Binary energy system for hydrogen and biochar production by integrating methanol partial oxidation and bamboo pyrolysis with life cycle analysis

Abstract

The transition to sustainable energy systems demands novel approaches to maximize resource utilization while minimizing environmental impact. This study conducts a hybrid thermochemical system that integrates partial oxidation of methanol (POM) for hydrogen production with bamboo pyrolysis for biochar synthesis, utilizing POM-generated waste heat. A Taguchi-based experimental design is employed to systematically optimize key POM operating parameters of preheating temperature, oxygen-to‑carbon (O<inf>2</inf>/C) ratio, gas hourly space velocity (GHSV), methanol flow rate, and catalyst mass, enhancing hydrogen yield while curbing carbon emissions. Experimental results reveal that methanol conversion ranges from 59.1 % to complete conversion, achieving hydrogen yields up to 1.901 mol∙(mol CH<inf>3</inf>OH)−1. Life cycle assessment (LCA) quantifies a reduction in global warming potential from 28.4 to 16.0 kg CO<inf>2eq</inf>∙(kg H<inf>2</inf>)−1, highlighting environmental improvements from the integrated process. Waste heat-driven bamboo pyrolysis yields biochar with enhanced energy density; the higher heating value increases from 17.25 to 25.41 MJ∙kg−1, while carbon content rises from 44.25 wt% to 68.77 wt%. The system's novelty lies in synergizing POM and biomass valorization to elevate thermal efficiency and mitigate environmental load. Unlike conventional standalone processes, this integrated configuration leverages exothermic POM reactions for biomass conversion, reducing auxiliary energy input. Furthermore, LCA outcomes demonstrate a 10.9 % reduction in human carcinogenic toxicity through co-production, reinforcing its sustainability credentials. This work offers a scalable pathway for low-carbon hydrogen and solid fuel production, aligning with circular bioeconomy principles and advancing next-generation renewable energy strategies.