Hydrogen production from biomass through integration of anaerobic digestion and biogas dry reforming

Abstract

Hydrogen is a clean fuel for heat and power generation and can serve as a feedstock for chemical synthesis. This study assesses the hydrogen production from biomass (e.g., cow manure) through integrating psychrophilic anaerobic digestion and dry methane reforming. For the first time, a rigorous model is developed for the low-temperature anaerobic digestion process by implementing the complex kinetics of the fermentation bioreactions. The produced biogas from the anaerobic digestion process is fed to the reforming process for hydrogen production. The kinetics of the dry methane reforming and water gas shift reactions over Co-Ni-Al2O3 catalyst are incorporated into the model. Validating the results of the proposed process using experimental data shows <5% relative deviation. The effects of total solids content, organic loading rate, hydraulic retention time, and digestate recirculation fraction on biogas and CH4 yield are investigated. The optimum values of operating parameters in the anaerobic digestion process as well as the dry methane reforming process are obtained. The process is designed to achieve the highest CH4-to-H2 conversion and the lowest energy consumption. A 48.07 kg/h biogas could produce 8.11 kg/h H2. The biomass-to-H2 process offers an energetic efficiency of 72.85%, revealing its superiority to similar processes, such as steam and auto-thermal reforming. The proposed process highlights a high potential for CO2 emission reduction (e.g., 398,736 t/y), compared to the direct biogas combustion for electricity production. Economic analysis shows that the cost of biogas-to-H2 production is 1.39 USD/kg H2 for a plant capacity of 45.5 kg/h H2.