Electrochemically Induced Crystallization as a Sustainable Method for Product Recovery of Building Block Chemicals: Techno-Economic Evaluation of Fumaric Acid Separation

Carboxylic acids are key platform chemicals for use as biobased alternatives for fossil-based applications. State-of-the-art fermentations of carboxylic acids at neutral pH with downstream product recovery by pH-shift crystallization are not sustainable due to the accompanied production of waste salts. To earn the label‘‘sustainable,’’ salts should be converted into the original base and acid required for fermentation and product recovery. This paper shows that electrochemically induced crystallization (EIC) integrated with fermentation reduces both capital and operating expenditures (CAPEX and OPEX, respectively). EIC is a novel process that utilizes electrolysis of water to induce localized pH-shift crystallization of the carboxylic acid, while neutral bulk conditions are maintained. In the current study, a techno-economic evaluation of the fermentative production of fumaric acid integrated with product removal by crystallization was performed. Three cases were evaluated, two based on classical pH-shift crystallization and one based on fermentation integrated with EIC. The first so-called base case produces a solid waste, while the second employs electrodialysis at the end of downstream processing to regenerate the waste salt and re-use the base and acid. With EIC, electrochemistry obviates the use of chemicals and hence solid waste cannot be formed. Cost estimates for EIC unit operation were based on the mass and energy balances of laboratory-scale experimental work and the resultant conceptual design. Assuming return on investment (ROI) of 15%, the first base case has the lowest required sales price of e2.2/kg fumaric acid (USD2.84/kg fumaric acid). EIC eliminates the necessity of water removal, hence reduces CAPEX and OPEX by 35% and 19%, respectively. Sensitivity analysis reveals that with an augmenting penalty on solid waste disposal (greater than e128/ton; USD164/ton), EIC is the most economical option. This paper demonstrates that the integration of fermentation with product recovery improves the overall process economics and, by applying EIC, a more sustainable process is obtained.Process and EnergyMechanical, Maritime and Materials Engineerin