Gas Fermentation: A Game Changer for the Circular Economy

The circular economy aims to close material cycles, reduce waste, and keep raw materials in use. Innovative technologies are crucial to achieving this, and gas fermentation is emerging as a particularly promising approach. This biotechnological process utilizes exhaust gases, like carbon dioxide, as feedstocks to produce valuable products, offering a new pathway for industrial emissions management. Professor Ralf Takors, head of the Institute of Biochemical Engineering (IBVT) at the University of Stuttgart, is leading research efforts to bring gas fermentation to market maturity.

Why Bioprocess Engineering is Key for a Sustainable Future

Bioprocess engineering employs microorganisms to convert materials into useful chemical compounds, forming the basis for efficient manufacturing processes. These processes are vital in modern industry for producing chemicals, food additives, and pharmaceuticals. A key advantage of biotechnological manufacturing is its sustainability, relying on renewable raw materials like sugar instead of fossil fuels [University of Stuttgart].

Beyond environmental benefits, bioprocess engineering is gaining strategic importance as geopolitical events disrupt access to fossil resources. Utilizing local resources for industrial manufacturing reduces dependence on fossil fuels and strengthens economic resilience, particularly in Europe [University of Stuttgart].

The Potential of Gas Fermentation

Researchers at the IBVT have been extensively researching gas fermentation, a process that converts gases – often exhaust gases like carbon dioxide – into valuable materials using microbial processes [University of Stuttgart]. This offers significant sustainability potential by transforming environmentally harmful emissions into resources for a circular economy.

From Plastic Waste to Valuable Feedstocks

One example of this potential is the University of Stuttgart’s research into recovering valuable feedstocks for the chemical industry from difficult-to-recycle mixed plastics. The plastic is first gasified at the Institute for Energy Process Engineering and Dynamics (IED), yielding a synthesis gas composed of carbon monoxide, carbon dioxide, and hydrogen.

This gas is then metabolized by anaerobic bacteria in a gas fermentation process, producing short-chain organic acids and alcohols that can serve as valuable feedstocks for the chemical industry [University of Stuttgart].

Expanding Applications Across Industries

Gas fermentation isn’t limited to plastic recycling. It has potential applications in several sectors, including:

• Steel Industry: Gas fermentation is already used commercially in some steel production processes.
• Cement Industry: The cement industry, a major source of carbon dioxide emissions, could utilize gas fermentation to convert its emissions into acetate or ethanol, which can then be used to produce plastics [University of Stuttgart].
• Chemical Industry: Ethanol for the chemical industry can be obtained from industrial waste gases.

This demonstrates that gas fermentation is not only environmentally sustainable but also presents a viable business model for companies seeking to reduce their emissions [University of Stuttgart].

Challenges and Future Research

Despite its promise, several research questions remain before gas fermentation can be widely adopted. These include addressing the limited solubility of gases in liquid media, which restricts their accessibility to microorganisms, and achieving successful industrial scaling [University of Stuttgart].

Bridging the Gap Between Lab and Industry

The IBVT’s research focuses on both fundamental and application-oriented research, bridging the gap between laboratory development and production scale. The institute aims to identify promising application areas, develop the necessary technologies, and address scaling challenges [University of Stuttgart].

The Importance of Scaling and Modeling

Scaling up gas fermentation requires reliable forecasts and robust mathematical modeling to prevent performance losses. The IBVT develops these approaches and conducts computational fluid dynamics studies for large-volume systems. Industrial bioreactors can reach volumes of around 800 cubic meters – comparable to a 25-meter swimming pool – necessitating careful design and operation [University of Stuttgart].

Professor Ralf Takors received his diploma of process engineering in 1993 and a Dr. Degree in Biochemical Engineering in 1997 [AIChE]. He has been the director of the Institute of Biochemical Engineering, University of Stuttgart, since 2009 [AIChE].