RESUMO
Anaerobic digestion (AD) of acidic kitchen waste (KW) streams is found to be unstable and leads to poor overall efficiency. This study assessed the effect of pongamia de-oiled cake addition on KW-AD. High acidic KW (pH: 2.00-5.00), medium acidic KW (pH: 5.00-7.00) and low alkaline KW (pH: 7.00-8.00) fed into digesters I, II and III at 10% total solids (TS) achieved biogas yields of 177.82 ± 19.30, 216.57 ± 7.42 and 280.45 ± 2.55 L/kg VS. d, respectively. Maximum synergistic effect of pongamia de-oiled cake was observed in digester I with increased methane production of 46.04% and volatile solids reduction of 11.18%. The principal component analysis and kinetic evaluation revealed that pongamia de-oiled cake addition had a positive effect on the AD parameters in all digesters. With energy efficiencies exceeded 96% in all the digesters, the study proposes the addition of protein-rich additives for KW-AD stabilization.