Rapid generation of volatile fatty acids (VFA) through anaerobic acidification of livestock organic waste at low hydraulic residence time (HRT)

•Rapid generation of VFA's through acidogenic anaerobic digestion from CM and PL.•Pre-treatment of CM and PL, optimization of pH, HRT and F/M ratio to maximize VFAs.•HRT of 4 days, pH of 5.5, and F/M ratio of 1.0 were found optimum for the process.•Pre-treated CM and PL yielded 0.43 and 0.67 kg of VFA/(kg VS reduced) respectively.

The purpose of this study was to investigate the effect of pre-treatment and F/M (Food to Microorganism) ratios for the rapid generation of volatile fatty acids (VFA) from livestock organic wastes (cattle manure (CM) and poultry litter (PL)) through an anaerobic acidification process at a pH range of 4.5-5.5. Experiments were organized using CM and PL in batch reactors (1 L and 25 L) with and with no pre-treatment of substrate at F/M ratios (0.4, 0.6, 0.8 and 1). Among various existing pre-treatments methods, thermal-acidic (120 °C; 1% H2SO4) pre-treatment was found effective. The results revealed that 0.31 and 0.47 kg VFA/(kg VS reduced) could be obtained from CM and PL respectively with no pre-treatment, whereas it improvised to 0.43 and 0.67 kg VFA/(kg VS reduced) correspondingly due to pre-treatment. Aforesaid, better yield of VFA was obtained at F/M ratio of 1.0, pH-5.5 and hydraulic residence time of 4 days.

Graphical abstractAcidogenic anaerobic digestion of livestock organic waste for the production of volatile fatty acids at low hydraulic residence time (HRT).Download high-res image (76KB)Download full-size image