CO2 is under 0.5%. Concentrating it is energetically expensive, although as energy cost continues down, cracking it may yet prove cheaper than mining and transp

CO2 is under 0.5%. Concentrating it is energetically expensive, although as energy cost continues down, cracking it may yet prove cheaper than mining and transporting CH4. Still, having concentrated CO2, it would be much better to fix it in a form from which it would not immediately be emitted back to the atmosphere, such as graphene, graphite fiber, nanotubes, or a polyester or polypropylene. Most uses also need hydrogen. There will be a great deal of waste oxygen. That might best be dissolved into river water.