An overview of waste lubricant oil management system: Physicochemical characterization contribution for its improvement

Waste lubricant oil (WLO) management systems across Europe can be very heterogeneous, with significant discrepancies in their performance. The objectives towards a circular economy represent a challenge to continuously maximize the collection and regeneration of this hazardous waste. The quality of WLO is a limiting factor towards its potential for regeneration, in which producers have a great responsibility on the handling phase. In this context, the main objectives of this work are the evaluation and improvement of a national management system, based on the physicochemical characteristics of WLO collected by different producers (garage, industry and others). Data of critical parameters (sediments, water, chlorine and PCB) of 30,242 samples collected from 2008 to 2015 were analyzed. About 4.8% of those samples exceeded the Portuguese regulatory limit regarding sediments (3 wt %) and 22.3% for water plus sediments (8 wt %). On the contrary, 0.73% of the samples did not comply with the limit of chlorine (2000 ppm) and only 0.08% for PCB (50 ppm). Chlorine nonconformities were mostly registered in industrial producers. In addition, 60 samples collected in 2015 were characterized regarding other important properties, namely density, kinematic viscosity at 40 °C, total acid number, saponification number, elemental analysis and functional groups. These results gave important clues about the performance of the different producers. In particular, FTIR analysis revealed that about 60% of the samples may be contaminated with glycol compounds regardless the type of producer. The overall management system can be improved by preventing contamination with chlorine from industry WLO or glycol-containing compounds (such as brake fluid and antifreeze) for all producers.