Closing the Loop: Valorization of Industrial Fats, Oils, and Grease as a Biodiesel Source

Guided by circular economy principles, this research presents a novel approach to biodiesel production. We explore the use of fats, oils, and grease (FOG) extracted from a food processing plant’s grease trap as a biodiesel source. The FOG underwent treatment using sulfuric acid (H₂SO₄) obtained from discarded lead-acid batteries, effectively reducing its acidity level from 8.4 mg NaOH/g to 0.65 mg NaOH/g. The transesterification process, optimized using Central Composite Design (CCD) with Design Expert 7.0 software, identified optimum conditions for biodiesel production: an 8:1 ratio of methanol to oil, a catalyst loading of 0.3 g, and a reaction time of 40 min, resulting in a yield of 84.21 ± 1.54%. Analysis revealed promising characteristics such as a density of 0.86 g/cm³, a high heating value (HHV) of 41.9 MJ/kg, and a viscosity ranging from 1.5 to 1.9 mm²/s. FTIR spectroscopy confirmed the presence of functional groups suitable for biodiesel production, and the fatty acid methyl ester (FAME) composition analysis indicated substantial amounts of oleic and stearic acids. These findings demonstrate a 5–10% increase in biodiesel yield over conventional methods, underscoring the study’s advances in resource efficiency and sustainable energy production.