Hydrogen and biofuel synergies in the transport sector: A systematic review and bibliometric analysis

Transport accounts for approximately 25% of global CO₂ emissions. Hard-to-abate segments such as heavy-duty road transport, aviation, and maritime shipping face significant barriers to full electrification, necessitating a diversified portfolio of alternative fuels. This article argues that the strategic integration of hydrogen and biofuel technologies is one of the most promising yet underexplored pathways to achieving climate neutrality in transport by 2050. Combining a narrative literature review with a bibliometric analysis of 793 scientific publications (2015–2025) drawn from Scopus, Web of Science, and Lens.org, the study maps the intellectual structure, geographic distribution, and publication landscape of this emerging research field. The bibliometric analysis, conducted using VOSviewer, identifies eight thematic clusters centred on hydrogen, renewable energy, and energy transition, with research output concentrated in the United States, China, Germany, and India, while Central and Eastern Europe remains largely absent from the international collaboration network. The literature review demonstrates that neither technology is sufficient on its own: hydrogen faces persistent infrastructure and cost barriers, while biofuels are constrained by feedstock availability. Their combination through four distinct synergy mechanisms, namely integrated biorefineries, Power-to-X coupling, infrastructure sharing, and policy coordination, reduces the weaknesses of each technology while amplifying their respective strengths. Key barriers – including the absence of globally consistent lifecycle emissions certification and a tenfold investment gap relative to net-zero requirements – remain unresolved. Five priority areas for future research are identified: Power-to-X value chain optimisation, harmonised lifecycle assessment, cross-sector governance frameworks, integrated energy system models, and investment decision-making for hydrogen–biofuel synergies. The study focuses on interactions between hydrogen and biofuel value chains rather than evaluating synthetic fuels as a separate technology category, although hydrogen-derived e-fuels are considered within the Power-to-X synergy framework.