Scale and Skepticism: Seaweed-Based Carbon Dioxide Removal
Scale and Skepticism: Seaweed-Based Carbon Dioxide Removal
by Paddy (Patricia) Estridge, CEO of Seaweed Generation.
The appeal of growing seaweed for CDR is obvious - it grows fast in the ocean, which covers the majority of the planet, without the need for freshwater or land. The potential scale is perhaps best captured by Antoine de Ramon N’Yert and his team at the University of the South Pacific, who estimated that 9% of the world’s ocean dedicated to seaweed cultivation could draw down 53 billion tonnes of CO2 a year.
Coupled with the existing capacity of the deep ocean for long-term carbon storage, and the fact that all oil was once ocean biomass, you’d be hard-pressed to find a solution that is more scalable and more aligned with Earth's natural systems.
Legitimate and vitally important skepticism largely boils down to three main areas: cost, environmental impacts and the CDR market itself.
Cost
Cost concerns are often bundled with observations such as ‘seaweed is too valuable to sink and must be used for other purposes’. But the pursuit of CDR with seaweed can be on the same track as pursuing large-scale seaweed cultivation for any industrial purpose.
All seaweeds have very different properties and are useful for different purposes. Roughly speaking the current price (approx $2,500) for a tonne of wet Kelp would begin to be economically competitive for industrial use cases with a price reduction of around 5-10x for bulk animal feeds, 8-12x for fertilisers, 50-100x for bioplastics, 70-120x for biofuels and 100-150x for CDR.
Seaweed cultivation is still at a very early stage. It has only existed on a commercial scale since the 1950’s, after British Phycologist Kathleen Mary Drew-Baker published groundbreaking research on the red algae, Porphyra Umbilicalis, which is used to make Nori. Today, around 11 species of seaweed (of a known 11,000) have been domesticated sufficiently for cultivation.
Coupled with technological developments using automation and AI, it is not difficult to imagine that the costs of cultivation will dramatically reduce in the near term. Add to that scale increases offered by remote monitoring and the expansion of seaweed cultivation into both near and far coastal areas (such as wind farms) and there is a high likelihood that cost decreases will be exponential.
Environmental Impacts
CDR with seaweed operates within complex ecosystems. At the very least, the impacts on the surface ocean ecology need to be deeply understood. If the seaweed is being sunk, then the deep ocean must be closely monitored, and, if (like us), you are dealing with seaweed that also impacts coastlines, then coastal areas must also be observed. Whilst this data gathering adds significant short-term costs, there is tremendous value (outside of CDR) in expanding our capabilities of ocean observation, from the surface to the deep.
At SeaGen, our starting point is existing problematic seaweed (Sargassum) in the Great Atlantic Sargassum Belt, working hand in hand with impacted nations. This allows us to develop solutions for environmental monitoring and sinking seaweed, whilst reducing an existing problem and starting to answer crucial questions about ecosystem impacts.
Observing the Surface
Worries about displacing other nutrient users, especially plankton, are common for all large-scale seaweed efforts. Yet, there’s evidence to suggest that seaweed cultivation can increase biodiversity and create positive feedback loops when done correctly. Ironically, the huge biodiversity abundance of old oil rigs offers us an idea of what might be possible in offshore environments. As does the Sargasso Sea, a biodiversity hotspot driven by floating seaweed in the Northern Central Atlantic, which has been in situ for many millennia.
The vast expanses of the ocean, which we consider to be largely lifeless, would likely be able to support (and propagate) significant marine life if they had something semi-permanent upon which to grow.
I call this idea ‘Generative Aquaculture’, as in, Aquaculture that generates biodiversity improvements that weren’t there before.
Observing the Deep
In the deep ocean, the ability to take baseline measurements, accurately model currents, and continue with ongoing measurements over time, will be crucial. Both for proving that carbon remains out of the fast carbon cycle and that there is no unacceptable side effect to sinking additional biomass.
Whilst close observation and measurement are vital, especially to establish the amounts of additional biomass that could be sunk without causing harm, it is unlikely that deep ocean (which contains 16x more carbon than the terrestrial sphere and atmosphere combined) ecologies would be harmed by small amounts of additional biomass. Indeed, they might actually be stimulated by additional food and energy.
The current consensus is that small-scale testing to answer these questions is the most pressing part of the sinking conundrum.
The CDR Market
Last but not least, is uncertainty in the CDR market itself. This poses the biggest barrier to seaweed (and all other) forms of CDR, and has proven to be a blocker to many fundraising efforts in recent months.
If you zoom out, the CDR market and the future of the planet are so closely aligned, that it is difficult to imagine the market failing to manifest in the next decade. EU legislation is moving at pace in this area, and other regions are likely to swiftly follow. With any market, there will be boom and bust cycles as investor excitement outpaces the market. However, much like the dot-com bubble, the future market leaders are likely to be those who get an early start and pull through tough times.
The real question isn't whether the CDR market will become more certain, but rather, who among the current operators is efficient enough to not only survive but also progress and thrive in the face of this uncertainty.
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I am all for 'all of the above' solutions to CDR, but skeptical of Bio/Nature enhanced CCS such as seaweed farming...
Exhibit A in my case is that *ALL* the explosion of the plant life /photosynthesis even human agriculture that occurs Spring ->Winter causes only a ~5ppm annual wiggle on the CO2 Keeling curve which , as we all know, is at 430ppm and climbing fast. Most of this plant life including seaweed, sargassum etc is on Land -and near the continental shelf in the Oceans - which is where the nutrient minerals upwell to the surface - and most of that is in the Northern Hemisphere. (the Amazon forests straddle the Equator, and Southern Ocean, have little life except around Antarctica, again continental shelf). If 5ppm ~ 1% oscillation on CO2 levels is all Nature/Spring can do with ~50% of the entire Earth to work with , can we humans really do much better, even if we can farm seaweed on '9%' of the oceans ?