The grownups are catching onto phytoplankton carbon

Notes on a landmark report by some very serious people

For the better part of fifteen years, ocean fertilization has been stuck in a peculiar limbo—too promising to ignore, too controversial to fund, too uncertain to deploy. To phytoplankton obsessives like me, it’s been an intolerable state of affairs. Last week, though, brought the promise of a reprieve from this limbo, in the form of the thing we crave most: big time validation from the institutional mainstream.

Ocean Visions —the nonprofit that’s become the closest thing the marine Carbon Dioxide Removal world has to a central nervous system—just released its Phytoplankton Carbon Solutions Research Framework, a landmark 47-page blueprint for how to investigate whether boosting the ocean’s biological carbon pump could actually work as a climate-relevant mCDR strategy. And not in the hand-wavy, wouldn’t-it-be-nice way that ocean fertilization has been talked about since the 1990s, but in a rigorous, stage-gated, outcome-agnostic way that can bring big time donors on board.

This is a big deal.

Ocean Visions isn’t some scrappy startup with a pitch deck and a prayer. Founded in 2020 with backing from the Grantham Environmental Trust and ClimateWorks Foundation, it’s become the field-building hub for marine CDR, sitting at the center of a network of leading oceanographic institutions and universities. Their CEO, Brad Ack, and chief scientist, David Koweek, have been methodically assembling the infrastructure—roadmaps, databases, assessment frameworks—that a serious research field needs to actually function.

And the money behind this particular report? The Ocean Resilience and Climate Alliance, better known as ORCA—a $250 million philanthropic coalition whose funders read like a who’s-who of serious climate money. Bloomberg Philanthropies. The Sergey Brin Family Foundation. The Packard Foundation. The Moore Foundation. Builders Vision (that’s Lukas Walton, i.e., Walmart money). Oceankind. The Grantham Trust, which leads ORCA’s mCDR pillar specifically.

We’re way past the fringe here. This is the institutional climate philanthropy establishment saying: we think this question deserves a serious answer.

The report itself was guided by an international advisory board, workshopped with 67 experts at the Ocean Visions Biennial Summit in Vancouver, and put through a 30-day public comment period that drew feedback from 56 individuals. We’re far beyond vibes here.

Ocean Visions starts by introducing a useful umbrella term—”Phytoplankton Carbon Solutions,” or PCS— that goes beyond just traditional ocean iron fertilization in High Nutrient, Low Chlorophyll cold water ecosystems — what I think of as GOFOIF (Good Old Fashioned OIF.)

Phytoplankton Carbon Solutions includes a broader family of approaches that leverage the biological carbon pump for CDR. This includes new approaches like nitrogen-fixation in low-nutrient (subtropical) waters, macronutrient fertilization, artificial upwelling, and newer categories like export-based approaches that enhance how much organic carbon sinks down to the deep ocean.

GOFOIF is still the headliner, simply because it’s been trialed already so we have some solid idea of how it would work. Idealized models suggest it has multi-gigaton gigatons removal potential, and its leverage ratio is extraordinary: one unit of iron could theoretically remove hundreds to tens of thousands of units of carbon from the surface ocean.

But the report makes it clear that Ocean Visions is still reserving judgment on whether GOFOIF can actually work in practice. Their cost estimates for OIF range from less than $25 to more than $53,000 per ton of CO₂, which is not a cost estimate, more like a confession of ignorance. Kudos to Ocean Visions for refusing to pretend to have answers they don’t yet have. The challenge for the field now is to constrain that uncertainty.

The report’s most consequential contribution here may be the four-stage decision framework for how to move these ideas forward.

Stage 1 is Pathway Characterization: define the mechanics, quantify the uncertainties, identify the risks. Basically, does this idea even make sense? Stage 2, Pathway Refinement, is where you start doing real science — model improvements, natural analog studies, small-scale field trials up to 100 tons of iron over 1,000 km², and serious community engagement. Stage 3, Evidence for Scale Up, is where it gets expensive and where you find out if your models were lying to you: large-scale field trials with over 100 tons of iron across 1,000+ km², rigorous MRV validation, co-designed research with affected communities, and full regulatory compliance. Stage 4, Deployment Optimization, is our shangri-la: gigaton-scale operations, independent standards development, and the kind of broad international public support that, let’s be honest, no ocean intervention has ever come close to achieving.

Each gate requires clearing specific feasibility and desirability hurdles before more money flows. What they’re building is a funnel designed to kill bad ideas early and cheap, before they become bad ideas that are late and expensive — a concept that, come to think of it, would save us all a lot of grief if applied more broadly in climate policy.

