Enhancement of biomethane yield rate in anaerobic co-digestion of cattle dung and untreated vegetable waste through the amendment of water-hyacinth biochar

Abstract

This study investigates the effect of biochar (BC) amendment on the anaerobic co-digestion (AcoD) of cattle dung (CD) and untreated vegetable waste (VW) performed at different co-substrates mixing ratios (CMR) of 70:30, 60:40, 50:50, 40:60, and 30:70 under ambient and mesophilic conditions. The mesophilic BC-added digester with a CMR of 60:40 exhibited 13.19 % and 39.26 % higher cumulative methane yield (CMY) than the corresponding uncontrolled digesters (CMR 60:40) with and without BC-added over 45 days of experiments. Subsequently, considering CMR 60:40, another group of biochemical methane potential experiments was conducted at ambient conditions, incorporating varying amounts of BC, viz. 5, 10, 15, 20, and 25 gL⁻¹. The digester comprising 15 gL⁻¹ BC achieved the highest CMY, recommending it as the optimal amount of BC addition for the AcoD of CD and VW. This study discloses that BC addition is a significant approach to increasing CH₄ yield.