A Comparative Analysis of Sustainable Hydrogen Production via Biogas Steam Reforming and Electrolysis

Abstract

Hydrogen is a critical clean fuel for decarbonizing transportation, power, and chemical sectors. This study evaluates the energy performance and efficiency of biogas steam reforming (BSR) and alkaline water electrolysis (AWE) for sustainable hydrogen production. The analysis was conducted using Aspen Plus® simulations to model and evaluate each process. This comparative study was necessary to address the limited and inconsistent integrated assessments of energy efficiency and carbon emissions across BSR and AWE processes in existing literature, providing a comprehensive analysis crucial for optimizing sustainable hydrogen production. Equilibrium and kinetic models for BSR, along with a custom electrochemical model for AWE, were developed to analyze thermodynamic limits, time-dependent behavior, and the effects of operational parameters. For BSR, the equilibrium model showed that higher temperatures (up to 900°C) boost methane conversion (85% at 500°C to 98% at 900°C for pure CH₄) and hydrogen yield (36.92 kmol/h at 1 bar), while increasing pressure (1 to 30 bar) reduces yield by approximately 12% due to the thermodynamic shift favoring reactants. The kinetic model yielded lower outputs (e.g., 33 kmol/h at 1 bar for pure CH₄) as equilibrium may not have been achieved due to factors such as catalytic bed height and other operating conditions, with CH₄-CO₂ mixtures further decreasing yield via the reverse water-gas shift reaction. For AWE, hydrogen production increased near-linearly with current density (0.35 to 0.6 A/cm²) and stack voltage (23.3 to 27.0 V) at 75°C, with 30% KOH optimizing efficiency. BSR achieves higher yields but emits approximately 41.71 kg CO₂/kg H₂ produced (e.g., 3104.76 kg/h CO₂ for 74.47 kg/h H₂), with an energy requirement of 11.60 kWh/kg H₂ for heating to maintain reactor temperature, while AWE, emission-free, requires approximately 0.58 kWh/kg H₂ produced, necessitating renewable energy sources. Sensitivity analyses identified optimal conditions and highlights needs for advanced catalysts and energy integration. Validated against literature, the findings offer insights for optimizing low-carbon hydrogen production, with recommendations for hybrid systems, model refinement, and policy support for renewable feedstocks.