Improve Aquaculture

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Summary

Improving aquaculture involves reducing CO₂ and other GHG emissions during the production of farmed fish and other aquatic animals through better feed efficiency and the decarbonization of on-farm energy use. Advantages include reduced demand for feedstocks produced from both wild capture fisheries and terrestrial sources, which benefits marine and terrestrial ecosystems. Disadvantages include the costs of transitioning to fossil-free energy sources. While these interventions are unlikely to lead to globally meaningful emissions reductions (>0.1 Gt CO₂‑eq/yr ), we consider Improve Aquaculture as “Worthwhile” given the rapid and ongoing expansion of the industry, its potential to replace higher-emission protein sources, and the ecosystem benefits of reducing feedstock demand.

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The Improve Aquaculture solution is coming soon.
Overview

What is our assessment?

While Improve Aquaculture is unlikely to have a major climate impact, our assessment concludes that it is “Worthwhile” due to its ability to reduce pressure on wild fish stocks and terrestrial biomass, and because efficiency improvements made now are likely to scale into greater climate impact as the sector continues to expand.

Plausible Could it work? Yes
Ready Is it ready? Yes
Evidence Are there data to evaluate it? Yes
Effective Does it consistently work? Yes
Impact Is it big enough to matter? No
Risk Is it risky or harmful? No
Cost Is it cheap? ?

What is it?

GHG emissions from aquaculture can be reduced by increasing the feed conversion efficiency of the cultured animals and decarbonizing on-farm energy use. Aquaculture – farming aquatic animals or plants for food or other purposes – is rapidly growing and now accounts for over half of the global production of aquatic animals, exceeding wild capture fisheries. Over 7% of human-consumed protein is aquaculture-produced. As this sector has grown, it has become increasingly reliant on external feed sources, with the share of non-fed aquaculture (e.g., bivalves that feed from the water column) dropping from nearly 40% in 2000 to 27% in 2022. Improving feed conversion ratios (FCR) – the amount of feed it takes to produce a given amount of biomass – can lower feed demand and reduce CO₂ and other GHG emissions tied to feed production and transport. FCRs can be improved by feed formulations that increase digestibility, genetic or breeding modifications to improve digestive efficiency in the cultured animal, species-specific feed formulations, and optimizing ration size and feeding frequency. At the same time, decarbonizing on-farm energy use can help reduce CO₂ emissions from common equipment, such as aerators and water pumps.

Does it work?

Interventions to improve feed and energy efficiency can reduce CO₂ emissions from aquaculture operations, although the potential achievable climate impact of these actions is currently unlikely to be globally meaningful (>0.1 Gt CO₂‑eq/yr ). Total annual emissions from aquaculture were estimated to be 0.26 Gt CO₂‑eq/yr in 2017, with nearly 60% of that attributed to feed production. Improving FCR is both plausible and effective, since it directly reduces the amount of food needed to cultivate fish and other species, thereby lowering emissions tied to feed production and transport. Between 1995 and 2007, improvements in FCR have ranged between 5 to 15% for a variety of species, including shrimp, salmon, carp, and tilapia.

Decarbonizing on-farm energy use can reduce equipment-related emissions, particularly in intensive systems that use energy for automated feeding systems, water temperature control, and circulation and aeration systems. In general, the potential impact of decarbonizing varies widely because on-farm energy use differs significantly across species and production systems. For instance, shrimp and prawn farming use nearly 20,000 MJ/t of live weight (LW), with over 75% from electricity, while bivalve production uses around 3,000 MJ/t of LW supplied largely by diesel.

Why are we excited?

Improving feed efficiency in aquaculture reduces demand for captured wild fish used in feed, reducing pressure on overfished stocks. It also lowers reliance on terrestrial biomass, such as soy, wheat, and rice, which come with additional land-use and emission costs. More efficient feeding can help reduce nutrient pollution, which can be responsible for high methane and nitrous oxide fluxes in some inland aquaculture systems. At the same time, decarbonizing on-farm energy use might ultimately lead to lower long-term operating costs and improved energy reliability.

Why are we concerned?

There are relatively few drawbacks associated with improving aquaculture. In the case of decarbonizing on-farm energy use, upfront costs could be high. For instance, installing solar panels or upgrading pumps can be financially challenging for small-scale operations. Energy use on farms can also vary throughout the day and night, which might not always align with renewable energy sources, like solar, without storage. 

Solution in Action

Badiola, M., Basurko, O. C., Piedrahita, R., Hundley, P., & Mendiola, D. (2018). Energy use in recirculating aquaculture systems (RAS): a review. Aquacultural Engineering, 81, 57-70. Link to source: https://doi.org/10.1016/j.aquaeng.2018.03.003

Boyd, C. E., McNevin, A. A., & Davis, R. P. (2022). The contribution of fisheries and aquaculture to the global protein supply. Food Security, 14(3), 805-827. Link to source: https://doi.org/10.1007/s12571-021-01246-9

Food and Agriculture Organization of the United Nations. (2018). The state of world fisheries and aquaculture. Food and Agriculture Organization of the United Nations. Link to source: https://openknowledge.fao.org/handle/20.500.14283/i9540en

Food and Agriculture Organization of the United Nations. (2024). The State of World Fisheries and Aquaculture 2024 – Blue Transformation in action. Food and Agriculture Organization of the United Nations. Link to source: https://openknowledge.fao.org/handle/20.500.14283/cd0683en

