Optimizing selected quality metrics of rice husk briquettes: a response surface methodology approach

Abstract

Rice husk is among the most generated biomass residues in developing countries. If this abundant resource is effectively valorized into fuel briquettes, the rate of deforestation and energy deficit in the region would be substantially reduced. In this paper, a process-based modeling was employed to optimize the quality metrics of briquettes made from rice husk as a measure of improving its efficiency and sustainability as an energy source. Two novel bio-binders (locust bean pulp and sweet potato peel) were assessed alongside cassava starch using a low-pressure technique. The experiment was designed using Box Behnken Design (BBD) in Design Expert 13 and Response Surface Methodology (RSM) was employed in optimizing the process metrics and response variables. A confirmatory test was employed to validate the optimal conditions. From the experimental results obtained, the compressed density is between 0.495 and 0.691 g/cm3, while the impact resistance is between 12.5 and 100%. The optimum process metrics predicted by the model are a 15% binder ratio, 1.1-mm-particle size rice husk, 0.5-min dwell time, and cassava starch binder. The optimal predicted responses are 0.689 g/cm3 compressed density and 109.6% impact resistance. The differences between the experimented and predicted values were statistically insignificant at a 95% confidence interval. Thus, the study affirms that under the above optimum conditions, rice husk briquettes suitable for domestic application can be sustainably produced. The above findings can serve as a reference in future studies and applications involving briquette production.