• Electrochemical technologies, as applied to ocean-based CDR, are very new. Because of the lack of proof-of-concept field experiments, it has so far been impossible to characterize benefits, risks, and scaling consideration of OAE in real-world settings (i.e. not benchtop). Controlled field experiments across diverse ecosystems to determine marine chemistry and biology impacts and feedbacks are needed (Develop New Modeling Tools to Support Design and Evaluation, Accelerate Design and Permitting of Controlled Field Trials).
• It is challenging to verify additional CO₂ uptake from the atmosphere as a result of electrochemical CDR given the ocean’s dynamic CO₂ flux “background state”. New methodologies are needed to observe additional sequestration from the atmosphere into the ocean (Develop New Modeling Tools to Support Design and Evaluation, Develop New In-Water Tools for Autonomous CDR Operations)
• Laboratory experiments are needed across a range of seawater chemistries expected because of expected electrochemical CDR variations in seawater total alkalinity and dissolved inorganic carbon^[1]Comments from Dr. Ros Rickaby, ‘Workshop on Ocean-based CDR Opportunities and Challenges, Part 2: Technological and Natural Approaches to Ocean Alkalinity Enhancement and CO₂ Removal’ on 27th January 2021 to characterize environmental impacts (Accelerate Design and Permitting of Controlled Field Trials).
  • Look to the ocean acidification community’s effort to develop standardized protocols for guidance^[2]Gattuso, Jean-Pierre, and Lina Hansson. “European Project on Ocean Acidification (EPOCA): Objectives, Products, and Scientific Highlights.” Oceanography 22, no. 4 (December 1, 2009): 190–201. https://doi.org/10.5670/oceanog.2009.108. as the community builds out standardized protocols and treatments levels for consistency and inter-comparability
• Global, local, and regional predictions of physical, chemical, and biological outcomes and feedbacks of electrochemical CDR from high-resolution models (Develop New Modeling Tools to Support Design and Evaluation)
• Life cycle assessments to calculate net CDR benefits, taking into account all emissions associated with supply chains (Develop CDR Monitoring and Verification Protocols). 

• Electrochemical technologies, as applied to ocean-based CDR, are very new. Because of the lack of proof-of-concept field experiments, it has so far been impossible to characterize benefits, risks, and scaling consideration of OAE in real-world settings (i.e. not benchtop). Controlled field experiments across diverse ecosystems to determine marine chemistry and biology impacts and feedbacks are needed (Develop New Modeling Tools to Support Design and Evaluation, Accelerate Design and Permitting of Controlled Field Trials).
• It is challenging to verify additional CO₂ uptake from the atmosphere as a result of electrochemical CDR given the ocean’s dynamic CO₂ flux “background state”. New methodologies are needed to observe additional sequestration from the atmosphere into the ocean (Develop New Modeling Tools to Support Design and Evaluation, Measure the Scale and Impacts of CDR via Macroalgae Sinking)
• Laboratory experiments are needed across a range of seawater chemistries expected because of expected electrochemical CDR variations in seawater total alkalinity and dissolved inorganic carbon^[1]Comments from Dr. Ros Rickaby, ‘Workshop on Ocean-based CDR Opportunities and Challenges, Part 2: Technological and Natural Approaches to Ocean Alkalinity Enhancement and CO₂ Removal’ on 27th January 2021 to characterize environmental impacts (Accelerate Design and Permitting of Controlled Field Trials).
  • Look to the ocean acidification community’s effort to develop standardized protocols for guidance^[2]Gattuso, Jean-Pierre, and Lina Hansson. “European Project on Ocean Acidification (EPOCA): Objectives, Products, and Scientific Highlights.” Oceanography 22, no. 4 (December 1, 2009): 190–201. https://doi.org/10.5670/oceanog.2009.108. as the community builds out standardized protocols and treatments levels for consistency and inter-comparability
• Global, local, and regional predictions of physical, chemical, and biological outcomes and feedbacks of electrochemical CDR from high-resolution models (Develop New Modeling Tools to Support Design and Evaluation)
• Life cycle assessments to calculate net CDR benefits, taking into account all emissions associated with supply chains (Develop New In-Water Tools for Autonomous CDR Operations). 

