2025 AIChE Annual Meeting

(302b) Thermodynamic Minimum Separation Energy of Five Short-Chain Carboxylic Acids from Aqueous Bioprocessing Streams

Authors

Ajinkya Pal, National University of Singapore
Quentin Ploussard, Argonne National Laboratory
Gregg T. Beckham, National Renewable Energy Laboratory
Lauren Valentino, Argonne National Laboratory
The biological production of short-chain carboxylic acids (SCCAs) from biomass feedstocks is gaining attention, given the desire for a more diversified and resilient national energy portfolio. To achieve cost parity with conventional methods, both emerging and established technologies for SCCA production must address key economic challenges, particularly in separations, which can account for up to 70% of total production energy and cost across bioenergy supply chains. While many studies assess separation energy requirements through process modeling and subsequent techno-economic analysis, it is difficult to compare energy consumption across multiple organic acid production schemes, especially because each acid can be subject to several purification process driven by different combinations of heat, work, and chemical energy. In this study, the thermodynamic minimum energy of separation is calculated to establish performance baselines that are independent of specific separation processes or cost assumptions. Implementing this analysis for bio-derived organic acids incurs additional challenges due to their acid/base behavior, which varies depending on solution conditions. This study presents a generalized framework to calculate the theoretical minimum energy of separation for the recovery of organic acids and pure water from simplified fermentation broth streams using the Gibbs free energy of separation. In addition to acid-base equilibria, binary interaction parameters and activity coefficients are incorporated to account for system non-idealities. Minimum separation energy requirements are computed across a range of concentration and pH conditions that are representative of fermentation processes for five organic acids (acetic, butyric, formic, lactic, and 3-hydroxypropionic acid), spannig a range of physicochemical properties (molecular weight, pKa, density, and aqueous solubility). These values are compared to the energy content and market value of each acid to evaluate the energy intensity and economic feasibility of separation in bioprocessing scenarios. Overall, this framework can be expanded as a tool to calculate the minimum energy consumption of separation across a wide range of organic acids and offers an accessible benchmark for use in process energetics studies.