Electrolytic Membrane Extraction Enables Production of Fine Chemicals from Biorefinery Sidestreams

• Published in: Environmental science & technology 2014-06, Vol.48 (12), p.7135-7142
• Main Authors: Andersen, Stephen J, Hennebel, Tom, Gildemyn, Sylvia, Coma, Marta, Desloover, Joachim, Berton, Jan, Tsukamoto, Junko, Stevens, Christian, Rabaey, Korneel
• Format: Article
• Language: English
• Subjects: Acetic Acid - chemical synthesis; Alternative energy sources; Applied sciences; Biofuels; Biogas; Biological and medical sciences; Bioreactors; Biotechnology; Carbon dioxide; Carboxylic Acids - chemical synthesis; Chemical industry. Chemical engineering; Climatology. Bioclimatology. Climate change; Earth, ocean, space; Electricity; Electrocatalysis; Electrolysis; Energy; Esterification; Exact sciences and technology; External geophysics; Fermentation; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; Industrial wastewaters; Ion exchange; Membranes; Membranes, Artificial; Meteorology; Pollution; Waste Products - analysis; Wastewaters; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es500483w

Short-chain carboxylates such as acetate are easily produced through mixed culture fermentation of many biological waste streams, although routinely digested to biogas and combusted rather than harvested. We developed a pipeline to extract and upgrade short-chain carboxylates to esters via membrane electrolysis and biphasic esterification. Carboxylate-rich broths are electrolyzed in a cathodic chamber from which anions flux across an anion exchange membrane into an anodic chamber, resulting in a clean acid concentrate with neither solids nor biomass. Next, the aqueous carboxylic acid concentrate reacts with added alcohol in a water-excluding phase to generate volatile esters. In a batch extraction, 96 ± 1.6% of the total acetate was extracted in 48 h from biorefinery thin stillage (5 g L–1 acetate) at 379 g m–2 d–1 (36% Coulombic efficiency). With continuously regenerated thin stillage, the anolyte was concentrated to 14 g/L acetic acid, and converted at 2.64 g (acetate) L–1 h–1 in the first hour to ethyl acetate by the addition of excess ethanol and heating to 70 °C, with a final total conversion of 58 ± 3%. This processing pipeline enables direct production of fine chemicals following undefined mixed culture fermentation, embedding carbon in industrial chemicals rather than returning them to the atmosphere as carbon dioxide.