Ocean-Based Carbon Dioxide Removal (CDR)

Electrochemical Ocean Carbon Dioxide Removal

Our planet is being transformed by climate disruption, with some of the worst impacts occurring in the ocean. Currently, most efforts to address climate change are focused on reducing emissions of greenhouse gases. While those efforts remain vital, they’re no longer enough. We must also clean up the “legacy” greenhouse gas pollution already in our atmosphere.

Ocean Visions believes that we may be able to harness the power of the ocean to restore the climate and the ocean itself. The ocean already holds more carbon than any other part of the biosphere and has the potential to contribute even more. The sheer scale of the ocean means that any ocean-based carbon dioxide removal (CDR) solutions proven to be viable and safe would have the potential to clean up billions of tons of CO₂.

A number of ocean-based CDR approaches are being explored—including electrochemical ocean carbon dioxide removal.

Electrochemical Ocean Carbon Dioxide Removal Overview

Electrochemical ocean carbon dioxide removal uses electricity to rearrange water and salt molecules in seawater into an acidic and basic solution. The acidic stream can be used to degas CO₂ from seawater for storage or use elsewhere, or to weather alkaline rocks to increase alkalinity. The basic stream can be used to enhance ocean alkalinity, which can then absorb CO₂ from the atmosphere and stabilize it in the ocean as bicarbonate and carbonate ions. The basic solution can also be used to precipitate carbonate directly out of the seawater, thereby stabilizing carbon in a durable solid form. Alkalinity lost during this precipitation must be replenished to maximize carbon negativity.

Electrochemical Ocean Carbon Dioxide Removal
Electrochemical Ocean Carbon Dioxide Removal © 2023 by Ocean Visions is licensed under CC BY-NC-ND 4.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-nd/4.0/

Technical Potential

The continued development, testing, and eventual scaling of a diverse array of electrochemical approaches requires expanded and accelerated research and development, and demonstration of these approaches at a pilot scale. The direct capture of dissolved carbon from seawater is energy intensive, similar to direct air capture, and the use of renewable energy is necessary to maximize net CO2 drawdown. Electrochemical methods that rely on fossil fuel energy sources, such as natural gas, might serve as important stepping stones in technological advancement and implementation, as long as more CO2 is removed than consumed in the process. For methods that extract carbon as pure CO2, a safe and secure form of storage must be identified to remove the risk of CO2 leaking back into the atmosphere.

Environmental Co-Benefits and Concerns

The environmental impacts of electrochemical ocean carbon dioxide removal are highly dependent on the specific process of CO2 removal. The removal of dissolved CO2 would increase pH, countering the trend of ocean acidification and potentially benefitting many marine species. Methods that remove bicarbonate and carbonate ions, on the other hand, would result in seawater that is more sensitive to acidification. Ancillary activities associated with processing of large volumes of water, such as water pumping, could result in additional environmental impacts.

Cost Considerations

Costs of electrochemical ocean carbon dioxide removal currently exceed USD $100 per net ton of CO2 removed, but several approaches are being explored that could significantly reduce the cost of drawdown. These include approaches that minimize costs of water pumping (a major cost driver) and the creation of side-products such as hydrogen and oxygen gas, as well as silica, or nickel and iron hydroxides, which could be sold for a profit.

Dive Deeper

Join the Ocean-Based CDR Community

Ocean Visions’ CDR Community brings together stakeholders to advance the state of knowledge, build bridges across disciplines, and help the community move towards safe and equitable testing and piloting of the most promising ocean-based CDR approaches.

Explore Ocean-Based CDR Road Maps

Ocean Visions’ ocean-based CDR road maps provide overviews of potential technologies, obstacles they face, and first-order priorities needing attention to advance the field. The road maps are intended to catalyze global collaboration and engagement and will be updated and refined as advances emerge in science, technology, governance, and policy.