They’re thinking in a structured way about what research to back and what research to step away, so they lay out specific criteria a PCS pathway should meet to advance to the next level of investment. To keep backing a thing, they want to make sure it has a clear pathway to:

1. Durability of at least 100 years.

2. Measurability on par with other CDR pathways.

3. Potential to reach a gigaton per year of CDR for multiple decades.

4. Cost trajectory toward $100 per ton or less.

5. Sufficient understanding of environmental and socio-economic risks to support informed decision-making.

6. Social and regulatory support from affected communities.

The flipside is that the approach builds in explicit offramps. If scalability potential drops below a gigaton per year, if there’s no feasible path to reduce uncertainty, if environmental risks prove insurmountable—you stop. This is exactly the kind of disciplined, outcome-agnostic structure the field has needed. Because the phytoplankton world needs advocates —a role I’m super happy to play— but it can’t be just about advocacy: the money people need a decision architecture, a structured way to tell if the light is green, yellow or red.

Currently, only GOFOIF qualifies for Stage 2 (Pathway Refinement), based on the knowledge built up through 15 field experiments between the 1990s and 2009. Everything else—LNLC iron fertilization, export innovations, macronutrient approaches—sits in Stage 1 (Pathway Characterization). No field trial has been conducted since 2009, when a rogue commercial operation in the Pacific poisoned the well for a generation of research.

Ocean Visions is definitely right that we need to reduce uncertainty in net CDR estimates and, especially, the biogeochemical models behind those estimates. This is my current main obsession: right now, models don’t agree on basic questions about fertilization’s carbon benefits, so we certainly can’t have that. The report does note we’d be much better off if we understood the nitty gritty of the biological carbon pump’s baseline behavior better. I know it sounds like motherhood and apple pie, but it matters.

The most exciting part is that Ocean Visions comes out emphatically in favor of doing field trials, but the report is clear-eyed about what they’re going to cost. Small-scale trials (less than 100 km², two months of observation) could run $3 to $25 million. A comprehensive program with multiple large-scale trials might come in at $250 million over ten years. For reference, the ExOIS consortium’s proposed northeast Pacific GOFOIF trial—currently the most advanced field trial concept—carries a price tag of $40 to $45 million for two trials over three years.

The pathway-specific priorities focus on sharpening the scalability picture for GOFOIF through realistic deployment scenarios (not idealized models), but also advancing the still-nascent science of subtropical nitrogen-fixation-based iron fertilization (building on the Tonga-Kermadec hydrothermal vent observations I’ve written about before), as well as funding early-stage innovation in export enhancement—clay flocculation, mineral ballasting, aluminum-based degradation resistance.

The implementation priorities are where the report earns its institutional credibility. Community co-design isn’t an afterthought—it’s baked into the stage-gate progression. Coastal community and fisheries capacity-building gets its own dedicated priority. And the report insists that PCS risks be contextualized against the alternative: doing nothing in a world where ocean primary production is already declining under climate stress.

It’s exciting to see people who command the respect of big-time funders thinking through these ideas in this way. This feels like the way you shift the whole concept from neat-in-theory to real-thing-we’re-going-to-do.

Still, though, if you’ve been tracking this space, you might ask: what does this add to the 2022 NASEM report or the ExOIS roadmap?

Three things, I’d say.

First, scope. By defining the PCS umbrella broadly enough to include export-based innovations alongside production-based fertilization, the framework opens up a richer design space for research. If the big problem with iron fertilization is that you can grow blooms but can’t reliably get the carbon to sink deep enough, then export enhancement can’t stay an afterthought.

Second, structure. The stage-gate approach provides something that previous roadmaps lacked: a clear, repeatable decision framework with explicit criteria for advancing, pausing, or killing a pathway. This is the kind of tool funders need to make defensible allocation decisions in a field full of uncertainty.

Third, realism about money. The report is designed for a world where PCS funding is scarce—starting with $1-5 million for initial sensitivity analyses and model improvements, scaling to $5-10 million for parallel pathway investigations and community engagement, building toward the $40+ million needed for large-scale field trials. If some random guy with a substack tells you that, that’s one thing. When the body set up by the biggest climate funders says it, it’s quite another.

That freeze is thawing. The NASEM report in 2022 gave scientific legitimacy back to the question. ORCA and the Grantham Trust put real money behind it. ExOIS started designing actual trials. Growing Oceans launched to study nitrogen-fixation pathways. And now Ocean Visions has produced the strategic architecture to coordinate the whole sector.

None of this means phytoplankton carbon is going to be a killer solution. The report levels with us about the possibility that it might just won’t work: uncertainties might prove irreducible, environmental risks might prove unacceptable, the math might simply not add up at scale. Those are legitimate outcomes of a well-designed research program: if we were sure it would work, there’d be no point to doing research.

But here’s the thing. We need 10 gigatons of CDR per year by 2050. We’re nowhere close. No other CDR approach combines scalability with affordability like phytoplankton does. The idea that we can afford not to rigorously investigate the ocean’s biological carbon pump—the planet’s largest natural carbon sequestration system—has always been more about politics than science.

The grownups are finally acting like it.