Waste- and Refuse-Derived Fuels: Circular Energy Solutions from Waste Streams

This review explores the potential of waste-derived fuels (WDF) and refuse-derived fuels (RDF) as sustainable alternatives to conventional fossil fuels, addressing both energy recovery and waste management challenges. WDF and RDF are generated from diverse feedstocks—such as municipal solid waste (MSW), industrial by-products, and biomass—via mechanical, thermochemical, and biochemical processing. These fuels can be utilized in cement kilns, power plants, and industrial furnaces, contributing to reduced fossil fuel consumption. The manuscript classifies WDF and RDF into solid, liquid, and gaseous forms, examining their energy characteristics and combustion properties in comparison to coal, diesel, and natural gas. A detailed analysis of calorific value, moisture and ash content, and emissions profiles is provided to assess their performance. The environmental benefits, including decreased landfill usage, methane mitigation, and lower greenhouse gas emissions, are emphasized through life cycle assessments (LCA). Economic aspects such as production costs, energy substitution potential, and global market adoption trends are also discussed. Technological pathways including shredding, drying, gasification, pyrolysis, and anaerobic digestion are analyzed for their efficiency, capital investment requirements, and environmental impacts. The review also highlights current challenges—such as feedstock heterogeneity, emissions control, and public perception—and outlines future prospects enabled by technological advancements, regulatory support, and integration into circular economy frameworks. This comprehensive evaluation positions WDF and RDF as viable contributors to a low-carbon energy future, offering pathways for sustainable waste valorization and renewable energy generation.