Heating and emission characteristics of briquettes developed from spent coffee grounds

The development of biomass fuels to replace fossil fuels is on the rise, with increased bioenergy research on spent coffee grounds (SCG). However, no biofuel can currently replace anthracite briquettes. Unlike ordinary solid fossil fuels, anthracite briquettes are heated for a long time and retain the same form after combustion, making them easier to transport. In this study, binders are used to develop a solid fuel that allows SCG to retain their shape after combustion. Specifically, bottom ash (BA) and kaolinite clay (KC) are mixed in different ratios then processed with a press machine and cured to produce briquettes that exhibit zero damage, even after combustion. The results show that the optimal composition for SGC briquette production according to fuel quality and ash shape retention is 20 wt.% SCG; 71 wt.% BA; 9 wt.% KC; and 15 wt.% solution with a 20:1 water/Ca(OH)₂ mixing ratio. This results in a low heating value of 15.8 MJ/kg, 86.82% durability before combustion, and 99.46% durability after combustion. In addition, combustion tests with SCG briquettes confirmed their potential as an environmentally friendly alternative fuel to anthracite briquettes.