Thermochemical Conversion of Automotive Paint Sludge: A Review

Automotive paint sludge (APS) is a hazardous and non-biodegradable waste generated during the painting process in the automotive sector. Approximately 40% of paint sprayed on automotive parts ends up as waste, resulting in huge amounts of APS generated every year. Its complex composition, which includes heavy metals and other toxic substances, poses significant environmental and health risks if not properly managed. Conventional disposal methods are increasingly unsustainable, necessitating for alternative approached that enable both waste reduction and resource recovery. This review explores existing literature on the thermochemical conversion of APS, with attention on combustion, incineration, pyrolysis and gasification. The paper looks at process performance, operational challenges, product distribution, and environmental implications, while identifying key knowledge gaps and emerging research directions. Thermochemical conversion technologies show potential for APS valorization via the production of syngas, liquid fuels, and char, alongside significant waste volume reduction. However, the high moisture content of APS presents serious difficulties, as it can lead to incomplete combustion, increased hazardous emissions, and the generation of heavy metal-contaminated ash requiring disposal. Mitigation strategies like pre-drying and advanced emission control systems are effective but energy-intensive and economically burdensome. Emerging approaches, particularly co-gasification and co-pyrolysis with high-calorific feedstocks, show promise in overcoming these challenges through synergistic interactions. Thermochemical conversion offers a viable route for sustainable APS management, enabling resource recovery and energy generation while lowering environmental impacts. However, technical and economic constraints associated with feedstock properties and process requirements limit its standalone application. Future research should focus on scale-up feasibility to support the transition of APS thermochemical conversion technologies from laboratory to industrial application, while considering environmental and economic requirements.