Used lubricating oil management options based on life cycle thinking

Used lubricating oil (ULO) is among those difficult-to-handle anthropogenic pollutants due to its toxicity and handling difficulty. The selection of proper abatement technologies for ULO depends significantly on the appropriateness of the technology not only in technical terms, but also in environmental points of view. In the present work, six management scenarios for the management of ULO were evaluated for their environmental impacts based on life cycle approach. Two of them, i.e. acid clay and solvent extraction are the treatment processes for the recovery of ULO and the main product from these processes is recycled used oil. The other four scenarios, i.e. small boiler, vaporizing burner boiler, atomizing burner boiler, and cement kiln, are to generate energy from ULO. Emissions were characterized into four environmental impact categories: global warming potential, acidification potential, eutrophication potential, and heavy metals. The acid clay process, which has generally been believed to generate high environmental load, actually produced high environmental impact only in terms of acidification. Cement kiln created the lowest impact in terms of global warming potential and heavy metals. This was due to high temperature in cement kiln which could rightly allow the complete combustion of organic compounds in ULO whereas other contaminants such as heavy metals were captured in mortar during the cement reaction.