basis,1 coal liquefaction yields about twice the greenhouse gas emissions produced by petroleum-based gasoline when the carbon dioxide (CO2) is vented to the atmosphere. Capturing this CO2 and geologically storing it underground—a process frequently referred to as carbon capture and storage, or CCS—is therefore a requirement for production of coal-based liquid fuels in a carbon-constrained world. However, the viability of CCS, its costs, and its safety could pose a barrier to commercialization.

Biomass is a renewable resource that, if properly produced and converted, can yield biofuels with lower greenhouse gas emissions than petroleum-based gasoline yields. However, biomass production on fertile land already cleared might displace food, feed, or fiber production; moreover, if ecosystems were cleared to produce biomass for biofuels, the accompanying releases of greenhouse gases could negate for decades to centuries any greenhouse gas benefits from the biofuels (Fargione et al., 2008). Thus, there are questions about using biomass for fuel without seriously competing with other crops and without causing adverse environmental impacts.

This chapter assesses the potential for using coal and biomass to produce liquid fuels in the United States; provides consistent analyses of technologies for the production of alternative liquid transportation fuels; and discusses the potential for use of coal and biomass to substantially reduce U.S. dependence on conventional crude oil and also reduce greenhouse gas emissions in the transportation sector. Quantities in this chapter are expressed in the standard units commonly used by biomass producers. Greenhouse gas emissions, however, are expressed in tonnes of CO2 equivalent, as in other chapters in this report. Details of the analyses and numerical estimates presented in this chapter can be found in the America’s Energy Future panel report Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts (NAS-NAE-NRC, 2009).

1

Life-cycle analyses include the “well-to-wheel,” “mine-to-wheel,” or “field-to-wheel” estimates of total greenhouse gas emissions—for example, from the time that the resource for the fuel is obtained from the oil well (in the case of petroleum-based gasoline) or from the coal mine (in the case of coal-to-liquid fuel) to the time that the fuel is combusted. In the case of biomass, the life-cycle analysis starts during the growth of biomass in the field and continues to the time that the fuel is combusted. Greenhouse gas emissions as a result of indirect land-use change, however, are not included in the estimates of greenhouse gas life-cycle emissions presented in this report.



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