• Measurement, reporting, and verification (MRV) procedures will need to be developed following advances in research and development. Advances in research and development will inform what parameters need to be monitored and verified, and how to do so. MRV protocols should include measurements of key ecological parameters as well as carbon fluxes to ensure that microalgae CDR activities do not exceed accepted limits of environmental impact.

• Life cycle analyses will need to be conducted for any approach that uses microalgae for CDR to determine the net carbon removal potential after accounting for process and embedded emissions.

• Social co-benefits are not well understood or identified. While research into social impacts is growing, there remain large uncertainties around the range of potential impacts that may result from large-scale environmental interventions. Integrating social risks and co-benefits into CDR research agendas may help this area of knowledge grow alongside the technical research and development. 
• Environmental co-benefits have not been well studied or articulated across microalgae-based CDR methods (NASEM, 2022). Identifying and understanding the potential array of co-benefits may help offset other risks, both environmental and social, and aid in decisions around which methods are to be pursued further.
• Location and siting: Siting analyses are needed to identify optimal locations for microalgae CDR and address potential synergies and/or conflicts with other marine resource users (e.g., fisheries, renewable energy, etc.) (Map optimal locations for microalgae-based approaches and engage with interested and affected constituents)

• Measurement, reporting, and verification (MRV) procedures will need to be developed following advances in research and development. Advances in research and development will inform what parameters need to be monitored and verified, and how to do so. MRV protocols should include measurements of key ecological parameters as well as carbon fluxes to ensure that microalgae CDR activities do not exceed accepted limits of environmental impact.

• Life cycle analyses will need to be conducted for any approach that uses microalgae for CDR to determine the net carbon removal potential after accounting for process and embedded emissions.

• Social co-benefits are not well understood or identified. While research into social impacts is growing, there remain large uncertainties around the range of potential impacts that may result from large-scale environmental interventions. Integrating social risks and co-benefits into CDR research agendas may help this area of knowledge grow alongside the technical research and development. 
• Environmental co-benefits have not been well studied or articulated across microalgae-based CDR methods . Identifying and understanding the potential array of co-benefits may help offset other risks, both environmental and social, and aid in decisions around which methods are to be pursued further.
• Location and siting: Siting analyses are needed to identify optimal locations for microalgae CDR and address potential synergies and/or conflicts with other marine resource users (e.g., fisheries, renewable energy, etc.) (Map optimal locations for microalgae-based approaches and engage with interested and affected constituents)

• Measurement, reporting, and verification (MRV) procedures will need to be developed following advances in research and development. Advances in research and development will inform what parameters need to be monitored and verified, and how to do so. MRV protocols should include measurements of key ecological parameters as well as carbon fluxes to ensure that microalgae CDR activities do not exceed accepted limits of environmental impact.

• Life cycle analyses will need to be conducted for any approach that uses microalgae for CDR to determine the net carbon removal potential after accounting for process and embedded emissions.

• Social co-benefits are not well understood or identified. While research into social impacts is growing, there remain large uncertainties around the range of potential impacts that may result from large-scale environmental interventions. Integrating social risks and co-benefits into CDR research agendas may help this area of knowledge grow alongside the technical research and development. 
• Environmental co-benefits have not been well studied or articulated across microalgae-based CDR methods ^[1]NASEM (National Academies of Sciences, Engineering, and Medicine.) A Research Strategy for Ocean-Based Carbon Dioxide Removal and Sequestration. The National Academies Press, https://doi.org/10.17226/26278. Accessed 18 Aug. 2022. . Identifying and understanding the potential array of co-benefits may help offset other risks, both environmental and social, and aid in decisions around which methods are to be pursued further.
• Location and siting: Siting analyses are needed to identify optimal locations for microalgae CDR and address potential synergies and/or conflicts with other marine resource users (e.g., fisheries, renewable energy, etc.). (Map optimal locations for microalgae-based approaches and engage with interested and affected constituents)

• Measurement, reporting, and verification (MRV) procedures will need to be developed following advances in research and development. Advances in research and development will inform what parameters need to be monitored and verified, and how to do so. MRV protocols should include measurements of key ecological parameters as well as carbon fluxes to ensure that microalgae CDR activities do not exceed accepted limits of environmental impact.

• Life cycle analyses will need to be conducted for any approach that uses microalgae for CDR to determine the net carbon removal potential after accounting for process and embedded emissions.

