Enhancing bioenergy from water hyacinth: pretreatment and anaerobic co-digestion

Abstract

The lignocellulosic content in water hyacinth (WH) reduces anaerobic digestion efficiency. This study investigated potassium hydroxide (KOH) pretreatment at 5 %, 7.5 %, and 10 % KOH for 24 h with WH mono and co-digestion with dairy manure (DM) using 3:1, 1:1, and 1:3 ratios of WH to DM based on volatile solids (VS). Results showed the pH ranged from 7.5 to 8 after pre-treatment when mixing DM and inoculum, with lignin content reduced from 14.3 to 29.82 %. The highest CH4 yield for mono-digestion was 275 NmL/g VS with 10 % KOH pretreatment (p < 0.001). Co-digestion (1:1) with 5 % KOH had the highest overall yield (412 NmL/g VS); 78.5 % higher than untreated WH (p < 0.001). The modified Gompertz model showed a R2 best fit value of 0.97 with experimental data. This work showed co-digestion increased bioenergy production without pH adjustment after KOH pre-treatment, which reduces pretreatment costs, loss of VS, and wastewater generation from KOH treatment.