Optimization of Physicochemical Properties of Rice Husk, Groundnut, and Coconut Shells Composite Briquettes, Using Cow Bone Catalyst

Abstract

The rising demand for sustainable and cost-effective energy alternatives has heightened research efforts in biomass briquetting, with a particular focus on optimizing physicochemical properties to enhance fuel quality. This study was carried out to enhance and optimize the physicochemical characteristics of composite briquettes produced from readily available agricultural residues. The main objective was to formulate an optimized composite briquette consisting of rice husk, groundnut shell, and coconut shell, augmented by a novel heterogeneous catalyst obtained from bovine bone. A highly pure calcium (II) oxide (CaO) catalyst was effectively synthesized via calcination of bovine bone at 900 °C, with XRD analysis indicating a prominent peak intensity of 1701.99 μ, thereby corroborating the presence and purity of CaO. Briquette formulation was guided by a Simplex Lattice Mixture Design (SLMD), executed with Design Expert 13.0, facilitating a systematic assessment of biomass component interactions and the identification of optimal mixture proportions. Optimization was conducted using dual criteria: reducing ash content and enhancing calorific value. The model determined an optimal mixture consisting of 20% rice fiber, 30% groundnut shell, and 50% coconut shell. This formulation yielded the most advantageous physicochemical properties, attaining a high calorific value of 19.21 MJ/kg and an exceptionally low ash content of 5.61%, reflecting substantial enhancements compared to non-optimized or catalyst-free briquettes. The improved performance affirms the catalytic efficacy of CaO in facilitating more efficient combustion properties and enhancing briquette quality. This study demonstrates that bovine bone serves as an effective, readily available, and economical precursor for the synthesis of high-purity heterogeneous catalysts, thereby supporting waste-to-wealth initiatives and sustainable biofuel generation. The optimized composite briquette not only complies with but also closely correlates with international standards for solid biofuels, providing a practical alternative for domestic and small-scale industrial energy use. Future research may investigate variations in catalyst dosage, emission profiles, and the feasibility of large-scale production to further promote the adoption of catalyst-enhanced biomass briquettes.