Techno-economic analysis of CO₂-based gas fermentation for acetic acid production

Gas fermentation using acetogens via the Wood–Ljungdahl pathway offers a sustainable route for converting CO₂ and hydrogen into valuable chemicals. This study presents a comprehensive techno-economic analysis of a 50,000 t/a acetic acid (AcOH) production plant based on gas fermentation. Three designs, composed of four process systems, are proposed and evaluated. A mathematical model of the gas fermentation process in a bubble column has been developed. The complete process is also modeled and simulated with Aspen Plus®, and the equipment costs are primarily estimated using Aspen Process Economic Analyzer™. A sensitivity analysis is conducted to evaluate the impacts of fluctuations in hydrogen prices and variations in project life on economic viability. With a hydrogen price of 5 USD/kg and CO₂ price of 60 USD/t, AcOH production integrated with a single pressure swing adsorption for hydrogen recovery is recognized as the optimal design due to its lowest total production costs of 1073.61 USD/t AcOH, with hydrogen comprising 64 %. The total capital investment for this design is 54.49 million USD. Assuming an AcOH selling price of 1 USD/kg, the plant generates an after-tax ROI of 15.66 %, and an IRR of 13.24 %, NPV of 62.61 million USD, breakeven hydrogen price is 6.18 USD/kg, over a 20-year project life. This work offers essential insights into the economic viability of CO₂-based gas fermentation and bolsters future efforts aimed at process optimization, cost reduction, and commercial deployment.