• Social co-benefits are not well understood or identified. While research into social impacts is growing, there remain large uncertainties around the range of potential impacts that may result from large-scale environmental interventions. Integrating social risks and co-benefits into CDR research agendas may help this area of knowledge grow alongside the technical research and development. 
• Environmental co-benefits have not been well studied or articulated across microalgae-based CDR methods ^[1]NASEM (National Academies of Sciences, Engineering, and Medicine.) A Research Strategy for Ocean-Based Carbon Dioxide Removal and Sequestration. The National Academies Press, https://doi.org/10.17226/26278. Accessed 18 Aug. 2022. . Identifying and understanding the potential array of co-benefits may help offset other risks, both environmental and social, and aid in decisions around which methods are to be pursued further.
• Location and siting: Siting analyses are needed to identify optimal locations for microalgae CDR and address potential synergies and/or conflicts with other marine resource users (e.g., fisheries, renewable energy, etc.) (Map optimal locations for microalgae-based approaches and engage with interested and affected constituents)

• Measurement, reporting, and verification (MRV) procedures will need to be developed following advances in research and development. Advances in research and development will inform what parameters need to be monitored and verified, and how to do so. MRV protocols should include measurements of key ecological parameters as well as carbon fluxes to ensure that microalgae CDR activities do not exceed accepted limits of environmental impact.

• Life cycle analyses will need to be conducted for any approach that uses microalgae for CDR to determine the net carbon removal potential after accounting for process and embedded emissions.

• Social co-benefits are not well understood or identified. While research into social impacts is growing, there remain large uncertainties around the range of potential impacts that may result from large-scale environmental interventions. Integrating social risks and co-benefits into CDR research agendas may help this area of knowledge grow alongside the technical research and development. 
• Environmental co-benefits have not been well studied or articulated across microalgae-based CDR methods ^[1]NASEM (National Academies of Sciences, Engineering, and Medicine.) A Research Strategy for Ocean-Based Carbon Dioxide Removal and Sequestration. The National Academies Press, https://doi.org/10.17226/26278. Accessed 18 Aug. 2022. . Identifying and understanding the potential array of co-benefits may help offset other risks, both environmental and social, and aid in decisions around which methods are to be pursued further.
• Location and siting: Siting analyses are needed to identify optimal locations for microalgae CDR and address potential synergies and/or conflicts with other marine resource users (e.g., fisheries, renewable energy, etc.) (Map optimal locations for microalgae-based approaches and engage with interested and affected constituents)

• Measurement, reporting, and verification (MRV) procedures will need to be developed following advances in research and development. Advances in research and development will inform what parameters need to be monitored and verified, and how to do so. MRV protocols should include measurements of key ecological parameters as well as carbon fluxes to ensure that microalgae CDR activities do not exceed accepted limits of environmental impact.

• Life cycle analyses will need to be conducted for any approach that uses microalgae for CDR to determine the net carbon removal potential after accounting for process and embedded emissions.

• Social co-benefits are not well understood or identified. While research into social impacts is growing, there remain large uncertainties around the range of potential impacts that may result from large-scale environmental interventions. Integrating social risks and co-benefits into CDR research agendas may help this area of knowledge grow alongside the technical research and development. 
• Environmental co-benefits have not been well studied or articulated across microalgae-based CDR methods . Identifying and understanding the potential array of co-benefits may help offset other risks, both environmental and social, and aid in decisions around which methods are to be pursued further.

• Measurement, reporting, and verification (MRV) procedures will need to be developed following advances in research and development. Advances in research and development will inform what parameters need to be monitored and verified, and how to do so. MRV protocols should include measurements of key ecological parameters as well as carbon fluxes to ensure that microalgae CDR activities do not exceed accepted limits of environmental impact (Based on the results of controlled field trials, identify appropriate protocols, and associated technologies, for approaches that provide evidence of efficacy and safety)

• Life cycle analyses will need to be conducted for any approach that uses microalgae for CDR to determine the net carbon removal potential after accounting for process and embedded emissions.(Based on the results of controlled field trials, identify appropriate protocols, and associated technologies, for approaches that provide evidence of efficacy and safety)

• Social co-benefits are not well understood or identified. While research into social impacts is growing, there remain large uncertainties around the range of potential impacts that may result from large-scale environmental interventions. Integrating social risks and co-benefits into CDR research agendas may help this area of knowledge grow alongside the technical research and development. 
• Environmental co-benefits have not been well studied or articulated across microalgae-based CDR methods . Identifying and understanding the potential array of co-benefits may help offset other risks, both environmental and social, and aid in decisions around which methods are to be pursued further.

