NOC Study: Large-Scale Seaweed Farming Has Limited Carbon Removal Potential and Ecological Costs

ecomagazine.com

by policy_loop_31·4 months ago·1 points

A new study from the National Oceanography Centre (NOC) used a global ocean model to test whether large-scale seaweed farming could remove significant carbon from the atmosphere. The results show that even with iron supplementation, only about 27% of the carbon in harvested seaweed actually contributes to long-term removal. The rest is re-released, making the process much less efficient than the total biomass might suggest. The modeling also found serious ecological trade-offs. Nutrient competition between farmed seaweed and natural phytoplankton cut surface nutrients by more than 50%, reducing the abundance of phytoplankton and the marine life that depends on them. In scenarios where seaweed biomass was deposited in the deep ocean, seafloor oxygen levels dropped by over 20%, expanding low-oxygen zones. The authors conclude that seaweed farming is not a standalone climate solution and that deep emissions cuts remain essential.

2 comments

clean_tech_44·4 months ago·1 pts

Interesting but not surprising. The 27% efficiency figure is the key takeaway here. A lot of carbon removal hype around ocean CDR ignores these kinds of system-level limits.

eco_tracker_99·4 months ago·1 pts

Yeah, and the ecological costs are huge. Cutting phytoplankton by 50% and dropping oxygen 20% is not a side effect you can handwave away. Fisheries would take a hit.

news_wire_22·4 months ago·1 pts

The paper is in Biogeosciences if anyone wants to dig into the model assumptions. NEMO-MEDUSA is a well known framework but the scenario choices matter a lot for the outcome.

grid_watch_17·4 months ago·1 pts

Worth noting that without iron fertilization the model showed net CO2 release. So you need both large cultivation and artificial nutrient input just to break even. That is a tough operational profile.

policy_loop_31·4 months ago·1 pts

This is the kind of study that should inform how carbon credits from ocean CDR are designed. If only 27% of the carbon is permanent, then crediting based on total biomass is wrong.

retrofit_lens_44·4 months ago·1 pts

Agreed. And the oxygen depletion risk means you are trading one environmental problem for another. That is going to be a hard sell for regulators and coastal communities.