[Evaluation of the cellulase cost during the cassava cellulose ethanol fermentation process].

Cellulose takes nearly 10% (W/W) dry weight of cassava tubers. In this study, the cellulase cost of different ethanol fermentation from cassava cellulose was evaluated. The processes include the direct saccharification and fermentation of original cassava cellulose residues, the direct saccharification and fermentation of pretreated cassava cellulose residues, and the simultaneous co-saccharification and fermentation of cassava starch and cassava cellulose. The results show that the cassava cellulose utilization in the first two processes were low with the enzyme cost of 13 602 and 11 659 RMB Yuan per tone of ethanol, respectively. In the third process, the final ethanol concentration increased from 101.5 g/L to 107.0 g/L when cassava cellulose and cassava starch were saccharified simultaneously. Comparing to the first two processes, the third one demonstrated the lowest enzyme cost at 3 589 RMB Yuan per ton of ethanol, which was less than the ethanol price and no additional equipment and operation cost input were added. The conclusion provided a practical way of cassava cellulose utilization in cassava ethanol industry.

Cost analysis of cassava cellulose utilization scenarios for ethanol production on flowsheet simulation platform.

Cassava cellulose accounts for one quarter of cassava residues and its utilization is important for improving the efficiency and profit in commercial scale cassava ethanol industry. In this study, three scenarios of cassava cellulose utilization for ethanol production were experimentally tested under same conditions and equipment. Based on the experimental results, a rigorous flowsheet simulation model was established on Aspen plus platform and the cost of cellulase enzyme and steam energy in the three cases was calculated. The results show that the simultaneous co-saccharification of cassava starch/cellulose and ethanol fermentation process (Co-SSF) provided a cost effective option of cassava cellulose utilization for ethanol production, while the utilization of cassava cellulose from cassava ethanol fermentation residues was not economically sound. Comparing to the current fuel ethanol selling price, the Co-SSF process may provide an important choice for enhancing cassava ethanol production efficiency and profit in commercial scale.