Mechanical and thermal properties of composite carbonized briquettes developed from cassava (Manihot esculenta) rhizomes and groundnut (Arachis hypogea. L.) stalks with jackfruit (Artocarpus heterophyllus) waste as binder

Abstract

Composite briquettes from agricultural residues are a potential sustainable domestic solid fuel resource. This study aimed to develop and characterize composite briquettes developed from cassava rhizomes and groundnut stalks with jackfruit waste binder as an alternative sustainable fuel for domestic cooking applications. Cassava rhizomes and groundnuts stalks feedstock were carbonized in a step-down kiln under slow pyrolysis conditions at temperatures between 400 and 500 ℃. Thermogravimetric analysis was used to determine the proximate and thermal properties of the developed composite briquettes. Bomb calorimetry was used to determine their heating values. Relaxed density, drop strength and compressive strength results were used to determine the mechanical properties of the developed briquettes. Design of Experiments (Box Behnken design) was used to evaluate the efect of factors (biochar amount, jackfruit waste binder amount, and amount of water) on the mechanical and thermal properties of the developed composite briquettes. The Coats-Redfern kinetic model was used to determine the activation energy for the developed briquettes. Calorifc values and drop strength of developed composite briquettes ranged from 18.1 to 24.0 MJ/kg and 92–99%, respectively. Combustion performance results indicated that ignition temperature increased from 155.1 to 184 ◦C, when heating rate was increased from 10 to 15 ◦C/min. However, burnout temperature decreased from 618.1 to 453 ◦C/min with a similar corresponding increase in heating rate. Optimum biochar amount, amount of water, and jackfruit waste binder amount for optimal mechanical and thermal properties were 89.3%, 893.0 ml, and 29.5 g, respectively. Composite briquettes developed from cassava rhizomes and groundnut stalks with jackfruit waste as binder are suitable potential domestic cooking fuels.