It's not an insurmountable level of effort per person, but if you try to do it on a large scale you inevitably end up with logistical problems, and it would require quite a lot of space.
Edit: strike that I see what you meant there with the a day. I just should have actually read what you wrote before I commented.
Also, they can't even get people to wear a mask or take a shot. Getting all these people to plant trees seems like an insurmountable task.
Actually 20 million trees every 2 days doesn’t sound that ridiculous. Especially as we build more green infrastructure and reduce the daily emissions.
https://www.greenandgrowing.org/how-many-trees-are-planted-e...
If we had an actual price on carbon seaweed production would be a boom industry.
EDIT: After some research I found an interesting article addressing this: https://www.technologyreview.com/2021/09/19/1035889/kelp-car...