Assessing the Potential of Spirogyra as a Sustainable Biodiesel Feedstock: A Systematic Literature Review and Experimental Characterization of Its Fatty Acid Profile

Abstract

Freshwater filamentous algae are increasingly investigated as non-food biomass for renewable fuels, yet evidence on the use of Spirogyra as a biodiesel feedstock remains fragmented across cultivation, extraction, conversion, and fuel-evaluation studies. This study integrated a systematic literature review, a bibliometric analysis, and experimental characterization to assess the research landscape and the potential of Spirogyra sp. as a feedstock. A predefined Scopus search identified 81 records; after removal of one duplicate and three ineligible records, 77 studies were included. Biblioshiny/Bibliometrix and VOSviewer were used to analyze publication trends, thematic structure, and research networks. A dried Spirogyra sp. sample obtained from Cianjur, Indonesia, was characterized for fatty acids according to AOAC 969.33, screened for polycyclic aromatic hydrocarbons, and evaluated by Fourier-transform infrared spectroscopy (FTIR). The literature was dominated by biodiesel, biomass, transesterification, bioethanol, fermentation, fatty acids, pyrolysis, and nutrient-related topics, with publication activity peaking in 2023. The sample contained 31.56% w/w quantified fatty acids on the laboratory’s concentration-in-fat basis, with palmitic acid (C16:0) dominant at 25.54% w/w. Calculated SFA, MUFA, and PUFA totals were 28.78%, 2.39%, and 0.39% w/w, respectively. FTIR bands indicated hydroxyl, aliphatic C-H, carbonyl, and C-O/C-O-C functionalities, consistent with mixed lipid and carbohydrate components but not diagnostic of biodiesel formation. These findings support Spirogyra sp. as a candidate biodiesel feedstock, while confirming that total lipid determination, conversion trials, fuel-quality testing, and sustainability assessment are still required.