Desulphurization for Biogas and Process Gas

How it works

Hydrogen sulphide can cause corrosion, create safety and odour concerns, and damage upgrading membranes, compressors, CHP engines, catalysts and liquefaction equipment. The right desulphurisation system must therefore be selected around the actual gas composition, flow, pressure and required outlet quality.

ECOTEC offers more than one treatment route. This allows the process to be matched to the project rather than forcing every application into the same technology.

dBiox® Bioscrubber — Biological, Two-Stage

The Bioscrubber is a two-stage system: a scrubber column handles gas-liquid contact, and a separate bioreactor handles biological regeneration of the liquid.

Biogas enters the scrubber column and contacts an alkaline recirculating liquid. H₂S dissolves immediately and reacts with hydroxide ions — H₂S + OH⁻ → HS⁻ + H₂O — removing it from the gas stream with transfer efficiencies above 99%. Because the Empty Bed Residence Time (EBRT) inside the scrubber is minimal, the column itself can be compact, reducing investment costs.

The H₂S-loaded liquid is then passed to the bioreactor, where anaerobic microorganisms perform biological oxidation at alkaline pH, converting the absorbed sulphide to sulphate. The regenerated liquid is recycled back to the scrubber. A small stream of sulphate-rich liquid effluent is produced — this can be returned directly to farmers as a soil amendment, closing the nutrient loop on site.

The system uses minimal NaOH to maintain pH, and small quantities of nutrients for the microorganisms.

Key advantages:

• Most suitable apllication for biogas upgrading: Does not add O₂ to the biogas stream

• Clean Technology: Biological desulphurisation

• Treats very high H₂S loads & high flow rates up to 40,000 ppmv at flows up to 20,000 m³/h

• Minimal reagent and water consumption

• Sulphate-rich effluent reusable as agricultural fertiliser — no waste disposal cost

• Low operational costs > short return on investment costs

• No biogas dilution

• Advanced automated control: air batching, temperature, redox, pH, and nutrient monitoring

• All operating parameters continuously logged for compliance and monitoring

dBiox® Biotrickling Filter — Biological, Single-Stage

The Biotrickling Filter combines gas contact and biological treatment in a single compact unit. A packed inorganic bed provides the habitat for microorganisms; a nutrient liquid trickles continuously through the bed while biogas flows upward through the packing.

The microorganisms in the bed oxidise H₂S directly as it contacts the wetted packing surface. Because the process is entirely biological, the system requires no chemical reagents under normal operation — or only minimal quantities — eliminating toxic effluent and reducing operating costs substantially.

Key advantages:

• No or minimal chemical reagent use

• No toxic effluent requiring further treatment

• Highly compact — single-unit design

• Low operating costs

• Well-suited to high H₂S loads and limited site space

• Scalable to large flows

Key specifications:

• Treats H₂S concentrations up to 5,000 ppmv

• Gas flows up to 3,000 m³/h

• Removal efficiency >98%

• Does not add O₂ to the biogas stream

• Minimal chemical and water consumption

• Low CAPEX and OPEX — short return on investment

• • Remote control, technical assistance, and after-sales service

Why ECOTEC?

One Specialist Across Gas, Air and Liquid Interfaces

Biogas desulphurisation, odour control and ammonia removal often meet at the same plant. ECOTEC can assess these interfaces as part of one environmental treatment concept while keeping the individual process responsibilities clear.

Biological and Chemical Treatment Routes

The portfolio includes dBiox® biological treatment, regenerative chemical desulphurisation, chemical scrubbers, biofilters, biotrickling, stripping and ventilation. This gives the project more than one technical route to evaluate.

Designed Around the Actual Stream

Gas composition, liquid chemistry, contaminant variability, flow, temperature, humidity, pressure and required outlet values are reviewed before the treatment system is selected and sized.

Nordic Project Support

Green Gas Solutions acts as ECOTEC's local commercial and technical interface across the Nordic market. GGS supports early process clarification, proposal development, project coordination and the agreed commissioning and service scope.

Established Environmental-Technology Experience

ECOTEC was founded in 1990 and is part of the TEFSA Group. Its portfolio covers gas and water treatment, with installations across more than 50 countries.

Planning a Gas, Air or NH₃ Treatment Project?

Send us the process data you already have. GGS and ECOTEC can use it to identify the appropriate treatment route, establish a preliminary design basis and clarify what must be verified before sizing and performance guarantees.

