Volatile Fatty Acid Production Using Heat-Treated Potato Starch: Impact of Hydraulic Retention Time

Abstract

Potato starch was thermally pretreated and the effect of its solubilization on the production of volatile fatty acids (VFA) using mesophilic anaerobic digestion was investigated in this study. Potato starch with three concentrations (10, 15, and 25 g/L) was pretreated at 50°C, 70°C, 80°C, 100°C, 120°C, and 140°C to establish the relationship between temperature and degree of solubilization yielding a linear relationship (R2=0.93–0.98) irrespective of the starch concentration. Anaerobic respirometric studies were performed with raw starch and starches pretreated at 100°C (THP_100) and 140°C (THP_140). The batch reactors were operated in parallel at hydraulic retention times (HRTs) of 0.5, 1, and 2 days and organic loading rates (OLRs) of 6 and 9 kg-COD/(m3·day). The VFA production from THP_140 starch reduced significantly, but the two other samples did not exhibit changes. A maximum VFA yield of (0.482±0.054) mg-VFA/mg-CODapplied was obtained at an OLR of 9 kg-COD/(m3·day) and an HRT of 2 days. Acetic acid and butyric acid remained the dominant products, irrespective of the operating conditions.