Ravalox writes "With alternate fuel becoming a fairly hot trend in recent months, some academics may have applied their theoretical know-how to give us a practical solution. They offer up the idea that certain types of algae are well-suited to biodiesel production as they are nearly 50 percent oil. The article speculates that large pools could be created to farm out biodiesel from algae in areas near waste streams and salt water. They postulate that to replace our fossil fuel usage it would take only a total of a little over ten thousand square miles, which could fit in an area like the Sonora Desert."
Price tag: estimated $183B capital investment (IMHO, probably pessimistic)
$50B/year operating costs.
This is for replacing all fossil fuels used for transportation purposes with biodiesel.
For more information, go to the report: Widescale Biodiesel Production from Algae
From my reading of the report, this is just about ready for prime time.