Successful utilization of waste cooking oil in Neem oil based fungicide formulation as an economic and eco-friendly green solvent for sustainable waste management

Globally, about 34.22 million liters of waste cooking oil (WCO) is produced with 2% increments per year. This increase may leads to environmental risks if disposed of untreated. Beneath this backdrop, this study was designed to develop Neem emulsifiable concentrate (EC) formulation (up-to 70% Neem oil content) by utilizing WCO as solvent system. This study opens new gate way to manage the over-rising increments of WCO and give safer and green agriculture product for pest management. The goal was also to explore the economic and industrial feasibility of WCO as alternate source to persistent toxic, non-renewable petroleum solvents. So, processed (transesterified) WCO and aromatic hydrocarbon solvent (C₉) based EC formulations were developed and different physico-chemical properties including physical appearance, acidity/alkalinity, flashpoint, emulsion stability, shelf–life, droplet size, interfacial tension etc were comparatively assessed as per CIPAC (Collaborative International Pesticides Analytical Council) protocols using Abel Flashpoint Apparatus, Particle Size Analyzer, High Performance Liquid Chromatography (HPLC), Fourier Transform Infrared Spectroscopy (FTIR) and Spinning Drop Tensiometer (SDT). Assessment results proved that WCO based formulation is more stable with brown color, low odor, high flashpoint (282.16 K) compared to solvent (C₉) based with less stable (crystallization/sedimentation), light colored, high smell, low flashpoint (268.46 K). Aqueous oil-in-water (O/W) emulsions of WCO and C₉ based formulations were measured with droplet size (2.6 and 3.5 μm) and emulsion stability (79.6 and 98.8%). Interfacial tension reading (0.8 Nmm⁻¹) in WCO based EC indicated good dispersion with no creaming or sedimentation. Furthermore, stability and compatibility study of active constituents recorded of 1.28 and 50% degradation in WCO and solvent based formulations respectively. WCO based EC inhibited 90% where as C₉ based formulations reduced only 68% growth of Rhizoctonia solani. WCO based EC is also free from dermal toxicity, inhalation hazards and phyototoxicity. Finally, average cost effectiveness and economic advantages were calculated and found significantly (60.32%, 1787.5 €t⁻¹) superior to C₉ based EC. Waste cooking oil can be ecologically, economically and commercially explored as an alternate green solvent and resourceful waste management.