Effect of ethanol pre-fermentation on organic load rate and stability of semi-continuous anaerobic digestion of food waste

This study investigated the effects of ethanol pre-fermentation on the organic load rate (OLR) and stability of single-phase semi-continuous anaerobic digestion system of food waste. Results revealed that the pre-fermentation group tolerated higher OLR, with a maximum OLR of 5.5 g-VS.L-1.d(-1). Moreover, the abundance of microbial community in relation to amino acid degradation in the pre-fermentation group was significantly higher than that in the control group, which made a higher concentration of ammonia nitrogen and caused a stronger system stability and higher alkalinity. Redundancy analysis was performed to explore the factors affecting system instability under high OLR. The instability of control group was found to be significantly influenced by the total volatile fatty acids (TVFA), whereas the pre-fermentation group was affected by total ammonia nitrogen and TVFA. Therefore, if the OLR of the pre-fermentation group is to be further increased, ammonia nitrogen inhibition should also be considered.