When you have too many lemons, make lemonade. Instead of a "carbon tax", why not incentivize something really useful, like a space elevator? How about a tax paid in carbon fiber nanotubules strong enough to make such a space elevator: http://en.wikipedia.org/wiki/Space_elevator If such an elevator were built in the form of a tube, it would be the world's tallest smokestack. Yes, you would probably have to pressurize the tube in order to lift the gasses inside, but that could be done relatively efficiently at ground level. Since the pressure would decrease with increasing height, the highest pressure would occur at the bottom, so there should be not problem with the pressure higher up. Presumably, other types of waste -- perhaps even radioactive waste -- could possibly be "sequestered" in space the same way. --- I noticed that 1) all of the proposals involve starting the elevator cable at the ground or some high tower, and 2) the exponential taper means that even small increases in elevation of the base of the elevator help a lot. So, why not start from a balloon which is itself tethered -- alternatively, include balloons along the lower portions of the elevator to increase the effective height of the beginning of the elevator ? Weather & winds would affect the balloons, but some sort of active station-keeping scheme could be used, because it could now be powered from the ground (most of the other proposals don't have enough lifting capacity to include a power cable from the ground).