• Electrochemical technologies, as applied to ocean-based CDR, are very new. Because of the lack of proof-of-concept field experiments, it has so far been impossible to characterize benefits, risks, and scaling consideration of OAE in real-world settings (i.e. not benchtop). Controlled field experiments across diverse ecosystems to determine marine chemistry and biology impacts and feedbacks are needed (3a, 3b).
• It is challenging to verify additional CO₂ uptake from the atmosphere as a result of electrochemical CDR given the ocean’s dynamic CO₂ flux “background state”. New methodologies are needed to observe additional sequestration from the atmosphere into the ocean (3a, 3c)
• Laboratory experiments are needed across a range of seawater chemistries expected because of expected electrochemical CDR variations in seawater total alkalinity and dissolved inorganic carbon^[1]Comments from Dr. Ros Rickaby, ‘Workshop on Ocean-based CDR Opportunities and Challenges, Part 2: Technological and Natural Approaches to Ocean Alkalinity Enhancement and CO₂ Removal’ on 27th January 2021 to characterize environmental impacts (3b).
  • Look to the ocean acidification community’s effort to develop standardized protocols for guidance^[2]Gattuso, Jean-Pierre, and Lina Hansson. “European Project on Ocean Acidification (EPOCA): Objectives, Products, and Scientific Highlights.” Oceanography 22, no. 4 (December 1, 2009): 190–201. https://doi.org/10.5670/oceanog.2009.108. as the community builds out standardized protocols and treatments levels for consistency and inter-comparability
• Global, local, and regional predictions of physical, chemical, and biological outcomes and feedbacks of electrochemical CDR from high-resolution models (3a)
• Life cycle assessments to calculate net CDR benefits, taking into account all emissions associated with supply chains (3d). 

• Electrochemical technologies, as applied to ocean-based CDR, are very new. Because of the lack of proof-of-concept field experiments, it has so far been impossible to characterize benefits, risks, and scaling consideration of OAE in real-world settings (i.e. not benchtop). Controlled field experiments across diverse ecosystems to determine marine chemistry and biology impacts and feedbacks are needed (3a, 3b).
• It is challenging to verify additional CO₂ uptake from the atmosphere as a result of electrochemical CDR given the ocean’s dynamic CO₂ flux “background state”. New methodologies are needed to observe additional sequestration from the atmosphere into the ocean (3a, 3c)
• Laboratory experiments are needed across a range of seawater chemistries expected because of expected electrochemical CDR variations in seawater total alkalinity and dissolved inorganic carbon to characterize environmental impacts (3b).
  • Look to the ocean acidification community’s effort to develop standardized protocols for guidance as the community builds out standardized protocols and treatments levels for consistency and inter-comparability
• Global, local, and regional predictions of physical, chemical, and biological outcomes and feedbacks of electrochemical CDR from high-resolution models (3a)
• Life cycle assessments to calculate net CDR benefits, taking into account all emissions associated with supply chains (3d). 

• Electrochemical technologies, as applied to ocean-based CDR, are very new. Because of the lack of proof-of-concept field experiments, it has so far been impossible to characterize benefits, risks, and scaling consideration of OAE in real-world settings (i.e. not benchtop). Controlled field experiments across diverse ecosystems to determine marine chemistry and biology impacts and feedbacks are needed (3a, 3b).
• It is challenging to verify additional CO₂ uptake from the atmosphere as a result of electrochemical CDR given the ocean’s dynamic CO₂ flux “background state”. New methodologies are needed to observe additional sequestration from the atmosphere into the ocean (3a, 3c)
• Laboratory experiments are needed across a range of seawater chemistries expected because of expected electrochemical CDR variations in seawater total alkalinity and dissolved inorganic carbon to characterize environmental impacts (3b).
  • Look to the ocean acidification community’s effort to develop standardized protocols for guidance as the community builds out standardized protocols and treatments levels for consistency and inter-comparability
• Global, local, and regional predictions of physical, chemical, and biological outcomes and feedbacks of electrochemical CDR from high-resolution models (3a)
• Life cycle assessments to calculate net CDR benefits, taking into account all emissions associated with supply chains (3d). 

