Many studies have investigated molecular transport within wood and other types of biomass with computational and experimental methods. Given suitable structural characterization of the macroporosity of wood tissue, often by imaging methods, bulk transport throughout the interconnected pores can be well-described by direct numerical simulation considering the structure explicitly, and coupling this structure to reduced order approximations for bulk transport in porous media . However, characterizing diffusive transport within the cell wall has proven far more challenging largely because the length scale at which intra-cell wall diffusion occurs (~ 10 -5 m) and the difficulty of decoupling intra-cell wall diffusion from bulk diffusion through the macropores precludes most bulk measurement techniques. From a materials perspective, unmodified lignocellulosic cell walls are solid polymers and intra-cell wall transport is expected to be a solid polymer diffusion process , with motions at the atomic scale by the individual polymers in the cell wall together with hydration levels controlling diffusion.