The effect of initial organic load of the kitchen waste on the production of VFA and H2 in dark fermentation

Dark fermentation of kitchen wastes was studied in batch bioreactors, with no pH adjustment, to evaluate the effect of the initial organic load on the process performance in terms of volatile fatty acids and H2 production. Initial organic load of the kitchen wastes ranged from 4.1 to 48.2 gVS/L. Acetic and butyric acids were produced in the largest amount. At the initial organic load of 48.2 KW gVS/L the highest concentration of volatile fatty acids was 9.81 g/L. The maximum production yield of H2 (76.1 mL/gVS) was found for the initial organic load of kitchen wastes at 14.3 gVS/L. The carbon balance calculation showed that the maximum CO2 yield of 0.34 gC/gC was attained in the bioreactor with the initial organic load of 14.3 gVS/L. The microbiological analysis revealed that the predominant microorganisms in the dark fermentation process were Bacteroidetes, Firmicutes, Spirochaetes and WWE1 at phyla level.