• Measurement, reporting, and verification (MRV) procedures will need to be developed following advances in research and development. Advances in research and development will inform what parameters need to be monitored and verified, and how to do so. MRV protocols should include measurements of key ecological parameters as well as carbon fluxes to ensure that microalgae CDR activities do not exceed accepted limits of environmental impact (Based on the results of controlled field trials, identify appropriate protocols, and associated technologies, for approaches that provide evidence of efficacy and safety)

• Life cycle analyses will need to be conducted for any approach that uses microalgae for CDR to determine the net carbon removal potential after accounting for process and embedded emissions.(Based on the results of controlled field trials, identify appropriate protocols, and associated technologies, for approaches that provide evidence of efficacy and safety)

• Social co-benefits are not well understood or identified. While research into social impacts is growing, there remain large uncertainties around the range of potential impacts that may result from large-scale environmental interventions. Integrating social risks and co-benefits into CDR research agendas may help this area of knowledge grow alongside the technical research and development. 
• Environmental co-benefits have not been well studied or articulated across microalgae-based CDR methods . Identifying and understanding the potential array of co-benefits may help offset other risks, both environmental and social, and aid in decisions around which methods are to be pursued further.

Open Ocean Systems 

• Export and fate of carbon from net primary production in the upper ocean to understand sequestration efficacy and durability: A fundamental understanding of the export and fate of net primary production from the upper ocean is critical to any development, testing, or deployment of approaches that hope to accelerate this process. Currently a number of field campaigns are working on answering these questions, including EXPORTS (USA), COMICS (UK), and ONCE (China). In addition to these large campaigns focused on fundamental understanding of the biological carbon pump, these questions must be answered in the context of purposeful nutrient additions (Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration)
• Natural iron cycle / anthropogenic iron input: There is a lack of knowledge about the current state of iron cycling in the ocean system, particularly how much anthropogenic iron is already input into the system and what the spatially specific distribution of impacts are likely to be (Liu et al., 2022). Research must prioritize understanding inputs and refining existing iron-cycle models. This will be critical work for ocean iron chemistry models to measure future changes in anthropogenic iron loading. Future research must also seek to better understand natural and pre-existing anthropogenic analogs that may be analyzed as simulations of future ocean iron fertilization (Bach & Boyd, 2021; Weis et al., 2022). Analogs may include volcanic ash and wildfire ash deposits into ocean systems.

Closed Systems 

• Harvesting efficiency: In the cultivation stage, harvesting microalgae from closed systems contributes to 20–30% of the total cost of microalgal biomass production, so opportunities to increase efficiency present the greatest opportunity for cost reductions through innovation (Singh & Ahluwalia, 2013). (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)

• Strain optimization: The algal industry is still relatively small, and primarily optimizes for lipid and/or protein content in microalgae strains. More research is thus needed to identify ideal species, strains, and specific growth conditions to maximize microalgal CO₂ uptake; and to estimate associated costs. (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)
• Fertilizer efficiency: High fertilizer needs are likely to be the most substantial constraint on closed onshore cultivation systems (Huntley et al., 2015). Research is needed into options to maximize fertilizer recycling and other strategies to lessen fertilizer needs. (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)
• Overall CDR potential: There exists virtually no information on overall CDR potential of closed offshore systems (e.g., towed photobioreactors). (Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration)

Open Ocean Systems 

• Export and fate of carbon from net primary production in the upper ocean to understand sequestration efficacy and durability: A fundamental understanding of the export and fate of net primary production from the upper ocean is critical to any development, testing, or deployment of approaches that hope to accelerate this process. Currently a number of field campaigns are working on answering these questions, including EXPORTS (USA), COMICS (UK), and ONCE (China). In addition to these large campaigns focused on fundamental understanding of the biological carbon pump, these questions must be answered in the context of purposeful nutrient additions (Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration)
• Natural iron cycle / anthropogenic iron input: There is a lack of knowledge about the current state of iron cycling in the ocean system, particularly how much anthropogenic iron is already input into the system and what the spatially specific distribution of impacts are likely to be . Research must prioritize understanding inputs and refining existing iron-cycle models. This will be critical work for ocean iron chemistry models to measure future changes in anthropogenic iron loading. Future research must also seek to better understand natural and pre-existing anthropogenic analogs that may be analyzed as simulations of future ocean iron fertilization. Analogs may include volcanic ash and wildfire ash deposits into ocean systems.

