(278c) Using Aqueous Renewable Solvents to Recover Lignin from Hybrid Poplar Lignin Cake

As biorefineries push closer to commercial viability, maximizing the usable yield of biomass is imperative for competing with traditional non-renewable alternatives. Lignin, as the only abundant aromatic biopolymer found in nature, can be used as a precursor in place of petrochemicals for applications such as carbon fibers, polyurethane foams, and activated carbon. Biomass from the hybrid poplar tree, a hardwood, has been targeted as a biorefinery feed crop, as it grows rapidly, is low maintenance, and has a high energy return. A by-product of enzymatic ethanol production from woody biomass, lignin cake, contains about 65% lignin, 35% sugars, and less than 1% ash by weight. To our knowledge, little research has been devoted to the purification of this lignin-rich waste stream. Thus, the proposed uses for lignin cake (aside from incineration for power generation) are scarce. Using renewable organic solvents with sulfuric acid as a catalyst, a high-purity lignin with very low ash and sugar content has been recovered from the impure lignin cake stream. The renewable solvents acetic acid and ethanol were used to dissolve the lignin, with the remaining solids being filtered out. Ash, glucose, and xylose content were measured via HPLC to determine the purity of the recovered lignin stream. Absolute (vs. relative by GPC) molecular weight was measured via SEC-MALS to determine the best application for the lignin fraction. Results for one of the applications delineated above will be presented.