Development and optimization of rice husk composite briquettes as a sustainable cooking energy solution in Nigeria

Abstract

The processing of biomass into fuel briquettes is one of the sustainable measures widely advocated for curtailing deforestation and meeting the energy needs of about 3 billion people living in energy poverty. Improving the efficiency and durability of the briquettes is essential for their effectiveness as an energy source. This paper explores the production, evaluation, and optimization of rice husk briquettes using response surface methodology (RSM). The process variables considered are binder type and ratio, particle size, and dwell time, while the responses are relaxed density and compressive strength. The experiment was designed using Box Behnken design (BBD). Briquettes were produced in a low-pressure (4.5 MPa) hydraulic piston press utilizing 2 novel biomass binders (sweet potato peel and locust bean pulp) and cassava starch. In addition to the optimized responses, the briquettes were characterized for quality and thermal performance. The results range from 0.196 g/cm³ to 0.306 g/cm³ for relaxed density and from 20 kN/m² to 410 kN/m² for compressive strength. Under optimal conditions, 15% binder content, 0.5 min dwell time, and 1 mm particle size could yield briquettes with a relaxed density of 0.30 g/cm³ and a transformed compressive strength of 0.032 m^0.5 s kg^−0.5, equivalent to 918 kN/m². The model’s predictions were validated through confirmatory experiments, with the differences between the predicted and actual values being statistically insignificant at a 95% confidence interval. These findings suggest that rice husk briquettes with an optimal quality for domestic use can be efficiently produced under low pressure, offering a viable solution for energy sustainability and environmental conservation.