A crash course in changing the world.
My sketch of how it could work.
I started thinking seriously about the kind of scale of intervention that might allow us to get back to 350 ppm CO2, and I did a calculation in this post following our useful discussion. Planetary management is a reality now, we humans are just doing it very badly at the moment. Step up!
Intensive worm beds are fed from inedible green waste scraps. (Lots of research exists about what worms will digest and what their outputs are.) The worm bed needs to be encased in a gas containment membrane to make sure that the greenhouse gas N2O doesn't escape into the atmosphere. (I've emailed some specialists about what kind of technical specification might be necessary for this. I imagine it will need close monitoring and that might be the most labour-intensive part of the project!)
The exhaust air from above the worm beds is drawn out through a treatment chamber (centre of sketch). N2O can be harmlessly decomposed to N2 + O2 through heat or catalysis so something like that is in the treatment chamber. Another option could be purely natural biological treament, for example venting the exhaust gases through beds containing high levels of denitrifying microbes.
The treated air goes out into a greenhouse, which also contains plants growing in the worm casts. Worm casts, the fixed carbon and treated compost that the worms make, is excellent as a growing medium. The air exhaust is monitored a second time when it vents from the greenhouse to make sure we have got rid of the N2O.
Although N2O is a very useful gas - it has medical and propellant applications - the partial pressure will probably be much too low in the outflow from the worm beds to make it possible to harvest it. Any ideas about how to harvest it very welcome!