alt Hacker NewsTrees and seagrass don't really address the sequestration side though, do they?
The carbon they latch onto and temporarily hold onto is still within the land / sea surface +/- a few metres layer.
The current largest scale carbon capture projects are catching a small amount of vented CO2 from LNG projects and pushing that back into the subsurface fields - they only capture 10 ton by releasing over a 100.
We're in need of readily powered true air capture of CO2 then sequestered deep underground.
Things like www.sciencedirect.com/science/article/pii/S036031992602269X have promise.
Trees and seagrass can address the sequestration side.
You can find examples here on Frontier's site of companies that are taking biomass (plant stuff like tree waste) and sequestering it in mines or other storage deep underground.
When thinking about sucking carbon from the sky, I find it useful to separate how I think about grabbing on to carbon dioxide from how to store carbon dioxide, rather than thinking of it as one step. I find it's easy to get lost and either over or undervalue things otherwise.
Plants and trees are excellent at grabbing on, for example, and with a good process they can lead to very cheap methods to store/remove carbon dioxide for a thousand years.