Henriksson, P. J. G., Troell, M., Banks, L. K., Belton, B., Beveridge, M. C. M., Klinger, D. H., ... & Tran, N. (2021). Interventions for improving the productivity and environmental performance of global aquaculture for future food security. One Earth, 4(9), 1220-1232. Link to source: https://doi.org/10.1016/j.oneear.2021.08.009

Jones, A. R., Alleway, H. K., McAfee, D., Reis-Santos, P., Theuerkauf, S. J., & Jones, R. C. (2022). Climate-friendly seafood: the potential for emissions reduction and carbon capture in marine aquaculture. BioScience, 72(2), 123-143. Link to source: https://doi.org/10.1093/biosci/biab126

MacLeod, M. J., Hasan, M. R., Robb, D. H., & Mamun-Ur-Rashid, M. (2020). Quantifying greenhouse gas emissions from global aquaculture. Scientific Reports, 10(1), 11679. Link to source: https://doi.org/10.1038/s41598-020-68231-8

Naylor, R. L., Hardy, R. W., Bureau, D. P., Chiu, A., Elliott, M., Farrell, A. P., ... & Nichols, P. D. (2009). Feeding aquaculture in an era of finite resources. Proceedings of the National Academy of Sciences106(36), 15103-15110. Link to source: https://doi.org/10.1073/pnas.0905235106

Naylor, R. L., Hardy, R. W., Buschmann, A. H., Bush, S. R., Cao, L., Klinger, D. H., ... & Troell, M. (2021). A 20-year retrospective review of global aquaculture. Nature, 591(7851), 551-563. Link to source: https://doi.org/10.1038/s41586-021-03308-6

Scroggins, R. E., Fry, J. P., Brown, M. T., Neff, R. A., Asche, F., Anderson, J. L., & Love, D. C. (2022). Renewable energy in fisheries and aquaculture: Case studies from the United States. Journal of Cleaner Production, 376, 134153. Link to source: https://doi.org/10.1016/j.jclepro.2022.134153

Shen, L., Wu, L., Wei, W., Yang, Y., MacLeod, M. J., Lin, J., ... & Zhuang, M. (2024). Marine aquaculture can deliver 40% lower carbon footprints than freshwater aquaculture based on feed, energy and biogeochemical cycles. Nature Food, 5(7), 615-624. Link to source: https://doi.org/10.1038/s43016-024-01004-y

Stentiford, G. D., Bateman, I. J., Hinchliffe, S. J., Bass, D. 1., Hartnell, R., Santos, E. M., ... & Tyler, C. R. (2020). Sustainable aquaculture through the One Health lens. Nature Food, 1(8), 468-474. Link to source: https://doi.org/10.1038/s43016-020-0127-5

Tacon, A. G., & Metian, M. (2008). Global overview on the use of fish meal and fish oil in industrially compounded aquafeeds: Trends and future prospects. Aquaculture, 285(1-4), 146-158. Link to source: https://doi.org/10.1016/j.aquaculture.2008.08.015

Vo, T. T. E., Ko, H., Huh, J. H., & Park, N. (2021). Overview of solar energy for aquaculture: The potential and future trends. Energies, 14(21), 6923. Link to source: https://doi.org/10.3390/en14216923

Zhang, Z., Liu, H., Jin, J., Zhu, X., Han, D., & Xie, S. (2024). Towards a low-carbon footprint: Current status and prospects for aquaculture. Water Biology and Security, 3(4), 100290. Link to source: https://doi.org/10.1016/j.watbs.2024.100290

Credits

Lead Fellow

  • Christina Richardson, Ph.D.

Internal Reviewer

  • Christina Swanson, Ph.D.
Speed of Action
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Caveats
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Risks
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Consensus
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Trade-offs
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Action Word
Improve
Solution Title
Aquaculture
Classification
Worthwhile
Lawmakers and Policymakers
Practitioners
Business Leaders
Nonprofit Leaders
Investors
Philanthropists and International Aid Agencies
Thought Leaders
Technologists and Researchers
Communities, Households, and Individuals
Updated Date

Deploy Ocean Biomass Sinking

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An image of kelp suspended in the water column
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Summary

Ocean biomass sinking involves sinking terrestrial plant material and/or seaweed in the deep sea, where the carbon it has converted into biomass can be stored. Using terrestrial material diverts biomass that might otherwise break down on land and release CO₂, while using seaweed removes carbon by cultivating and sinking new biomass produced in the ocean. This practice might be able to remove over 0.1 Gt CO₂‑eq/yr, but estimates remain highly uncertain due to limited data, and the adoption levels needed to reach this threshold are probably impractical. Advantages include the use of terrestrial biomass that might otherwise degrade on land and emit CO₂, and the ability to reduce nutrient pollution in some ocean areas when cultivating marine biomass. Disadvantages include its unclear effectiveness and durability, potentially high environmental risks, limited feasibility to operate at scale (particularly for seaweed biomass), and complex monitoring and verification. We conclude that Deploy Ocean Biomass Sinking is “Not Recommended” as a climate solution.

Description for Social and Search
The Deploy Ocean Biomass Sinking solution is coming soon.
Overview

What is our assessment?

