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A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration (2022)

Chapter:9 Synthesis and Research Strategy

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Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
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9

Synthesis and Research Strategy

9.1 A GENERAL FRAMEWORK FOR OCEAN-BASED CARBON DIOXIDE REMOVAL STRATEGIES

By acting to remove carbon dioxide (CO2) from the atmosphere and upper ocean and then store the excess carbon either in marine or geological reservoirs for some period of time, ocean CO2 removal (CDR) approaches could complement CO2 emission reductions and contribute to the portfolio of climate response strategies needed to limit climate change and surface ocean acidification over coming decades and centuries. While rapid and extensive decarbonization and abatement of other greenhouse gases in the United States and global economies are the primary action required to meet international climate goals, ocean and other CDR approaches can help balance difficult-to-mitigate human CO2 emissions and contribute to mid-century to late-century net-zero carbon dioxide emissions targets.

The present state of knowledge on many ocean CDR approaches is inadequate, based in many cases only on laboratory-scale experiments, conceptual theory, and/or numerical models. Given the inadequate knowledge base and lack of time to develop climate solutions, it will be important to pursue research on multiple approaches in parallel to progress understanding of ocean CDR as a contributor to climate targets. Expanded research including field research is needed to assess the techniques’ potential efficacy in removing and sequestering excess carbon away from the atmosphere and the permanence or durability of the carbon sequestration on timescales relevant to societal policy decisions. Research is also needed to identify and quantify environmental impacts, risks, benefits, and co-benefits as well as other factors governing possible decisions on deployment such as technological readiness, development timelines, energy and resource needs, economic costs, and potential social, policy, legal, and regulatory considerations. Additionally, research on ocean CDR would greatly benefit from targeted studies on the interactions and trade-offs between ocean CDR, terrestrial CDR, greenhouse gas abatement and mitigation, and climate adaptation, including the potential of mitigation deterrence.

Implementation of any ocean CDR strategy would require decision makers to make difficult trade-offs. Gathering and synthesizing as much information as possible can help to anticipate what

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

those trade-offs will be. For example, it may seem premature to think about the social and livelihood implications of some of these techniques, or to assess their co-benefits to particular groups, when they are just in laboratory or demonstration stages. However, interest in ocean CDR approaches could move quickly as countries and companies seek to build roadmaps to the net-zero targets they have set. Pilot projects are sites for both demonstrating new technologies and for social learning, and an integrated research strategy would involve social scientists working together with geoscientists and engineers early in the research process to provide a broader evidence base around what the trade-offs for different communities might be.

Core Principles for Developing a Research Strategy

Research on societal responses to climate change has been approached through a number of conceptual and science policy frameworks. This report has not prescribed a single approach for policy makers, researchers, and stakeholders, but it has drawn from several complementary frameworks (see Box 9.1).

Recommendation 1: Ocean CDR Research Program Goals. To inform future societal decisions on a broader climate response mitigation portfolio, a research program for ocean CDR should be implemented, in parallel across multiple approaches, to address current knowledge gaps. The research program should not advocate for or lock in future ocean CDR deployments but rather provide an improved and unbiased knowledge base for the public, stakeholders, and policy makers. Funding for this research could come from both the public and private sectors, and collaboration between the two is encouraged. The integrated research program should include the following elements:

  1. Assessment of whether the approach removes atmospheric CO2, in net, and of the durability of the CDR, as a primary goal.
  2. Assessment of intended and unintended environmental impacts beyond CDR.
  3. Assessment of social and livelihood impacts, examining both potential harms and benefits.
  4. Integration of research on social, legal, regulatory, policy, and economic questions relevant to ocean CDR research and possible future deployment with the natural science, engineering, and technological aspects.
  5. Systematic examination of the biophysical and social interactions, synergies, and tensions between ocean CDR, terrestrial CDR, mitigation, and adaptation.

9.2 COMMON COMPONENTS OF ANY RESEARCH IMPLEMENTATION

The suite of six ocean CDR approaches, defined broadly and addressed in detail in the report chapters, covers a wide range from ecosystem recovery and alteration of marine ecosystems to more industrial-based techniques. The knowledge base and readiness levels for the approaches differ substantially as do the carbon sequestration potential, environmental impacts, and human dimensions. As such, the development of a comprehensive research strategy will require different emphasis for different approaches—no single research framework will be adequate for all CDR approaches. There are, however, several common components that are relevant to research into any ocean CDR approach.

Research Code of Conduct

The lack of a comprehensive international or domestic legal framework specific to ocean CDR research creates a risk that ill-considered projects, including projects that do little to

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×
Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

advance scientific knowledge and/or present significant risks, will be pursued. Developing a code of conduct for ocean CDR research may help to mitigate that risk. To maximize participation by researchers, compliance with the code of conduct could be made a condition of government or private funding for ocean CDR research.

Codes of conduct for geoengineering research have already been developed by academic researchers, in some cases with input from stakeholders (e.g., Leinen, 2008; Hubert and Reichwein, 2015; Hubert, 2017; Chhetri, 2018), but have not been widely adopted by the research community (NASEM, 2021b). Although not a full code of conduct, the so-called “Oxford Principles” for geoengineering do provide some guidance to researchers, and have been more widely accepted (see Box 9.2).1

Scholars have also suggested four principles for CDR research in just climate policy: emission cuts must remain in the center of climate policy; social, economic, and environmental impacts matter; CDR projects and approaches should be assessed individually; and climate policy needs

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1 See http://www.geoengineering.ox.ac.uk/www.geoengineering.ox.ac.uk/oxford-principles/principles/index.html.

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

to be resilient against unexpected outcomes (Morrow et al., 2020). However, neither the Oxford Principles nor the geoengineering codes of conduct specifically address ocean CDR research. Given the unique nature of such research, development of a specific code of conduct is likely to be useful. Some nongovernment organizations (NGOs) have recently advocated for the adoption of, and identified key principles that should be included in an ocean CDR-specific code of conduct.2

Ideally, a code of conduct for ocean CDR research would be developed and maintained by an international body, with input from the research community and other stakeholders. Key issues to be addressed in the code of conduct would include (among other things):

  • the need for transparency in research planning, including ex ante review and disclosure of potential environmental and other impacts, and stakeholder and public engagement;
  • use of independent review panels to evaluate research plans and outcomes;
  • compliance with all applicable domestic and international laws and associated guidelines (even if not legally binding) in conducting research;
  • use of open data systems with adequate metadata to evaluate data quality;
  • use of peer-reviewed literature for reporting results as well as open presentations to stakeholders and the public;
  • use of accepted carbon accounting methodologies, where available, for constraining CO2 removal, permanence of CO2 sequestration, and net greenhouse gas emissions;
  • consideration and disclosure of other environmental and social impacts, both within and outside of the study area;
  • consideration of full life-cycle impacts and costs; and
  • responsibilities for post-research activities and site closure.

Permitting of Research

Significant permitting issues could arise in connection with ocean CDR research, particularly field trials and other in situ research. As discussed in Chapter 2, while there is no domestic legal framework specific to ocean CDR, research projects may be subject to a number of domestic environmental and other laws, which impose permitting requirements. Further study is needed to identify and analyze the full range of potentially applicable laws, explore gaps in and barriers created by the application of those laws to ocean CDR, and evaluate possible alternative approaches to regulation.

Requiring ocean CDR research projects to be permitted ensures some level of government oversight, which should, in turn, help to promote responsible research and minimize the risk of negative environmental and other outcomes. At the same time, however, unnecessarily burdensome or overly complex permitting requirements could create barriers to ocean CDR research.

