engineering wise I can't see why it wouldn't be possible to selectively genetic-engineer some kind of plant or algae or something that sucks up tons and tons of carbon that you can then sequester manually by compressing it into, I don't know, artificial peat or something.
I have no idea why massive factory growing operations for produce aren't everywhere. Every city should have one by now, growing produce locally and shaving down the price of transport and waste to almost nothing.
There’s really no need. Ever heard of an algal bloom? Also happens with jellyfish. On freshwater plants like duckweed do similar things.
Given the right nutrients population explosions happen. Environmentalists usually treat these as bad things but they certainly could be good ways to sink carbon. They could be triggered by fertilizing some of the more barren sections of ocean selected to minimize ecological effect. Quite a lot of the biomass simply falls to the ocean floor and gets buried, it could also be harvested and sequestered another way or used as a biomass fuel.
On freshwater lakes you could grow and harvest duckweed.
Investigate the biochar process as an alternative. You can also buy biochar for your houseplant needs [0]. Creating that much artifical peat in a small area would be a massive fire hazard but probably could be managed.
"Vertical" or indoor farming is one of those silicon valley tropes. VC lost billions during the last decade and I don't know of a single success story that is still going / profitable. I'm sure after enough time passes people forget and will try again.
I have no idea why massive factory growing operations for produce aren't everywhere. Every city should have one by now, growing produce locally and shaving down the price of transport and waste to almost nothing.