Recent Advances in Refining of Waste Lubricating Oil: A Comprehensive Review

ABSTRACT

Used lubricating oil (waste lubricating oil [WLO]) is a hazardous waste generated across numerous industrial and transportation sectors, requiring appropriate management to minimize its environmental impact. Improper handling or disposal can lead to significant contamination of soil and water resources. During service, lubricating oils undergo thermal degradation, oxidation, and contamination, resulting in the accumulation of hazardous constituents, including heavy metals, sulfur‐ and chlorine‐containing compounds, as well as toxic organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). These contaminants pose considerable risks to both ecosystems and human health. Given the increasing quantities of WLO generated worldwide and the environmental challenges associated with its disposal, there is growing interest in developing sustainable technologies for its recovery, re‐refining, regeneration, and conversion into valuable products.