Advancements in sludge-to-energy strategies for rubber processing industries: a comprehensive review

This study explores the energy potential of rubber sludge, highlighting its calorific value (13.92–22.15 MJ/kg) and significant organic content, making it a promising feedstock for renewable energy. Techniques such as pyrolysis, anaerobic digestion, combustion, and gasification can effectively harness this potential. Comparative analysis indicates that rubber sludge has an energy recovery potential comparable to or even higher than lignite. Thermochemical processes, including hydrothermal liquefaction and gasification, offer benefits such as reduced waste toxicity and volume, alongside energy and material recovery. However, challenges such as high costs, technical difficulties, and potential pollutant emissions persist. Cost–benefit analyses indicate economic feasibility under specific conditions like high conversion efficiency and favorable policies. Current global practices in rubber sludge management vary, with countries like Denmark, Germany, and Sweden implementing advanced treatments, while others face challenges in coordination and technology. Future research emphasizes improving conversion technologies and integrating hybrid energy systems to enhance energy recovery and reduce environmental impact. The study underscores the importance of life cycle assessments in optimizing the sustainability of rubber sludge-to-energy processes and advocates for innovative approaches through Design Thinking to develop tailored solutions. This comprehensive review highlights the potential of rubber sludge as a renewable energy source and provides a framework for future research and policy development.