Economic assessment of the conversion of bleached eucalyptus Kraft pulp into cellulose nanocrystals in a stand-alone facility via acid and enzymatic hydrolysis

Cellulose nanocrystals (CNCs) have become valued bionanomaterials with enormous potential to bring fundamental changes and benefits to society. We evaluated the techno-economic viability of using sulfuric acid and enzymatic hydrolysis technologies to produce CNCs from bleached eucalyptus Kraft pulp (BEKP) in stand-alone facilities. Experiments were performed on the enzymatic and acid hydrolysis of BEKP and the separation and isolation of the generated CNCs. The results obtained were used to determine reaction yields and compositions through the process stages and to build mass balances for the production of CNCs via acid and enzymatic hydrolysis. We used the process data that were generated to simulate and scale up process models of the production of CNCs using Aspen Plus. Techno-economic analyses of the simulated processes were performed using Aspen Process Economic Analyzer to generate capital and operating cost estimates. At an estimated minimum selling price (MSP) of $10 031/dry tonne of CNCs, the production of CNCs via acid hydrolysis can be technically and economically competitive. Further research and process optimization efforts should focus on low-cost technologies that minimize water use and on sulfuric acid recovery technologies that lead to lower production costs. The production of CNCs via enzymatic hydrolysis requires a low capital investment. However, due to its low reaction yield, a reflection of the still early stage of process development, the production cost of the enzymatic CNCs, with an MSP of $65 740 dry tonne of CNCs t(-1), is too high to be commercially attractive. Nonetheless, the low capital cost of producing CNCs by using enzymatic hydrolysis indicates that the process may be profitable if the enzymatic hydrolysis yield is drastically improved. Research efforts towards developing an enzyme cocktail designed and optimized specifically for CNCs production and the introduction of an efficient and low-cost pretreatment stage prior to enzymatic hydrolysis to increase the accessibility of enzymes to cellulose may improve the hydrolysis yield. (c) 2021 Society of Chemical Industry and John Wiley & Sons, Ltd