Recycling mixed biowaste into valuable chemicals as medium-chain carboxylic acids: the role of thermal pretreatment

Nowadays, anaerobic fermentation is considered a sustainable strategy for biochemical production from waste streams. This process offers an economical platform for producing medium-chain carboxylates (MCCs) through chain elongation (CE) which converts short fatty acids (SCFAs ) and electron donor like alcohols and lactate into more valuable MCCs. MCCs, carboxylates with 6-12 carbon atoms, have wide applications in several industries (Wang and Yin, 2022). Recently, the production of caproate (C6), from acetate or butyrate through the reverse ?-oxidation pathway has been gaining increasing attention. Several substrates have been used as carbon source for MCCs production, and the focus has been typically set on the improvement of caproate production by addition of electron donor or the optimization of reactor configuration (Wu et al., 2021). However, there is a lack of knowledge regarding the effect of organic waste co-fermentation on chain elongation. Waste activated sludge (WAS) is generated during the biological wastewater treatment process, and its amount increased dramatically along with costs of treatment and management. Besides, the high organic content makes food waste (FW) the ideal substrate for MCCs production. This collaborative study between University, CNR and a water company aimed to assess the potential of co-fermentation of urban biowaste as WAS and FW by exploiting both synergistic effects and feedstock pre-treatments on the productivity of caproate, without chemicals supplementation.