Seaweed is a fast growing plant that can produce many tons of dry mass, while sequestring many tons of CO2 every year. The farming practice is part of the ”Blue economy” that is now being developed around the world. Greenwave is an production oriented initiative that is helping off shore farmers around the US with so called 3D and vertical farming.
In Holland seaweed, or algae grown on manure are allowed in the animal food chain, a company (Ingrepro) produced it a while back but has stopped. Seaweed is better as animal feed, although it can not be super easily digested, it produces less methane. Even mixing in some seaweed can reduce methane emissions.
There are some seaweed initiatives that want to grow the plant on land, that approach is high input, part of the fossil fertilizer economy, and not sustainable. Usually this involves growing high value plants that sometimes have been genetically altered. There certainly is a justification for it.
Then there are number of projects set up with some support of the state, but also because the product has a market.
Over the world there are many seaweed companies popping up now..
Robot seaweed companies are most interesting.
For ocean carbon sequestriation there’s even a website OceanCDR