Ocean CDR {marine biogeochemistry}

How this knowledge space works

The spine — read this before the org chart

The atmosphere and the surface ocean share carbon dioxide. When CO₂ dissolves it does not stay a gas in the drink. It reacts. Most of it becomes bicarbonate (HCO₃⁻). A smaller share becomes carbonate (CO₃²⁻). Together with leftover dissolved CO₂ they are DIC — dissolved inorganic carbon. The ocean already holds on the order of forty to fifty times more carbon than the air, almost all as those ions.

Alkalinity (often written TA, total alkalinity) is not “how much carbon.” It is how many protons (H⁺) the water can soak up. Bicarbonate is worth one unit, carbonate two, hydroxide one. Sulfate is doubly charged and worth zero, because at seawater pH it will not take a proton. Charge ≠ drawdown.

Add base — dissolve olivine or basalt, dose magnesium hydroxide, run an electrochemical cell, dissolve limestone in high-CO₂ wastewater — and you consume protons. The carbonate equilibrium shifts: dissolved CO₂ becomes bicarbonate. The surface is then short of CO₂ relative to the air, so more CO₂ crosses in. That extra carbon sits as HCO₃⁻ for ~10,000 years if you do not let it crash out as rock. That is ocean alkalinity enhancement (OAE). Enhanced rock weathering (ERW) is the same chemistry started on a field; rain and soil acids do the dissolving; rivers deliver the bicarbonate.

Build a shell and you run the reaction backwards. Calcite (CaCO₃) takes two bicarbonates and keeps one carbon; the other leaves as CO₂. Calcification from seawater alkalinity is a CO₂ source per mole of shell, or at best a half-efficient durable sink if you insist on counting the carbon left in the mineral.

Photosynthesis is a third ledger. It builds POC — particulate organic carbon, soft tissue. That carbon is only “removed” until something eats it. PIC — particulate inorganic carbon is the mineral particles (coccoliths, shell hash). PIC:POC is how shell-heavy a cell or a bloom is. The biological carbon pump is the natural process that sends some POC (and PIC ballast) downward as marine snow. Most of it is respired in the top few hundred meters. Enhancing that pump means competing for the same nutrients the food web already uses, and then proving a stranger’s carbon actually arrived at depth.

The sorting question for every lab and company: after the intervention, where is the extra carbon, in what molecule, and how would a stranger measure that it is still there a year later?

Paradigm shifts · Step 1

• Store as rock → store as dissolved bicarbonate — precipitation halves efficiency; DIC for ~10⁴ yr is “durable enough” for climate, even if it offends a geologist’s sense of forever.
• Grow biomass = sink → biomass is a leaky inventory — the climate product is permanence + MRV, not wet tons of algae.
• Open-ocean fertilization as the big lever → point-source alkalinity and farmland ERW — outfalls, wastewater, existing tractors beat mid-ocean science projects on measurability.
• Credits will fund Gt scale → philanthropy + public MRV + offtakes like Frontier, not a carbon coin — verification is the scarce asset that any new entrant has to solve before revenue.
• Building objects won’t scale / growing will → the constraint is chemistry and proof, not whether the actuator is a cell or a mill — ERW already uses farm equipment; calcification “grows” a CO₂ source.

Carbonate chemistry, with pictures

Numbers: cropland ERW potential ~0.5–2 Gt CO₂/yr by 2050 (Beerling et al. 2020) · OAE plausible Gt-scale with siting caveats · DIC lifetime ~10⁴ yr · wastewater CO₂ up to ~100× atmospheric equilibrium · human emissions ~40 Gt/yr.

Routes — four sectors, one ledger

Coccolithophores sit on the joint of pump + calcification. Photosynthesis writes POC. Plates write PIC and vent CO₂. They only help as (a) ballast for export you can prove, or (b) a harvested mineral whose alkalinity came from waste, not seawater. There is no third path that makes seawater-fed shell growth a full sink.

