Recycling and Regeneration of Used Lubricating Oils
Summary
Used lubricating oils represent both an environmental hazard and a valuable resource. After prolonged service in engines and machinery, oils accumulate sludge, metallic wear particles, oxidised compounds and fuel residues, all of which degrade performance and may harm ecosystems if oils are mismanaged. Recycling and regeneration aim to recover base oils and additives for reuse, closing the loop on a critical non-renewable resource. Core processes include physical separation (settling, centrifugation), chemical treatments (solvent extraction, acid activation), adsorption (clays, activated carbons), thermal methods (vacuum distillation, catalytic hydrogenation) and emerging membrane techniques. These approaches remove contaminants, restore viscosity and thermal stability, and rebuild additive packages. Beyond technical refinements, life-cycle analyses and circular-economy strategies guide collection networks, logistics and process selection to balance environmental impacts, energy demands and economic viability. Globally, re-refining delivers significant reductions in greenhouse-gas emissions, conserves crude oil, and mitigates soil and water pollution, supporting sustainable industrial growth and regulatory compliance.
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Recycling and Regeneration of Used Lubricating Oils publication trend
The graph below shows the total number of articles in recycling and regeneration of used lubricating oils across all publications each year (not limited to Nature Index journals).
Technical terms
Re-refining: Recycling process that removes contaminants from spent lubricants to regenerate base oils suitable for fresh formulations.
Ultrafiltration Membrane: Porous polymeric barrier that separates high-molecular-weight degradation products and particles from oil under pressure.
Acid–clay Treatment: Re-refining method using acid-activated clay adsorbents to capture polar impurities, water and metallic residues.
Base Oil: Primary lubricating fraction obtained after purification, serving as feedstock for additive blending.
Total Base Number (TBN): Measure of alkaline reserve in oil, indicating its capacity to neutralise acidic degradation products.
Life Cycle Assessment (LCA): Holistic evaluation of environmental impacts from resource extraction through disposal for a given process or product.
References
- Polyacrylonitrile Ultrafiltration Membrane for Separation of Used Engine Oil. Polymers (2024).
- Life Cycle Assessment of Different Waste Lubrication Oil Management Options in Serbia. Applied Sciences (2021).
- Assessment of the Conventional Acid‐Clay Method in Reclaiming Waste Crankcase Lubricating Oil. Advances in Tribology (2023).
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