Continuous Subcritical Water Hydrolysis for Pre-treatment of Palm Oil Mill Effluent (POME)

Abstract

The pre-treatment of palm oil mill effluent (POME) was carried out using subcritical water (Sub-CW). Sub-CW has the potential as a clean and green method to extract, hydrolyze, gasifier, and carbonize biomass to produce valuable materials. The experiment was conducted continuously for 1 hour at 190, 220, and 260°C between 40 and 140 bars. The hydrolysate obtained was separated into liquid and solid phases. The continuous mode stability was investigated at 3 and 7 mL/min, corresponding to the reactor residence time (RT) of 7 and 3 min, respectively. The flowrate gave a steady trendline with less variation at lower temperatures and slight fluctuation for higher temperatures. The highest solid yield was 0.085 wt.% obtained at 260°C and RT=3 min. The highest sugar yield was 4.44 wt.% at 230°C and RT=3 min. The lowest COD value was 5,504 mg/L achieved at 230°C and RT=3 min. The COD was reduced by 78.9 % of the raw POME. High sugar yield paired with reduced COD reached at 230°C in only 3 min, which is significantly low compared to the ponding system. In conclusion, integrating Sub-CW in a continuous mode as a pre-treatment method offers a promising alternative and sustainable solution for POME treatment.