Plug-in Hybrids a Better Use of Coal = -25% Greenhouse Gas Emissions, Coal-to-Liquids = -6% or +60%
John went over this here, but we wanted to put into stark relief the findings of this recent study from the Carnegie Mellon Electricity Industry Center (CEIC). It concludes that while enacting policies to subsidize the production of coal-to-liquids (CTL) transportation fuel would enhance national security by lowering oil imports, encouraging plug-in hybrids (PHEV) powered by coal-generated electricity is a less costly policy that also reduces oil imports and does more to lower greenhouse gas (GHG) emissions.
Gasoline derived from CTL plants with no CCS could increase GHG emissions from vehicles by almost 60%. If CCS is available, then a reduction of less than 6% could be obtained. It is important to note, once again, that in this best-case CTL scenario, not only is there CCS at the CTL plant, but also a low-carbon electricity source is used for CTL production. This might not be a very realistic assumption, but is presented here to show that at best we could only obtain a very small reduction in GHG emissions following a path of increased CTL production.
Plug-in hybrids look more promising as a pathway for reduction of greenhouse gas (GHG) emissions. Even if coal electricity without carbon capture and sequestration (CCS) is used, plug-in hybrids could lead to a GHG emissions reduction of almost 25%. This demonstrates the worst case for plug-in hybrids, as GHGs would be further reduced with a low-carbon electricity portfolio.
That portfolio including renewables such as solar and wind. Green Car Congress has a good overview here. CTL usually produces diesel, but for the purpose of the study CEIC converted to gasoline and leveraged CTL inputs and outputs data derived by Bechtel in 1993. It bears investigation as to whether there is more recent data which might be based on advances in CTL technology should they exist.
The study compares five scenarios using various combinations of coal-to-liquids (CTL), plug-in hybrids (PHEV) with coal-generated energy and carbon capture and sequestration (CCS):
1) a base case of conventional gasoline
2) CTL gasoline
3) CTL w/ CCS gasoline
4) PHEV coal generation -- bituminous coal in a pulverized coal power plant
5) PHEV coal generation -- integrated gasification combined cycle power plant with carbon capture and sequestration (IGCC w/ CCS)
The results: total well-to-wheel emissions of 264.6 g/mi for the conventional coal-generated scenario; 105.8 g/mi for the scenario with advanced IGCC with CCS). The conventional gasoline baseline in the study was 344 g/mi.