Biomass-based hydrogen production pathways and their application in internal combustion engines: global research trends and future prospects

Biomass is an abundant and renewable resource with strong potential for sustainable hydrogen production. It offers a practical route toward low-carbon energy systems. To assess the research progress, key themes, and technological evolution in this field, a bibliometric analysis of publications indexed in the Scopus database (2005–2025) was conducted. It focuses on hydrogen production from biomass and its application as a clean fuel in internal combustion (IC) engines. The analysis has shown a steady growth in research activity, with major attention focused on thermochemical methods, such as gasification, pyrolysis, and steam reforming. These processes remain the most efficient pathways for converting different biomass feedstocks into hydrogen-rich gas. Recent advances in catalyst design, reaction intensification, and process optimization have further improved yield and cost-effectiveness. Further review of engine studies established that hydrogen enrichment significantly enhances engine performance, such as higher brake thermal efficiency (BTE) by 5–20%, lower specific fuel consumption (SFC) by 8–25%, and smoother combustion. Moreover, the use of hydrogen, either as a primary or blended fuel, significantly reduces carbon-based emissions (CO, CO₂, HC, soot, and PM) by 70–90% in both spark-ignition (SI) and compression-ignition (CI) engines. Although an increase in NO_x emissions is commonly observed under stoichiometric operation. This concern can be effectively mitigated through lean-burn strategies, exhaust gas recirculation (EGR), or water injection. Studies employing EGR rates of 15–20% or moderate water addition reported NO_x reductions between 35 and 60%, without major efficiency drops. The analysis confirms that biomass-derived hydrogen offers a dual advantage, a sustainable production route through renewable thermochemical processes and a high-efficiency, near-zero-carbon fuel for IC engines.