From kitchen to cosmetics: Study on the physicochemical and antioxidant properties of waste cooking oil-derived soap

A large amount of used cooking oil (UCO) is improperly disposed of in sewage and rivers, leading to environmental pollution and posing health risks such as carcinogenic diseases. This study explores an eco-friendly approach to addressing this issue by repurposing UCO for laundry soap production, contributing to waste management and environmental decontamination. The soap was prepared by treating UCO with an alkaline solution (NaOH) through a simple saponification process, providing a greener alternative to traditional methods that rely on imported vegetable oils. The prepared soaps were evaluated for cleansing capacity as well as physical, chemical, and physicochemical properties. The results showed moisture content of 9.27 % to 10.34 %, pH ranging from 6.03 to 4.46, chloride percentage from 0.055 % to 0.29 %, free caustic alkali between 0.152 and 0.175, and total alkali content from 0.29 % to 0.73 %. These values meet the requirements of East African Standards (EAS), validating the quality of UCO-based soaps. By diverting UCO from waste streams and utilizing it in soap production, this approach supports waste management, minimizes environmental pollution, and contributes to sustainable production practices.