Efficient solid fuel combustion models use semi-global mechanisms with effective parameters, traditionally derived from a small set of reference fuels and conditions. This limits their transferability. Atomistic simulations can compute thermodynamic properties such as reaction enthalpies and adsorption energies. This enables the determination of rate coefficients for elementary reaction steps and diffusion constants across a broad range of temperatures and pressures, including those inaccessible to experiments. Unlike empirical data tied to specific fuels, kinetic parameters from simulations depend on molecular composition and structure. This allows for seamless kinetic models applicable to different solid fuels. Computational results on diffusion and adsorption also complement experiments, aiding the development of improved sorption models. To achieve this, various computational chemistry tools are employed. Char models are built using reactive and non-reactive molecular dynamics. Small molecule diffusivity is isolated via non-reactive simulations, while reactive dynamics combined with molecular graph analysis are used to identify possible reaction pathways. Accurate electronic structure methods are used to compute rate coefficients.