Closed Systems 

• Harvesting efficiency: In the cultivation stage, harvesting microalgae from closed systems contributes to 20–30% of the total cost of microalgal biomass production, so opportunities to increase efficiency present the greatest opportunity for cost reductions through innovation . (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)

• Strain optimization: The algal industry is still relatively small, and primarily optimizes for lipid and/or protein content in microalgae strains. More research is thus needed to identify ideal species, strains, and specific growth conditions to maximize microalgal CO₂ uptake; and to estimate associated costs. (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)
• Fertilizer efficiency: High fertilizer needs are likely to be the most substantial constraint on closed onshore cultivation systems. Research is needed into options to maximize fertilizer recycling and other strategies to lessen fertilizer needs. (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)
• Overall CDR potential: There exists virtually no information on overall CDR potential of closed offshore systems (e.g., towed photobioreactors). (Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration)

Open Ocean Systems 

• Export and fate of carbon from net primary production in the upper ocean to understand sequestration efficacy and durability: A fundamental understanding of the export and fate of net primary production from the upper ocean is critical to any development, testing, or deployment of approaches that hope to accelerate this process. Currently a number of field campaigns are working on answering these questions, including EXPORTS (USA), COMICS (UK), and ONCE (China). In addition to these large campaigns focused on fundamental understanding of the biological carbon pump, these questions must be answered in the context of purposeful nutrient additions (Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration)
• Natural iron cycle / anthropogenic iron input: There is a lack of knowledge about the current state of iron cycling in the ocean system, particularly how much anthropogenic iron is already input into the system and what the spatially specific distribution of impacts are likely to be ^[1]Liu, Mingxu, et al. “The Underappreciated Role of Anthropogenic Sources in Atmospheric Soluble Iron Flux to the Southern Ocean.” Npj Climate and Atmospheric Science, vol. 5, no. 1, Apr. 2022, pp. 1–9, https://doi.org/10.1038/s41612-022-00250-w. . Research must prioritize understanding inputs and refining existing iron-cycle models. This will be critical work for ocean iron chemistry models to measure future changes in anthropogenic iron loading. Future research must also seek to better understand natural and pre-existing anthropogenic analogs that may be analyzed as simulations of future ocean iron fertilization^[2]Bach, Lennart T., and Philip W. Boyd. “Seeking Natural Analogs to Fast-Forward the Assessment of Marine CO 2 Removal.” Proceedings of the National Academy of Sciences, vol. 118, no. 40, Oct. 2021, p. e2106147118, https://doi.org/10.1073/pnas.2106147118. ^[3]Weis, Jakob, et al. “Southern Ocean Phytoplankton Stimulated by Wildfire Emissions and Sustained by Iron Recycling.” Geophysical Research Letters, vol. 49, no. 11, June 2022, https://doi.org/10.1029/2021GL097538. . Analogs may include volcanic ash and wildfire ash deposits into ocean systems.

Closed Systems 

• Harvesting efficiency: In the cultivation stage, harvesting microalgae from closed systems contributes to 20–30% of the total cost of microalgal biomass production, so opportunities to increase efficiency present the greatest opportunity for cost reductions through innovation ^[4]Singh, U. B., & Ahluwalia, A. S. “Microalgae: a promising tool for carbon sequestration. Mitigation and Adaptation Strategies for Global Change, vol. 18, no. 1, 2013, pp. 73-95. . (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)

• Strain optimization: The algal industry is still relatively small, and primarily optimizes for lipid and/or protein content in microalgae strains. More research is thus needed to identify ideal species, strains, and specific growth conditions to maximize microalgal CO₂ uptake; and to estimate associated costs. (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)
• Fertilizer efficiency: High fertilizer needs are likely to be the most substantial constraint on closed onshore cultivation systems^[5]Huntley, M.E., et al. (2015). Demonstrated large-scale production of marine microalgae for fuels and feed. Algal Research, 10, 249-265. https://doi.org/10.1016/j.algal.2015.04.016 . Research is needed into options to maximize fertilizer recycling and other strategies to lessen fertilizer needs. (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)
• Overall CDR potential: There exists virtually no information on overall CDR potential of closed offshore systems (e.g., towed photobioreactors). (Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration)

