Lignocellulosic Biomass Fractionation and Depolymerization with Sub/Supercritical Fluids

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Development of new environmentally friendly technologies is crucial to generate value-added products from vast lignocellulosic biomass, herein after referred to as biomass. Fluids under sub/supercritical conditions are versatile solvents for biomass processing of agricultural by-products (unmarketable crop straw) and food industry by-products (potato peel). Pressurized liquid (PL, e.g. subcritical water) and supercritical fluids (SCF), such as supercritical water and supercritical carbon dioxide (SC-CO2) provide a green processing platform to obtain new value-added products using fractionation techniques. Recently, the use of PL/SCF as reaction media has attracted attention for depolymerization. Reports have shown that by optimizing the reaction temperature and pressure, hydrolysis can be controlled to achieve targeted value-added compounds for specific applications. However, the reaction mechanisms involved need to be further investigated as well as their activation energy and volume. The applicant's research program to date has focused on the use of subcritical water and SC-CO2 to determine solubility of selected sugars and phenolics, extraction of bioactives, such as phenolics, carbohydrates, artemisinin, etc, as well as reactions in SC-CO2 media and under high pressure assisted by thermal processing, and modeling of phase equilibria of compounds in new solvent mixtures. Future work would therefore continue to build on this expertise by further contributions to novel combined processing development in PL/SCF media. The main objectives of this proposal are to expand fundamental knowledge on solubility behavior of value-added compounds in PL, and to determine how thermodynamic variables and transport properties influence fractionation, reaction, particle formation and the combination of these processes in PL/SCF media to develop further new green technologies to obtain value-added products of biomass that can have a number of uses in food and non-food industrial applications. In the proposed research program, thermodynamic properties, such as solubility will be measured experimentally. Equilibrium studies will allow the selection of optimum pressure and temperature for fractionation and reaction processes. For the reaction process, potato peel and straw will be used where their contents of cellulose, hemicellulose and lignin will be determined before and after treatments with PL/SCF. Novel combination of processes will be experimentally investigated. After fractionation, further depolymerization will be assessed to obtain a diverse range of value-added compounds. Value-added compounds found in hemicellulose can be first removed and then the residues can be converted to value-added compounds through specific reactions or enriching the residue in cellulose. Then, nano-cellulose fiber/crystal will be obtained by novel process development. The overall goal of developing value-added compounds relying on innovative processing technologies will be accomplished through fundamental research at laboratory scale for proof-of-concept. Once the novel process is established, applications involving diverse biomasses of cereal crops will be investigated. Valuable information on the effect of process parameters will be obtained for a batch and semi-continuous system with a future goal to implement it on a continuous system. The use of PL/SCF technology minimizes or eliminates the use of organic solvents and catalysts, thus minimizing environmental impact and meeting the growing demands of environment- and health-conscious consumers as well as boosting Canada’s bioeconomy with the exploration of vast biomass available.