Our analysis finds that Deploy Ocean Biomass Sinking could have high potential environmental risks, including unknown impacts on marine ecosystems. It is also unclear how effective or durable carbon storage in the deep sea is from this approach. There are likely better alternative uses for terrestrial biomass, and cultivating seaweed at climate-relevant scales is probably not feasible. Even if it were, seaweed would probably provide greater value through other applications. Therefore, Deploy Ocean Biomass Sinking is currently “Not Recommended” as a climate solution.

Plausible Could it work? Yes
Ready Is it ready? No
Evidence Are there data to evaluate it? Limited
Effective Does it consistently work? No
Impact Is it big enough to matter? No
Risk Is it risky or harmful? Yes
Cost Is it cheap? ?

What is it?

Ocean biomass sinking relies on sinking terrestrial plant material and/or seaweed grown in the ocean to the deep sea or seafloor where it can be stored long-term. Cultivating and sinking seaweed removes carbon from the surface ocean, whereas sinking terrestrial biomass material can help reduce emissions that might otherwise occur if the material instead decomposed on land. While not a current practice, terrestrial biomass grown explicitly for sinking would also constitute a form of carbon removal. When biomass sinks naturally, most of it is degraded into CO₂ or other forms of carbon before reaching the deep sea. Deliberate sinking of biomass might avoid some of this degradation by expediting its delivery to the deep sea, depending on the method used. Once sunk, the biomass and any CO₂ or other forms of carbon produced from its degradation can be isolated from the atmosphere for decades to centuries due to the ocean’s slow circulation times at depth. Biomass sinking can be accomplished using active methods, like submersibles, or passive methods, like letting weighted bundles sink on their own. There has been a recent focus on sinking material in low-oxygen ocean basins (e.g., the Black Sea), which might help further minimize degradation, while improving the durability of sequestered carbon due to the long circulation time-scales typical of these regions.

Does it work?

Global estimates suggest that ~11% of carbon produced in natural seaweed ecosystems might be sequestered at depth, generally defined as below the mixed layer at around 1,000 m. However, very few studies have documented the export efficiency, or the fraction of carbon in surface waters that makes its way to the deep sea, of purposefully sunk terrestrial and seaweed biomass, as this practice is currently in the early stages of development and research. If biomass is quickly sunk, most carbon might make its way to the deep sea, while passive sinking techniques, if slower, could result in higher degradation rates. Sequestration also depends on the storage efficiency and durability of carbon once at depth. Some initial research suggests that biomass degradation may be slowed in low-oxygen basins, but this also remains poorly characterized in field studies. It is similarly unclear how durable the carbon stored below the mixed layer will be over climate-relevant timescales, both in the deep sea in general and in low-oxygen basins specifically.

Why are we excited?

The advantages of ocean biomass sinking include its potential ability to use land-based biomass that might otherwise be degraded in landfills or incinerated, both of which lead to CO₂ emissions. In some regions, seaweed cultivation could help reduce nutrient pollution, provide habitat for marine organisms, and locally buffer against ocean acidification. Estimates of potential climate impacts suggest that ocean biomass sinking using biomass from seaweed farms could theoretically exceed 0.1 Gt CO₂‑eq/yr. Still, those estimates remain highly speculative and require more research. Costs are poorly quantified, but some estimates suggest they could be low to moderately expensive compared to other marine carbon dioxide removal approaches, close to US$100/t CO₂.

Why are we concerned?

Ocean biomass sinking has many environmental and social risks that, though not currently fully understood, could make it unfeasible to deploy the technology at scale. Deep-sea and seafloor ecosystems are highly understudied, and it's unclear how new biomass might alter these unique environments. Potential impacts include increased acidification, nutrient pollution, and oxygen depletion of the deep sea, which could affect diverse marine life. Large-scale seaweed cultivation could reduce phytoplankton abundance, disrupt food webs, and deplete nutrients needed by other ecosystems. Cultivation in open ocean areas might relieve demand for coastal space, but they are often nutrient-poor, and adding nutrients raises serious concerns (see Ocean Fertilization). Terrestrial biomass sources could introduce contaminants into the ocean due to inadvertent inclusion of plastics or other pollutants in sunken biomass. This practice also comes with social risks. Some countries might disproportionately bear negative impacts wherever biomass is cultivated and/or sunk, as it could alter marine food webs and livelihoods. There could also be issues with public perception due to historical injustices around ocean dumping, potentially impeding future projects without meaningful community engagement and transparency. 

Moreover, there are numerous technical challenges relating to the effectiveness and durability of carbon sequestration. Biomass sources differ in how easily they break down, affecting how much carbon is stored at depth. Sunk biomass could also potentially release other greenhouse gases, such as methane and nitrous oxide. The location where biomass is disposed of also matters, impacting how much carbon reaches and stays at depth. However, all of these factors remain poorly constrained. Operational and technical challenges are also significant. To remove at least 0.1 Gt CO₂‑eq/yr using marine biomass, nearly 7 million ha of ocean – over 60% of the global coastline – could be needed for seaweed cultivation, which is impractical. Measurement and verification pose additional hurdles. In the case of seaweed cultivation, tracking carbon removal requires monitoring both CO₂ uptake at the ocean’s surface and export as well as storage at depth across large spatial and temporal scales. In addition, the opportunity cost of sinking terrestrial biomass is high due to competing land-based uses, as waste biomass and crop residues are finite resources. Growing new biomass explicitly for ocean sinking would introduce new risks, given that land is also a finite resource. Similarly, seaweed probably has higher value and carbon benefits as food, fertilizer, and other products.

