Valorizing biomass waste for the electrochemical production of hydrogen peroxide

Abstract

This study investigates the potential of integrating and valorizing two biomass wastes, anaerobic digestate (AD), generated in biogas plants, and Phragmites australis (PA), a lignocellulosic biomass from Castilla-La Mancha region, in different mass ratios. These substrates were treated by hydrothermal carbonization (HTC) as a sustainable and second-generation feedstock to produce hydrochar viable for hydrogen peroxide production by an electrochemical process. Hydrogen peroxide from this process could be used for wastewater disinfection. The resulting sludge from these facilities, rich in organic matter, serves as ideal feedstock for biogas production, thus closing the loop in this circular economy approach. The aim of this work is to evaluate the physicochemical properties, thermal stability, surface morphology, and electrochemical performance of the hydrochars. Additionally, several chemical activation and pyrolysis processes were conducted to analyze the improvement in the electrochemical response for the H2O2 production. Results demonstrate that HTC effectively converts an equal mixture of AD and PA into hydrochar with enhanced electrochemical properties and thermal stability, without the need for activation processes. The presence of nitrogen, increment of oxygenated functional groups and graphitic carbonaceous structure were crucial parameters for the electrochemical performance of the materials. Non-activated hydrochars achieved the highest H2O2 accumulated concentrations attaining 106.38 ppm. This research highlights the applicability of HTC in converting waste materials into high-value carbon products, offering a sustainable approach to waste management and hydrogen peroxide production.