Effects of salt and oil concentrations on volatile fatty acid generation in food waste fermentation

The main objective of this study was to evaluate the effects of salt and oil on volatile fatty acid (VFA) generation during anaerobic digestion. Lab-scale sequencing batch reactor experiments were operated at various salt concentrations of 3 g/L (S3), 6 g/L (S6), 9 g/L (S9), 12 g/L (S12) and oil concentrations of 5 g/L (O5), 15 g/L (O15), 25 g/L (O25), 35 g/L (O35) under previously determined optimal conditions (35 °C and pH of 6). The results revealed that VFA generation was reduced 18.7% and 89.9% at S6 and S12. Similarly, VFA generation decreased by 6% and 67.2% at O5 and O35, respectively. The salt concentration ＜ 6 g/L or the oil concentration ＜ 5 g/L minimally inhibited the VFA yield. Moreover, the VFA yield remain stable and the lag phase was shorten at salt and oil concentration at 6 g/L and 5 g/L, respectively (S6O5) compared with a single addition. The above finding indicates the possibility of VFA generation under conditions where salt and oil coexist. Thus, a salt concentration ＜ 6 g/L and/or oil concentration＜5 g/L in food waste was suitable for VFA generation in food waste fermentation.