Solution in Action

Arzeno-Soltero, I. B., Saenz, B. T., Frieder, C. A., Long, M. C., DeAngelo, J., Davis, S. J., & Davis, K. A. (2023). Large global variations in the carbon dioxide removal potential of seaweed farming due to biophysical constraints. Communications Earth & Environment, 4(1), 185. Link to source: https://doi.org/10.1038/s43247-023-00833-2

Bach, L. T., Tamsitt, V., Gower, J., Hurd, C. L., Raven, J. A., & Boyd, P. W. (2021). Testing the climate intervention potential of ocean afforestation using the Great Atlantic Sargassum Belt. Nature Communications, 12(1), 2556. Link to source: https://doi.org/10.1038/s41467-021-22837-2

Boettcher, M., Chai, F., Canothan, M., Cooley, S., Keller, D. P., Klinsky, S., ... & Webb, R. M. (2023). A code of conduct for marine carbon dioxide removal research. Link to source: https://www.aspeninstitute.org/publications/a-code-of-conduct-for-marine-carbon-dioxide-removal-research/

Chopin, T., Costa-Pierce, B. A., Troell, M., Hurd, C. L., Costello, M. J., Backman, S., ... & Yarish, C. (2024). Deep-ocean seaweed dumping for carbon sequestration: Questionable, risky, and not the best use of valuable biomass. One Earth, 7(3), 359-364. Link to source: https://doi.org/10.1016/j.oneear.2024.01.013

Duarte, C. M., Wu, J., Xiao, X., Bruhn, A., & Krause-Jensen, D. (2017). Can seaweed farming play a role in climate change mitigation and adaptation?. Frontiers in Marine Science, 4, 100. Link to source: https://doi.org/10.3389/fmars.2017.00100

Hurd, C. L., Gattuso, J. P., & Boyd, P. W. (2024). Air‐sea carbon dioxide equilibrium: Will it be possible to use seaweeds for carbon removal offsets?. Journal of Phycology, 60(1), 4-14. Link to source: https://doi.org/10.1111/jpy.13405

Hurd, C. L., Law, C. S., Bach, L. T., Britton, D., Hovenden, M., Paine, E. R., ... & Boyd, P. W. (2022). Forensic carbon accounting: Assessing the role of seaweeds for carbon sequestration. Journal of Phycology, 58(3), 347-363. Link to source: https://doi.org/10.1111/jpy.13249

Jones, D. C., Ito, T., Takano, Y., & Hsu, W. C. (2014). Spatial and seasonal variability of the air‐sea equilibration timescale of carbon dioxide. Global Biogeochemical Cycles, 28(11), 1163-1178. Link to source: https://doi.org/10.1002/2014GB004813

Keil, R. G., Nuwer, J. M., & Strand, S. E. (2010). Burial of agricultural byproducts in the deep sea as a form of carbon sequestration: A preliminary experiment. Marine Chemistry, 122(1-4), 91-95. Link to source: https://doi.org/10.1016/j.marchem.2010.07.007

National Academies of Sciences, Engineering, and Medicine. (2021). A research strategy for ocean-based carbon dioxide removal and sequestration. Link to source: https://www.nationalacademies.org/our-work/a-research-strategy-for-ocean-carbon-dioxide-removal-and-sequestration

Raven, M. R., Crotteau, M. A., Evans, N., Girard, Z. C., Martinez, A. M., Young, I., & Valentine, D. L. (2024). Biomass storage in anoxic marine basins: Initial estimates of geochemical impacts and CO2 sequestration capacity. AGU Advances, 5(1), e2023AV000950. Link to source: https://doi.org/10.1029/2023AV000950

Raven, M. R., Evans, N., Martinez, A. M., & Phillips, A. A. (2025). Big decisions from small experiments: observational strategies for biomass-based marine carbon storage. Environmental Research Letters, 20(5), 051001. Link to source: https://doi.org/10.1088/1748-9326/adc28d

Ricart, A. M., Krause-Jensen, D., Hancke, K., Price, N. N., Masqué, P., & Duarte, C. M. (2022). Sinking seaweed in the deep ocean for carbon neutrality is ahead of science and beyond the ethics. Environmental Research Letters, 17(8), 081003. Link to source: https://doi.org/10.1088/1748-9326/ac82ff

Ross, F. W., Boyd, P. W., Filbee-Dexter, K., Watanabe, K., Ortega, A., Krause-Jensen, D., ... & Macreadie, P. I. (2023). Potential role of seaweeds in climate change mitigation. Science of the Total Environment, 885, 163699. Link to source: https://doi.org/10.1016/j.scitotenv.2023.163699

Sheppard, E. J., Hurd, C. L., Britton, D. D., Reed, D. C., & Bach, L. T. (2023). Seaweed biogeochemistry: Global assessment of C: N and C: P ratios and implications for ocean afforestation. Journal of Phycology, 59(5), 879-892. Link to source: https://doi.org/10.1111/jpy.13381

