Mild pyrolysis, or torrefaction, is a thermochemical pretreatment for biomass used to address these issues. In this process, biomass is heated in an oxygen-free environment at temperatures of 200-300°C. Torrefaction of biomass increases the brittleness of the material, thus reducing the energy requirements for grinding it. Grinding of biomass is important for applications such as pyrolysis and gasification, where particle size is critical for efficiency. In this study, torrefied corn stover and untreated corn stover were ground using a ball mill reactor. The ground material was then sieved to determine the particle size distribution of the respective materials. The particle size distribution was used to quantify the effect of torrefaction on grinding biomass. The torrefaction process increased the brittleness of the corn stover, yielding a more finely ground material than the untreated biomass. The final objective was to combine the torrefaction and particle size reduction stages into a single process. A limiting factor in the torrefaction process is heat transfer through large particles. By combining the torrefaction and particle size reduction stages, a more uniform final product can be created.