Mature processing technology scenarios for cellulosic biomass will be presented based on detailed computer (ASPEN) models. These include stand-alone production of power, Fischer-Tropsch (FT) fuels, and hydrogen, as well as co-production scenarios involving ethanol-power, ethanol-power-FT fuels, ethanol-hydrogen, ethanol-FT fuels-natural gas, and several of these products in conjunction with feed protein. Working hypotheses will be presented regarding product combinations that are particularly promising from the point of view of economic, thermodynamic, and environmental efficacy. Our results suggest that both the overall attractiveness of biomass processing and the attractiveness of several specific product combinations increase markedly when viewed in the context of mature technology as compared to current technology. In particular, we project that some mature processing technology scenarios will have overall efficiency (heating value of products/heating value of biomass) in excess of 70% and be economically competitive with conventional processes based on fossil resources at prices seen over recent years.