Strand, S. E., & Benford, G. (2009). Ocean sequestration of crop residue carbon: recycling fossil fuel carbon back to deep sediments. Environmental Science and TechnologyLink to source: https://doi.org/10.1021/es8015556

Visions, O. (2022). Answering Critical Questions About Sinking Macroalgae for Carbon Dioxide Removal: A Research Framework to Investigate Sequestration Efficacy and Environmental Impacts.Link to source: https://oceanvisions.org/wp-content/uploads/2022/10/Ocean-Visions-Sinking-Seaweed-Report_FINAL.pdf

Wu, J., Keller, D. P., & Oschlies, A. (2023). Carbon dioxide removal via macroalgae open-ocean mariculture and sinking: an Earth system modeling study. Earth System Dynamics, 14(1), 185-221. Link to source: https://doi.org/10.5194/esd-14-185-2023

Xiao, X., Agusti, S., Lin, F., Li, K., Pan, Y., Yu, Y., ... & Duarte, C. M. (2017). Nutrient removal from Chinese coastal waters by large-scale seaweed aquaculture. Scientific Reports, 7(1), 46613. Link to source: https://doi.org/10.1038/srep46613

Xiao, X., Agustí, S., Yu, Y., Huang, Y., Chen, W., Hu, J., ... & Duarte, C. M. (2021). Seaweed farms provide refugia from ocean acidification. Science of the Total Environment, 776, 145192. Link to source: https://doi.org/10.1016/j.scitotenv.2021.145192

Credits

Lead Fellow

  • Christina Richardson, Ph.D.

Internal Reviewer

  • Christina Swanson, Ph.D.
Speed of Action
left_text_column_width
Caveats
left_text_column_width
Risks
left_text_column_width
Consensus
left_text_column_width
Trade-offs
left_text_column_width
Action Word
Deploy
Solution Title
Ocean Biomass Sinking
Classification
Not Recommended
Lawmakers and Policymakers
Practitioners
Business Leaders
Nonprofit Leaders
Investors
Philanthropists and International Aid Agencies
Thought Leaders
Technologists and Researchers
Communities, Households, and Individuals
Updated Date

Deploy Blue Hydrogen

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An image of a large, metal hydrogen storage tank that says 'H2 Hydrogen' on the side
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Summary

Blue hydrogen is hydrogen produced from fossil fuel sources, with some of the GHG emissions captured and stored to prevent their release. This hydrogen, considered a low-carbon fuel or feedstock, is an alternative to hydrogen produced from fossil fuels without carbon capture (gray hydrogen). Blue hydrogen production uses available technologies and is less expensive than some other low-carbon hydrogen fuels, such as green hydrogen produced from renewable-powered electrolysis. However, concerns exist about its low adoption, variable effectiveness, and competition with technologies that offer greater climate benefits. Even if implemented effectively, blue hydrogen is higher-emitting than green hydrogen and more expensive than gray hydrogen. Blue hydrogen could be a “less-bad” interim alternative to gray hydrogen, but at the risk of perpetuating fossil fuel use. Blue hydrogen is theoretically an effective climate solution, but there are open questions around whether realistic deployment can meet its potential. Based on our assessment, we will “Keep Watching” this potential solution.

Description for Social and Search
Blue hydrogen is hydrogen produced from fossil fuels, with some of the GHGs captured and stored to prevent their release. This hydrogen, considered a low-carbon fuel or feedstock, is an alternative to hydrogen produced from fossil fuels without carbon capture (gray hydrogen).
Overview

What is our assessment?

Based on our analysis, blue hydrogen is ready to deploy and feasible, but there is mixed consensus and limited data on its effectiveness in reducing emissions. Its climate impact has the potential to be high, but only if adopted effectively and at a large scale, both of which are currently unproven. If deployed correctly, this technology could serve as an interim solution to reduce gray hydrogen emissions while progress is made on scaling and reducing the costs of green hydrogen. Based on our assessment, we will “Keep Watching” this potential solution.

Plausible Could it work? Yes
Ready Is it ready? Yes
Evidence Are there data to evaluate it? Limited
Effective Does it consistently work? No
Impact Is it big enough to matter? No
Risk Is it risky or harmful? No
Cost Is it cheap? Yes

What is it?

Hydrogen is a fuel that can be used in place of fossil fuels in industrial, transportation, and energy systems. To deploy hydrogen as an energy source or feedstock, it first needs to be extracted from other compounds. Each “color” is an informal term specifying hydrogen produced through a unique hydrogen production path, each with different associated supply chains, processes, and energy GHG emissions. Gray hydrogen, which uses natural gas as the source of hydrogen atoms and electricity, is the most produced and has high production emissions, estimated at 10–12 t CO-eq/t hydrogen on a 100-yr basis. One way to reduce emissions is by switching to blue hydrogen, which still uses fossil fuels but also uses CCS technologies to prevent the release of some of the CO generated during production. Blue hydrogen has the potential to be a lower-emission source of energy relative to gray hydrogen or direct fossil fuel combustion.

Does it work?

