Biogas reforming in a microwave plasma environment : a sustainable approach to hydrogen production using plasma technology

Abstract

The growing energy demand, fossil fuel depletion, and greenhouse gas emissions have created an urgent need for sustainable fuels. Biogas, a renewable and widely available resource, is a promising feedstock for syngas and hydrogen production. This study explores microwave plasma-assisted biogas reforming, focusing on input power (1800-3000 W), flow rates (20-40 SL/min), and CO₂:CH₄ ratios (2:1 and 3:1). Microwave plasma enables rapid heating, high electron density, and non-thermal conditions, improving yield, conversion, and selectivity. Higher power enhanced conversion but also favored side reactions such as the reverse water-gas shift, which reduced hydrogen yield. Lower flow rates improved conversion due to longer residence times, while a 3:1 CO₂:CH₄ ratio minimized soot formation. Integrating steam reforming and H₂S removal further improved performance. Experiments showed methane conversion in the range of 70-100%, with values above 90% at 3000 W and 20 SL/min. CO₂ conversion ranged between 10 and 60 %, depending on power and flow. CO selectivity remained consistently high at 99-100 %, while hydrogen selectivity varied from about 57% at lower power to about 49 % at higher power. Hydrogen yield was in the range of 20-55 % and decreased with increasing flow rate, and CO yield reached 40-90 %. Specific energy consumption for hydrogen production was in the range of 30-150 kWh/kg H2, decreasing with higher flow but increasing with power. These findings underline the trade-offs between conversion, yield, and efficiency, offering insights into sustainable plasma-based syngas and hydrogen production.