• Current observational technologies (sensors, ROVs, AUVs, etc.) and modeling tools are not widespread and easily available to support field trials with the necessary spatial and temporal frequency of monitoring and sampling (Develop New In-Water Tools for Autonomous CDR Operations)
• In the case of surface seawater alkalinity addition from electrolysis or electrodialysis, cost-effective and safe methods need to be developed that optimize the distribution, dispersal and dilution of any strong chemical bases to avoid impacts of excessively alkaline (pH>9) waters on marine ecosystems. Dilution may require pumping large amounts of seawater, which need to be optimized for energy and cost (Develop New In-Water Tools for Autonomous CDR Operations).
• Offshore deployment of either electrodialysis or electrolysis would require further development to overcome challenges of working in the ocean (corrosion, biofouling, storms, physical and chemical stress on electrodes, catalysts, and membranes, etc.) (Develop New In-Water Tools for Autonomous CDR Operations). 
• Questions remain about how variations in seawater particulate and dissolved organic matter, temperature, and salinity affect electrochemical CDR efficiency (Develop New In-Water Tools for Autonomous CDR Operations). 
  • • Methods of handling chlorine gas produced as a byproduct of seawater electrolysis are needed (Develop New In-Water Tools for Autonomous CDR Operations, Improve Understanding of Markets for Co-Products)
    • Development of feedback control systems that integrate nearby observational data to determine optimal levels of electrochemical CDR (Develop New Modeling Tools to Support Design and Evaluation, Develop New In-Water Tools for Autonomous CDR Operations). 
    • Identifying and understanding how equipment, energy, and cost scale from benchtop experiments to small field experiments to globally-relevant deployments (Develop New Modeling Tools to Support Design and Evaluation, Develop New In-Water Tools for Autonomous CDR Operations, Develop CDR Monitoring and Verification Protocols, Accelerate RD&D Through New Partnerships)

• Current observational technologies (sensors, ROVs, AUVs, etc.) and modeling tools are not widespread and easily available to support field trials with the necessary spatial and temporal frequency of monitoring and sampling (Develop New In-Water Tools for Autonomous CDR Operations)
• In the case of surface seawater alkalinity addition from electrolysis or electrodialysis, cost-effective and safe methods need to be developed that optimize the distribution, dispersal and dilution of any strong chemical bases to avoid impacts of excessively alkaline (pH>9) waters on marine ecosystems. Dilution may require pumping large amounts of seawater, which need to be optimized for energy and cost (Develop New In-Water Tools for Autonomous CDR Operations).
• Offshore deployment of either electrodialysis or electrolysis would require further development to overcome challenges of working in the ocean (corrosion, biofouling, storms, physical and chemical stress on electrodes, catalysts, and membranes, etc.) (Develop New In-Water Tools for Autonomous CDR Operations). 
• Questions remain about how variations in seawater particulate and dissolved organic matter, temperature, and salinity affect electrochemical CDR efficiency (Develop New In-Water Tools for Autonomous CDR Operations). 
  • • Methods of handling chlorine gas produced as a byproduct of seawater electrolysis are needed. (Develop New In-Water Tools for Autonomous CDR Operations, Improve Understanding of Markets for Co-Products). As an example, chlorine can be used to extract lipids from microalgae ^[1]Garoma, T., Yazdi, R.E. Investigation of the disruption of algal biomass with chlorine. BMC Plant Biol 19, 18 (2019). and the oil can then be used to produce high density polyethylene (HDPE) ^[2]Degradation Rates of Plastics in the Environment Ali Chamas, Hyunjin Moon, Jiajia Zheng, Yang Qiu, Tarnuma Tabassum, Jun Hee Jang, Mahdi Abu-Omar, Susannah L. Scott, and Sangwon Suh ACS Sustainable Chemistry & Engineering 2020 8 (9), 3494-3511 DOI: 10.1021/acssuschemeng.9b06635 . As such, this chlorine management path may lead to a largely self replicating HDPE-based CDR infrastructure at the basic materials level. Moreover, combining both hydrogen production numbers and bio oil production numbers may offer an accurate proxy form of CDR verification.
    • Development of feedback control systems that integrate nearby observational data to determine optimal levels of electrochemical CDR (Develop New Modeling Tools to Support Design and Evaluation, Develop New In-Water Tools for Autonomous CDR Operations). 
    • Identifying and understanding how equipment, energy, and cost scale from benchtop experiments to small field experiments to globally-relevant deployments (Develop New Modeling Tools to Support Design and Evaluation, Develop New In-Water Tools for Autonomous CDR Operations, Develop CDR Monitoring and Verification Protocols, Accelerate RD&D Through New Partnerships)