Open Ocean Systems 

• Export and fate of carbon from net primary production in the upper ocean to understand sequestration efficacy and durability: A fundamental understanding of the export and fate of net primary production from the upper ocean is critical to any development, testing, or deployment of approaches that hope to accelerate this process. Currently a number of field campaigns are working on answering these questions, including EXPORTS (USA), COMICS (UK), and ONCE (China). In addition to these large campaigns focused on fundamental understanding of the biological carbon pump, these questions must be answered in the context of purposeful nutrient additions (Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration)
• Natural iron cycle / anthropogenic iron input: There is a lack of knowledge about the current state of iron cycling in the ocean system, particularly how much anthropogenic iron is already input into the system and what the spatially specific distribution of impacts are likely to be ^[1]Liu et al., 2022 . Research must prioritize understanding inputs and refining existing iron-cycle models. This will be critical work for ocean iron chemistry models to measure future changes in anthropogenic iron loading. Future research must also seek to better understand natural and pre-existing anthropogenic analogs that may be analyzed as simulations of future ocean iron fertilization^[2]Bach & Boyd, 2021 ^[3]Weis et al., 2021 . Analogs may include volcanic ash and wildfire ash deposits into ocean systems.

Closed Systems 

• Harvesting efficiency: In the cultivation stage, harvesting microalgae from closed systems contributes to 20–30% of the total cost of microalgal biomass production, so opportunities to increase efficiency present the greatest opportunity for cost reductions through innovation ^[4]Singh & Ahluwalia, 2013 . (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)

• Strain optimization: The algal industry is still relatively small, and primarily optimizes for lipid and/or protein content in microalgae strains. More research is thus needed to identify ideal species, strains, and specific growth conditions to maximize microalgal CO₂ uptake; and to estimate associated costs. (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)
• Fertilizer efficiency: High fertilizer needs are likely to be the most substantial constraint on closed onshore cultivation systems^[5]Huntley et al., 2015 . Research is needed into options to maximize fertilizer recycling and other strategies to lessen fertilizer needs. (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)
• Overall CDR potential: There exists virtually no information on overall CDR potential of closed offshore systems (e.g., towed photobioreactors) (Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration)

• Location and siting: Siting analyses are needed to identify optimal locations for microalgae CDR and address potential synergies and/or conflicts with other marine resource users (e.g., fisheries, renewable energy, etc.) (Map optimal locations for microalgae-based approaches and engage with interested and affected constituents)

Open Ocean Systems 

• Export and fate of carbon from net primary production in the upper ocean to understand sequestration efficacy and durability: A fundamental understanding of the export and fate of net primary production from the upper ocean is critical to any development, testing, or deployment of approaches that hope to accelerate this process. Currently a number of field campaigns are working on answering these questions, including EXPORTS (USA), COMICS (UK), and ONCE (China). In addition to these large campaigns focused on fundamental understanding of the biological carbon pump, these questions must be answered in the context of purposeful nutrient additions (Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration)
• Natural iron cycle / anthropogenic iron input: There is a lack of knowledge about the current state of iron cycling in the ocean system, particularly how much anthropogenic iron is already input into the system and what the spatially specific distribution of impacts are likely to be ^[1]Liu et al., 2022 . Research must prioritize understanding inputs and refining existing iron-cycle models. This will be critical work for ocean iron chemistry models to measure future changes in anthropogenic iron loading. Future research must also seek to better understand natural and pre-existing anthropogenic analogs that may be analyzed as simulations of future ocean iron fertilization^[2]Bach & Boyd, 2021 ^[3]Weis et al., 2021 . Analogs may include volcanic ash and wildfire ash deposits into ocean systems.

