08 June 2023 |

The depth to scale


Last week we hosted our first-ever virtual event, a fantastic discussion about scaling ocean-based carbon removal. Many thanks to Sifang Chen from Carbon180 and Mike Kelland from Planetary for sharing the stage with me and their expertise with us. Check out the recording here if you missed it. 

There were also several questions posed by the audience that we didn’t have time to answer during Q&A. I’ll take today’s newsletter to go deeper on these. Beyond elucidating important considerations for ocean-based carbon removal, these illustrate the nitty gritty types of q’s inherent to scaling any new industry. 

A nice pic I snapped of the world’s largest carbon removal membrane in Montara, CA, last month

Here are some ‘catch-up-quick’ stats that we covered in the session last week:

  • Scale: The ocean is already the world’s largest carbon sink. There’s 50x more carbon sequestered and stored in the ocean than there is in the atmosphere. That’s one of the main reasons that companies, scientists, and policymakers alike are taking an interest in using the ocean as a lever to fight climate change.
  • Methods: Still, as you know as a reader of this newsletter, there’s too much carbon in the atmosphere. There are many different approaches to ocean CDR, but they all focus on finding and testing safe, responsible ways to help the ocean both continue to do its work as a giant carbon removal membrane and to explore how we might accelerate its ability to remove carbon in a provable, responsible fashion in the future.
  • Other potential and pitfalls: Of course, this isn’t just about carbon. There are a lot of other benefits and potential pitfalls inherent to working with the ocean, its chemistry, and all of its biodiversity to consider. How local communities participate and are impacted by ocean-based CDR, particularly, is a pivotal area to consider as private companies scale.

Ocean-based carbon removal in general also continues to remain in the spotlight; yesterday, a new nonprofit, the Carbon to Sea Initiative, launched formally with more than $50M to support R&D in ocean-based carbon removal, especially in ocean alkalinity enhancement.

On to the questions from last week’s session! Mike and Sifang did the heavy lifting answering these; I edited for clarity and added a few of my thoughts.

Q: What makes for a good field test site? What environmental, social, and policy factors are most important?

Mike: There are a lot of factors here, like ocean conditions that keep CO2-depleted water at the surface for long periods of time or a responsible permitting regime. It also helps to have an academic institution with a good baseline understanding of the local area to participate in the research. Finally, having a source of alkalinity nearby, or a resource that can become a source of low-carbon alkalinity nearby, helps bring down the entire system’s carbon footprint. 

Sifang: Great question. What makes a good field test site will be different for different ocean CDR approaches. In general, you’d want to replicate essential aspects of the at-scale version of the approach, and ideally, you’d also have similar ecosystem composition at the deployment site. I agree with Mike that having a research institution nearby is very helpful. 

From talking to researchers, “What makes a good test site” is a question they are actively trying to figure out, and I’m hoping we’ll see some guidelines on this soon. Section 6 of a new paper from the Sabin Center also outlines important social considerations for designating ocean CDR research zones, including consent from state, local, and tribal governments.

Nick: I’d also add that we spent considerable time during the session discussing equity, i.e., making sure local communities are educated and ‘brought along for the journey,’ as it were, as field trials take place. This isn’t just a nice-to-have, it’s crucial; people are rightly skeptical of experimental technology deploying in their backyard and impacting their livelihoods if they work on the water.

Q: What are the disadvantages of coastal-focused CDR vs. an international approach? Are there risks of it being unevenly distributed?

Mike: Personally, I don’t know of any for ocean alkalinity enhancement specifically. Coastal ocean alkalinity is easier to deal with for a variety of reasons:

  • Regulatory: Competent regulators are used to dealing with the dynamics at play here, for instance, based on existing effluents from wastewater treatment plants.
  • Ownership: Carbon budgets can be appropriately tracked based on host country coastlines. This would be challenging in international waters.
  • MRV: MRV is more straightforward in well-modeled coastal regions.
  • Logistics: Logistics are far more simple when ships don’t need to be used (which also reduces the carbon footprint of the process)

Sifang: There are a lot of advantages to coastal-focused CDR for the reasons Mike listed. This may change in the future as open ocean CDR tech scales up and international governance issues are ironed out, but that will take time. At the same time, there may be additional considerations to take into account because coastal deployment could overlap with communities, coastal ecosystems, and other ocean uses like offshore wind and aquaculture. Again, speaking about ocean alkalinity enhancement more generally, the more rapid mixing conditions on the open ocean could make it more efficient. For something like seaweed sinking, research suggests that we will need to look at open ocean deployment in order to reach gigaton removal scale. 

Q: Immature tech can benefit from open knowledge sharing for faster progress and accountability. How can we safeguard that openness with so many private actors?

