Here's a random idea. Remember the Kyoto Protocol was an international agreement to cut CO2 emissions in an effort to curb global warning? Granted that it's dead now, thanks to the Bush administration (I've never understood what the problem was there), but it was a good idea while it lasted. Back to the point: I had a completely off-the-wall idea as to how net CO2 emissions could be reduced by a country, even if not eliminated.
Recent proposals for a Mars mission have recommended that an away team do not take oxidiser or propellant for the way back, but rather generate them in situ. The preferred way of doing this seems to be to take hydrogen to Mars (it has a low molar mass, so you can take a large amount of it for a relatively small mass), and then use the hydrogen to "crack" the CO2 in the Martian atmosphere to make methane and oxygen, which would be used to fuel the homebound trip. Note that this process:
- generates 1 mole of methane for every 4 moles of hydrogen
- generates 11 kg of reaction mass for each kilogram of hydrogen
- requires some technology to store the generated gases
- is pretty power-hungry.
- electrolyses water to generate hydrogen and oxygen
- stores the oxygen, and uses the hydrogen to "crack" carbon dioxide
- stores the generated methane and oxygen
Advantages over growing forests: methane can be burnt a lot more cleanly than wood can (lower soot output), and the system can be used in areas where vegetation can't be grown easily. Disadvantages: forests look nicer, they can be used to generate secondary income (through visitors etc), they're good for the local ecology, they have lower maintainance requirements and building them doesn't generate pollution. Basically, if I had the choice I'd plant trees rather than use the scrubber.
The sad thing is that I can envision getting governments to adopt the scrubber a lot more easily than getting them to plant extensive forests.