Global energy consumption will continue to increase, even as the reserves of eas­ily available fossil fuels decline. Until alternative energy sources are developed for transportation, liquid fuels will remain in high demand. Crude oil production will be unable to meet future demands at affordable prices and fuels from renewable feedstocks will play a key role in contributing to the supply of liquid transport fuels.

Lignocellulose is a natural abundant material created by plants from sunlight, nutrients, and CO2 capture. The potential volume of lignocellulose that can be the­oretically produced and harvested is considerable and sufficient to make a major contribution to liquid transport fuel volume. In practice, there are several major chal­lenges to lignocellulosic biomass production, collection, and storage that were not addressed in this chapter but are the focus of research in many projects. Ultimately, the real cost of feedstock delivered to the conversion facility will be a major factor determining the magnitude of success for lignocellulosic biomass. Potential out­put products could include ethanol, butanol, biogasoline, FT liquids, and a range of chemical intermediates. Reaching this potential in an economically acceptable man­ner is a challenge, and requires an improved ability to convert the lignocellulosic feedstock to a useable fuel.

After more than two decades of intensive R&D, several technologies have been evaluated for biofuel production at the laboratory level. A few are now at the stage of advanced testing and pilot-scale evaluations. Presently, the challenges facing com­mercial conversion are such that no one technology has an absolute advantage over the others. The approach of thermochemical pretreatment and enzymatic hydroly­sis followed by microbial fermentation has been the most extensively studied. The remaining challenges for this approach include further lowering pretreatment cost, improving hydrolysis efficiency and cost of cellulases (and hemicellulases), and improving the performance of fermentation organisms. The approach of thermo­chemical gasification combined with FT catalytic conversion has also been widely explored and may be promising under the appropriate conditions. The gasifica­tion approach would benefit from improved gasification efficiency, easier syngas cleanup, and better FT factors such as catalyst selectivity and longevity.

In some projects, various combinations (thermochemical front + biochemical, biochemical front + thermochemical) have been evaluated. For economic operation in an integrated biorefinery, it may be that such combinations of approaches will be required and that the combination utilized will depend on the feedstock, the location, the desired product stream, the degree of environmental impact, and the level of investment available. It is expected that the best technologies for specific challenges will be selected and implemented over the next 5-10 years and that the definitive answer on the size of the contribution from lignocellulosic biomass will become evident during that time.