Improving the Hydrolysis and Fibrillation of Wood Into Cellulose Nanomaterials
Cellulose nanofibrils (CNFs) are nanometer-sized (one billionth of a meter) fibers extracted from lignocellulosic plants, such as trees. They have numerous interesting properties and exciting applications, including super-absorbent materials, electronic components, energy harvesting devices, ink and paint stabilizers, and reinforcements and/or aids for polymers and concrete. The production of these CNFs is often energy-intensive and chemically expensive. Therefore, strategies to improve the processing efficiency of these materials is highly desirable. Forest Service scientists have adopted multiple strategies for facilitating the processing of wood pulp to CNFs. Some of these strategies include high-solids processing, developing and using thermally stable enzymes for high-temperature processing, integrating their production with coproducts, such as sugar streams, for creating fuel and chemical precursors, and other creative processing approaches, such as using postrefining enzyme treatments. For instance, commercial enzyme cocktails adequately hydrolyze cellulose fibers for creating both sugar streams and starting materials for CNFs under moderate temperatures and shear rates, but they are limited in their ability to perform at high temperatures and large shear rates at high solids loadings. The scientists recently produced thermally stable enzymes, which they found suitable for hydrolysis at 90 degrees Celsuis and solid loadings of 20 percent. With the appropriate combination of enzymes, temperature, shear, and additives, the time and energy required to perform the hydrolysis can be greatly decreased. For example, they found synergy between enzymes and surfactants that led to sufficient levels of hydrolysis in about one hour instead of days.