Industry · Step 3

Centers of excellence & organizations · Step 3

• Yale Center for Natural Carbon Capture (YCNCC) — natural carbon capture and enhanced weathering research; Noah Planavsky geochem group among its affiliated labs. Field partners wanted.
• Ocean Visions — the map (their mCDR roadmap covers export/avoided-degradation holes). Coordinating with EDF on a phytoplankton carbon research program (RFPs expected late 2026/early 2027).
• Carbon to Sea Initiative — $5M "Global OAE Field Research Network" RFP plus a $1M targeted research track, part of a larger $50M+ effort backed by Additional Ventures.
• ORCA (Ocean Resilience and Climate Alliance) — $300M+ philanthropic coalition (Bloomberg Philanthropies, Rockefeller Brothers Fund, and others) where marine CDR is one of seven priorities.
• Renaissance Philanthropy — climate-funding intermediary active in the broader carbon-removal philanthropy space.
• GEOMAR, PML, WHOI, MBARI, University of Exeter, Heriot-Watt, Dalhousie — classical marine carbonate labs; Dalhousie and GEOMAR co-run the "Ocean Alk-Align" OAE project, PML and Exeter co-lead SeaCURE and related OAE workshops.
• Standards / methods: best-practice OAE guides (Ocean Visions, NASEM ocean CDR), new PIC:POC protocol (this year).

Core competencies & skills · Step 2

• Seawater carbonate system (DIC, TA, pH, pCO₂, speciation) and the Revelle factor
• Silicate weathering kinetics (olivine vs basalt vs limestone)
• Biological pump: export efficiency, Martin curve, ballast hypothesis, PIC:POC
• MRV design: tracers, mixing models, air–sea flux, additionality
• Tools: coulometric DIC, open-cell TA titration, GC-MS, ICP-MS for cations, sat imagery for blooms
• Feedstock logistics: slag, demolition fines, mine tailings vs coasts and cement plants
• Honesty about scale: Gt math, not demo-tank math

Key players · Step 4

• Noah Planavsky — Yale geochemist. Lithos + Crew Carbon lineage. ERW + wastewater limestone.

Long tail to fill later: Ocean Visions authors, Carbon to Sea grantees, GigaBlue scientific advisors, Vesta researchers on olivine Ni/Cr, PIC:POC protocol authors.

MRV is the product

• OAE / ERW: alkali added, cations released, extra DIC after mixing and air–sea exchange. Never count precipitated CaCO₃ as a full tonne.
• Bio export: flux at depth, remineralization profile, additionality vs the natural pump. No cheap trusted meter. GigaBlue lives or dies here.
• Materials: mass of product − process emissions − origin of the alkali.

A modest research budget can buy a closed-tank mass balance that shows the 2 HCO₃⁻ → CO₂ vent, a PIC:POC strain comparison under the new protocol, or a public waste-alkali map. It cannot buy “we learned to grow coccolithophores at climate scale.”

Useful links · checked

Every URL below was fetched and confirmed live before publishing.

Primers & field maps

• Ocean Visions — hub
• Ocean Visions mCDR roadmap
• Ocean Visions mCDR database
• Ocean Visions field-trial tracker
• Ocean Visions — phytoplankton CDR
• NASEM research strategy for ocean CDR
• Carbon to Sea
• Yale Center for Natural Carbon Capture
• NOAA PMEL carbon program
• NOAA — ocean acidification (same chemistry)
• NOAA — coccolithophores
• NASA Earth Observatory — coccolithophores
• Wikipedia — coccolithophore (use for pictures, then go to papers)
• Wikipedia — enhanced weathering

Papers that still resolve

• Beerling et al. 2020 Nature — ERW on cropland (paywall possible; abstract is public)

Buyers & funders

• Frontier
• Renaissance Philanthropy

Companies (live homepages)

• Planetary
• Ebb Carbon
• Lithos
• Mati Carbon
• Terradot
• Vesta
• GigaBlue
• Bloomineral
• Crew Carbon

Videos that exist (oEmbed-confirmed titles)

• mCDR Explained — Capitol Hill Ocean Week · Carbon to Sea
• About Carbon to Sea
• OAE Field Research — Irene Polnyi · Carbon to Sea
• Planetary’s Nova Scotia OAE project — Will Burt · Carbon to Sea
• Planetary Technologies: intro explainer
• Where does all the carbon go? · WHOI
• The ocean’s carbon pump works better than we thought · WHOI
• Gigablue · Katapult Ocean — useful as their story, not as proof