For H₂S Removal

• Gas source and intended downstream use

• Minimum, nominal and maximum gas flow

• H₂S concentration at minimum, nominal and maximum conditions

• CH₄, CO₂, O₂, N₂ and relevant trace components

• Pressure, temperature, humidity and operating hours

• Required outlet H₂S and oxygen specification

• Available footprint, utilities and redundancy requirements

For Air and Odour Treatment

• Emission source and enclosure or extraction arrangement

• Minimum, nominal and peak air flow

• Contaminants, concentrations and odour data where available

• Air temperature, humidity and particulate content

• Required emission or odour limit

• Existing ventilation, ducting or scrubber equipment

For NH₃ Stripping

• Liquid source and minimum, nominal and maximum flow

• NH₃-N or total ammoniacal-nitrogen concentration

• pH, alkalinity, temperature and suspended solids

• Relevant salts, hardness and scaling indicators

• Required outlet concentration

• Potential route for the ammonium-sulphate stream

• Available heat, power, chemicals, water and compressed air

Q-REN — Regenerative Chemical Desulphurisation

Q-REN is ECOTEC's chemical regenerative H₂S removal system, developed specifically for applications where biological systems face limitations — particularly plants requiring exceptionally stable outlet gas quality for sensitive downstream equipment such as membrane upgrading systems.

Unlike conventional chemical scrubbers that consume reagent continuously, Q-REN's regenerative process continuously restores the chemical medium, minimising chemical consumption and operating costs. Critically, Q-REN does not add O₂ to the biogas stream — making it the preferred choice where downstream membrane upgrading or other oxygen-sensitive processes are in use.

Best for: High H₂S loads, high flow rates, variable gas compositions, or where zero oxygen addition to the gas stream is required.

Air and Odour Treatment

Odour and air-emission problems vary widely between plants. A wastewater facility, receiving hall, digestate area, food-production process and chemical plant may have very different air flows, contaminant combinations and regulatory requirements.

ECOTEC therefore combines air capture and ventilation engineering with biological or chemical treatment. The solution is selected from the contaminant profile, concentration, air volume, temperature, humidity, variability and required emission limit.

Chemical Scrubbers

Chemical scrubbers remove gaseous contaminants through physical absorption and chemical reaction in a circulating liquid. ECOTEC configures vertical or horizontal systems for pollutants including sulphur compounds, ammonia and amines, acidic gases and other industrial emissions.

The packing, number of treatment stages, chemicals, liquid circulation and control system are designed around the specific air stream and required outlet values.

Biotrickling for Odour Control

Biotrickling combines a packed biological reactor with continuous liquid circulation. It can treat H₂S and other biodegradable odour compounds with little or no chemical-reagent consumption, depending on the application.

Existing chemical scrubber towers may in some cases be converted to biological operation, allowing suitable infrastructure to be reused. Retrofit feasibility must be assessed from the tower, packing, materials, hydraulics and required performance.

Industrial Ventilation and Air Capture

Effective treatment begins with collecting the contaminated air. ECOTEC designs local extraction, suction hoods, ducting, anticorrosive fans and general ventilation systems around the emission source and working environment.

ECOTEC publishes ventilation references up to approximately 200,000 m³/h. The required capture rate and final configuration are determined for the specific building, process and contaminant source.

Typical Air-Treatment Applications

• Biogas receiving and processing areas

• Digestate storage and handling

• Wastewater treatment plants and pumping stations

• Composting and municipal-waste facilities

• Food and beverage production

• Rendering and other odour-intensive industries

• Chemical and pharmaceutical processes

NH₃ Stripping and Recovery

ECOTEC's NH₃ stripping systems are designed to remove dissolved ammonia from a liquid stream. Typical applications include slurry, leachate and industrial wastewater. This is different from removing trace ammonia directly from biogas.

How the Process Works

1. Feed-Liquid Assessment

The incoming liquid is characterised for flow, ammonia concentration, pH, alkalinity, temperature, suspended solids and other components that influence stripping and scaling behaviour.

2. pH Adjustment

The pH is adjusted to shift dissolved ammonium towards gaseous ammonia. The exact chemical demand and operating point depend on the composition and temperature of the liquid.

3. Countercurrent Air Stripping

The conditioned liquid and air pass countercurrently through a packed stripping tower. Ammonia transfers from the liquid into the air stream.

4. Acid Scrubbing

The ammonia-containing air is directed to a second chemical washing stage under acidic conditions. The NH₃ is captured instead of being released to the atmosphere.

5. Ammonium-Sulphate Production

The capture stage produces an ammonium-sulphate solution. Its concentration, quality, potential reuse and regulatory status depend on the feed stream and the project-specific process design.

Why Consider NH₃ Stripping?

• Reduce the ammonia load in slurry, leachate or industrial wastewater

• Support downstream water-treatment performance

• Control ammonia emissions and odour

• Capture nitrogen in a more manageable ammonium-sulphate stream

• Create potential for nutrient reuse where product quality and local requirements allow it

ECOTEC reports NH₃ stripping references that have operated for more than 25 years. Final removal efficiency, chemical consumption, energy use and product quality must be established from the confirmed liquid analysis and project conditions.

WHAT THE CLIENTS SAY