Navigating alternative diesel pathways for a diversified energy future: Biodiesel or renewable diesel?

Liquid fuels remain essential for transportation sectors where batteries and hydrogen face practical limitations, particularly in heavy-duty, marine, and aviation applications. Biofuels offer a promising near-term decarbonization pathway by leveraging photosynthetic carbon capture through biomass production. Among these, biodiesel and renewable diesel have emerged as leading alternatives to petroleum-based diesel. Although produced from similar feedstocks, they differ substantially in their chemical properties, production pathways, engine compatibility, and lifecycle emissions. This review critically compares the two fuels across four key dimensions: feedstocks, environmental performance, process efficiency, and recent technological advances in catalysis, spanning the shift from homogeneous and heterogeneous catalysts. Key trade-offs, deployment barriers, and opportunities shaping their roles in the energy transition are examined, alongside the market and policy forces influencing their deployment across the U.S., Europe, and Asia. By clarifying these distinctions, this review provides a framework to guide research, regulation, and investment toward scalable liquid-fuel diversification. Finally, the emerging role of artificial intelligence and machine learning (AI/ML) approaches in optimizing biofuel production processes and accelerating technological development are highlighted.