Biodiesel Beyond Fuel: A Review of Expanding Applications and Embracing Circularity

Biodiesel, which is traditionally viewed as a cleaner alternative to fossil fuels, is also gaining new applications outside of energy. In this review, 182 peer-reviewed articles and patents retrieved via Google Scholar, Semantic Scholar, MDPI, ResearchGate, Scopus, ScienceDirect, among others were systematically synthesized concerning 2012-2025 as of August 2025. These 94 studies represent the percentage of traditional fuel applications, the 47 studies non-fuel applications (with 18 studies on green solvents, 16 on biodegradable lubricants, and 13 on specialty polymers), 28 studies into glycerol valorization into chemicals, e.g. of 1,2-propanediol, organic monomers and polymer additives, and 13 studies on circular economy strategies. Results demonstrate that biodiesel can be utilized as a raw material to develop quality and environmental-friendly products. Critical issues such as the cost of production, quality control, and regulatory gaps are also highlighted. Researchers, industry practitioners, and policymakers can use this review as a source of actionable insights by focusing on recent research, patents, and industrial developments significant to obtain a sustainable and circular bioeconomy.