A bit energy wonky but interesting: The Oil Drum has a breakdown of a recent Department of Energy presentation on current cost of various renewable fuels and how inexpensive DoE thinks those analyzed might get over the next five years.
What caught my attention most is the state of algae biofuels (mostly because I've been thinking about how we're ever going to be able to keep flying without fossil fuels and algae is one of the few biofuels still in the running without serious land use and/or human rights and/or yield issues).
DoE looked at both triglycerides and finished diesel produced from algae, in either open ponds or photobioreactors.
Let's just look at the finished fuel: Algae diesel produced in open ponds currently is at $10.66 per gallon; from bioreactors it's $19.89 per gallon.
Where DoE thinks we're going: In the most optimistic case, algae diesel from open ponds may get down to $6.10 per gallon, $10 per gallon from bioreactors.
No word on whether these prices are based on full-cost pricing (where all the environmental externalities are accounted for). I suspect not. But for a point of comparison, for gasoline, if you take into all its costs, it really should be about $15 per gallon.