Innovative Bioelectrochemical Leach-Bed Reactor for Enhanced Methane Production in Percolation Dry Anaerobic Digestion of Food Waste

Abstract

Percolation-based dry anaerobic digestion (AD) is an attractive technology for treating high-solids food waste (FW) because it requires minimal water addition and eliminates the need for mechanical mixing. However, its methane production is often limited by slow hydrolysis and inefficient conversion of soluble intermediates. To overcome these limitations, this study developed a bioelectrochemical leach-bed reactor (BLBR) by integrating a microbial electrolysis cell with a percolation-based dry AD system to enhance methane production kinetics. Two 10-L reactors were operated in 10-day batch mode: an open-circuit control reactor and a bioelectrochemical reactor operated with applied voltages ranging from 0.3 to 1.2 V. Moderate voltage application significantly enhanced methane production, with the highest cumulative methane yield reaching 293 mL CH4/gVSadded at 0.9 V, representing a 47% increase over the control (199 mL CH4/gVSadded), while volatile solids removal remained comparable between treatments. Voltage-assisted operation promoted a rapid increase in soluble chemical oxygen demand (SCOD), followed by faster consumption than in the control. Similarly, acetate and propionate accumulated and were depleted earlier, indicating accelerated conversion of soluble intermediates. A transient butyrate concentration of 8.8 g COD/L was observed at 0.9 V, suggesting enhanced fermentative activity under moderate bioelectrochemical stimulation.