In some variations, the invention provides a process for producing a microcrystalline cellulose material, comprising: fractionating lignocellulosic biomass feedstock in the presence of an acid, a solvent for lignin, and water, to generate cellulose-rich solids and a liquid containing hemicellulose and lignin； chemically and/or mechanically treating the cellulose-rich solids to form microcrystalline cellulose having an average crystallinity of at least 60%； and recovering the microcrystalline cellulose as a pharmaceutical excipient. The pharmaceutical excipient may function as an antiadherent, a binder, a coating, or a disintegrant. In some embodiments, the pharmaceutical excipient further comprises a lignin-derived lubricant, glidant, sorbent, preservative, or other component. The pharmaceutical excipient may be present in a pill, tablet, capsule, powder, slurry, or other pharmaceutically effective and acceptable form.
