The primary goal of the proposed work is to study and understand using both experimental and computational approaches, the depolymerization of lignin generated during the ionic liquid (IL) pretreatment-based lignocellulosic biofuel production process and valorization of the degraded products as value-added chemicals. Lignin is a complex biopolymer, holding together cellulose and hemicelluloses and forming a recalcitrant matrix. At the Joint BioEnergy Institute (JBEI), we are focused on IL-pretreatment based lignocellulosic biofuel production, where lignin is generated as a byproduct. To improve the economic viability of current lignocellulose-based biofuel technology, lignin upgrading and valorization is needed. The ability of certain ILs to dissolve cellulose and/or lignin enables the possibility of commercial lignin upgrading and valorization to improve overall biorefinery economics. However, currently, the depolymerization mechanisms of lignin in ILs is not well understood. In our ongoing work with EMSL using lignin model compounds and alkaline lignin, we are studying lignin depolymerization in a variety of ILs. We will use the mechanistic understanding gathered in this work as our baseline for the study and development of efficient depolymerization method for the lignin stream generated during lignocellulosic biofuel production process using IL-pretreatment technology. We will explore various techniques such as high pressure, catalysis, etc. to integrate with our current technology to maximize lignin depolymerization rates and product yield. We will leverage EMSLs expertise in mass, NMR and EPR spectroscopic techniques to evaluate and optimize the depolymerization process and a comprehensive library of analytical data for lignin depolymerization products will be developed. We will also develop new applications for polymeric, oligomeric and depolymerized monomeric lignin utilizing the analytical tools developed at EMSL. Understanding the mechanism of lignin depolymerization and identification of intrinsic reaction intermediates and products is essential for the accurate quantification of depolymerization of lignin. In parallel to the experimental study, the proposal also details a theoretical investigation of the depolymerization process and mapping the products using QM calculations.