I once thought long ago, What about pond scum? as in pumping CO2 into algae reactors.
I just looked it up, you Pump CO2 into giant glass solar algae photobioreactors....then you got two options...1) make biodiesel from the algae, or 2) Make it anaerobic and collect the Hydrogen gas. In the first case, the entire cycle would be carbon neutral process to the atmosphere. In the second case, it be carbon reducing. (Not that I'm taking a side on global warming or anything)
I'm not saying that it will be feasable, but I suspect algae reactors would be more energy rich and more efficient to maintain than ethanol production from corn or grass fields.
It might also be possible to do this on the ocean surface somehow, so as not to take up much land area.
Ooh, I like this idea!
A "sea-snake" power production facility, with enclosed algae ponds soaking up sunshine and producing biodiesel.
What's not to like?
made a mistake..#2 wouldn't be carbon reducing...sorry