Some in situ research projects may require multiple permits from multiple federal, state, and/or local regulatory agencies. Due to the novelty of the research, regulatory agencies may lack established processes for evaluating projects and issuing permits, which could lead to delays and other costs. Members of the scientific community may lack the time, resources, and expertise to navigate the permitting process and ensure compliance with other regulatory requirements.

The following actions can be taken by the research community, and by those funding or otherwise supporting research, to begin to address these complex permitting issues:

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2 See e.g., https://oceanvisions.org/roadmaps/growing-public-support/first-order-priorities/#developacodeofconducttoguidescientificexperimentationandfieldtrials and https://www.youtube.com/watch?v=2K_J2uaX--I&t=372s.

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×
  1. Encourage interdisciplinary research. See description in the section, Research Collaboration.
  2. Share knowledge. It is imperative that government agency staff and other stakeholders, including the general public, have a solid understanding of ocean CDR techniques and the known and unknown benefits and risks that their use presents. To help build knowledge, researchers and other groups could offer briefings to agency staff and other stakeholders, or share information with them in other ways.
  3. Engage early. When a field trial or other in situ research is being considered, the researchers should engage with relevant government agencies and other stakeholders early in the project design process wherever possible, and continue to share information during and after the project as appropriate. A clear data management plan should also be articulated early on and complied with throughout the project.

Government agencies can also play an important role, most notably by clarifying and, where possible, simplifying permitting processes. It is, however, important that any action taken not compromise existing safeguards designed to ensure that research is conducted responsibly and minimize the potential for negative environmental and other outcomes.

Research Collaboration

Co-production has been emphasized in marine sustainability science as a way of developing solutions that are adapted to local ecological, economic, and cultural contexts. Through projects that work with communities and discuss the changing ocean, blue economy, and energy and conservation, we can learn what other issues are informing how people think about ocean CDR and understand their priorities. Having communities participate from the outset and guide the research can increase the likelihood of ocean CDR implementations that are compatible with environmental justice, and avoid ocean CDR implementations that would exacerbate environmental injustice. Engagement with stakeholders from local government, business, NGOs, and other stakeholders as identified through stakeholder assessment will also be important.

Traditional ecological knowledge and traditional land and resource management systems would have many insights for some of the techniques discussed in this report, such as ecological restoration and seaweed cultivation. However, reversing the damage to marine ecosystems needs to be done with the permission, guidance, and collaboration of Indigenous peoples (Turner and Neis, 2020). Research conducted without consent and outside of a collaborative framework can be a form of colonialism that can potentially harm Indigenous peoples (Ban et al., 2018). Some of the challenges to doing this kind of research include the history of extractivist research by settler-colonial scholars; the fact that co-produced research takes more time, which can be in tension with the urgency of environmental and climate action; the fact that Indigenous resource offices are often under-resourced and swamped with other priority items; and the lack of scientists who are trained in co-production because it is at odds with publish-or-perish career incentives within science. However, funders can address at least some of these challenges by funding co-produced research, consulting with Indigenous communities on what resources they would need to undertake such collaborations according to their existing research protocols, and developing a pipeline of researchers who have the capacity and skills to carry out such work.

As well as being co-produced with communities, research into ocean CDR should also be interdisciplinary. Research into the scientific, social, legal, and other dimensions of ocean CDR tends to be highly siloed. Scientific research projects are, therefore, often designed without consideration of social or legal issues. Early engagement with those issues can avoid surprises and lead

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

to improved project design. Examples of successful integration of legal and scientific research in the ocean CDR space include:

  • CDRmare,3 a project of the Germany Marine Research Alliance, which aims to determine whether and to what extent the oceans can be used to remove and store CO2 from the atmosphere. The project is analyzing “individual actions that aim to enhance marine carbon sinks,” with a “[s]trong emphasis on non-natural science aspects,” including “legal, social, and ethical aspects.”
  • Solid Carbon,4 a project funded by the Pacific Institute for Climate Solutions, which is exploring the feasibility of capturing and storing CO2 in the sub-seabed. The project combines a study of key scientific and engineering questions with an analysis of potential regulatory and other challenges (Webb and Gerrard, 2021).

With oceans as a global commons, it is critical that research in this area be international—for social legitimacy, for research that is applicable to multiple cultural and geographic contexts, and for research that addresses the priorities of communities where ocean CDR may be used. Both prioritizing or mandating international collaborations and support of early-career researchers to build capacity can work toward the goal of supporting an international research community of ocean CDR research.

Recommendation 2: Common Components of an Ocean CDR Research Program. Implementation of the research program in Recommendation 1 should include several key common components:

  1. The development and adherence to a common research code of conduct that emphasizes transparency and open public data access, verification of carbon sequestration, monitoring for intended and unintended environmental and other impacts, and stakeholder and public engagement.
  2. Full consideration of, and compliance with, permitting and other regulatory requirements. Regulatory agencies should establish clear processes and criteria for permitting ocean CDR research, with input from funding entities and other stakeholders.
  3. Co-production of knowledge and design of experiments with communities, Indigenous collaborators, and other key stakeholders.
  4. Promotion of international cooperation in scientific research and issues relating to the governance of ocean CDR research, through prioritizing international research collaborations and enhancement of international oversight of projects (e.g., by establishing an independent expert review board with international representation).
  5. Capacity building among researchers in the United States and other countries, including fellowships for early-career researchers in climate-vulnerable communities and underrepresented groups, including from Indigenous populations and the Global South.

9.3 SUMMARY OF ASSESSED OCEAN-BASED CARBON DIOXIDE REMOVAL STRATEGIES

Chapters 3 through 8 include detailed assessments of the current state of understanding of each of the six ocean-based CDR approaches examined within this report, as defined by the com-

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3 See https://www.cdrmare.de/en/die-mission/.

4 See https://pics.uvic.ca/projects/solid-carbon-negative-emissions-technology-feasibility-study.

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
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mittee’s statement of task (Box 1.1). The committee assessed the potential of each approach as a viable mechanism for CDR according to common criteria described in Chapter 1, and listed here:

  • Knowledge base: What do we know about the approach?
  • Efficacy: Can effective CO2 removal from the atmosphere be demonstrated?
  • Durability: How long would the excess carbon be stored?
  • Scale: How much CO2 could potentially be removed and what are the temporal and geographic constraints?
  • Monitoring and verification: What would be needed to monitor for both environmental impact and for carbon accounting?
  • Viability and barriers: What is the potential viability based on technical, scientific, economic, safety, and sociopolitical factors? What are the intended and unintended environmental impacts, and what are the co-benefits?
  • Governance and social dimensions: What is the governance landscape for both research on and possible future deployment of the approach?
  • R&D opportunities: What needs to be done to fill the important gaps in understanding?

As previously stated, the knowledge base and readiness levels for the six ocean CDR approaches examined differ substantially as do the carbon sequestration potential, environmental impacts, and human dimensions. The committee’s assessment on potential of scale-up for each approach is described in the sections that follow and is also summarized in Table 9.1 (see Box 9.3 for specifics on estimating costs). This assessment is the result of literature review, a series of public workshops and meetings convened by the committee, as well as committee member expertise and judgment, where needed. Although the report addresses in detail only a subset of all possible ocean CDR approaches, the criteria above and the research program elements in Recommendations 1 and 2 provide a general framework applicable more broadly to other ocean CDR approaches.