• Current observational technologies (sensors, ROVs, AUVs, etc.) and modeling tools are not widespread and easily available to support field trials with the necessary spatial and temporal frequency of monitoring and sampling (Develop New In-Water Tools for Autonomous CDR Operations)
• In the case of surface seawater alkalinity addition from electrolysis or electrodialysis, cost-effective and safe methods need to be developed that optimize the distribution, dispersal and dilution of any strong chemical bases to avoid impacts of excessively alkaline (pH>9) waters on marine ecosystems. Dilution may require pumping large amounts of seawater, which need to be optimized for energy and cost (Develop New In-Water Tools for Autonomous CDR Operations).
• Offshore deployment of either electrodialysis or electrolysis would require further development to overcome challenges of working in the ocean (corrosion, biofouling, storms, physical and chemical stress on electrodes, catalysts, and membranes, etc.) (Develop New In-Water Tools for Autonomous CDR Operations). 
• Questions remain about how variations in seawater particulate and dissolved organic matter, temperature, and salinity affect electrochemical CDR efficiency (Develop New In-Water Tools for Autonomous CDR Operations). 
  • • Methods of handling chlorine gas produced as a byproduct of seawater electrolysis are needed. As an example, chlorine can be used to extract lipids from microalgae ^[1]Garoma, T., Yazdi, R.E. Investigation of the disruption of algal biomass with chlorine. BMC Plant Biol 19, 18 (2019). and the oil can then be used to produce high density polyethylene. As such, this chlorine management path may lead to a largely self replicating HDPE-based CDR infrastructure at the basic materials level. Moreover, combining both hydrogen production numbers and bio oil production numbers may offer an accurate proxy form of CDR verification. (Develop New In-Water Tools for Autonomous CDR Operations, Improve Understanding of Markets for Co-Products)
    • Development of feedback control systems that integrate nearby observational data to determine optimal levels of electrochemical CDR (Develop New Modeling Tools to Support Design and Evaluation, Develop New In-Water Tools for Autonomous CDR Operations). 
    • Identifying and understanding how equipment, energy, and cost scale from benchtop experiments to small field experiments to globally-relevant deployments (Develop New Modeling Tools to Support Design and Evaluation, Develop New In-Water Tools for Autonomous CDR Operations, Develop CDR Monitoring and Verification Protocols, Accelerate RD&D Through New Partnerships)

