Sustainable fuel from agricultural waste: Mixture design optimization of refuse-derived fuel for enhanced energy output

The growing demand for sustainable energy sources drives interest in utilizing agricultural waste for energy production. Refuse-Derived Fuel (RDF) offers a promising opportunity to convert this waste into a valuable alternative fuel comparable to coal. This study employs a statistical approach to identify the optimal combination of mixed agricultural waste for producing RDF while maximizing its energy content. RDF is formulated using empty fruit bunch (EFB), coconut shell (CS), coconut husk (CH) and palm kernel shell (PKS) in varying ratios ranging from 10 % to 50 %, comprising 20 combinations. Moisture content (MC, 5–8 %) was treated as a variable parameter in the model. The proximate analysis of RDF is conducted using a Thermo-Gravimetric Analyzer (TGA) to estimate the Higher Heating Value (HHV). Experimental data are fitted into a linear polynomial model using Design Expert Software V7 with D-optimal analysis to enhance statistical significance. The results indicate that HHV values range from 20.19 MJ/kg to 22.21 MJ/kg, depending on RDF composition and moisture content. Overall, this study highlights the potential of RDF derived from agricultural waste as a viable solid biofuel, providing both energy security and environmental benefits. The findings support the development of sustainable energy solutions by optimizing agricultural waste utilization for cleaner and more efficient fuel production. The model achieved an R 2 of 0.95 with a prediction error below 3 %, confirming its reliability and strong statistical evidence. These findings have practical applications for guiding RDF formulation strategies in industry to maximize calorific value while reducing dependence on coal.