Electrochemical
Ocean CDR
TTS v1.0 - Annex L
Electrochemical Ocean CDR uses bipolar membrane electrodialysis or direct seawater electrolysis to actively remove dissolved inorganic carbon from seawater, releasing it as a concentrated CO₂ stream for capture and storage while returning carbon-depleted, alkalinity-enhanced seawater to the ocean. As treated water re-equilibrates with the atmosphere, it draws down additional atmospheric CO₂ - combining direct extraction with the ocean's natural carbon buffering capacity in a single engineered system.
Submit Electrochemical Ocean CDR Project View TTS v1.0 Annex L →How this pathway works
Seawater carries the overwhelming majority of Earth's readily accessible carbon as dissolved inorganic carbon (DIC) - a much higher concentration per unit volume than atmospheric CO₂. Electrochemical Ocean CDR directly extracts a portion of this dissolved carbon using electrochemical processes, most commonly bipolar membrane electrodialysis (BPMED), which splits seawater into an acidified stream (where DIC converts to gaseous CO₂ for capture) and an alkalinised stream (returned to the ocean, where it can absorb additional atmospheric CO₂ to restore chemical equilibrium). The net effect is atmospheric carbon removal achieved through the ocean as an intermediary reservoir, extracted and concentrated for confirmed capture rather than left dissolved.
Under the Teravent Technology-Based Carbon Standard (TTS v1.0) Annex L, Electrochemical Ocean CDR projects earn Teravent Technology Credits of the Removal type (TTC-R) for verified net tonnes of atmospheric CO₂ removed via this combined extraction-and-rebalancing mechanism, net of full lifecycle project emissions. This pathway is explicitly recognised as eligible for Frontier Technology designation given its very early commercial deployment stage, reflecting both the scientific promise and the elevated uncertainty inherent in a pathway still transitioning from pilot to demonstration scale.
Two methodology variants are approved under Annex L, differentiated by the specific electrochemical process employed. Both require the captured CO₂ stream to be routed to a qualifying storage or utilisation pathway (typically Geologic CO₂ Storage, Annex G) for the removal claim to be finalised.
TTS v1.0 - Annex L
This pathway is governed exclusively by the Teravent Technology-Based Carbon Standard (TTS v1.0). No external registry, standard, or methodology is referenced or incorporated. All requirements - additionality, quantification, durability, safeguards, and credit issuance - are defined within TTS v1.0 and Annex L, with reference to Annex G for the geological storage component of the captured CO₂ stream.
Two approved methodology variants
TTS v1.0 Annex L approves two discrete methodology types for Electrochemical Ocean CDR, both requiring the extracted CO₂ stream to be routed to a qualifying storage or utilisation destination for the removal claim to finalise.
Bipolar membrane electrodialysis applies an electric potential across a stack of ion-exchange membranes to split seawater into two streams: an acidified stream, in which the applied acidity converts dissolved bicarbonate and carbonate ions into gaseous CO₂ that off-gasses for capture, and an alkalinised stream, which is returned to the ocean carrying elevated alkalinity capable of absorbing additional atmospheric CO₂ as it re-equilibrates. The captured CO₂ stream must be transported to a qualifying storage site (typically under Annex G) to complete the removal claim.
- Captured CO₂ gas stream flow rate at the electrodialysis unit outlet, metered at ±3% accuracy
- dMRV sensor network at the alkalinised stream discharge point, measuring seawater pH, alkalinity, and pCO₂
- Ocean carbon uptake model validated against dMRV data, quantifying additional atmospheric CO₂ drawn down by the alkalinised discharge
- Electrodialysis cell energy consumption per tonne CO₂ extracted, logged for lifecycle deduction
- Confirmed storage or utilisation of the captured CO₂ stream at its final destination, per the applicable annex requirements
Rather than the membrane-based ion separation used in BPMED, this methodology applies direct seawater electrolysis to induce a localised pH swing, driving dissolved bicarbonate to precipitate as solid calcium carbonate or off-gas as CO₂, which is then captured. The treated, carbon-depleted seawater is returned to the ocean, where it re-establishes equilibrium by absorbing additional atmospheric CO₂. This methodology remains at an earlier technology readiness stage than BPMED, with fewer demonstrated commercial-scale deployments to date.