• Current observational technologies (sensors, ROVs, AUVs, etc.) and modeling tools are not widespread and easily available to support field trials with the necessary spatial and temporal frequency of monitoring and sampling (Develop New In-Water Tools for Autonomous CDR Operations)
• In the case of surface seawater alkalinity addition from electrolysis or electrodialysis, cost-effective and safe methods need to be developed that optimize the distribution, dispersal and dilution of any strong chemical bases to avoid impacts of excessively alkaline (pH>9) waters on marine ecosystems. Dilution may require pumping large amounts of seawater, which need to be optimized for energy and cost (Develop New In-Water Tools for Autonomous CDR Operations).
• Offshore deployment of either electrodialysis or electrolysis would require further development to overcome challenges of working in the ocean (corrosion, biofouling, storms, physical and chemical stress on electrodes, catalysts, and membranes, etc.) (Develop New In-Water Tools for Autonomous CDR Operations). 
• Questions remain about how variations in seawater particulate and dissolved organic matter, temperature, and salinity affect electrochemical CDR efficiency (Develop New In-Water Tools for Autonomous CDR Operations). 
  • • Methods of handling chlorine gas produced as a byproduct of seawater electrolysis are needed (Develop New In-Water Tools for Autonomous CDR Operations, Improve Understanding of Markets for Co-Products)
    • Development of feedback control systems that integrate nearby observational data to determine optimal levels of electrochemical CDR (Develop New Modeling Tools to Support Design and Evaluation, Develop New In-Water Tools for Autonomous CDR Operations). 
    • Identifying and understanding how equipment, energy, and cost scale from benchtop experiments to small field experiments to globally-relevant deployments (Develop New Modeling Tools to Support Design and Evaluation, Develop New In-Water Tools for Autonomous CDR Operations, Develop CDR Monitoring and Verification Protocols, Accelerate RD&D Through New Partnerships)

• Current observational technologies (sensors, ROVs, AUVs, etc.) and modeling tools are not widespread and easily available to support field trials with the necessary spatial and temporal frequency of monitoring and sampling (Develop New In-Water Tools for Autonomous CDR Operations)
• In the case of surface seawater alkalinity addition from electrolysis or electrodialysis, cost-effective and safe methods need to be developed that optimize the distribution, dispersal and dilution of any strong chemical bases to avoid impacts of excessively alkaline (pH>9) waters on marine ecosystems. Dilution may require pumping large amounts of seawater, which need to be optimized for energy and cost (Develop New In-Water Tools for Autonomous CDR Operations).
• Offshore deployment of either electrodialysis or electrolysis would require further development to overcome challenges of working in the ocean (corrosion, biofouling, storms, physical and chemical stress on electrodes, catalysts, and membranes, etc.) (Develop New In-Water Tools for Autonomous CDR Operations). 
• Questions remain about how variations in seawater particulate and dissolved organic matter, temperature, and salinity affect electrochemical CDR efficiency (Develop New In-Water Tools for Autonomous CDR Operations). 
  • • Methods of handling chlorine gas produced as a byproduct of seawater electrolysis are needed ()
    • Development of feedback control systems that integrate nearby observational data to determine optimal levels of electrochemical CDR (). 
    • Identifying and understanding how equipment, energy, and cost scale from benchtop experiments to small field experiments to globally-relevant deployments (Develop New Modeling Tools to Support Design and Evaluation, Develop New In-Water Tools for Autonomous CDR Operations, Develop CDR Monitoring and Verification Protocols, Accelerate RD&D Through New Partnerships)