The following text describes research priorities to focus on, in parallel, as next steps to increasing understanding of each of the six approaches as a viable and responsible mechanism for durably removing CO2 from the atmosphere. Tables 9.2 and 9.3 then summarize the research needed, including rough time frame and cost estimates. Table 9.2 summarizes the foundational research identified in Chapters 2 and 9 as research priorities common across ocean CDR approaches on potential social, policy, legal, and regulatory considerations. The research included in Table 9.2 is meant to inform the framework for any future ocean-based CDR effort. Table 9.3 then summarizes research needs identified within Chapters 38, with bolded text indicating research needed as next steps to better understanding the feasibility of that particular approach. The research costs listed in Tables 9.2 and 9.3 are approximate and were compiled by the committee based on publicly available information, experience, and judgment (see Box 9.3). Some caveats are appropriate, particularly when comparing across different research fields from ocean science and social science to more engineering and technological research. Further, these cost estimates are primarily for research and early development work, and costs could grow for some demonstration-phase projects.

Social and regulatory acceptability is likely to be a barrier to many ocean CDR approaches, both at the research and possible deployment stages, particularly ones requiring industrial infrastructure either in the ocean or on the coasts or ones involving restructuring of marine ecosystems. There will be both project-specific and approach-specific social, political, and regulatory discussions, as well as the possibility for diverging perspectives around the role of CDR broadly. Field-scale trials are likely to be a site of wider debates within the scientific community and in society around decarbonization and climate response strategies.

Ocean CDR approaches are already being discussed widely, and in some cases promoted, by some scientists, NGOs, and entrepreneurs as potential climate response strategies. At present,

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

society and policy makers lack sufficient knowledge to fully evaluate ocean CDR outcomes and weigh the trade-offs with other climate response approaches and with environmental and sustainable development goals. Research on ocean CDR, therefore, is needed whether or not society moves ahead with deployment, and/or to assess at what scales and locations the consequences would be acceptable. Research would also provide a framework for evaluating under what conditions various ocean CDR projects may be acceptable and thereby enable the development and implementation of an effective regulatory framework for deployment (if any).

Ocean Nutrient Fertilization

Ocean fertilization has received the most attention of any ocean CDR approach due to fieldwork that began more than 25 years ago focused on iron and its unique role as a micronutrient

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

that is limiting phytoplankton growth, and hence CO2 uptake, in large parts of the ocean. Those experiments were not large enough or long enough (<5 tons of iron, weeks to just over a month of observations) to observe the full cycle of carbon uptake and loss to the deep sea via the biological pump. Because of these limitations, carbon sequestration efficiencies are still poorly constrained, and concerns about unintended consequences, such as harmful algal blooms or production of other greenhouse gases such as nitrous oxide, along with models demonstrating downstream impacts and permanence issues led to a cessation of follow-on open-ocean iron fertilization experiments. However, studies of naturally iron-rich systems, for example, around Southern Ocean islands, and the biological response to episodic iron inputs, such as volcanic eruptions, suggest higher sequestration efficiencies and little harmful side effects with the possible co-benefit of enhanced fisheries.

With this background in mind, continued research is warranted, building on these earlier results to address key remaining issues related to how carbon uptake and sequestration efficiencies could be enhanced, and how carbon transport could be more readily tracked and thus accounted for. Some of this would be laboratory and mesocosm based, but a more complete understanding will require demonstration-scale field experiments—>100 tons of iron added over >10,000 km2 and full seasonal and annual sampling of impacts. Monitoring for a full suite of geochemical and ecological shifts is needed using advanced autonomous platforms with sensors and samplers that would allow a continuous presence to observe changes. These demonstration-scale studies would need to be conducted in several ocean regimes. In addition to high-nutrient, low-chlorophyll areas, studies should be carried out in low-nutrient settings and in regions where the depth of permanent (>100-year) sequestration is shallower. Remote sensing and complementary measurements from ships will be needed to fully track the consequences. Models to plan out the best strategies for inducing blooms and measurement strategies for quantifying impacts are needed, as well as three-dimensional ocean ecosystem and Earth system models to extrapolate the regional impacts to areas outside of the immediate study site.

In part due to early and unsupported optimism by commercial interests in this CDR approach, many in the public and scientific community have urged caution on proceeding with ocean iron fertilization research. One response to these concerns was the development of a framework for evaluating and permitting research under the London Convention and Protocol. This is a necessary step in moving ahead and could possibly provide a model for regulating some other types of ocean CDR research. However, a broader investment in gathering stakeholders and regulatory agencies together is needed to assess the implications of CDR research and deployment at scale. The development of frameworks to assess CDR magnitude and durability as well as environmental impacts would need to be site- and scale-specific and include a delineation of responsibilities before, during, and after deployment for those deploying ocean fertilization and those regulating it. This is complicated in that those receiving the most benefit in terms of carbon credits or markets may not be the ones facing the greatest impact. Providing information for policy makers and the public about the trade-offs between ocean fertilization and other land- and ocean-based CDR approaches and the consequences of doing nothing for negative C emissions also needs attention.

The largest cost for research would be the demonstration-scale field experiments, which if upscaled from prior studies would be on the order of $25M/yr for 10 years to complete work at multiple sites. In parallel, laboratory/mesocosm studies to optimize conditions and methods to improve carbon accounting and the technologies to do so would total $18M/yr, which along with modeling ($5M/yr) and social and governance aspects ($4M/yr) would round out a comprehensive ocean fertilization research agenda.

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

Artificial Upwelling and Downwelling

The vertical movement of water in the ocean, termed upwelling and downwelling, acts to transfer heat, salt, nutrients, and energy between the well-lit surface ocean and the dark, nutrient-, and CO2-rich deep ocean. Since the 1950s, researchers have sought to artificially simulate these physical transport processes to geoengineer localized regions of the ocean using a variety of technologies including wave pumps, airlift pumps, and salt fountains, each of which has varying pumping mechanisms, efficiencies, and energy requirements. Several field deployments have proven that at least some of these technologies can indeed deliver deep water to the surface ocean, and in some cases there is a measurable biological response. To date, however, in situ experiments with artificial upwelling have been short (generally less than weeks), limited in scale (a small number of pumps in smaller-than-kilometer regions, mostly coastal), and have not measured and/or demonstrated any net enhancement of carbon flux even though mesocosm studies and small-scale enrichment experiments do confirm that nutrient delivery via deep water can stimulate primary production.

In principle, as a CDR approach, artificial upwelling provides a means to supply growth-limiting nutrients to the upper ocean and generate increased primary production and net carbon sequestration. For this reason, it has been proposed as a potentially effective component of a portfolio of CDR approaches, either stand-alone or in concert with aquaculture. The important caveat for artificial upwelling is that to achieve the durable drawdown of atmospheric CO2, the net enhancement of the biological production of carbon must exceed the delivery of dissolved inorganic carbon from the upwelled source water. This is an important distinction, because deep water contains relatively high levels of CO2 that have been generated over time as sinking organic matter is remineralized, and so any stimulation of carbon export must exceed upwelled CO2. Determination of where in the ocean this is feasible requires knowledge of the ratio (stoichiometry) of elements (carbon:nitrogen:phosphorus:trace elements) in source waters relative to the elemental needs of biological communities. This knowledge is not well constrained in the global ocean, and hence there is significant uncertainty as to where and when upwelling could generate net carbon sequestration. Moreover, natural analogs where upwelling occurs are generally net sources of CO2 to the atmosphere (Takahashi et al., 1997) versus net sinks. In the particularly well-studied site of the Hawaii Ocean Time-series in the oligotrophic North Pacific Subtropical Gyre, Karl and Letelier (2008) estimate that artificial upwelling could only generate net carbon sequestration if the process of biological nitrogen gas fixation were stimulated to draw down residual nutrients not consumed by non-nitrogen gas-fixing phytoplankton. This hypothesis has not been proven or disproven, but it does illustrate that careful consideration must be paid to carbon accounting between deep-water sources and the long-term (> weeks to years) response of biological communities. In practice, as opposed to ocean iron fertilization, there exists no proof-of-concept sea trials that have demonstrated that artificial upwelling could act to sequester carbon below the ocean pycnocline. Lacking field demonstrations of the CDR efficacy (or lack thereof) of artificial upwelling, continued research is warranted to address key remaining issues related to regions where net CO2 uptake could occur, how sequestration efficiencies could be enhanced, and how carbon transport could or should be tracked and thus accounted for.