Closed Systems 

• Harvesting efficiency: In the cultivation stage, harvesting microalgae from closed systems contributes to 20–30% of the total cost of microalgal biomass production, so opportunities to increase efficiency present the greatest opportunity for cost reductions through innovation ^[4]Singh & Ahluwalia, 2013 . (Optimize and/or efficiently automate all approaches for scalability and economic feasibility)

• Strain optimization: The algal industry is still relatively small, and primarily optimizes for lipid and/or protein content in microalgae strains. More research is thus needed to identify ideal species, strains, and specific growth conditions to maximize microalgal CO₂ uptake; and to estimate associated costs.
• Fertilizer efficiency: High fertilizer needs are likely to be the most substantial constraint on closed onshore cultivation systems^[5]Huntley et al., 2015 . Research is needed into options to maximize fertilizer recycling and other strategies to lessen fertilizer needs.
• Overall CDR potential: There exists virtually no information on overall CDR potential of closed offshore systems (e.g., towed photobioreactors) (Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration)

• Location and siting: Siting analyses are needed to identify optimal locations for microalgae CDR and address potential synergies and/or conflicts with other marine resource users (e.g., fisheries, renewable energy, etc.) [see First Order Priority: Map optimal locations for microalgae-based approaches and engage with interested and affected constituents]

Open Ocean Systems 

• Export and fate of carbon from net primary production in the upper ocean to understand sequestration efficacy and durability: A fundamental understanding of the export and fate of net primary production from the upper ocean is critical to any development, testing, or deployment of approaches that hope to accelerate this process. Currently a number of field campaigns are working on answering these questions, including EXPORTS (USA), COMICS (UK), and ONCE (China). In addition to these large campaigns focused on fundamental understanding of the biological carbon pump, these questions must be answered in the context of purposeful nutrient additions (Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration)
• Natural iron cycle / anthropogenic iron input: There is a lack of knowledge about the current state of iron cycling in the ocean system, particularly how much anthropogenic iron is already input into the system and what the spatially specific distribution of impacts are likely to be ^[1]Liu et al., 2022 . Research must prioritize understanding inputs and refining existing iron-cycle models. This will be critical work for ocean iron chemistry models to measure future changes in anthropogenic iron loading. Future research must also seek to better understand natural and pre-existing anthropogenic analogs that may be analyzed as simulations of future ocean iron fertilization^[2]Bach & Boyd, 2021 ^[3]Weis et al., 2021 . Analogs may include volcanic ash and wildfire ash deposits into ocean systems.

Closed Systems 

• Harvesting efficiency: In the cultivation stage, harvesting microalgae from closed systems contributes to 20–30% of the total cost of microalgal biomass production, so opportunities to increase efficiency present the greatest opportunity for cost reductions through innovation ^[4]Singh & Ahluwalia, 2013 . [see First Order Priority: Optimize and/or efficiently automate all approaches for scalability and economic feasibility]

• Strain optimization: The algal industry is still relatively small, and primarily optimizes for lipid and/or protein content in microalgae strains. More research is thus needed to identify ideal species, strains, and specific growth conditions to maximize microalgal CO₂ uptake; and to estimate associated costs.
• Fertilizer efficiency: High fertilizer needs are likely to be the most substantial constraint on closed onshore cultivation systems^[5]Huntley et al., 2015 . Research is needed into options to maximize fertilizer recycling and other strategies to lessen fertilizer needs.
• Overall CDR potential: There exists virtually no information on overall CDR potential of closed offshore systems (e.g., towed photobioreactors) [see First Order Priority: Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration]

• Location and siting: Siting analyses are needed to identify optimal locations for microalgae CDR and address potential synergies and/or conflicts with other marine resource users (e.g., fisheries, renewable energy, etc.) [see First Order Priority: Map optimal locations for microalgae-based approaches and engage with interested and affected constituents]

Open Ocean Systems 

• Export and fate of carbon from net primary production in the upper ocean to understand sequestration efficacy and durability: A fundamental understanding of the export and fate of net primary production from the upper ocean is critical to any development, testing, or deployment of approaches that hope to accelerate this process. Currently a number of field campaigns are working on answering these questions, including EXPORTS (USA), COMICS (UK), and ONCE (China). In addition to these large campaigns focused on fundamental understanding of the biological carbon pump, these questions must be answered in the context of purposeful nutrient additions (Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration)
• Natural iron cycle / anthropogenic iron input: There is a lack of knowledge about the current state of iron cycling in the ocean system, particularly how much anthropogenic iron is already input into the system and what the spatially specific distribution of impacts are likely to be ^[1]Liu et al., 2022 . Research must prioritize understanding inputs and refining existing iron-cycle models. This will be critical work for ocean iron chemistry models to measure future changes in anthropogenic iron loading. Future research must also seek to better understand natural and pre-existing anthropogenic analogs that may be analyzed as simulations of future ocean iron fertilization^[2]Bach & Boyd, 2021 ^[3]Weis et al., 2021 . Analogs may include volcanic ash and wildfire ash deposits into ocean systems.