• Current observational technologies (sensors, ROVs, AUVs, etc.) and modeling tools are not widespread and easily available to support field trials with the necessary spatial and temporal frequency of monitoring and sampling (Measure the Scale and Impacts of CDR via Macroalgae Sinking)
• In the case of surface seawater alkalinity addition from electrolysis or electrodialysis, cost-effective and safe methods need to be developed that optimize the distribution, dispersal and dilution of any strong chemical bases to avoid impacts of excessively alkaline (pH>9) waters on marine ecosystems. Dilution may require pumping large amounts of seawater, which need to be optimized for energy and cost (Measure the Scale and Impacts of CDR via Macroalgae Sinking).
• Offshore deployment of either electrodialysis or electrolysis would require further development to overcome challenges of working in the ocean (corrosion, biofouling, storms, physical and chemical stress on electrodes, catalysts, and membranes, etc.) (Measure the Scale and Impacts of CDR via Macroalgae Sinking). 
• Questions remain about how variations in seawater particulate and dissolved organic matter, temperature, and salinity affect electrochemical CDR efficiency (Measure the Scale and Impacts of CDR via Macroalgae Sinking). 
  • • Methods of handling chlorine gas produced as a byproduct of seawater electrolysis are needed (Measure the Scale and Impacts of CDR via Macroalgae Sinking, Accelerate RD&D Through New Partnerships)
    • Development of feedback control systems that integrate nearby observational data to determine optimal levels of electrochemical CDR (Develop New Modeling Tools to Support Design and Evaluation, Measure the Scale and Impacts of CDR via Macroalgae Sinking). 
    • Identifying and understanding how equipment, energy, and cost scale from benchtop experiments to small field experiments to globally-relevant deployments (Develop New Modeling Tools to Support Design and Evaluation, Measure the Scale and Impacts of CDR via Macroalgae Sinking, Develop New In-Water Tools for Autonomous CDR Operations, Develop CDR Monitoring and Verification Protocols)

• Current observational technologies (sensors, ROVs, AUVs, etc.) and modeling tools are not widespread and easily available to support field trials with the necessary spatial and temporal frequency of monitoring and sampling (3c)
• In the case of surface seawater alkalinity addition from electrolysis or electrodialysis, cost-effective and safe methods need to be developed that optimize the distribution, dispersal and dilution of any strong chemical bases to avoid impacts of excessively alkaline (pH>9) waters on marine ecosystems. Dilution may require pumping large amounts of seawater, which need to be optimized for energy and cost (3c).
• Offshore deployment of either electrodialysis or electrolysis would require further development to overcome challenges of working in the ocean (corrosion, biofouling, storms, physical and chemical stress on electrodes, catalysts, and membranes, etc.) (3c). 
• Questions remain about how variations in seawater particulate and dissolved organic matter, temperature, and salinity affect electrochemical CDR efficiency (3c). 
  • • Methods of handling chlorine gas produced as a byproduct of seawater electrolysis are needed (3c, 3f)
    • Development of feedback control systems that integrate nearby observational data to determine optimal levels of electrochemical CDR (3a, 3c). 
    • Identifying and understanding how equipment, energy, and cost scale from benchtop experiments to small field experiments to globally-relevant deployments (3a, 3c, 3d, 3e)

Many of the opportunities and challenges around building public support are not specific to electrochemical CDR, but there are several points of interest specific to electrochemical CDR: 

• Electrochemical CDR faces challenges in terms of public perception regarding potential environmental risks not necessarily faced by more “nature-based” approaches, such as coastal blue carbon restoration^[1]Bertram C and Merk C (2020) Public Perceptions of Ocean-Based Carbon Dioxide Removal: The Nature-Engineering Divide? Front. Clim. 2:594194. doi: 10.3389/fclim.2020.594194 (Accelerate RD&D Through New Partnerships)

• Complexities of electrochemical CDR pathways inhibit understanding and evaluation by non-technical audiences
• There is a great deal of uncertainty and confusion around any ocean-based CDR pathway that relies on adding materials to the ocean. This point applies to both electrochemical alkalinity additions, which return a base to the seawater, and pathways that precipitate out calcium carbonate.
• Earlier ocean iron fertilization experiments^[2]Schiermeier, Q. (2009a). Ocean Fertilization Experiment Draws Fire: Indo-German Research Cruise Sets Sail Despite Criticism. Available online at: https://www. nature.com/news/2009/090109/full/news.2009.13.html could offer opportunities to adopt best practices and avoid mistakes made when building public support for electrochemical CDR. 
• Electrochemical CDR has the advantage that it can be “turned off” more easily than the other approaches, enabling great control over its application

• Clearer communication strategies need to be developed to respond to the “engineering” narrative of electrochemical CDR.