In silico, the potential efficacy of artificial upwelling as a means of CDR has been assessed via simulations of the biological impact of large-scale (millions of “ocean pipes”) global deployments operating efficiently over years to decades. As a composite, these models suggest that artificial upwelling would be an ineffective means for large-scale carbon sequestration (Dutreuil et al., 2009; Yool et al., 2009; Oschlies et al., 2010b; Keller et al., 2014) and would require a persistent and effective deployment of tens of million to hundreds of million functional pumps across the global ocean (Yool et al., 2009) operating at upwelling velocities generally in excess of what has been demonstrated in limited sea trials (Figure 4.3). Redistributing large amounts of deep ocean water is also expected to affect density and pressure fields in the surface ocean. If artificial upwelling

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

(and the concomitant downwelling that will take place) is to be scaled up, research will need to investigate possible long-term changes in ocean circulation as well as dynamical termination effects once or if the millions of pumps are turned off.

Only targeted, regulated, and transparent field studies can help to minimize current uncertainties and determine whether this strategy could be an effective component of an ocean CDR portfolio. The largest cost for research would be the demonstration-scale field experiments in addition to the cost of materials, fabrication, and maintenance for pumping systems. Using ocean iron fertilization cost estimates as an analogy, field studies at multiple sites could be on the order of $25M/yr for 10 years to complete work at multiple sites, whereas current commercial estimates of instrumented wave pumps are on the order of $60K per pump.5 “Cradle to grave” carbon-based life-cycle analyses for the pumping technology used would of course also be needed. A robust research agenda would also include parallel laboratory/mesocosm studies to address potential biological responses to deep-water additions of varying stoichiometry as well as modeling efforts to refine deployment scaling in space and time. Social and governance aspects would also be added as per any comprehensive ocean CDR research agenda.

Seaweed Cultivation

Seaweed cultivation and sequestration appears to be a compelling ocean CDR strategy. There is a good understanding of the underlying biology of seaweeds, their interactions with the ocean and its biogeochemistry, and decades of experience in farming seaweed. Seaweed cultivation has advantages over some other biotic CDR strategies as the fixed carbon biomass could be, in principle, conveyed to a known durable reservoir, which will increase the permanence of the sequestered carbon and in turn should simplify the carbon accounting. However, there remains uncertainty about how much productivity and carbon export that seaweed cultivation would displace as well as the durability of the sequestered carbon when conveyed to depth or the seafloor. Scaling to CDR-worthy levels will be challenging due to the large amount of farmed area required (many millions of hectares). However, much has been learned already from ongoing U.S. agency research programs, and the scale of the engineering and logistic efforts are similar to the many marine engineering accomplishments made by the marine engineering and oil and gas industries. The costs and energy expenditures should be small relative to some other CDR strategies. On the other hand, there will be environmental impacts where the farming occurs and where the seaweed biomass will be sequestered that are potentially detrimental, yet uncertain. There are both positive and negative social impacts from seaweed cultivation and sequestration CDR. If conducted at scale, seaweed cultivation will clearly enhance aspects of the blue economy associated with macroalagal farming (while perhaps diminishing other marine economic activities if there is competition for coastal space and resources), and it is an open question about the extent of net benefit for both coastal communities and many marine industries. There may also be several co-benefits from placing farms adjacent to other uses (e.g., fish farming, etc.) that could help mitigate some of the potential environmental damages conducted by these practices. On the negative side, the vast farms could represent hazards to navigation, and they may displace fishing and other uses of the ocean due to the implementation of farm infrastructure or the reduction in planktonic productivity and trophic exchanges that large-scale cultivation of seaweed biomass would create.

A decadal-scale research agenda for seaweed cultivation CDR should be focused on reducing the uncertainties outlined here as well as deploying demonstration-scale cultivation (several square kilometers in scale) and sequestration infrastructure. The accomplishment of these two elements will involve developing a predictive understanding of the entire process from farming on demonstration

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5 See https://ocean-based.com/frequently-asked-questions-faqs-about-our-autonomous-upwelling-pumps-aups/.

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

scales (many square kilometers) and its environmental and social impacts, to engineering conveyances to bring farmed biomass to depth, to understanding the biogeochemical fates, permanence, and environmental impacts of the farmed biomass and its by-products, to validating the end-to-end performance. In situ, in the laboratory, mesocosm experimentation and, in particular, numerical modeling will be required with the goal of creating modeling systems that can assess the potential of and impacts on local to global scales. Social and governance considerations would also need to be addressed in any research program. This research agenda should logically occur in phases (as mentioned in Section 4.6) and, based on present investment levels, will require approximately $25M per year.

Ecosystem Recovery

The research agenda for ecosystem recovery includes basic scientific research on the carbon removal potential and permanence of different organisms, ecosystems, and processes; an examination of the expected outcomes from different policy tools; and the socioeconomic and governance aspects of managing marine ecosystems and organisms for carbon removal. As with seaweed cultivation, there remains uncertainty in how much net carbon sequestration would result from protecting and restoring marine ecosystems. There are trade-offs to marine conservation efforts, with potential winners and losers if the focus of the ocean economy shifts from extraction to rebuilding marine life, with an emphasis on CDR and other services. Understanding of net carbon sequestration could be gained if carbon accounting and research became a central aspect of the monitoring of marine protected areas in the coming decades, including the examination of multiple systems, with geographic, ecological, and taxonomic differences, and varying levels of anthropogenic pressure.

For each of the systems discussed in Chapter 6, such as macroalgae reforestation, benthic algae and sediment protection, and animals in the carbon cycle, it is essential to understand the impact of human perturbation, which requires estimating the current and historical contribution of different species across the size spectrum in terms of annual carbon flux. Note that this agenda only focuses on the restoration of degraded ecosystems and recovery of depleted species to determine the respective CDR potential. In the absence of effective management, human activities will continue to threaten marine habitats, and any loss in ecosystem function and services via further marine degradation could have large consequences for the uptake of carbon by the oceans.

A logical next step to this work would be analysis of the best tools that could enhance marine ecosystem CDR, such as marine protected areas and habitat restoration, fish and fisheries management, and the restoration of food webs and large marine organisms. Kelp forest restoration, in particular, has been promoted for its CDR potential. All of these activities could have biodiversity and research co-benefits, such as improving the status of endangered or depleted species and enhancing the monitoring of marine mammals, fish, and other species. Research on the vulnerabilities of marine species and ecosystems, and their CDR potential, to rising sea-surface temperatures and reduced sea ice would also be valuable. Social and governance considerations would also need to be integrated into the research agenda. A budget of at least $20M per year would be required to comprehensively examine the carbon impacts of marine ecosystem-based recovery in the United States. Unlike several of the other approaches in this report, however, individual tools, such as macroalgal reforestation or marine protected areas, could be funded individually.

Ocean Alkalinity Enhancement

Approaches to increase ocean alkalinity have been proposed since the mid-1990s but remain at a relatively early stage of development. Ocean alkalinity enhancement attempts to mimic natural weathering processes either by adding crushed minerals directly to the ocean, to coastal, or to terrestrial environments. Given that the surface ocean is supersaturated with common carbonate

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

minerals, they cannot be added directly to the ocean. To facilitate mineral dissolution, the reaction of carbonate minerals with elevated CO2 has been suggested, initially for reducing fossil fuel emissions, but potentially for CDR by coupling with direct air capture or biomass energy carbon capture and storage. Others have proposed converting carbonate minerals into more reactive forms (e.g., lime or hydrated lime) for addition to the ocean. Finally, electrochemical approaches may be used to create basic and acidic solutions at each electrode; the former could be used for ocean alkalinity enhancement while the latter would need to be neutralized through reaction with silicate minerals.

