of atmospheric air

Atmospheric air is injected into the gas cleaners. The amount of air required depends on the H2S level in the raw biogas. Approximately 7.5 % air is needed for 3,000 ppm of H2S. The volume of methane will remain unchanged, and air injection into the process will dilute the relative CH4 content in the clean gas proportionally.

A frequency regulated air blower is used for adjustable air injection. The main part of the O2 is used for oxidation of the H2S to SO4, and the oxygen in the clean gas will be between 0.5 and 1.5%.

The effluent from the BiogasCleaner is mixed into the treated waste water or degassed manure and recycled to the field. It is also possible to mix the effluent with compost at a composting facility. The volume of effluent is small compared to the volumes of treated water and substrate from the digesters and the pH is neutralized quickly.

The BiogasCleaner H2S scrubbers are reinforced fiberglass (FRP) tanks that are normally supplied with ladders and platforms. The tanks can be provided with insulation cover. Pumps, blower, PLC controller, etc., are installed in a prefabricated housing, adjacent to  the tank. This simplifies operations and maintenance requirements and insures all components are installed properly.

All key-components, sub-systems, PLC control, etc., are installed in a Process Technique Unit (PTU) built into a 20’ or 40’ container.


QSR® (Quick Sludge Remover)

All filters must be cleaned to preserve their efficiency and avoid clogging and operational interruptions. The BiogasCleaners are constructed so that the filter can be completely cleaned in one to two working days without removing the packing media from the tank.  The system is called QSR® (Quick Sludge Remover) and is unique to the BiogasCleaner system.

Please contact your local Varec Sales representative for more information on this exciting new offering, or for more information on any Varec Biogas product.