Enhancement of Biogas via CO2 Sequestration and Concurrent Production of Acetic Acid by Newly Isolated Bacteria

Sizuki Nishimu^*
*Correspondence: Sizuki Nishimu, Department of Industrial Ecology and Sustainability, Nagoya University, Nagoya, Japan, Email:

Keywords

Biogas • CO₂ sequestration • Acetic acid

Introduction

Biogas, primarily composed of methane (CH₄) and Carbon dioxide (CO₂), is a renewable energy source derived from the anaerobic digestion of organic materials such as agricultural waste, sewage sludge, and food waste. It holds significant potential as a sustainable alternative to fossil fuels, offering environmental benefits by reducing greenhouse gas emissions and providing decentralized energy solutions. However, the presence of CO₂ in biogas reduces its energy content and limits its applicability for various energy-intensive applications. The enhancement of biogas quality by reducing CO₂ content has thus become a focal point in biogas research. Various methods such as chemical absorption, membrane separation, and biological processes have been explored for CO₂ removal. Among these, biological CO₂ sequestration using specialized microorganisms offers a promising and environmentally friendly approach. In this context, the concurrent production of value-added products such as organic acids adds economic value to the biogas production process [1].

Literature Review

Biogas production involves the anaerobic degradation of organic materials by a consortium of microorganisms, primarily bacteria and archaea. The main components of biogas are methane (CH₄) and Carbon dioxide (CO₂), along with trace amounts of other gases such as Hydrogen Sulfide (H₂S), Nitrogen (N₂), and water vapor. The composition of biogas can vary depending on the feedstock used and the operating conditions of the anaerobic digester. The presence of CO₂ in biogas decreases its calorific value and limits its use in certain applications such as vehicle fuel and power generation. Various methods have been developed to remove or reduce CO₂ from biogas, including physical and chemical processes. However, these methods often involve high costs, energy consumption, and environmental impacts [2].

Biological CO₂ sequestration presents an attractive alternative, leveraging the metabolic capabilities of microorganisms to convert CO₂ into biomass or other products. Several bacterial strains have been identified for their CO₂ fixation abilities, including acetogenic bacteria that can produce acetic acid through CO₂ reduction. Integrating these bacteria into biogas production systems offers a dual benefit of CO₂ removal and valuable product synthesis. Acetic acid, a key organic acid used in various industries such as food, pharmaceuticals, and chemicals, has garnered significant interest due to its versatile applications. Bacteria capable of producing acetic acid through fermentation or CO₂ reduction pathways have been extensively studied. Acetogenic bacteria, such as Clostridium ljungdahlii and Acetobacterium woodii, are known for their ability to convert CO₂ and H₂ into acetic acid under anaerobic conditions [3].

The production of acetic acid by bacteria involves complex metabolic pathways, including the Wood-Ljungdahl pathway utilized by acetogenic bacteria. Optimization of culture conditions, substrate availability, and reactor design are crucial factors influencing acetic acid yield and productivity. The integration of acetic acid production with biogas upgrading presents a synergistic approach towards sustainable bioprocesses. The isolation and characterization of novel bacterial strains with desirable traits such as CO₂ fixation and acetic acid production are fundamental to this research area. Microbial isolation techniques involve selective enrichment, isolation on specific media, and molecular identification using techniques like 16S rRNA gene sequencing [4].

Discussion

The isolation of bacterial strains with CO₂ fixation and acetic acid production capabilities begins with environmental sampling from diverse sources such as soil, sediments, and wastewater treatment plants. Selective enrichment techniques, coupled with culture on specific media containing CO₂ as a substrate, aid in isolating target bacteria. Screening assays for CO₂ fixation and acetic acid production help identify promising isolates for further characterization. Characterizing isolated bacterial strains involves assessing their growth kinetics, substrate utilization profiles, metabolic pathways, and product formation rates. Molecular techniques such as PCR, sequencing, and genome analysis provide insights into the genetic basis of CO₂ fixation and acetic acid production. Physiological studies under varying environmental conditions elucidate the optimal parameters for bacterial performance [5].

Once characterized, selected bacterial strains are integrated into biogas production systems for CO₂ sequestration and acetic acid synthesis. Strategies such as co-culturing acetogenic bacteria with methanogenic consortia enhance CO₂ utilization and overall process efficiency. Bioreactor design considerations, nutrient supplementation, and pH control play crucial roles in maximizing CO₂ conversion and acetic acid yield. Optimizing the biogas upgrading process involves fine-tuning operational parameters such as temperature, pressure, retention time, and gas flow rates. Continuous monitoring of bioreactor performance, product concentrations, and microbial activity ensures stable operation and high productivity. Economic assessments, including cost analysis, market demand for acetic acid, and potential carbon credits, determine the overall feasibility and commercial viability of the enhanced biogas production system [6].

Conclusion

Optimizing the biogas upgrading process involves fine-tuning operational parameters such as temperature, pressure, retention time, and gas flow rates. Continuous monitoring of bioreactor performance, product concentrations, and microbial activity ensures stable operation and high productivity. Economic assessments, including cost analysis, market demand for acetic acid, and potential carbon credits, determine the overall feasibility and commercial viability of the enhanced biogas production system.

Acknowledgement

None.

Conflict of Interest

None.

References

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