Comparative life-cycle assessment of traditional and emerging oily sludge treatment approaches

This study presents a comparative life cycle assessment (LCA) of traditional and emerging treatment approaches for hazardous refinery oily sludge handling. Two traditional oily sludge disposal approaches, including incineration and landfilling, and two emerging energy recovery approaches, including solvent extraction and pyrolysis, were investigated. Life cycle inventories listing all energy and material flows were established for the two emerging treatment approaches, and the life cycle environmental impacts were assessed by following the International Organization for Standardization (ISO) 14040 procedure. The TRACI 2.1 method and Ecoinvent 3 database were used in the LCA. The results show that the two emerging energy recovery approaches only account for <10% of the total impacts posed by the traditional alternatives. Traditional oily sludge treatment approaches are generally associated with relatively high global warming potential, ecotoxicity, and adverse human health effects. Solvent extraction has the lowest total effect on the environment, and the main adverse effects are related to ecotoxicity and fossil fuel depletion. In solvent extraction treatment, vacuum distillation and combustion of recovered oil account for the main impacts. In pyrolysis treatment, processes such as drying, pyrolysis, and combustion of pyrolysis products are the main contributors to the total impact. The energy recovery processes used in the two emerging approaches can significantly offset the total adverse impacts. The two energy recovery approaches have great potential to be used for low-impact oily sludge treatment.