[cogitator]

As I understand it, production of ethanol apparently produces prodigious amounts of carbon dioxide in itself (land clearing, manufacture, and use). If taxing fossil fuels becomes a viable option in the future, I think ethanol and other biofuels should be added to the list.

Based on a digested compendium of what I've read, it's fairly clear that corn ethanol doesn't gain much in CO2 "savings". Biomass and cellulosic ethanol should, if the digestion process can become large-scale. So I think it depends on the source.

But large-scale production from algal ponds might be the most efficient.

[Tolerance Sucks Rocks]

But large-scale production from algal ponds might be the most efficient.

You could use captured CO₂ from power plant emissions to force-feed the algae. As I understand it, there is already at least one prototype CO₂ scrubber out there. :-)