CELLULOSIC AND LIGNOCELLULOSIC STRUCTURAL MATERIALS AND METHODS AND SYSTEMS FOR MANUFACTURING SUCH MATERIALS BY IRRADIATION Abstract Biomass (e.g. plant biomass, animal biomass, and municipal waste biomass) is 10 processed to produce useful products, such as fuels. For example, systems can use feedstock materials, such as cellulosic and/or lignocellulosic materials and/or starchy or sugary materials, to produce ethanol and/or butanol, e.g. by fermentation.