Evaluation of Esterification and Membrane Based Solvent Extraction as Methods for the Recovery of Short Chain Volatile Fatty Acids from Slaughterhouse Blood Anaerobic Mixed Fermentation

CO2 per year by 2030 [1]. Petroleum-based materials and chemical have been replaced by biological-based materials and chemicals with environmental advantages such as sustainability and biodegradability [2, 3]. One of these petroleum based-chemicals is the short chain carboxylic acids or volatile fatty acids (VFA). VFA are carboxylic acids with a carbon chain between 2 and 7 carbons [acetic (2), propionic (3), iso-butyric (4), n-butyric (4), iso-valeric (5), valeric (5), hexanoic (6), and heptanoic (7)]. Industrially, VFA are produced in a petroleum-based process using different types of chemical reactions such as oxidations, dehydrogenation, carbonylation, etc. VFA are utilized in several industries as precursor of different products such as solvents (methyl acetate, ethyl acetate), inks, coatings (cellulose acetate, cellulose butyrate) [4], polymers [cellulose acetate, polyvinyl acetate, polyhydroxialkanoates (PHA)], artificial flavors (ethyl butyrate, ethyl propionate), and scents (methyl butyrate, methyl valerate). The several VFA uses have generated a multibillion dollars industry with a considerably predicted increment in the next years [5]. Besides petroleum-based processes, VFA can be produced by biological methods. Acetic acid production by anaerobic fermentation is the most well-known VFA production. This process is only applied in the vinegar production because it is still economically uncompetitive compared with the acetic acid petroleum-based production. To reduce the difference between petroleum and biological based VFA production it is necessary to improve the upstream and downstream processing. The upstream processes have been improved by using wastes as substrates to produce VFA [6–9]. Carbohydrate based residues such as paper wastes, lignocellulosic material, municipal solid wastes, etc. are the most common wastes employed in the production of VFA. In our past research, we evaluated the production of VFA using protein rich Abstract Two routes, esterification and membrane based solvent extraction, were tested for their efficiency to extract volatile fatty acids (VFA) (acetic, propionic, butyric, isobutyric, iso-valeric and valeric acids) produced from the anaerobic-mixed fermentation of slaughterhouse blood. A range of operational parameters and reagents were assessed to optimize each system. Esterification recovered VFA as methyl esters with the production of ammonium sulphate as a value-added by-product of the esterification reaction. A membrane extraction system, comprised of a hydrophobic membrane and extractant using octanol/TOA (trioctylamine), was efficient to separate butyric and iso-valeric acids in favour of acetic acid from the fermentation broth. These results provided important information for the development of a carboxylate-platform bio-refinery using highprotein wastes as substrate.