The two key mechanisms by which ocean alkalinity enhancement could impact the environment are (1) elevated alkalinity that is “unequilibrated,” that is, high-pH, low-CO2 concentrations that may be more acute around the point of addition; and (2) the addition of other biologically active elements (i.e., iron, silica, as in ocean fertilization, or nickel, chromium, or other trace metals). Research is needed to assess the ecological response to ocean alkalinity enhancement. Although much can still be learned from laboratory-based and “contained” (mesocosm) experiments, including exploring the impacts of ocean alkalinity enhancement on the physiology and functionality of organisms and communities, pathways to responsible deployment will require field trials. Such trials will be essential in assessing how euphotic and benthic biogeochemical processes are affected, the response from complex communities, the indirect effects of ocean alkalinity enhancement, and optimal environments and treatment methods. Coupling this research to a rigorous monitoring program will be essential in accounting for CDR and the environmental impact of the experiments, but would help scope the requirements for monitoring of scaled-up ocean alkalinity enhancement.

The environmental impact of ocean alkalinity enhancement would be closely related to the methods or technologies that promote alkalinity changes (e.g., the choice of rock or mineral and the mechanisms by which it is dissolved). An experimental program that considers the environmental response to ocean alkalinity enhancement will be most effective if it were constrained by what might be practical. Research and development is required to explore and improve the technical feasibility and readiness level of ocean alkalinity enhancement approaches (including the development of pilot-scale facilities). Research on social and governance considerations associated with contained and pilot-scale experiments and deployment (if any) is also required.

Electrochemical Processes

The research agenda for electrochemical processes focuses on activities that reduce the cost and environmental impact of the approaches. Presently, only a small number of system configurations have been investigated for either CDR from seawater or as methods for increasing ocean alkalinity. These should be broadened to also consider novel designs of electrolyzers and electrochemical reactors, electrode materials that can minimize the production of unwanted by-products (e.g., chlorine gas), electrochemical reactor architectures, and hybrid approaches that both remove CO2 and increase ocean alkalinity. Wider impacts on ocean ecosystems are included in the research agenda for ocean alkalinity enhancement and are not repeated here. Meaningfully large demonstration-scale projects (>1,000 kg per day, and approaching the scale of several or tens of tonnes per day) are central to the research agenda. While part of this research agenda may focus on the development of specific technologies or materials (e.g., electrolyzer design or novel electrode materials), it also focuses on systems integration (particularly with rock dissolution processes) and scale-up strategies that allow for process cost reductions to be discovered.

The processes explored by the research agenda will need to demonstrate pathways to large-scale deployment and thus include provisions for resource mapping, stakeholder engagement, and wider economic impact from an ocean-based electrochemical CDR industry operating at a climate-relevant scale. Transparent dissemination of the research outcomes would allow independent assessment of cost and environmental impact. Social and governance considerations are also important components of the research program.

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

TABLE 9.1 Summary of Scale-Up Potential of Ocean-Based CDR Approaches (summarized from Chapters 3–8)

