Acetate and lactate production during two-stage anaerobic digestion of food waste

Single-stage anaerobic digestion were compared with two-stage processes, using either food waste alone or mixed with thin stillage as substrate. The overall methane yield increased (by 12%) in two-stage compared with single-stage digestion when using food waste, but decreased when food waste was co-digested with thin stillage. Process analyses also revealed some differences in VFA levels in the first-stage reactor that could have caused the difference in methane yield. To shed some additional light on possible causes of the large difference in methane and VFA yield the microbial community in both the first- and second-stage reactors were analysed, using a combined Illumina sequencing and qPCR approach.