Improving the Quality of Agricultural Wastes for Solid Fuels Employing Torrefaction: A Case Study in Indonesia

Using biomass as a fuel has some limitations, including high moisture and volatile contents, low energy density, and easily degraded. Furthermore, torrefaction can be used as a pretreatment to reduce the weakness. The process is pyrolysis at low temperatures. Therefore, the aim of this study is to improve the quality of biomass using torrefaction. Three biomass samples were used: rice husk, cocoa pod shell, and sawdust. The results showed that rice husk has the lowest bulk density, while the highest is the cocoa pod shell. Sawdust possesses the highest mass yield, while the energy yield of cocoa husk is the highest. The torrefaction reduced the moisture and volatile contents, thereby increasing the fixed carbon and heating value. The results also showed that rice husk has the highest ash content before and after torrefaction. Furthermore, the samples changed from hydrophilic to hydrophobic with reduced reactivity. Also, the raw and torrefied rice husks had the highest residue after combustion, while the lowest was found in sawdust. Finally, the cocoa pod shell had the lowest combustion temperature, while the highest was found in the torrefied sawdust.