results of the relatively small co-fed coal and biomass plant (total feed, 8000 tons per day) are particularly interesting. Fuels produced by that plant cost about $95/bbl on a gasoline-equivalent basis without CCS, and CO₂ atmospheric releases from plants with CCS are negative. Those results point to the importance of that option in the U.S. energy strategy.

The important influence of CO₂ price on fuel price is shown in Figure 5.6. In reading the graph, it is important to note that it shows the breakdown of all costs, including negative costs such as credit from electricity generation or carbon uptake. These negative costs must be subtracted from the positive ones in order to obtain the actual costs. For example, the cost of biomass-to-liquid fuel with CCS is $151/bbl – $37/bbl = $114/bbl. CO₂ emissions for corn grain ethanol are slightly lower than for gasoline. In contrast, CO₂ emissions of cellulosic ethanol without CCS are close to zero.

Figure 5.6 shows that a CO₂ price of $50 per tonne significantly increases the costs of the fossil-fuel options, including the costs of petroleum-based gasoline. The large amount of CO₂ vented in the coal-to-liquids process without CO₂ storage almost doubles the cost of product once a carbon price of $50 per tonne of CO₂ is imposed. The carbon price brings the cost of biochemical conversion options down to about $110/bbl.