Innovative Use of Fly Ash as a Free Fatty Acid Reducer in Used Cooking Oil for Enhanced Biodiesel Production

High free fatty acid (FFA) levels in used cooking oil (UCO) hinder biodiesel production by reducing yield and complicating purification due to soap formation during transesterification. Traditional FFA reduction methods, such as acid-catalyzed esterification, have environmental and cost drawbacks. This study explores the use of activated fly ash, a coal combustion byproduct, as an eco-friendly, low-cost adsorbent for FFA reduction. Fly ash was treated with NaOH to enhance adsorption capacity, with effects of reaction time (1–4 hours) and adsorbent mass (1–5 grams) evaluated. Results showed that longer reaction times and higher fly ash masses significantly reduced FFA content, reaching equilibrium at extended times and higher masses. A power-law kinetic model (R² = 0.9895) confirmed the accuracy of FFA degradation data. The study concludes that activated fly ash offers a viable solution for improving biodiesel efficiency by repurposing industrial waste, supporting both renewable energy production and waste management.