Lignocellulosic bioplastics and composites, and methods for forming and use thereof

A method comprising:

• (a) subjecting a biomass to a first chemical treatment by immersing the biomass in a first solution comprising a deep eutectic solvent that comprises choline chloride and oxalic acid, the biomass comprising an intertwined structure of lignin, hemicellulose, and cellulose, the intertwined structure being comprised of microbundles having a cross-sectional diameter of at least 50 μm, the first chemical treatment being effective to dissolve the lignin in the biomass and to fibrillate the cellulose into microfibrils, nanofibrils, or both microfibrils and nanofibrils;
• (b) after (a), adding one or more second chemicals to the first solution and then mechanically agitating for a predetermined time such that at least some of the dissolved lignin is in situ regenerated, the regenerated lignin being deposited on the cellulose microfibrils and/or nanofibrils and forming hydrogen bonds between adjacent ones of the cellulose microfibrils and/or nanofibrils;
• (c) after (b), removing the deep eutectic solvent from the first solution while retaining the regenerated lignin and cellulose microfibrils and/or nanofibrils in the first solution so as to form a slurry of lignin-cellulose solids in solution;
• and
• (d) after (c), drying the slurry to form a solid lignocellulosic bioplastic from the lignin-cellulose solids, the bioplastic comprising an interconnected network formed by the cellulose microfibrils and/or nanofibrils bound together by the regenerated lignin.