Environmental Microbiology Reports
The study focuses on converting waste cooking oils into soap and assessing their biodegradation through microbial respiration activity and biological oxygen demand (BOD). The results show effective degradation under both conditions, with anaerobic treatment additionally yielding methane as a valuable biofuel. No toxic effects on sludge microorganisms were observed, confirming the safe integration of these products into treatment processes. Furthermore, we demonstrate that biosurfactants from used oils can be produced at a significantly lower cost (0.12–3.0 EUR/kg) than traditional chemical additives (1–20 EUR/kg). This work highlights a sustainable, cost-effective approach to enhancing microbial performance in WWTPs while supporting circular economy principles.