Fuel Characteristics of Coconut Shell and Spent Coffee Ground Briquettes Prepared with Different Binders

Abstract

Coconut shells and spent coffee grounds are biomass residues with potential for conversion into solid fuels through carbonization and densification. Binder selection plays an important role in determining the physical and fuel properties of biomass briquettes. This study evaluated the characteristics of coconut shell and spent coffee ground briquettes prepared using four different binders: tapioca starch, corn starch, poly(vinyl alcohol) (PVA), and Gohsenx Z-200. The raw materials were carbonized at 400 °C for 1 h, ground, and sieved to a particle size of 60 mesh. Coconut shell charcoal and carbonized spent coffee grounds were mixed at a mass ratio of 3:2. The mixture was combined with a 25% binder solution, compacted at 2 ton/cm², and subsequently dried. The resulting briquettes were characterized in terms of moisture content, ash content, volatile matter, fixed carbon, density, and calorific value. The moisture content, ash content, volatile matter, fixed carbon, apparent density, and gross calorific value ranged from 6.60–7.13%, 0.79–1.76%, 0.79–0.92%, 97.45–98.38%, 1.00–1.22 g/cm³, and 6159–6314 cal/g, respectively. Among the tested formulations, tapioca-starch briquettes produced the highest observed gross calorific value of 6314 cal/g and apparent density of 1.22 g/cm³, whereas corn-starch briquettes produced the lowest moisture and ash contents. Therefore, binder performance depended on the selected evaluation criterion, and no single binder demonstrated the best performance for all measured properties.