- Captured CO₂ gas or precipitated carbonate mass at the electrolysis cell outlet, metered at ±5% accuracy
- dMRV sensor network at the treated seawater discharge point, measuring pH, alkalinity, and pCO₂
- Ocean carbon uptake model validated against dMRV data at each verification
- Electrolysis cell energy consumption per tonne DIC removed, logged for lifecycle deduction
- Confirmed final disposition of captured carbon - geologic storage or stable mineral product - per the applicable annex requirements
Which emission sources must be counted
TTS v1.0 Module 3 requires a full lifecycle GHG emissions inventory within the project boundary, deducted from the modelled net atmospheric CO₂ uptake to arrive at the Net TTC figure.
Measurement, reporting
& verification
Teravent's Science Advisory Board assesses each pathway against four MRV dimensions. Electrochemical Ocean CDR presents a compound measurement challenge - combining direct extraction metering (high confidence) with ocean re-equilibration modelling (medium confidence) - reflected in its comparatively lower overall permanence confidence relative to purely terrestrial or industrial pathways, balanced by very high additionality clarity given its Frontier Technology status.
The captured CO₂ gas or precipitated carbonate stream is metered directly at the electrochemical facility outlet, providing relatively high-confidence quantification of the direct extraction component. The compound challenge is confirming the additional atmospheric CO₂ uptake attributable to the returned alkalinised or carbon-depleted seawater - this requires the same distributed monitoring, reporting, and verification (dMRV) sensor network approach used for Ocean Alkalinity Enhancement (Annex K), tracking pH, alkalinity, and pCO₂ at the discharge point and paired reference sites, feeding a validated ocean carbon uptake model. Because this pathway remains at an earlier commercial stage than most engineered CDR approaches, an independent oceanographic and electrochemical engineering expert review is required at each verification.
Demonstrating additionality
TTS v1.0 Module 2 requires all projects to pass a three-test additionality framework. Given this pathway's Frontier Technology status and early TRL, virtually all current Electrochemical Ocean CDR projects qualify for the automatic TRL-based common practice screen.
Leakage types & deductions
TTS v1.0 Module 3 defines three leakage types applicable across all engineered pathways. Electrochemical Ocean CDR is primarily subject to energy-source leakage given its high electricity intensity, plus marine ecosystem considerations shared with Ocean Alkalinity Enhancement.
Buffer pool & reversal risk
Durability class for Annex L credits reflects both the confirmed storage destination of the extracted CO₂ and the confidence of the ocean re-equilibration modelling for the returned seawater stream. As an early-stage Frontier Technology, buffer pool rates for this pathway run higher than for more established engineered pathways.
| Methodology | Durability Class | Buffer Pool Rate | Primary Uncertainty Drivers |
|---|---|---|---|
| ECO-M01 BPMED | Class II (default); Class III once storage confirmed | 15–25% | Ocean re-equilibration model uncertainty; storage-stage reversal risk (per Annex G) |
| ECO-M02 Direct Electrolysis | Class II (default); Class III once storage confirmed | 18–30% | Earliest-stage technology in the Teravent system; limited operating track record |
Key registration criteria
Projects must meet all of the following minimum requirements to qualify for registration under TTS Annex L. Additional methodology-specific requirements are detailed in the Annex L methodology tables for each ECO-M code.
Sustainable Development
Goal alignment
All Teravent registered Electrochemical Ocean CDR projects must complete an SDG impact assessment at registration and at each verification period. Three SDGs are systematically tracked for this pathway. Projects may apply for co-benefit quality labels where independently verified indicators are met.
Deployment scope: Coastal regions with access to reliable low-carbon electricity, deep-water seawater intake infrastructure, and nearby geologic storage sites - currently limited to a small number of pilot and demonstration facilities in North America, Northern Europe, and East Asia.
Ready to register your
electrochemical ocean CDR project?
Submit a Project Concept Note under TTS v1.0 Annex L to begin your registration. Select the ECO-M code matching your electrochemical process, deploy a dMRV sensor network, confirm your CO₂ storage destination, and appoint an accredited VVB to review your PDD.