In these analyses, the viability of CCS was assumed to have been demonstrated by 2015 so that integrated coal-to-liquid fuel plants could start up by 2020. This assumption is ambitious, and focused and aggressive government action will be needed to make it happen. Four technologies, with and without CCS, were evaluated:
A 50,000 bbl/d plant converting coal into diesel and naphtha using FT and then upgrading the naphtha to gasoline.
A 50,000 bbl/d plant converting coal into gasoline using MTG.
A 4,000 bbl/d plant converting biomass into diesel and naphtha using FT and then upgrading the naphtha to gasoline. The capacity of the plant is limited by the biomass supply of 4,000 dry tons per day.
A 10,000 bbl/d plant converting biomass and coal into gasoline and diesel at a 40:60 ratio by feedstock energy (about 4,000 tons per day of biomass) using FT or MTG.
Some key results of the analysis are given in Table 5.4, and the complete results are contained in the report Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts (NAS-NAE-NRC, 2009). Details of models can be found in Kreutz et al. (2008) and Larson et al. (2008).
Table 5.4 shows that a large-scale coal plant with a 50,000 bbl/d capacity could produce fuels at a cost of about $50–70/bbl of crude oil (or about $60–80/bbl of gasoline equivalent). However, without CCS, the plant’s CO2 emissions would be double those of petroleum-based gasoline on a life-cycle or well-to-wheels basis. Results with MTG are comparable. But even with CCS, both the FT and the MTG process produce low-cost fuels, and the CO2 emissions are similar to those of petroleum gasoline.
The engineering cost of CCS is about $10–15 per tonne of CO2 avoided. The coal-to-liquid plant configurations produce a concentrated stream of CO2 as an integral part of the process, so CO2 capture can be readily and more cheaply achievable than that, for example, in integrated gasification combined-cycle or pulverized-coal plants. The FT and MTG options without CCS are relevant if reduced CO2 emissions are not desired and if energy supply and diversity of supply are the overriding societal issues. However, in a carbon-constrained world, there will be a drive to produce fuels with zero net CO2 emissions. A plant that used combined coal and biomass as a feedstock with CCS could produce