It sounds like the aluminum is consumed. Aluminum is plentiful stuff, but energetically speaking, it's very costly to refine. I sure hope this goes somewhere, but I'm not holding my breath, all the same.

For all of CO2's bad rap, it is a known quantity, and its effect of the atmosphere is largely non-disruptive. The potential for releasing billions of kgs of hydrogen into the atmosphere, well:

http://www.physlink.com/Reference/AirComposition.cfm

...there isn't much of it, and I'm not sure we can predict what will happen if the amount goes up 100 fold.

Wow - lets hope they pull it off!

carbon is black = bad, hydrogen is clear = good. this is all the science you need.