Blue hydrogen is a plausible way to reduce emissions from gray hydrogen production. However, expert opinions are mixed on the magnitude of emissions that can be abated by producing blue hydrogen in place of gray hydrogen. The effectiveness of emissions reduction hinges on two main factors: the rate at which upstream methane leaks and carbon capture rates, both of which are challenging to predict on a global scale. There is uncertainty around these performance metrics and the ability to effectively store and transport captured CO at scale. Due to low current adoption, there is little real-world data to answer these questions. As of 2023, blue hydrogen comprised <1% of worldwide hydrogen production. While adding carbon capture to gray hydrogen production should help prevent emissions, there is limited evidence for both effectiveness and the ability to scale of this technology.

Why are we excited?

Compared to other types of low-carbon hydrogen, including green hydrogen produced from electrolysis powered by renewable energy, blue hydrogen is a technologically developed and lower-cost option. Without a currently viable and cost-effective alternative to gray hydrogen that does not use fossil fuels, blue hydrogen can be a near-term option to facilitate the transition to a global hydrogen economy. Expert estimates of cost per emissions avoided range widely, but the International Energy Agency (IEA) estimates US$60–85/t CO for lower carbon capture rates (55–70%) and US$85–110/t CO for higher carbon capture rates (>90%). However, these costs are uncertain: with lower estimates of effectiveness, the cost could increase to ~US$260/t CO, including the cost to transport and store CO. If implemented with low GHG fugitive emissions and high CCS efficiencies, blue hydrogen can reduce emissions by more than 60% relative to current gray hydrogen production on a 100-yr CO₂‑eq basis. In this case, the climate impact of scaling blue hydrogen could be high. Estimates and targets for blue hydrogen production by 2050 range from ~30–85 Mt hydrogen. At that scale, even modest emissions savings relative to gray hydrogen (3 t CO₂‑eq/t hydrogen, 20-yr basis) would have a climate impact above 0.09 Gt CO-eq/yr by 2050. However, achieving this depends on the quality of the infrastructure and rate of technology scaling, both of which are unproven.

Why are we concerned?

While it has some advantages, blue hydrogen is still a less effective solution than green hydrogen, while costing more than gray hydrogen. Though it could be useful for near-term energy decarbonization, this risks taking resources away from renewable energy and green hydrogen development while perpetuating and increasing fossil fuel use. The infrastructure required to scale hydrogen-based energy is expensive and will require technical advances and policy incentives to be competitive with fossil fuels. There are mixed expert opinions about the realistic level of avoided emissions that blue hydrogen may reach. The theoretical worst-performing blue hydrogen plants (low capture rates, high methane leaks, high-emission electricity sources) have been predicted to lead to more emissions on a near-term basis than direct natural gas combustion. Additionally, there is uncertainty around whether CCS can meet its technical potential at a reasonable cost. While experts predict >95% carbon capture rates are possible, facilities currently in operation capture less than this target, some less than 60% of all emitted carbon. For blue hydrogen to be feasible and scalable, CO transport and storage need to be low-emitting, stable, and available. Only ~8% of CO currently captured from blue hydrogen production is injected in dedicated storage, with the rest used in industry, enhanced oil recovery, and other applications. Finally, an understudied risk is hydrogen leaks. Hydrogen transport and storage require larger volumes than fossil fuels, increasing the risk of leaks. Hydrogen has an indirect planet-warming effect by increasing the levels of other atmospheric GHGs. At scale, the IEA estimates that high hydrogen leak rates could contribute 0.1 Gt CO-eq/yr in emissions, potentially canceling out any positive climate impacts.

Solution in Action

Arcos, J. M. M., & Santos, D. M. F. (2023). The hydrogen color spectrum: Techno-economic analysis of the available technologies for hydrogen production. Gases, 3(1), Article 1. Link to source: https://doi.org/10.3390/gases3010002

Bauer, C., Treyer, K., Antonini, C., Bergerson, J., Gazzani, M., Gencer, E., Gibbins, J., Mazzotti, M., McCoy, S. T., McKenna, R., Pietzcker, R., Ravikumar, A. P., Romano, M. C., Ueckerdt, F., Vente, J., & Spek, M. van der. (2021). On the climate impacts of blue hydrogen production. Sustainable Energy & Fuels, 6(1), 66–75. Link to source: https://doi.org/10.1039/D1SE01508G

Blank, T. K., Molloy, P., Ramirez, K., Wall, A., & Weiss, T. (2022, April 13). Clean energy 101: The colors of hydrogen. RMI. Link to source: https://rmi.org/clean-energy-101-hydrogen/

Collodi, G., Azzaro, G., Ferrari, N., & Santos, S. (2017). Techno-economic Evaluation of Deploying CCS in SMR Based Merchant H2 Production with NG as Feedstock and Fuel. Energy Procedia, 114, 2690–2712. Link to source: https://doi.org/10.1016/j.egypro.2017.03.1533

Gorski, J., Jutt, T., & Wu, K. T. (2021). Carbon intensity of blue hydrogen production. Link to source: https://www.pembina.org/reports/carbon-intensity-of-blue-hydrogen-revised.pdf

Hossain Bhuiyan, M. M., & Siddique, Z. (2025). Hydrogen as an alternative fuel: A comprehensive review of challenges and opportunities in production, storage, and transportation. International Journal of Hydrogen Energy, 102, 1026–1044. Link to source: https://doi.org/10.1016/j.ijhydene.2025.01.033

Howarth, R. W., & Jacobson, M. Z. (2021). How green is blue hydrogen? Energy Science & Engineering, 9(10), 1676–1687. Link to source: https://doi.org/10.1002/ese3.956

