Industrial biogas is a high-quality combustible gas, primarily composed of methane, produced through large-scale, controlled anaerobic digestion technology that converts organic waste. It is a green energy product characterized by stable supply, environmental benefits, and commercial value.

Agricultural Waste

Pig manure, cattle manure, sheep manure, chicken manure, corn stalks, wheat straw, rice straw, cotton stalks, bagasse, beet pulp, peanut shells, rice husks, soybean residue, distiller's grains.

Aquatic Plants

Water hyacinth, alligator weed, duckweed, reed, freshwater algae.

Municipal Organic Waste

Food scraps, fruit/vegetable peels, eggshells, fish bones, human feces.

Industrial Organic Wastewater/Sludge

Wastewater from starch plants, soybean product plants, slaughterhouses; waste from breweries; black liquor and waste pulp residue from paper mills; wastewater from large-scale livestock farm cleaning.

Industrial biogas systems offer strong controllability, high gas production efficiency, and continuous operation capability. They represent a vital pathway for the resource recovery and energy utilization of organic waste, while also delivering direct commercial advantages such as carbon trading revenue, tax optimization, and reduced compliance costs.

Biogas Enrichment

Industrial biogas is a mixed gas produced on a large scale from organic waste via extensive anaerobic digestion systems. Its main components are methane (55%–75%) and carbon dioxide (25%–40%), along with impurities such as hydrogen sulfide (H₂S), water vapor, siloxanes, and trace VOCs. This raw biogas cannot be directly emitted and must undergo purification to be converted into high-grade biomethane (meeting natural gas standards) for power generation, vehicle fuel, or grid injection, thereby achieving energy self-sufficiency and carbon emission reduction.

The core of upgrading lies in impurity removal, with treatment technologies for various components as follows:

Biogas Purification

High-pressure water scrubbing is one of the mainstream technologies for industrial biogas upgrading. Based on the principle of physical absorption, it selectively dissolves acid gases in water under pressure to upgrade raw biogas to pipeline natural gas or vehicle fuel standards. This mature technology offers strong adaptability and good tolerance to fluctuations in biogas composition and feed gas load.

Technical Characteristics of High-Pressure Water Scrubbing for Biogas Upgrading

• The process core is physical absorption, consuming no chemical agents, with water and electricity as the main operating media.
• It enables simultaneous and efficient removal of carbon dioxide (CO₂) and hydrogen sulfide (H₂S), with relatively lenient requirements for pre-desulfurization.
• The system employs a modular design, offering flexible treatment capacity and easy expansion.
• High methane recovery rate, with a typical design value ≥99%.
• No external heat source is required; primary energy consumption involves gas compression and water pump circulation.
• Process water is regenerated and recirculated, resulting in minimal wastewater generation.

In the standard process, biogas first undergoes pre-treatment (impurity removal, preliminary dehydration) and is then compressed to a pressure of 6-8 bar. Subsequently, the high-pressure biogas enters the absorption column (scrubber) from the bottom, flowing counter-currently to cold scrubbing water sprayed from the top. Due to the significantly higher solubility of CO₂ and H₂S in water compared to methane, they dissolve into the water phase, leaving purified methane.

The scrubbing water rich in CO₂ and H₂S (rich liquid) is conveyed to a desorption column (flash tank or stripping column). By reducing pressure or introducing a small amount of air for stripping, the dissolved acid gases are released from the water, achieving water regeneration. The regenerated water (lean liquid) is cooled and returned to the absorption column for reuse.

This process ultimately yields three product streams:

1️⃣Product Gas (Biomethane): Purified gas exiting the top of the absorption column undergoes subsequent coalescing filtration and adsorption-based deep dehydration (typically requiring a dew point ≤ -40°C) to meet strict pipeline or vehicle fuel standards.

2️⃣Regeneration Off-Gas: Primarily composed of CO₂, containing trace H₂S and residual methane (<1%). This stream must be treated to comply with environmental emission regulations.

3️⃣Recirculated Process Water: Internally closed-loop system, with a small amount of wastewater periodically discharged to control salt accumulation.

Treatment of Desorption Off-Gas – Regenerative Thermal Oxidizer (RTO) Technology

To meet strict emission control requirements for residual methane (a greenhouse gas) and odorous substances (e.g., H₂S) in the desorption off-gas, Regenerative Thermal Oxidizers (RTOs) are widely adopted as an efficient end-of-pipe treatment technology.

