[adrianN]

You're joking, but producing biochar is actually a decent way of doing carbon capture that doesn't require any fancy technology. You even get some energy out of it. Unfortunately you'd need to plant absolutely massive amounts of trees to put a dent into the trillion tonnes of CO2 we've released in the last 150 years.

[Twisell]

Also algae could be neat allies. But there we are playing with fire, maybe GMO algae can be engineered to be supper efficient, but at the risk of compromising marine ecosystems.

[knob]

The fern Azolla already did this once! linky --> https://en.wikipedia.org/wiki/Azolla_event

[twic]

There's a lower-tech way to get algae on board - feed them the micronutrients they're limited by in the ocean, which is mostly iron:

https://en.wikipedia.org/wiki/Ocean_fertilization

https://en.wikipedia.org/wiki/Iron_fertilization