IEA. (2023). Hydrogen: Net zero emissions guide. Link to source: https://www.iea.org/reports/hydrogen-2156#overview

IEA. (2023). Net zero roadmap: A global pathway to keep the 1.5 °C goal in reach. Link to source: https://www.iea.org/reports/net-zero-roadmap-a-global-pathway-to-keep-the-15-0c-goal-in-reach

IEA. (2024). Global hydrogen review 2024. Link to source: https://www.iea.org/reports/global-hydrogen-review-2024

Incer-Valverde, J., Korayem, A., Tsatsaronis, G., & Morosuk, T. (2023). “Colors” of hydrogen: Definitions and carbon intensity. Energy Conversion and Management, 291, 117294. Link to source: https://doi.org/10.1016/j.enconman.2023.117294

Lewis, E., McNaul, S., Jamieson, M., Henriksen, M. S., Matthews, H. S., White, J., Walsh, L., Grove, J., Shultz, T., Skone, T. J., & Stevens, R. (2022). Comparison of commercial, state-of-the-art, fossil-based hydrogen production technologies. Link to source: https://www.osti.gov/biblio/1862910  

Pettersen, J., Steeneveldt, R., Grainger, D., Scott, T., Holst, L.-M., & Hamborg, E. S. (2022). Blue hydrogen must be done properly. Energy Science & Engineering, 10(9), 3220–3236. Link to source: https://doi.org/10.1002/ese3.1232

Romano, M. C., Antonini, C., Bardow, A., Bertsch, V., Brandon, N. P., Brouwer, J., Campanari, S., Crema, L., Dodds, P. E., Gardarsdottir, S., Gazzani, M., Jan Kramer, G., Lund, P. D., Mac Dowell, N., Martelli, E., Mastropasqua, L., McKenna, R. C., Monteiro, J. G. M.-S., Paltrinieri, N., … Wiley, D. (2022). Comment on “How green is blue hydrogen?” Energy Science & Engineering, 10(7), 1944–1954. Link to source: https://doi.org/10.1002/ese3.1126

Sun, T., Shrestha, E., Hamburg, S. P., Kupers, R., & Ocko, I. B. (2024). Climate impacts of hydrogen and methane emissions can considerably reduce the climate benefits across key hydrogen use cases and time scales. Environmental Science & Technology, 58(12), 5299–5309. Link to source: https://doi.org/10.1021/acs.est.3c09030

Udemu, C., & Font-Palma, C. (2024). Potential cost savings of large-scale blue hydrogen production via sorption-enhanced steam reforming process. Energy Conversion and Management, 302, 118132. Link to source: https://doi.org/10.1016/j.enconman.2024.118132

Vallejo, V., Nguyen, Q., & Ravikumar, A. P. (2024). Geospatial variation in carbon accounting of hydrogen production and implications for the US Inflation Reduction Act. Nature Energy, 9(12), 1571–1582. Link to source: https://doi.org/10.1038/s41560-024-01653-0

Wu, W., Zhai, H., & Holubnyak, E. (2024). Technological evolution of large-scale blue hydrogen production toward the U.S. Hydrogen Energy Earthshot. Nature Communications, 15(1), 5684. Link to source: https://doi.org/10.1038/s41467-024-50090-w 

Credits

Lead Fellow 

  • Sarah Gleeson, Ph.D.

Internal Reviewer

  • Christina Swanson, Ph.D.
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Deploy
Solution Title
Blue Hydrogen
Classification
Not Recommended
Lawmakers and Policymakers
Practitioners
Business Leaders
Nonprofit Leaders
Investors
Philanthropists and International Aid Agencies
Thought Leaders
Technologists and Researchers
Communities, Households, and Individuals
Updated Date

Deploy Vertical Farms

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Summary

Vertical farms are facilities that grow crops indoors, vertically stacking multiple layers of plants and providing controlled conditions using artificial light, indoor heating and cooling systems, humidity controls, water pumps, and advanced automation systems. In theory, vertical farms could reduce the need to clear more agricultural land and the distance food travels to market. However, because vertical farms are so energy and material intensive, and food transportation emissions are a small fraction of the overall carbon footprint of food, vertical farms do not reduce emissions overall. We conclude that vertical farms are “Not Recommended” as an effective climate solution.

Description for Social and Search
Because vertical farms are so energy and material intensive, and food transportation emissions are a small fraction of the overall carbon footprint of food, vertical farms do not reduce emissions overall. We conclude that vertical farms are “Not Recommended” as an effective climate solution.
Overview

What is our assessment?

Based on our analysis, vertical farms are not an effective climate solution. The tremendous energy use and embodied emissions of vertical farm operations outweigh any potential savings of reducing food miles or land expansion. Moreover, the ability of vertical farms to truly scale to be a meaningful part of the global food system is extremely limited. We therefore classify this as “Not Recommended” as an effective climate solution.

Plausible Could it work? No
Ready Is it ready? Yes
Evidence Are there data to evaluate it? Yes
Effective Does it consistently work? No
Impact Is it big enough to matter? No
Risk Is it risky or harmful? No
Cost Is it cheap? No

What is it?