The core of an RTO system lies in its highly efficient regenerative heat exchanger. The system is filled with high-performance ceramic heat storage media, used to recover heat from the high-temperature flue gas generated during oxidation. By periodically switching the airflow direction, the incoming low-temperature contaminated gas is preheated by the media to a temperature close to the oxidation temperature, significantly reducing auxiliary fuel consumption.

The combustion chamber temperature is typically maintained above 800°C, ensuring a Destruction and Removal Efficiency (DRE) exceeding 99% for methane, VOCs, and odorous compounds. A high thermal recovery efficiency of up to 95% allows RTOs to maintain very low operating energy consumption even when treating low-calorific-value waste gases.

Common RTO types in industrial applications include:

Two-Chamber RTO: Simple structure, lower investment, suitable for continuous, stable conditions. May have minimal momentary airflow fluctuations during valve switching.

Three-Chamber (or Multi-Chamber) RTO: One chamber is always purging, ensuring the waste gas inlet and clean gas outlet are never directly connected at any moment. This enables smooth, continuous airflow transition, higher purification efficiency, and eliminates transient emissions, making it the mainstream choice under stricter emission standards.

The main advantages of this technology are:

High Thermal Recovery Efficiency: Significantly reduces fuel consumption, offering outstanding operational economy.

High Purification Efficiency: Thorough removal of methane and various organic compounds ensures stable, compliant emissions.

Reliable Operation: No moving parts in the high-temperature zone, leading to long equipment life and low maintenance requirements.

Strong Adaptability: Capable of handling fluctuations in waste gas concentration and flow within a certain range.

In practical engineering selection and configuration, RTO specifications must be precisely designed based on the specific flow rate, composition of the desorption off-gas, and local emission regulations. For scenarios with high H₂S content, the emission concentration of its oxidation product (SO₂) also requires subsequent assessment or consideration of adding an alkaline scrubber for control.

Uses of Biogas

For industrially produced biogas, its commercial utilization primarily follows two main technological pathways: on-site Combined Heat and Power (CHP) generation and upgrading to produce biomethane.

Combined Heat and Power (CHP): This is the preferred solution for achieving energy self-sufficiency and optimal economics in settings like livestock farms or food processing plants that have stable heat and electricity demands. Biogas drives generators to produce electricity for self-use or grid feed-in, while the recovered waste heat is used to maintain digester temperature or for process heating, achieving cascaded energy utilization.

Biogas Upgrading: When on-site heat utilization is challenging or the upgraded gas commands higher market value, purifying biogas into biomethane becomes the more advantageous choice. Technologies like high-pressure water scrubbing or membrane separation can produce biomethane with methane concentrations as high as 95%-99%, meeting stringent national standards for pipeline natural gas or vehicle fuel.

The resulting biomethane, as a renewable, low-carbon green gas, finds primary applications in:

✅Injection into Natural Gas Grids: After metering and pressure regulation, it is fed into urban gas networks for long-distance transport and large-scale consumption, serving residential, commercial, and industrial users.

✅Vehicle Fuel: Compressed into Bio-CNG or liquefied into Bio-LNG to provide clean power for public transport and freight vehicles, serving as a key pathway for deep decarbonization in the transport sector.

✅Direct Supply to Industry and Commerce: Supplied directly to nearby factories or commercial facilities for clean combustion in boilers or kilns, or used as a chemical feedstock.

✅Optimizing Regional Integrated Energy Costs: As a distributed clean energy source, integrated into park-level comprehensive energy systems, it significantly reduces corporate energy costs and can realize the appreciation of environmental assets through carbon quota trading                                                                                                         

Industrial biogas, whether enabling energy recycling via CHP or entering the energy market after upgrading, represents a key technology for realizing waste resource recovery, producing green energy, and creating carbon revenue. It holds significant value in promoting the circular economy and energy transition.

Wuxi Powermax Renewable Energy Technology Co., Ltd.

Wuxi Powermax Renewable Energy Technology Co., Ltd. is a technology enterprise specializing in green renewable energy, green chemical engineering, and energy conservation and environmental protection. The company's core technologies include biomass pyrolysis and gasification, low-speed gas power generation, and syngas-to-green hydrogen, green ammonia, and green methanol production technologies.

If you are exploring the optimal utilization pathways for biogas, please feel free to contact our biogas expert team. We will tailor a personalized solution based on your specific needs.