A research strategy for ocean carbon dioxide removal and sequestration

The ocean covers about 70% of the Earth's surface and already buffers a large fraction of anthropogenic CO2 emissions (NRC, 2017); hence, much of the global capacity for natural carbon sequestration is in the ocean. Natural processes on land and ocean have removed roughly 55% of emitted CO2, but it may be possible to enhance both the uptake and longer-term sequestration potential of these processes.

The National Academies will appoint an ad-hoc committee to explore ocean-based approaches to carbon dioxide removal (CDR) and sequestration and provides a path forward for research and development of promising CDR approaches.

As of 2021, atmospheric carbon dioxide levels have reached historically unprecedented levels, higher than at any time in the past 800,000 years. Worldwide efforts to reduce emissions by creating a more efficient, carbon-free energy system may not be enough to stabilize the climate and avoid the worst impacts of climate change.

Carbon dioxide removal (CDR) strategies, which remove and sequester carbon from the atmosphere, likely will be needed to meet global climate goals. The ocean, covering 70% of the Earth's surface, includes much of the global capacity for natural carbon sequestration; the ocean also holds great potential for uptake and longerterm sequestration of human-produced CO2.

This report builds on previous work from the National Academies to assess what is currently known about the benefits, risks, and potential for responsible scale-up of six specific ocean-based CDR strategies as identified by the sponsor, ClimateWorks Foundation. It describes the research needed to advance understanding of those approaches and address knowledge gaps.

The resulting research agenda is meant to provide an improved and unbiased knowledge base for the public, stakeholders, and policymakers to make informed decisions on the next steps for ocean CDR, as part of a larger climate mitigation strategy; it is not meant to lock in or advocate for any particular approach.

With the goal of reducing atmospheric carbon dioxide, an ad hoc committee will conduct a study exclusively focused on carbon dioxide removal and sequestration conducted in coastal and open ocean waters to:

A. Identify the most urgent unanswered scientific and technical questions, as well as questions surrounding governance, needed to: (I.) assess the benefits, risks, and potential scale for carbon dioxide removal and sequestration approaches; and (ii.) increase the viability of responsible carbon dioxide removal and sequestration;

B. Define the essential components of a research and development program and specific steps that would be required to answer these questions;

C. Estimate the costs and potential environmental impacts of such a research and development program to the extent possible in the timeframe of the study.

D. Recommend ways to implement such a research and development program that could be used by public or private organizations.

The carbon dioxide removal approaches to be examined include:

+ Recovery of ocean and coastal ecosystems, including large marine organisms
+ Iron, nitrogen or phosphorus fertilization
+ Artificial upwelling and downwelling
+ Electrochemical ocean CDR approaches
+ Seaweed cultivation
+ Ocean alkalinity enhancement