Closed Systems 

• Harvesting efficiency: In the cultivation stage, harvesting microalgae from closed systems contributes to 20–30% of the total cost of microalgal biomass production, so opportunities to increase efficiency present the greatest opportunity for cost reductions through innovation ^[4]Singh & Ahluwalia, 2013 . [see First Order Priority: Optimize and/or efficiently automate all approaches for scalability and economic feasibility]

• Strain optimization: The algal industry is still relatively small, and primarily optimizes for lipid and/or protein content in microalgae strains. More research is thus needed to identify ideal species, strains, and specific growth conditions to maximize microalgal CO₂ uptake; and to estimate associated costs.
• Fertilizer efficiency: High fertilizer needs are likely to be the most substantial constraint on closed onshore cultivation systems^[5]Huntley et al., 2015 . Research is needed into options to maximize fertilizer recycling and other strategies to lessen fertilizer needs.
• Overall CDR potential: There exists virtually no information on overall CDR potential of closed offshore systems (e.g., towed photobioreactors) [see First Order Priority: Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration]

• Location and siting: Siting analyses are needed to identify optimal locations for microalgae CDR and address potential synergies and/or conflicts with other marine resource users (e.g., fisheries, renewable energy, etc.) [see First Order Priority: Map optimal locations for microalgae-based approaches and engage with interested and affected constituents]

Open Ocean Systems 

• Export and fate of carbon from net primary production in the upper ocean to understand sequestration efficacy and durability: A fundamental understanding of the export and fate of net primary production from the upper ocean is critical to any development, testing, or deployment of approaches that hope to accelerate this process. Currently a number of field campaigns are working on answering these questions, including EXPORTS (USA), COMICS (UK), and ONCE (China). In addition to these large campaigns focused on fundamental understanding of the biological carbon pump, these questions must be answered in the context of purposeful nutrient additions [see First Order Priority: Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration]
• Natural iron cycle / anthropogenic iron input: There is a lack of knowledge about the current state of iron cycling in the ocean system, particularly how much anthropogenic iron is already input into the system and what the spatially specific distribution of impacts are likely to be . Research must prioritize understanding inputs and refining existing iron-cycle models. This will be critical work for ocean iron chemistry models to measure future changes in anthropogenic iron loading. Future research must also seek to better understand natural and pre-existing anthropogenic analogs that may be analyzed as simulations of future ocean iron fertilization. Analogs may include volcanic ash and wildfire ash deposits into ocean systems.

Closed Systems 

• Harvesting efficiency: In the cultivation stage, harvesting microalgae from closed systems contributes to 20–30% of the total cost of microalgal biomass production, so opportunities to increase efficiency present the greatest opportunity for cost reductions through innovation . [see First Order Priority: Optimize and/or efficiently automate all approaches for scalability and economic feasibility]

• Strain optimization: The algal industry is still relatively small, and primarily optimizes for lipid and/or protein content in microalgae strains. More research is thus needed to identify ideal species, strains, and specific growth conditions to maximize microalgal CO₂ uptake; and to estimate associated costs.
• Fertilizer efficiency: High fertilizer needs are likely to be the most substantial constraint on closed onshore cultivation systems. Research is needed into options to maximize fertilizer recycling and other strategies to lessen fertilizer needs.
• Overall CDR potential: There exists virtually no information on overall CDR potential of closed offshore systems (e.g., towed photobioreactors) [see First Order Priority: Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration]

• Location and siting: Siting analyses are needed to identify optimal locations for microalgae CDR and address potential synergies and/or conflicts with other marine resource users (e.g., fisheries, renewable energy, etc.) [see First Order Priority: Map optimal locations for microalgae-based approaches and engage with interested and affected constituents]

