Significantly greater research and development effort in the conversion of ligno — cellulosic biomass, spurred by economic, national security and climate change concerns over the past few years have led to significant strides in development of a fundamental understanding of transport processes that could appreciably

improve overall performance and make renewable liquid transportation fuels sus­tainable and affordable. A thorough understanding of fundamental issues related to transport processes and the development of predictive models that integrate heat, mass and momentum transport are essential to the design, development and imple­mentation of scale-independent processes. Continued synergism between science and engineering disciplines along with participation by industry is crucial to the development of cost-effective alternative motor fuels by 2012 and the significant displacement of fossil-derived fuels specified by the DOE (Energy Independence and Security Act of 2007) EISA for 2022. Improvements in process equipment,

enzymes and microbial systems, as well as improved understanding of the basis for biomass recalcitrance are critical determinants of the successful implementation of biorefineries.

Acknowledgements This work was funded by the US DOE Office of the Biomass Program. The authors also acknowledge the valuable intellectual insights provided by Dr. James McMillan, National Bioenergy Center, National Renewable Energy Laboratory, on issues related to transport processes in biochemical conversion of lignocellulosic biomass.