Monitoring and Verification of Ocean-Based Carbon Dioxide Removal

Ocean-based carbon dioxide removal (mCDR) — including biomass sinking, ocean alkalinity enhancement, and artificial upwelling — lacks a reliable system for monitoring, reporting, and verifying (MRV) that carbon has been durably sequestered. Running Tide, the largest marine carbon removal startup, admitted before its 2024 shutdown that it could not monitor sunk biomass for more than three hours after release and could not distinguish its alkalinity signal from natural ocean variability. Without credible MRV, carbon credits from ocean-based approaches cannot be trusted, buyers cannot assess what they're purchasing, and the entire market mechanism fails.

The ocean absorbs roughly 25% of anthropogenic CO2 emissions and has vastly more sequestration capacity than terrestrial systems. Marine CDR is considered essential for meeting Paris Agreement targets — the IPCC estimates 5–10 gigatons per year of carbon removal may be needed by 2050. Companies including Microsoft, Stripe, and Shopify have committed hundreds of millions to carbon removal purchases. But without verifiable measurement, ocean-based approaches remain scientifically unproven at scale. Running Tide's collapse — despite $54 million in funding and contracts with major tech companies — demonstrates that the market will not sustain companies that cannot prove their climate impact.

Running Tide sank wood biomass coated with limestone into deep ocean waters off Iceland. Their monitoring approach relied on short-term tracking of material as it descended, but signal was lost within hours. The company's carbon accounting relied on theoretical models of what happens to submerged biomass rather than empirical measurement. Scientists criticized the carbon cycle framing as a "vast oversimplification that substantially overstates the net climate benefits." Ship-based monitoring is prohibitively expensive for tracking dispersed material across thousands of square kilometers of ocean. Satellite remote sensing can detect surface changes but cannot observe processes in the deep ocean where sequestration occurs. Existing oceanographic sensor networks (Argo floats, moored buoys) are not designed to detect the chemical signatures of deliberate carbon sequestration against the background variability of ocean chemistry. The fundamental challenge is that the ocean is vast, opaque to most remote sensing, and chemically noisy.

A breakthrough in low-cost, persistent deep-ocean chemical sensing could transform marine CDR from speculative to verifiable. This might involve: autonomous underwater vehicles with carbon-isotope sensors that can distinguish anthropogenic from natural carbon signals; degradation-resistant tracer compounds that co-sink with biomass and can be detected months later; or distributed sensor networks (building on existing Argo float infrastructure) calibrated for alkalinity and dissolved inorganic carbon at the precision needed to detect CDR signals. Acoustic monitoring of biomass descent trajectories could extend the tracking window. Adjacent fields with relevant approaches include deep-sea mining environmental monitoring, submarine hydrothermal vent sensing, and radiocarbon tracing in paleoceanography.

A student team could: (1) design and prototype a low-cost chemical tracer system that could be embedded in sinkable biomass and detected at depth weeks or months later, focusing on tracer selection and detection limits; (2) model the minimum sensor density and precision needed to distinguish a CDR alkalinity signal from natural ocean variability in a specific ocean region; (3) prototype an acoustic tracking system for monitoring biomass descent and dispersal in a controlled water column (tank or coastal environment). Relevant disciplines include oceanography, environmental engineering, sensor design, chemical engineering, and data science.