Tribological Applications of Recycled and Waste Materials: A Review of Recent Advances and Future Directions

Conventional tribological materials such as metals, ceramics, and synthetic polymers demand energy-intensive processing and create end-of-life waste. This motivates the search for more sustainable alternatives. Recent research demonstrates that agricultural residues, industrial by-products, post-consumer waste, and recycled polymers can be engineered into tribological systems that provide competitive wear resistance, stable friction, and multifunctional benefits, including thermal dissipation and vibration damping. This review summarizes progress across these material categories, highlighting how fillers like rice husk ash, fly ash, tire-derived carbon black, and reprocessed plastics transition from low-value waste into high-performance tribomaterials. System-level strategies such as interface engineering, hybrid reinforcement, and advanced processing are essential for overcoming material variability and achieving reliable tribological performance. In parallel, optimization approaches, including predictive modeling and smart material design, are increasingly enabling improved consistency, reproducibility, and scalability. Applications in automotive braking systems, recycled carbon black composites, acoustic damping structures, coatings, and reinforced polymers confirm the industrial viability of waste-derived materials. While challenges remain in feedstock variability, standardization, and long-term durability, these developments point to waste-based tribology as a practical pathway toward circular economy solutions that unite sustainability with engineering performance.