Chain elongation is one of the common anaerobic fermentation processes in which bacteria convert ethanol and short chain fatty acids (SCFA) into medium chain fatty acids (MCFA). These are single carboxylic acids having six to twelve carbon atoms, with several applications, such as biofuels. Caproate is a promising MCFA, and several technologies were proposed for the valorization of waste to obtain it.
Bioelectrochemical systems (BESs) are technologies that are capable of converting the chemical energy of organic/inorganic wastes into value‐added products, using in situ generated H2 or electricity as energy sources. To convert waste biomass into caproate, an electron donor in the form of hydrogen or ethanol should be supplemented within the anaerobic fermentation, which can be used as the electron donor in the cathodic compartment for the conversion of acetate into caproate.
This review highlights recent anaerobic and bioelectrochemical processes for the production of caproate. The discussion will also cover the potential applications of this technology, together with obstacles to its use, compared with the conventional anaerobic digestion (AD) process, and considers whether it could be a standalone technology or a complementary one for AD.