Ocean Nutrient Fertilization Artificial Upwelling/Downwelling Seaweed Cultivation Ecosystem Recovery Ocean Alkalinity Enhancement Electrochemical Processes
Knowledge base
What is known about the system (low, mostly theoretical, few in situ experiments; medium, lab and some fieldwork, few carbon dioxide removal (CDR) publications; high, multiple in situ studies, growing body of literature)
Medium–High
Considerable experience relative to any other ocean CDR approach with strong science on phytoplankton growth in response to iron, less experience on fate of carbon and unintended consequences. Natural iron-rich analogs provide valuable insight on larger temporal and spatial scales.
Low–Medium
Various technologies have been demonstrated for artificial upwelling (AU), although primarily in coastal regimes for short duration. Uncertainty is high and confidence is low for CDR efficacy due to upwelling of CO2, which may counteract any stimulation of the biological carbon pump (BCP).
Medium–High
Science of macrophyte biology and ecology is mature; many mariculture facilities are in place globally. Less is known about the fate of macrophyte organic carbon and methods for transport to deep ocean or sediments.
Low–Medium
There is abundant evidence that marine ecosystems can uptake large amounts of carbon and that anthropogenic impacts are widespread, but quantifying the collective impact of these changes and the CDR benefits of reversing them is complex and difficult.
Low–Medium
Seawater CO2 system and alkalinity thermodynamics are well understood. Need for empirical data on alkalinity enhancement; currently, knowledge is based on modeling work. Uncertainty is high for possible impacts.
Low–Medium
Processes are based on well-understood chemistry with a long history of commercial deployment, but is yet to be adapted for CO2 removal by ocean alkalinity enhancement (OAE) beyond benchtop scale.
Efficacy
What is the confidence level that this approach will remove atmospheric CO2 and lead to net increase in ocean carbon storage (low, medium, high)
Medium–High Confidence
BCP known to work and productivity enhancement evident. Natural systems have higher rates of carbon sequestration in response to iron but low efficiencies seen thus far would limit effectiveness for CDR.
Low Confidence
Upwelling of deep water also brings a source of CO2 that can be exchanged with the atmosphere. Modeling studies generally predict that large-scale AU would not be effective for CDR.
Medium Confidence
The growth and sequestration of seaweed crops should lead to net CDR. Uncertainties about how much existing net primary production (NPP) and carbon export downstream would be reduced due to large-scale farming.
Low–Medium Confidence
Given the diversity of approaches and ecosystems, CDR efficacy is likely to vary considerably. Kelp forest restoration, marine protected areas, fisheries management, and restoring marine vertebrate carbon are promising tools.
High Confidence
Need to conduct field deployments to assess CDR, alterations of ocean chemistry (carbon but also metals), how organic matter can impact aggregation, etc.
High Confidence
Monitoring within an enclosed engineered system, CO2 stored either as increased alkalinity, solid carbonate, or aqueous CO2 species. Additionality possible with the utilization of by-products to reduce carbon intensity.
Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×
Ocean Nutrient Fertilization Artificial Upwelling/Downwelling Seaweed Cultivation Ecosystem Recovery Ocean Alkalinity Enhancement Electrochemical Processes
Durability
Will it remove CO2 durably away from surface ocean and atmosphere (low, <10 years; medium, >10 years and <100 years; high, >100 years), and what is the confidence (low, medium, high)
Medium
10–100 years
Depends highly on location and BCP efficiencies, with some fraction of carbon flux recycled faster or at shallower ocean depths; however, some carbon will reach the deep ocean with >100-year horizons for return of excess CO2 to surface ocean.
Low–Medium
<10–100 years
As with ocean iron fertilization (OIF), dependent on the efficiency of the BCP to transport carbon to deep ocean.
Medium–High
>10–100 years
Dependent on whether the sequestered biomass is conveyed to appropriate sites (e.g., deep ocean with slow return time of waters to surface ocean).
Medium
10–100 years
The durability of ecosystem recovery ranges from biomass in macroalgae to deep-sea whale falls expected to last >100 years.
Medium–High
>100 years
Processes for removing added alkalinity from seawater generally quite slow; durability not dependent simply on return time of waters with excess CO2 to ocean surface.
Medium–High
>100 years
Dynamics similar to OAE.
Scalability
Potential scalability at some future date with global-scale implementation (low, <0.1 Gt CO2/ yr; medium, >0.1 Gt CO2/yr and <1.0 Gt CO2/yr; high, >1.0 Gt CO2/yr), and what is the confidence level (low, medium, high)
Medium–High
Potential C removal >0.1–1.0 Gt CO2/yr (medium confidence) Large areas of ocean have high-nutrient, low-chlorophyll conditions suitable to sequester >1 Gt CO2/yr. Co-limitation of macronutrients and ecological impacts at large scales are likely. Low-nutrient, low-chlorophyll areas have not been explored to increase areas of possible deployment. (Medium confidence based on 13 field experiments).
Medium
Potential C removal >0.1 Gt CO2/yr and <1.0 Gt CO2/yr (low confidence) Could be coupled with aquaculture efforts. Would require pilot trials to test materials durability for open ocean and assess CDR potential. Current model predictions would require deployment of tens of millions to hundreds of millions of pumps to enhance carbon sequestration. (Low confidence that this large-scale deployment would lead to permanent and durable CDR).
Medium
Potential C removal >0.1 Gt CO2/yr and <1.0 Gt CO2/yr (medium confidence) Farms need to be many million hectares, which creates many logistic and cost issues. Uncertainties about nutrient availability and durability of sequestration, seasonality will limit sites, etc.
Low–Medium
Potential C removal <0.1–1.0 Gt CO2/yr (low–medium confidence) Given the widespread degradation of much of the coastal ocean, there are plenty of opportunities to restore ecosystems and depleted species. However, ecosystems and trophic interactions are complex and changing and research will be necessary to explore upper limits.
Medium–High
Potential C removal >0.1–1.0 Gt CO2/yr (medium confidence) Potential for sequestering >1 Gt CO2/yr if applied globally. High uncertainty coming from potential aggregation and export to depth of added minerals and unintended chemical impacts of alkalinity addition.
Medium–High Potential C removal >0.1–1.0 Gt CO2/yr (medium confidence) Energy and water requirements may limit scale. For climate relevancy, the scale will be double to an order of magnitude greater than the current chlor-alkali industry.
Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×
Environmental risk
Intended and unintended undesirable consequences at scale (unknown, low, medium, high), and what is the confidence level (low, medium, high)
Medium
(low to medium confidence)
Intended environmental impacts increase NPP and carbon sequestration due to changes in surface ocean biology. If effective, there are deep-ocean impacts and concern for undesirable geochemical and ecological consequences. Impacts at scale uncertain.
Medium–High
(low confidence)
Similar impacts to OIF but upwelling also affects the ocean’s density field and sea-surface temperature and brings likely ecological shifts due to bringing colder, inorganic carbon, and nutrient-rich waters to surface.
Medium–High
(low confidence)
Environmental impacts are potentially detrimental especially on local scales where seaweeds are farmed (i.e., nutrient removal due to farming will reduce NPP, carbon export, and trophic transfers) and in the deep ocean where the biomass is sequestered (leading to increases in acidification, hypoxia, eutrophication, and organic carbon inputs). The scale and nature of these impacts are highly uncertain.
Low
(medium–high confidence)
Environmental impacts would be generally viewed as positive. Restoration efforts are intended to provide measurable benefits to biodiversity across a diversity of marine ecosystems and taxa.
Medium
(low confidence)
Possible toxic effect of nickel and other leachates of olivine on biota, bio-optical impacts, removal of particles by grazers, unknown responses to increased alkalinity on functional diversity and community composition. Effects also from expanded mining activities (on land) on local pollution, CO2 emissions.
Medium–High
(low confidence)
Impact on the ocean is possibly constrained to the point of effluent discharge. Poorly-known possible ecosystem impacts similar to alkalinity enhancement. Excess acid (or gases, particularly chlorine) will need to be treated and safely disposed. Provision of sufficient electrical power will likely have remote impacts.
Social considerations
Encompass use conflicts, governance-readiness, opportunities for livelihoods, etc.
Potential conflicts with other uses of high seas and protections; downstream effects from displaced nutrients will need to be considered; legal uncertainties; potential for public acceptability and governance challenges (i.e., perception of “dumping”). Potential conflicts with other uses (shipping, marine protected areas, fishing, recreation); potential for public acceptability and governance challenges (i.e., perception of dumping). Possibility for jobs and livelihoods in seaweed cultivation; potential conflicts with other marine uses. Downstream effects from displaced nutrients will need to be considered. Trade-offs in marine uses to enhance ecosystem protection and recovery. Social and governance challenges may be less significant than with other approaches. Expansion of mining production, with public health and economic implications; general public’s potential for public acceptability and governance challenges (e.g., if perceived as “dumping”). Similar to OAE and to any industrial site. Substantial electrical power demand may generate social impacts.
Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×
Ocean Nutrient Fertilization Artificial Upwelling/Downwelling Seaweed Cultivation Ecosystem Recovery Ocean Alkalinity Enhancement Electrochemical Processes
Co-benefits
How significant are the co-benefits as compared to the main goal of CDR and how confident is that assessment
Medium
(low confidence)
Enhanced fisheries possible but not shown and difficult to attribute. Seawater dimethyl sulfide increase seen in some field studies that could enhance climate cooling impacts. Surface ocean decrease in ocean acidity possible.
Medium–High
(low confidence)
May be used as a tool in coordination with localized enhancement of aquaculture and fisheries.
Medium–High
(medium confidence)
Placing cultivation facilities near fish or shellfish aquaculture facilities could help alleviate environmental damages from these activities. Bio-fuels also possible.
High
(medium–high confidence)
Enhanced biodiversity conservation and the restoration of many ecological functions and ecosystem services damaged by human activities. Existence, spiritual, and other nonuse values. Potential to enhance marine stewardship and tourism.
Medium
(low confidence)
Mitigation of ocean acidification; positive impact on fisheries.
Medium–High
(medium confidence)
Mitigation of ocean acidification; production of H2, Cl2, silica.
Cost of scale-up
Estimated costs in dollars per metric ton CO2 for future deployment at scale; does not include all of monitoring and verification costs needed for smaller deployments during R&D phases (low, <$50/t CO2; medium, ~$100/t CO2; high, >>$150/t CO2) and confidence in estimate (low, medium, high)
Low
<$50/t CO2
(low–medium confidence)
Deployment of <$25/t CO2 sequestered for deployment at scale are possible, but need to be demonstrated at scale
Medium–High.
>$100–$150/t CO2
(low confidence)
Development of a robust monitoring program is the likely largest cost and would be of similar magnitude as OIF. Materials costs for pump assembly could be moderate for large-scale persistent deployments. Estimates for a kilometer-scale deployment are in the tens of million dollars.
Medium
~$100/t CO2
(medium confidence)
Costs should be less than $100/t CO2. No direct energy used to fix CO2.
Low
<$50/t CO2
(medium confidence)
Varies, but direct costs would largely be for management and opportunity costs for restricting uses of marine species and the environment. No direct energy used.
Medium–High
>$100–$150/t CO2
(low–medium confidence)
Cost estimates range between tens of dollars and $160/t CO2. Need for expansion of mining, transportation, and ocean transport fleet.
High
>$150/t CO2
(medium confidence)
Gross current estimates $150–$2,500/t CO2 removed. With further R&D, it may be possible to reduce this to <$100/t CO2.
Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×
Cost and challenges of carbon accounting
Relative cost and scientific challenge associated with transparent and quantifiable carbon tracking (low, medium, high)
Medium
Challenges tracking additional local carbon sequestration and impacts on carbon fluxes outside of boundaries of CDR application (additionality).
High
Local and additionality monitoring needed for carbon accounting similar to OIF.
Low–Medium
The amount of harvested and sequestered carbon will be known. However, an accounting of the carbon cycle impacts of the displaced nutrients will be required (additionality).
High
Monitoring net effect on carbon sequestration is challenging.
Low–Medium
Accounting more difficult for addition of minerals and non-equilibrated addition of alkalinity, than equilibrated addition.
Low–Medium
Cost of environmental monitoring
Need to track impacts beyond carbon cycle on marine ecosystems (low, medium, high)
Medium
(medium–high confidence)
All CDR will require monitoring for intended and unintended consequences both locally and downstream of CDR site, and these monitoring costs may be substantial fraction of overall costs during R&D and demonstration-scale field projects. This cost of monitoring for ecosystem recovery may be lower.
Additional resources needed
Relative low, medium, high to primary costs of scale-up
Low–Medium
Cost of material: iron is low and energy is sunlight.
Medium–High
Materials, deployment, and potential recovery costs.
Medium
Farms will require large amounts of ocean (many million hectares) to achieve CDR at scale.
Low
Most recovery efforts will likely require few materials and little energy, though enforcement could be an issue. Active restoration of kelp and other ecosystems would require more resources.
Medium–High
Adaptation and likely expansion of existing fleet for deployment; infrastructure for storage at ports. Infrastructure support for expansion of mineral extraction, processing, transportation, and deployment.
Medium–High
High energy requirements (1–2.5 MWh/t CO2 removed) and build-out of industrial CDR.
Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

