The cellulase cost accounts for nearly 25–50% of the total ligno- cellulose bioprocessing cost (Wingren et al., 2003; Zhuang et al., 2004). Therefore, the cost of these three cassava cellulose utiliza- tion scenarios, including the SSF of the untreated cassava residue (Case 1, the Direct SSF) and the pretreated cassava residue