Cassava as an additive in biomass fuel pellet production

Abstract: In this study, the effects of using fine milled cassava stems as an additive in biofuel pellet production was compared to the effects of refined starch addition. The bulk biomass fuel raw material, to which the additive was added, was a blend of spruce and pine sawdust. An experimental design in the factors cassava/starch content, moisture content and material temperature was used. Measured responses were pellet bulk density, pellet durability, amount of fines, pelletizer motor current, pellet temperature, die temperature and CV for pelletizer motor current (a measure of process stability). Each response was modeled by multiple linear regression (MLR). Good models were found for pellet bulk density, pellet durability and amount of fines, verified by the model performance indicators R2 and Q2. The effects of cassava stem and starch addition showed strong similarities. Both additives have a weak positive effect on pellet bulk density. Both cassava and starch had positive effect on pellet durability, in particular at low moisture contents (MC) ~11 %. At ~14 % the effect of the cassava stems was less pronounced. The highest durability was achieved at low moisture content (11 % MC) when using cassava as an additive. Both additives have a negative effect on amount of fines. Consequently, results from this study show that cassava stems can be used as a substitute to refined starch for increasing fuel pellet durability.