TABLE 9.2 Foundational Research Priorities Common to all Ocean-Based CDR

Research Priority Estimated Budget Duration (years) Total
Model international governance framework for ocean CDR research $2M–$3M/yr 2–4 $4M–$12M
Application of domestic laws to ocean CDR research $1M/yr 1–2 $1M–$2M
Assessment of need for domestic legal framework specific to ocean CDR $1M/yr 2–4 $2M–$4M
Development of domestic legal framework specific to ocean CDR
Mixed methods, multisited research to understand community priorities and assessment of benefits and risks for ocean CDR as a strategy $5M/yr 4 $20M
Interactions and trade-offs between ocean CDR, terrestrial CDR, adaptation, and mitigation, including the potential of mitigation deterrence $2M/yr 4 $8M
Cross-sectoral research analyzing food system, energy, sustainable development goals, and other systems in their interaction with ocean CDR approaches $1M/yr 4 $4M
Capacity-building research fellowship for diverse early-career scholars in ocean CDR $1.5M/yr 2 $3M
Transparent, publicly accessible system for monitoring impacts from projects $0.25M/yr 4 $1M
Research on how user communities (companies buying and selling CDR, nongovernmental organizations, practitioners, policy makers) view and use monitoring data, including certification $0.5M/yr 4 $2M
Analysis of policy mechanisms and innovation pathways, including on the economics of scale-up $1M–2M/yr 2 $2M–$4M
Development of standardized environmental monitoring and carbon accounting methods for ocean CDR $0.2M/yr 3 $0.6M
Development of a coordinated research infrastructure to promote transparent research $2M/yr 3–4 $6M–$8M
Development of a publicly accessible data management strategy for ocean CDR research $2M–3M/yr 2 $4M–$6M
Development of a coordinated plan for science communication and public engagement of ocean CDR research in the context of decarbonization and climate response $5M/yr 10 $50M
Development of a common code of conduct for ocean CDR research $1M/yr 2 $2M
Total Estimated Research Budget
(Assumes all six CDR approaches moving ahead)
~$29M/yr 2–10 ~$125M
Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

TABLE 9.3 Research Needed to Advance Understanding of Each Ocean CDR Approach

Estimated Budget Duration (years) Total Budget
Ocean Fertilization
Carbon sequestration delivery and bioavailability $5M/yr 5 ~$25M
Tracking carbon sequestration $3M/yr 5 ~$15M
In field experiments- >100 t Fe and >1,000 km2 initial patch size followed over annual cycles $25M/yr 10 ~$250M
Monitoring carbon and ecological shifts $10M/yr 10 ~$100M
Experimental planning and extrapolation to global scales $5M/yr 10 ~$50M
Total Estimated Research Budget $48M/yr 5–10 $440M
Estimated Budget of Research Priorities $33M/yr 5–10 $290M
Artificial Upwelling and Downwelling
Technological readiness: Limited and controlled open-ocean trials to determine durability and operability of artificial upwelling technologies $5M/yr 5 $25M
(~100 pumps tested in various conditions)
Feasibility studies $1M/yr 1 $1M
Tracking carbon sequestration $3M/yr 5 $15M
Modeling of carbon sequestration based upon achievable upwelling velocities and known stoichiometry of deep-water sources. Parallel mesocosm and laboratory experiments to assess potential biological responses to deep water of varying sources $5M/yr 5 $25M
Planning and implementation of demonstration-scale in situ experimentation (>1 year, >1,000 km) in region sited-based input from modeling and preliminary experiments $25M/yr 10 $250M
Monitoring carbon and ecological shifts $10M/yr 10 $100M
Experimental planning and extrapolation to global scales (early for planning and later for impact assessments) $5M/yr 10 $50M
Total Estimated Research Budget ~$54/yr 5–10 $466M
Estimated Budget of Research Priorities $5M/yr 5–10 $25M
Seaweed Cultivation
Technologies for efficient large-scale farming and harvesting of seaweed biomass $15M/yr 10 $150M
Engineering studies focused on the conveying of harvested biomass to durable oceanic reservoir with minimal losses of carbon $2M/yr 10 $20M
Assessment of long-term fates of seaweed biomass and by-products $5M/yr 5 $25M
Implementation and deployment of a demonstration-scale seaweed cultivation and sequestration system $10M/yr 10 $100M
Validation and monitoring the CDR performance of a demonstration-scale seaweed cultivation and sequestration system $5M/yr 10 $50M
Evaluation of the environmental impacts of large-scale seaweed farming and sequestration $4M/yr 10 $40M
Total Estimated Research Budget $41M/yr 5–10 $385M
Estimated Budget of Research Priorities $26M/yr 5 $235M
Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×
Estimated Budget Duration (years) Total Budget
Ecosystem Recovery
Restoration ecology and carbon $8M/yr 5 $40M
Marine protected areas: Do ecosystem-level protection and restoration scale for marine CDR? $8M/yr 10 $80M
Macroalgae: Carbon measurements, global range, and levers of protection $5M/yr 10 $50M
Benthic communities: disturbance and restoration $5M/yr 5 $25M
Marine animals and CO2 removal $5M/yr 10 $50M
Animal nutrient cycling $5M/yr 5 $25M
Commercial fisheries and marine carbon $5M/yr 5 $25M
Total Estimated Research Budget $41M/yr 5–10 $295M
Estimated Budget of Research Priorities $26M/yr 5–10 $220M
Ocean Alkalinity Enhancement
Research and development to explore and improve the technical feasibility and readiness level of ocean alkalinity enhancement approaches (including the development of pilot-scale facilities) $10M/yr 5 $50M
Laboratory and mesocosm experiments to explore impacts on physiology and functionality of organisms and communities $10M/yr 5 $50M
Field experiments $15M/yr 5–10 $75M–$150M
Research into the development of appropriate monitoring and accounting schemes, covering CDR potential and possible side effects $10 5–10 $50M–$100M
Total Estimated Research Budget $45M/yr 5–10 $180M–$350M
Estimated Budget of Research Priorities $25M/yr 5–10 $125M–$200M
Electrochemical Processes
Demonstration projects including CDR verification and environmental monitoring $30M/yr 5 $150M
Development and assessment of novel and improved electrode and membrane materials $10M/yr 5 $50M
Assessment of environmental impact and acid management strategies $7.5M/yr 10 $75M
Coupling whole-rock dissolution to electrochemical reactors and systems $7.5M/yr 10 $75M
Development of hybrid approaches $7.5M/yr 10 $75M
Resource mapping and pathway assessment $10M/yr 5 $50M
Total Estimated Research Budget $73M/yr 5–10 $475M
Estimated Budget of Research Priorities $55M/yr 5–10 $350M

NOTE: Bold type identifies priorities for taking the next step to advance understanding of each particular approach.

