Critical retrospection and evaluation of waste engine oil recycling methods

Engine oil is a non-renewable resource; hence, it will be increasingly difficult to find its new reserves in future. As the reserves are getting depleted, the price of oil increases. Depletion of oil reserves have forced the researchers to look for alternate sources as the demand has increased immensely in the last few decades. Also taking into consideration, the enormous environmental pollution caused by disposal of waste engine oil into the environment. Recycling of waste engine oil has provided an effective solution as it will provide time for development of alternate fuels and reusing waste oil will prove to be economical as well. Various methods are currently in practice for recycling of waste engine oil on industrial and commercial level, whereas some methods are still in development stage. These methods have shown different rate of success in engine oil recycling. This review paper will evaluate these recycling methods and present their efficacy rate for comparison. © The Author(s), under exclusive licence to Iranian Society of Environmentalists (IRSEN) and Science and Research Branch, Islamic Azad University 2023.