Open Ocean Systems 

• Export and fate of carbon from net primary production in the upper ocean to understand sequestration efficacy and durability: A fundamental understanding of the export and fate of net primary production from the upper ocean is critical to any development, testing, or deployment of approaches that hope to accelerate this process. Currently a number of field campaigns are working on answering these questions, including EXPORTS (USA), COMICS (UK), and ONCE (China). In addition to these large campaigns focused on fundamental understanding of the biological carbon pump, these questions must be answered in the context of purposeful nutrient additions [see First Order Priority: Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration]
• Natural iron cycle / anthropogenic iron input: There is a lack of knowledge about the current state of iron cycling in the ocean system, particularly how much anthropogenic iron is already input into the system and what the spatially specific distribution of impacts are likely to be ^[1]Liu, Mingxu, et al. “The Underappreciated Role of Anthropogenic Sources in Atmospheric Soluble Iron Flux to the Southern Ocean.” Npj Climate and Atmospheric Science, vol. 5, no. 1, Apr. 2022, pp. 1–9, https://doi.org/10.1038/s41612-022-00250-w. . Research must prioritize understanding inputs and refining existing iron-cycle models. This will be critical work for ocean iron chemistry models to measure future changes in anthropogenic iron loading. Future research must also seek to better understand natural and pre-existing anthropogenic analogs that may be analyzed as simulations of future ocean iron fertilization^[2]Bach, Lennart T., and Philip W. Boyd. “Seeking Natural Analogs to Fast-Forward the Assessment of Marine CO 2 Removal.” Proceedings of the National Academy of Sciences, vol. 118, no. 40, Oct. 2021, p. e2106147118, https://doi.org/10.1073/pnas.2106147118. ^[3]Weis, Jakob, et al. “Southern Ocean Phytoplankton Stimulated by Wildfire Emissions and Sustained by Iron Recycling.” Geophysical Research Letters, vol. 49, no. 11, June 2022, https://doi.org/10.1029/2021GL097538. . Analogs may include volcanic ash and wildfire ash deposits into ocean systems.

Closed Systems 

• Harvesting efficiency: In the cultivation stage, harvesting microalgae from closed systems contributes to 20–30% of the total cost of microalgal biomass production, so opportunities to increase efficiency present the greatest opportunity for cost reductions through innovation ^[4]Singh, U. B., & Ahluwalia, A. S. “Microalgae: a promising tool for carbon sequestration. Mitigation and Adaptation Strategies for Global Change, vol. 18, no. 1, 2013, pp. 73-95. . [see First Order Priority: Optimize and/or efficiently automate all approaches for scalability and economic feasibility]

• Strain optimization: The algal industry is still relatively small, and primarily optimizes for lipid and/or protein content in microalgae strains. More research is thus needed to identify ideal species, strains, and specific growth conditions to maximize microalgal CO₂ uptake; and to estimate associated costs.
• Fertilizer efficiency: High fertilizer needs are likely to be the most substantial constraint on closed onshore cultivation systems^[5]Huntely, M.E., et al. (2015). Demonstrated large-scale production of marine microalgae for fuels and feed. Algal Research, 10, 249-265. https://doi.org/10.1016/j.algal.2015.04.016 . Research is needed into options to maximize fertilizer recycling and other strategies to lessen fertilizer needs.
• Overall CDR potential: There exists virtually no information on overall CDR potential of closed offshore systems (e.g., towed photobioreactors) [see First Order Priority: Accelerate the design, permitting, and execution of the next generation of controlled field trials to answer questions specifically pertaining to carbon sequestration]

• Mapping interested and affected constituencies: It will be important to identify the diverse stakeholders for microalgae CDR, including producers, potential buyers for carbon removal, potential buyers for other useful co-products, and communities where projects may be sited. Understanding perceptions, needs, concerns, and opportunities across multiple stakeholder groups is necessary to scale microalgae-based CDR.
• Industry transitions: Microalgae is already cultivated around the world today but is done so for non-CDR purposes—primarily feeds and fuels. Analysis of industry willingness and needs for transitioning from CO₂ reuse to CO₂ removal could ease the creation of onshore microalgae CDR pathways, but more research is necessary to determine if this is possible and under what conditions. 

• Mapping interested and affected constituencies: It will be important to identify the diverse stakeholders for microalgae CDR, including producers, potential buyers for carbon removal, potential buyers for other useful co-products, and communities where projects may be sited. Understanding perceptions, needs, concerns, and opportunities across multiple stakeholder groups is necessary to scale microalgae-based CDR. 

• Mapping interested and affected constituencies: It will be important to identify the diverse stakeholders for microalgae CDR, including producers, potential buyers for carbon removal, potential buyers for other useful co-products, and communities where projects may be sited. Understanding perceptions, needs, concerns, and opportunities across multiple stakeholder groups is necessary to scale microalgae-based CDR.