impact, and technology status. Coal liquefaction is a potentially important source of alternative liquid transportation fuels, but the technology is capital-intensive. More important, fuel from liquefaction produces about twice the amount of greenhouse gas emissions on a life-cycle basis1 as does petroleum-based gasoline if the process CO2 is vented to the atmosphere. Capture of the process CO2 and its geologic storage in the subsurface, often referred to as carbon capture and storage (CCS), will be required for producing coal-based liquid fuels in a carbon-constrained world. Thus, the viability, costs, and safety of lifetime geologic CO2 storage could be barriers to commercialization.

Biomass is a renewable resource and, if properly produced and converted, can yield biofuels that have lower greenhouse gas emissions than do petroleum-based gasoline and diesel. Biomass production on already-cleared fertile land might compete with food, feed, and fiber production. If ecosystems are cleared directly or indirectly to produce biomass for biofuels, the resulting release of greenhouse gases from the cleared lands could negate for decades to centuries any greenhouse gas benefits of using biofuels. Thus, there are questions about how much biomass could be used for fuel without competing with food, feed, and fiber production to an important degree and without having adverse environmental effects.

STUDY SCOPE AND APPROACH

As part of its America’s Energy Future (AEF) study (see Appendix A), the National Research Council appointed the 16-member Panel on Alternative Liquid Transportation Fuels to assess the potential for using coal and biomass to produce liquid fuels in the United States; provide thorough and consistent analyses of technologies for the production of alternative liquid transportation fuels; and prepare a report addressing the potential for use of coal and biomass to substantially reduce

1

Life-cycle analysis yields an estimate of the emissions that will occur over the life cycle of a fuel. For example, life-cycle estimates cover the period from the time when the resource for the fuel is obtained (from the oil well in the case of petroleum-based gasoline, from the coal mine in the case of coal-to-liquid fuel) to the time when the fuel is combusted. In the case of biomass, the life cycle starts with the growth of biomass in the field and ends when the fuel is combusted. Greenhouse gas emissions that result from indirect land-use change, however, are not included in the estimates of life-cycle greenhouse gas emissions presented in this report.



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