Two of the most significant challenges to the large-scale implementation of biomass torrefaction technology to generate a renewable solid fuel for co-firing in existing coalfired power stations, and thus reducing greenhouse gas emissions from coal power plants, is related to 1) a lack of feedstock flexibility and 2) emissions of biomass torrefaction. In an effort to address these challenges this project will investigate the fundamental relationships that define the influence that biomass feedstock chemical structure and torrefaction process parameters have on 1) the performance of biomass torrefaction; 2) torrefied biomass structure; 3) torrefied biomass fuel properties and 4) torrefaction emissions. Ultimately, this research will be used in efforts to utilize biomass torrefaction for the generation of a renewable solid fuel for optimal coal co-firing and the reduction of carbon emissions from existing coal-fired power plants. This project is a collaboration between three PIs with unique and synergistic expertise and capability in 1) biomass characterization, 2) torrefaction of biomass, and 3) biomass and coal combustion. This project will focus on understanding the chemical evolution in biomass occurring during torrefaction and its effect on torrefied biomass properties; studying the unique emission of torrefied biomass and coal blend combustion; and determining the influence of biomass chemical structure on co-firing emissions.