BECCS is probably the most realistic option: https://en.wikipedia.org/wiki/Bio-energy_with_carbon_capture...

... because removing carbon from 99% pure flue gas is a lot easier than removing carbon at 400PPM from the atmosphere.

Even if every bit of farmland on the planet was growing sugarcane for BECCS, we still would only pull ~9GT/y out of the atmosphere, on par with our current net emissions.

Of course, solving climate change is not actually a difficult problem. A $50/ton carbon tax would make all of these things profitable, including CCS on existing natural gas plants.

(source: climate R&D group)