Steam Methane Reforming (SMR) is the dominant method for hydrogen production, accounting for a significant share of global output. While methane is the conventional feedstock, non-methane alternatives such as biogas, ethanol, and propane offer potential pathways to diversify hydrogen production while leveraging existing SMR infrastructure. These feedstocks introduce distinct reaction mechanisms, efficiency profiles, and operational challenges, necessitating adaptations in catalyst formulations and process conditions.

Biogas, derived from anaerobic digestion of organic waste, contains methane but also includes carbon dioxide and trace contaminants like hydrogen sulfide. In SMR, biogas undergoes the same primary reactions as natural gas: methane reacts with steam to produce syngas (hydrogen and carbon monoxide) in the presence of a nickel-based catalyst. However, the presence of CO2 in biogas alters the equilibrium of the water-gas shift reaction, potentially increasing hydrogen yield if managed properly. Impurities such as sulfur compounds require robust pre-treatment to avoid catalyst poisoning. Industrial applications include wastewater treatment plants and agricultural facilities, where biogas is reformed on-site to produce hydrogen for fuel cells or industrial use.

Ethanol, a renewable feedstock, can also serve as an SMR input. The reaction pathway involves steam reforming of ethanol (C2H5OH) to produce hydrogen, carbon monoxide, and carbon dioxide. The process typically occurs in two stages: ethanol dehydrogenation to acetaldehyde, followed by reforming into syngas. Compared to methane, ethanol reforming operates at lower temperatures (500–700°C) but faces challenges such as coke formation and catalyst deactivation. Rhodium and nickel-based catalysts modified with ceria or other promoters have shown improved resistance to coking. Brazil has piloted ethanol-based SMR projects, leveraging its sugarcane-derived ethanol supply to produce low-carbon hydrogen for transportation and industrial sectors.

Propane, a liquefied petroleum gas (LPG) component, is another viable feedstock. Its reforming reaction (C3H8 + 6H2O → 10H2 + 3CO2) requires higher steam-to-carbon ratios to mitigate carbon deposition. Propane’s advantage lies in its ease of storage and transport, making it suitable for decentralized hydrogen production. However, the process demands careful temperature control to avoid side reactions that reduce efficiency. Japan has explored propane SMR for small-scale hydrogen refueling stations, particularly in regions lacking natural gas infrastructure.

Efficiency comparisons among these feedstocks reveal trade-offs. Biogas-SMR can achieve efficiencies of 65–75%, similar to natural gas, but energy penalties for impurity removal must be factored in. Ethanol-SMR efficiencies range from 60–70%, with lower thermal inputs partially offset by higher catalyst costs. Propane-SMR efficiencies hover around 70–75%, though energy losses during LPG production affect the overall lifecycle performance.

Catalyst adaptation is critical for non-methane feedstocks. Sulfur-resistant catalysts, such as those doped with molybdenum or tungsten, are essential for biogas processing. For ethanol, catalysts with high oxygen mobility (e.g., ceria-zirconia supports) reduce coke accumulation. Propane reforming benefits from nickel catalysts with alkaline earth promoters to enhance stability. Each feedstock demands tailored catalyst formulations to address unique deactivation mechanisms.

Industrial case studies illustrate practical applications. In Germany, a biogas-SMR plant coupled with carbon capture supplies hydrogen for refinery operations, achieving a 20% reduction in carbon intensity compared to conventional SMR. In the U.S., a demonstration project using ethanol-SMR produces hydrogen for fuel cell buses, with system efficiencies nearing 68%. South Korea’s propane-SMR units support urban hydrogen mobility, demonstrating adaptability in areas without pipeline gas access.

Challenges persist. Feedstock variability, particularly in biogas composition, complicates process optimization. Ethanol’s hygroscopic nature demands additional handling steps, while propane’s reliance on fossil-derived LPG limits its sustainability appeal. Regulatory frameworks and subsidies play a pivotal role in incentivizing non-methane SMR adoption, as higher production costs remain a barrier.

Non-methane feedstocks expand the versatility of SMR, enabling hydrogen production from diverse sources without abandoning established infrastructure. While technical hurdles exist, ongoing advancements in catalyst science and process engineering are gradually improving the viability of these alternatives. The choice of feedstock ultimately depends on regional availability, cost considerations, and environmental objectives, underscoring the need for context-specific solutions in the hydrogen economy.