Valorisation of food waste using salt to alleviate inhibition by animal fats and vegetable oils during anaerobic digestion

Valorisation of lipid-rich food waste by enhancing the efficiency of its conversion to value-added products has drawn significant attention. This study aimed to confirm the feasibility of alleviating animal fats and vegetable oils (FO) inhibition using salt, the typical component of FO, instead of an extra chemical agent. For this purpose, the output, and compositions of volatile fatty acids (VFAs) were quantified with and without FO exposure. Intermediates, in the form of long-chain fatty acids (LCFAs), were also investigated. Experimental results showed FO inhibited VFA production in a dose-dependent manner. A maximum reduction of 73.2% and 67.5% in VFA production was reached in the animal fat and vegetable oil batches, respectively. A more severe negative effect was detected on exposure to animal fats. Investigation of VFA production revealed that salt addition (6 g/L) prevented mild oil inhibition (<15 g/L). Stronger oil inhibition (35 g/L) could not be mitigated. Moreover, the inhibition profile of various LCFA components differed, a longer duration was required for oleic acid degradation, which could cause more severe inhibition. Future research must focus on the effects of FO on the microbial community.