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

9.4 PROPOSED RESEARCH AGENDA

As summarized in this report, the state of knowledge and uncertainty surrounding ocean CDR varies greatly among and within different CDR approaches, with knowledge gaps remaining in determining carbon sequestration efficiencies, scaling, and permanence, as well as environmental and social impacts and costs. At present, the current state of scientific understanding precludes choosing among different ocean CDR approaches, and there are opportunities and benefits from pursuing research along multiple pathways in parallel. The resulting increased understanding and confidence will allow for more informed choices on the viability of ocean CDR relative to other climate change response options, given the ever-increasing and visible impacts of climate change.

Based on the present state of knowledge, there are substantial uncertainties in all of the ocean CDR approaches evaluated in this report. The knowledge gaps differ among the CDR approaches as highlighted by the research elements and priorities (marked in bold) in Table 9.2. The best approach for reducing knowledge gaps will involve a diversified research investment strategy that includes both crosscutting, common components (Table 9.2) and coordination across multiple individual CDR approaches (Table 9.3) in parallel (Figure 9.1). The development of a robust research portfolio will reflect a balance among several factors: common elements and infrastructure versus targeted studies on specific approaches; biotic versus abiotic CDR approaches; and more established versus emerging CDR approaches. The research cost values in Table 9.2 and 9.3 are only rough estimates, and as an ocean CDR research program develops and priorities are refined with time, improved cost estimates will likely become clearer.

Crosscutting foundation research priorities listed in Table 9.2 include research on international governance and the domestic legal framework of ocean CDR research. Other priorities include the development of a common code of conduct for ocean CDR research and coordinated research infrastructure including components on standardized environmental monitoring and carbon accounting methods, publicly accessible data management, and science communication and public engagement.

The research priorities in Table 9.3 for each of the four biotic ocean CDR approaches (Chapters 36) differ based on the current knowledge base, extent of previous research, and distinctions in the underlying biological processes. As discussed above, evaluation of research needs across CDR approaches is more challenging, suggesting some investment in all methods; however, a first-order attempt at prioritization can be constructed based on current knowledge using the CDR criteria outlined at the beginning of Section 9.3. Among the biotic approaches, research on ocean iron fertilization and seaweed cultivation offer the greatest opportunities for evaluating the viability of possible biotic ocean CDR approaches; research on the potential CDR and sequestration permanence for ecosystem recovery would also be beneficial in the context of ongoing marine conservation efforts.

For abiotic ocean CDR approaches (Chapters 7 and 8), the research agenda (Table 9.2) will be most impactful if it combines a thorough understanding of potential environmental impacts alongside technology development and upscaling efforts. Based on present understanding, there is considerable CDR potential for ocean alkalinity enhancement, which spans a number of approaches including, but not restricted to, ocean liming, accelerated rock weathering, and electrochemical methods for alkalinity enhancement, among others. Next steps for alkalinity enhancement research offer large opportunities for closing knowledge gaps but include the complexity of undertaking large-scale experimentation to assess whole-ecosystem responses across the range of technologies and approaches for increasing alkalinity. Therefore, among the abiotic approaches, research on ocean alkalinity enhancement, including electrochemical alkalinity enhancement, have priority over electrochemical approaches that only seek to achieve CDR from seawater (also known as carbon dioxide stripping).

Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

Early research findings might indicate a low viability for particular approaches. The approach advocated in the research agenda below is to be adaptive, meaning that decisions on future investments in research activities will need to take into account new findings on the efficacy and durability of a technique, whether the social and environmental impacts outweigh benefits, or face social and governance challenges. This is in line with a responsible research and innovation approach (Box 9.1). Generally speaking, we can anticipate that there may be showstoppers for some approaches from factors both internal and external to the research. Internal showstoppers include findings that indicate that the viability is so low as to not warrant further research investments. For example, there are questions about whether artificial upwelling/downwelling technologies will be operable at sufficient scales; this is why the technique has a priority item to better evaluate technological readiness (Table 9.3), recommending limited and controlled open ocean trials to determine durability and operability of artificial upwelling technologies.

There may also be external showstoppers to the research, such as lack of social license or governance actions, which preclude further investigation. Given that climate change governance and politics are dynamic, it is impossible to predict what these showstoppers will be. However, there are examples of research that was deemed too risky or unnecessary by social stakeholders. For example, in the early 2000s, scientists were researching injecting CO2 directly into the mid-depth ocean using small-scale experiments. In 1997 in Kyoto, during UNFCCC COP-3, an international project agreement was signed for the study of direct CO2 injection, with sponsors from the U.S. Department of Energy, the New Energy and Industrial Technology Development Organization of Japan, and the Norwegian Research Council; researchers from Australia, Canada, and Switzerland also joined. However, the research faced criticism from local civil society organizations as well as larger organizations such as Greenpeace, and planned experiments off the coasts of Hawaii and Norway were halted, with the Norwegian Environmental Minister stating that using deep marine areas as future storage places for CO2 required more international discussion and the clarification of legal implications (de Figueiredo, 2003). Within the scientific community, there was discussion of what research could be done to identify potential harms to deep-sea biology, with some recommending very aggressive research to provide information on impacts on deep-sea organisms within a relevant time frame (Seibel and Walsh, 2003). In other words, direct deep-sea CO2 injection faced external social showstoppers and may have also faced potential scientific, internal showstoppers, should it have proceeded further. Scientists must be alert and responsive to potential showstoppers. Early investment in public engagement and governance activities may help advance understanding of what external showstoppers may be, and structuring the research agenda to focus on priority items can help advance understanding of internal showstoppers.

Recommendation 3: Ocean CDR Research Program Priorities. A research program should move forward integrating studies, in parallel, on multiple aspects of different ocean CDR approaches, recognizing the different stages of the knowledge base and technological readiness of specific ocean CDR approaches. Priorities for the research program should include development of:

  1. Overarching implementation plan for the next decade adhering to the crosscutting strategy elements in Recommendation 1 and incorporating from its onset the common research components in Recommendation 2 and Table 9.2. Achieving progress on these common research components is essential to lay a foundation for all other recommended research.
  2. Tailored implementation planning for specific ocean CDR approaches focused on reducing critical knowledge gaps by moving sequentially from laboratory-scale to pilot-scale field experiments, as appropriate, with adequate environmental and social risk reduction measures and transparent decision-making processes (priority components bolded in Table 9.3).
Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×
Image
FIGURE 9.1 Conceptual timeline of ocean-based CDR research based on Tables 9.2 and 9.3. Stops included on the diagram represent possible internal and external showstoppers or barriers to a particular approach.
  1. Common framework for intercomparing the viability of ocean CDR approaches with each other and with other climate response measures using standard criteria for efficacy, permanence, costs, environmental and social impacts, and governance and social dimensions.
  2. Research framework including program-wide components for experimental planning and public engagement, monitoring and verification (carbon accounting), and open publicly accessible data management.
  3. Strategy and implementation for engaging and communicating with stakeholders, policy makers, and publics.
  4. Research agenda that emphasizes advancing understanding of ocean fertilization, seaweed cultivation, and ocean alkalinity enhancement.
Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
×

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Suggested Citation:"9 Synthesis and Research Strategy." National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. doi: 10.17226/26278.
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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.

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