Many of the opportunities and challenges around building public support are not specific to electrochemical CDR, but there are several points of interest specific to electrochemical CDR: 

• Electrochemical CDR faces challenges in terms of public perception regarding potential environmental risks not necessarily faced by more “nature-based” approaches, such as coastal blue carbon restoration^[1]Bertram C and Merk C (2020) Public Perceptions of Ocean-Based Carbon Dioxide Removal: The Nature-Engineering Divide? Front. Clim. 2:594194. doi: 10.3389/fclim.2020.594194 (Develop CDR Monitoring and Verification Protocols)

• Complexities of electrochemical CDR pathways inhibit understanding and evaluation by non-technical audiences
• There is a great deal of uncertainty and confusion around any ocean-based CDR pathway that relies on adding materials to the ocean. This point applies to both electrochemical alkalinity additions, which return a base to the seawater, and pathways that precipitate out calcium carbonate.
• Earlier ocean iron fertilization experiments^[2]Schiermeier, Q. (2009a). Ocean Fertilization Experiment Draws Fire: Indo-German Research Cruise Sets Sail Despite Criticism. Available online at: https://www. nature.com/news/2009/090109/full/news.2009.13.html could offer opportunities to adopt best practices and avoid mistakes made when building public support for electrochemical CDR. 
• Electrochemical CDR has the advantage that it can be “turned off” more easily than the other approaches, enabling great control over its application

• Clearer communication strategies need to be developed to respond to the “engineering” narrative of electrochemical CDR.

Many of the opportunities and challenges around building public support are not specific to electrochemical CDR, but there are several points of interest specific to electrochemical CDR: 

• Electrochemical CDR faces challenges in terms of public perception regarding potential environmental risks not necessarily faced by more “nature-based” approaches, such as coastal blue carbon restoration^[1]Bertram C and Merk C (2020) Public Perceptions of Ocean-Based Carbon Dioxide Removal: The Nature-Engineering Divide? Front. Clim. 2:594194. doi: 10.3389/fclim.2020.594194 (3e)

• Complexities of electrochemical CDR pathways inhibit understanding and evaluation by non-technical audiences
• There is a great deal of uncertainty and confusion around any ocean-based CDR pathway that relies on adding materials to the ocean. This point applies to both electrochemical alkalinity additions, which return a base to the seawater, and pathways that precipitate out calcium carbonate.
• Earlier ocean iron fertilization experiments^[2]Schiermeier, Q. (2009a). Ocean Fertilization Experiment Draws Fire: Indo-German Research Cruise Sets Sail Despite Criticism. Available online at: https://www. nature.com/news/2009/090109/full/news.2009.13.html could offer opportunities to adopt best practices and avoid mistakes made when building public support for electrochemical CDR. 
• Electrochemical CDR has the advantage that it can be “turned off” more easily than the other approaches, enabling great control over its application

• Clearer communication strategies need to be developed to respond to the “engineering” narrative of electrochemical CDR.

Many of the opportunities and challenges around building public support are not specific to electrochemical CDR, but there are several points of interest specific to electrochemical CDR: 

• Electrochemical CDR faces challenges in terms of public perception regarding potential environmental risks not necessarily faced by more “nature-based” approaches, such as coastal blue carbon restoration (3e)

• Complexities of electrochemical CDR pathways inhibit understanding and evaluation by non-technical audiences
• There is a great deal of uncertainty and confusion around any ocean-based CDR pathway that relies on adding materials to the ocean. This point applies to both electrochemical alkalinity additions, which return a base to the seawater, and pathways that precipitate out calcium carbonate.
• Earlier ocean iron fertilization experiments could offer opportunities to adopt best practices and avoid mistakes made when building public support for electrochemical CDR. 
• Electrochemical CDR has the advantage that it can be “turned off” more easily than the other approaches, enabling great control over its application

• Clearer communication strategies need to be developed to respond to the “engineering” narrative of electrochemical CDR.