Abstract
Two routes, esterification and membrane based solvent extraction, were tested for their efficiency to extract volatile fatty acids (VFA) (acetic, propionic, butyric, iso-butyric, 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 high-protein wastes as substrate.
Highlights
The transformation of petroleum-based processes into biological-based processes expects to save 2.5 billion tons ofWater and Environmental Engineering Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, UKMedical School, Centre for Cytochrome P450 Biodiversity, Institute of Life Science (ILS 1), Swansea University, Room 529, Swansea SA2 8PP, Wales, UKCO2 per year by 2030 [1]
The analytical-grade reagents used in this study, as listed below, were all obtained from Sigma-Aldrich (Dorset, UK): Acetic, propionic, iso-butyric, n-butyric, iso-valeric, valeric acid, sulphuric acid, methanol, methyl acetate, methyl propionate, methyl butyrate, methyl iso-butyrate, methyl iso-valerate, ammonium hydroxide, trioctylamine (TOA), and octanol
Neutral pH affected the esterification reaction in both volatile fatty acids (VFA):CH3OH ratios; the pH effect was greater in the 1:1 VFA:CH3OH ratio
Summary
Petroleum-based materials and chemical have been replaced by biological-based materials and chemicals with environmental advantages such as sustainability and biodegradability [2, 3].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 produced in a petroleum-based process using different types of chemical reactions such as oxidations, dehydrogenation, carbonylation, etc. The several VFA uses have generated a multibillion dollars industry with a considerably predicted increment in the years [5]
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