If you can download this file dclversussicl.pdf from the Princeton Environmental Institute (no link) it suggests CTL has well-to-wheels CO2 omissions 80% higher than petrofuels. However I believe this estimate uses optimistic assumptions and the figure is more like the 200% excess attributed to Canadian tar sands. The same kinds of negatives from tar sands also apply to CTL such as water requirements, strip mining, declining EROI and inevitable depletion. Positives are electricity co-generation and the fact the fuel is low in sulphur and aromatics. If you believe we must move towards carbon neutral fuels then CTL has no place.