Of the "pitch it overboard and let it sink" variety:
ScienceDaily (Feb. 19, 2008) — Imagine a gigantic, inflatable, sausage-like bag capable of storing 160 million tonnes of CO2 -- the equivalent of 2.2 days of current global emissions. Now try to picture that container, measuring up to 100 metres in radius and several kilometres long, resting benignly on the seabed more than 3 kilometres below the ocean's surface.
At first blush, this might appear like science fiction, but it's an idea that gets serious attention from Dr. David Keith, one of Canada's foremost experts on carbon capture and sequestration.
Well, actually, you would pump it through long pipes way out into the middle of the ocean past the steep slopes of the continental shelves and fill up a whack of these long bags on the flat ocean floor and...
Apparently, one of the more workable carbon sequestraion schemes. Dr. Keith's homepage is here.
Funny, nobody has taken up my Carbopult(TM) idea