Mechanistic Pathways and Sustainable Innovations in Bio-Based Surfactant Synthesis from Renewable Feedstocks: A Review

The accelerating transition from petroleum-derived surfactants to renewable and biodegradable alternatives reflects a critical move toward sustainable chemical manufacturing. This review presents an integrated analysis of bio-based surfactant synthesis derived from vegetable oils, fatty acids, and citric acid esters, emphasizing reaction mechanisms, catalytic pathways, and process innovations aligned with green chemistry principles. Mechanistic discussions encompass transesterification, ethoxylation, amidation, sulfonation, and esterification reactions, detailing their key catalytic systems including heterogeneous and enzymatic catalysis and the adoption of environmentally benign methods such as microwave-assisted synthesis. Particular attention is given to non-ionic and anionic surfactants such as fatty acid esters, fatty amides, citric acid esters, and methyl ester sulfonates, highlighting their structure function relationships and biodegradability advantages. Advances in catalysis, including solid base and lipase-based systems, demonstrate high selectivity and yield under mild conditions while minimizing waste generation. Additionally, the valorization of non-edible and waste oils such as jatropha, neem, and used cooking oil supports circular economy objectives by transforming low-value residues into high-performance, biodegradable surfactants. Collectively, the coupling of renewable feedstocks, mechanistic insight, and catalytic optimization establishes a credible framework for developing next-generation surfactants that integrate performance efficiency, ecological compatibility, and economic viability.