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Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts
affecting the food supply and costs. Processes for biochemical conversion of cellulosic biomass to ethanol are in the early stages of commercial development, and process improvements are expected over the next decade from evolutionary improvements through commercial experience and from economies of scale as production becomes more widespread and expands to an optimal size. The panel estimated that incremental improvements in biochemical conversion technologies can be expected to reduce nonfeedstock process costs by about 25 percent by 2020 and by 40 percent by 2035. An expanded distribution infrastructure will be required because ethanol cannot be transported in the pipelines used to transport petroleum. Studies should be conducted to identify the infrastructure needed to accommodate increasing volumes of ethanol and to identify and address the challenges of distributing and integrating larger volumes into the fuel system. Research on biochemical pathways for converting biomass to fuels that are more compatible with the current distribution infrastructure could lead to the development of relevant technologies over the next 10–15 years.
If all necessary conversion and distribution infrastructure is in place, 550 million dry tons of biomass can in theory be used to produce up to 2 million barrels per day (30 billion gallons) of gasoline-equivalent fuels. However, potential supply does not translate to actual fuel supply. When the production of corn-grain ethanol was commercialized, U.S. production capacity grew by 25 percent each year over a 6-year period. Assuming that the rate of building cellulosic-ethanol plants exceeds that of corn-grain-ethanol plants by 100 percent, alternative fuels could be added to the U.S. fuel portfolio at a rate of up to 0.5 million barrels of gasoline equivalent per day by 2020 (1 bbl of oil yields about 0.85 bbl of gasoline and diesel). By 2035, up to 1.7 million barrels per day could be produced in this manner, leading to about a 20 percent reduction in oil used for light-duty transportation at current consumption levels.
Technologies for the indirect liquefaction of coal to transportation fuels (gasification with Fischer-Tropsch or a methanol-to-gasoline process) without geologic carbon dioxide (CO2) storage are commercially deployable today, but CO2 life-cycle emission will be more than twice that of petroleum-based fuels. Requiring geologic CO2 storage with these processes would have a relatively small effect on engineering costs and efficiency. However, the viability of geologic CO2 storage