Circular bioeconomy solutions: driving anaerobic digestion of waste streams towards production of high value medium chain fatty acids

Abstract

This review outlines the road map for the production of medium chain fatty acids (MCFAs) from organic wastes by adapting the conventionally methanogenic process of anaerobic digestion (AD) for the production of volatile acids and the subsequent chain elongation, as well as for the production of hydrogen. The article analyses the state-of-the-art of these processes and discusses the modifications involved, the bottlenecks, challenges and opportunities. In particular, the various methods of inhibition of methanogenesis are described, their applicability is discussed and investigation of the use of naturally occurring inhibitors like bromoform is suggested. The review concludes that the using AD for MCFA production has a strong potential as a circular economy solution, avoiding many issues with the use of AD for biogas production while creating more economically viable products. The main bottleneck identified here is the downstream separation and extraction of the products. Standardization across studies and implementation of the various methods at pilot scale levels are critical to develop a clearer idea of the viability of the MCFA production process. More in-depth studies on the inhibition process and detailed cost–benefit and life cycle analysis are also recommended to for the use of this process and for its acceptance as a bioeconomy solution.