Mike: Most actors and money in the field are still concentrated in academic institutions. Those institutions are the hubs for knowledge sharing. There’s also the incredible Carbon to Sea, which launched with more than $50M in funding this week, which is creating a community of practice around ocean alkalinity enhancement through philanthropic grants. Finally, several institutions bring private companies together to share knowledge, like the Carbon Business Council, World Ocean Council, and Ocean Visions

Sifang: Industry consortia and public-private partnerships have worked well (though not perfectly) in other emerging tech sectors, like synthetic biology. From what I’ve seen, the ocean CDR industry scores quite high on openness and transparency, which is excellent. If anything, the drive to hit that high bar for transparency can make it hard for companies to keep certain information proprietary, making it challenging when talking to investors. This is one of several things I’m thinking about for our future work on ocean CDR and how federal policy could help in this regard. 

Q: When implementing ocean alkalinity enhancement techniques, how do we guarantee the capture of CO2 is not re-released back into the atmosphere within a “short” time (~100 years)?

Mike: This is one of the more “well-understood” things about ocean alkalinity enhancement; the risk of reversal is low. Reversal is only possible if atmospheric CO2 concentrations drop below current levels. Since there’s no immediate risk of that, the CO2 will remain sequestered. 

Bicarbonate in seawater has a mean residence time of over 100,000 years. This is measured by looking at the rate of bicarbonate addition through rock weathering annually and then analyzing the concentration change over time. Even once that time is up, only half the bicarbonate is lost through carbonate precipitation.

Sifang: One nuance lies in ‘secondary precipitation,’ which can occur when adding alkaline minerals into the ocean. This refers to when increased pH from alkalinity enhancement leads to calcite formation + CO2 release. Here’s a paper that talks about it, for example. 

I wouldn’t count this as a reversal, but it’s a good example of an area that deserves more study, as it could reduce the efficiency of ocean alkalinity enhancement. It’s also a function of dosing, i.e., if alkaline addition is dilute, it’s less likely to happen. And the CO2 that’s been shifted into bicarbonates can stay in the ocean for a very long time, as Mike said.

Q: Was the issue of the supply of alkaline products discussed? That seems like a massive amount would be needed to make a dent.

Nick: I can take this one on. Having discussed ocean alkalinity enhancement with several companies over the past year, this is a question they all think a lot about and recognize as a potential constraint. If you want to reach a scale that would allow for gigatons of carbon removal, you have to think about every component of your supply chain and what has to happen to scale it up to that capacity. As Jason Vallis, VP of Operations at Planetary, once told me:

If you want to remove billions of tons of CO2 from the atmosphere, you need billions of tons of feedstock. That’s just a chemistry equation.

Further, here’s what I wrote in a deep dive on Planetary last year:

“One great place to get alkalinity is from rocks and metals. But you also need a source of alkalinity that doesn’t require opening new mines and crushing new rocks. Those are highly energy-intensive processes with significant emissions footprints, and which can harm the environment for other reasons. If you trade in carbon removal, it doesn’t make sense if your supply chain is emission-intensive – you want to remove CO2 without generating additional emissions. 

As a solution, Planetary works with existing mine tailings that can offer alkalinity, too. There are billions of tons of rocks in mine tailings globally sitting around idly. They’re already mined, and the surrounding land could often benefit from a clean-up. Sourcing alkalinity from there helps solve the feedstock challenge and can be a bonus for the local environment. 

The challenge remains. If ocean-based carbon removal scales significantly, material constraints will intensify. Like sourcing enough copper, lithium, and other metals for energy transition and electrification, the broad hope is that constraints are catalytic to new solutions and supply.” 

Q: Any early indicators on OAE pricing for removing a ton of carbon?

Mike: It depends on the pathway, but we believe <$80/t is possible with no co-products, and potentially $0/t cost is possible with co-products. 

Sifang: Speaking generally about ocean alkalinity enhancement, there’s also a cost to measurement, reporting, and verification (‘MRV’) on top of the removal cost. MRV cost could range from small to substantial, depending on the method, the desired accuracy, and the spatiotemporal scale you want to cover. E.g., Planetary’s MRV might cost less, given they’re working with wastewater streams. But overall, the more we can drive down the cost curve on sensors, modeling, etc., the more cost-efficient the whole process will be.

Q: Do you feel that ocean-based carbon removal could benefit from more widespread promotion? It seems that R&D could be expedited if the general public would be more supportive.

Mike: Absolutely! 

Sifang: Yes, as long as it’s done thoughtfully. I think it’s really important to be transparent about the benefits and risks associated with deploying vs. not deploying ocean CDR, balancing urgency with caution, and putting ocean CDR in the context of reaching climate goals more broadly (decarbonization should always be the priority, and we will need some CDR, including potentially ocean-based CDR). Another critical part of the conversation concerns answering the questions of who pays, who benefits, and who bears the burden of risk.

Nick: Yes, and that’s my job!