of a supply curve for biomass that shows the quantities of biomass feedstocks that would potentially be available at various unit costs. Coal was assumed to be available in sufficient quantities at a constant unit cost if used with biomass in thermochemical conversion processes. Quantitative analyses were developed to compare alternative pathways to convert biomass, coal, or combined coal and biomass to liquid transportation fuels using thermochemical technologies. Biochemical technology that produced ethanol from biomass was also evaluated quantitatively on as consistent a basis as possible. Various combinations of biomass feedstocks could, in principle, be converted with either thermochemical or biochemical conversion processes.6 However, rather than examining all possible combinations, the committee first examined the cost of and CO2 emission associated with each of the various thermochemical and biochemical conversion processes by using a generic biomass feedstock with approximately a median cost and biochemical composition (the committee used Miscanthus in the analysis) and then examined the costs, supplies, and CO2 emissions associated with one thermochemical conversion process and one biochemical conversion process that would use each of the different biomass feedstocks. The following assumptions underlie the analyses:
All suitable CRP land is allocated to the growing of biomass for liquid fuels. Conversion plants that use biomass as a feedstock by itself or combined with coal (with 60 percent coal and 40 percent biomass on an energy basis) have the capacity of about 4000 dry tons of biomass per day.
All product prices are free of government subsidies. The total cost of CO2 avoided, which includes the costs of drying, compression, pipelining, and geologic storage of CO2, is estimated to be in the range of $10–15 per tonne.
If a carbon price is imposed, it applies to the entire life-cycle CO2 net emissions—the balance of CO2 removal from the atmosphere by plants, CO2 released in the production of biomass, emissions from conversion of the feedstock to fuel, and emissions from combustion of the fuel. A process that removes more CO2 from the atmosphere than it produces receives a net payment for CO2.