Vertical farms are facilities that grow crops indoors, with multiple layers of plants stacked on top of each other, using artificial lights, large heating and cooling systems, humidity controls, water pumps, and complex building automation systems. In principle, vertical farms can dramatically shrink the land “footprint” of agriculture, and this could help reduce the need for agricultural land. Moreover, by growing crops closer to urban centers, vertical farms could potentially reduce “food miles” and the emissions related to food transport.

Does it work? 

The technology of growing some kinds of crops – especially greens and herbs – in indoor facilities is well developed, but there is no evidence to show that doing so can reduce GHG emissions compared to growing the same food on traditional farms. Theoretically, vertical farms could reduce emissions associated with agricultural land expansion and food transportation. However, the operation and construction of vertical farms require enormous amounts of energy and materials, all of which cause significant emissions. Vertical farms require artificial lighting (even with efficient LEDs, this is a considerable energy cost), heating, cooling, humidity control, air circulation, and water pumping – all of which require energy. Vertical farms could be powered by renewable sources; however, this is an inefficient method for reducing GHG emissions compared to using that renewable energy to replace fossil-fuel-powered electricity generation. Growing food closer to urban centers also does not meaningfully reduce emissions because emissions from “food miles” are only a small fraction of the life cycle emissions for most farmed foods. Recent research has found that the carbon footprint of lettuce grown in vertical farms can be 5.6 to 16.7 times greater than that of lettuce grown with traditional methods.

Why are we excited?

While vertical farms are not an effective strategy for reducing emissions, they may have some value for climate resilience and adaptation. Vertical farms offer a protected environment for crop growth and well-managed water use, and they can potentially shield plants from pests, diseases, and natural disasters. Moreover, the controlled environment can be adjusted to adapt to changing climate conditions, helping ensure continuous production and lowering the risks of crop loss.

Why are we concerned?

Vertical farms use enormous amounts of energy and material to grow a limited array of food, all at significant cost. That energy and material have a significant carbon emissions cost, no matter how efficient the technology becomes. On the whole, vertical farms appear to emit far more GHGs than traditional farms do. Moreover, vertical farms are expensive to build and operate, and are unlikely to play a major role in the world’s food system. At present, they are mainly used to grow high-priced greens, vegetables, herbs, and cannabis, which do not address the tremendous pressure points in the global food system to feed the world sustainably. There are also concerns about the future of the vertical farming business. While early efforts were funded by venture capital, vertical farming has struggled to become profitable, putting its future in doubt.
 

Solution in Action

Blom, T. et al.., (2022). The embodied carbon emissions of lettuce production in vertical farming, greenhouse horticulture, and open-field farming in the Netherlands. Journal of Cleaner Production, 377, 134443. Link to source: https://www.sciencedirect.com/science/article/pii/S095965262204015X 

Cornell Chronicle, (2014). Indoor urban farms called wasteful, “pie in the sky”. Link to source: https://news.cornell.edu/stories/2014/02/indoor-urban-farms-called-wasteful-pie-sky

Cox, S., (2012). The vertical farming scam, Counterpunch. Link to source: https://www.counterpunch.org/2012/12/11/the-vertical-farming-scam/ 

Cox, S., (2016). Enough with the vertical farming fantasies: There are still too many unanswered questions about the trendy practice, Salon. Link to source: https://www.salon.com/2016/02/17/enough_with_the_vertical_farming_partner/ 

Foley, J.A. et al., (2011). Solutions for a cultivated planet, Nature. Link to source: http://doi.org/10.1038/nature10452

Foley, J.A., (2018). No, vertical farms won’t feed the world, Medium. Link to source: https://globalecoguy.org/no-vertical-farms-wont-feed-the-world-5313e3e961c0 

Hamm, M., (2015). The buzz around indoor farms and artificial lighting makes no sense. The Guardian. Link to source: https://www.theguardian.com/sustainable-business/2015/apr/10/indoor-farming-makes-no-economic-environmental-sense 

Peters, A., (2023). The vertical farming bubble is finally popping, Fast Company. Link to source: https://www.fastcompany.com/90824702/vertical-farming-failing-profitable-appharvest-aerofarms-bowery

Ritchie, H., (2022). Eating local is still not a good way to reduce the carbon footprint of your diet, Sustainability by the numbers. Link to source: https://www.sustainabilitybynumbers.com/p/food-miles 

Tabibi, A. (2024). Vertical farms: A tool for climate change adaptation, Green.org. January 30, 2024. Link to source: https://green.org/2024/01/30/vertical-farms-a-tool-for-climate-change-adaptation/   

Credits

Lead Author

  • Jonathan Foley, Ph.D.

Internal Reviewer

  • Christina Swanson, Ph.D.
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Action Word
Deploy
Solution Title
Vertical Farms
Classification
Not Recommended
Updated Date

Use Corn-Based Ethanol

Cluster
Fuel Switching
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Peatland
Coming Soon
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Description for Social and Search
The Use Corn-Based Ethanol solution is coming soon.
Solution in Action
Speed of Action
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Action Word
Use
Solution Title
Corn-Based Ethanol
Classification
Not Recommended
Updated Date

Deploy Waste to Energy

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Peatland
Coming Soon
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Description for Social and Search
The Use Waste to Energy solution is coming soon.
Solution in Action
Speed of Action
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Deploy
Solution Title
Waste to Energy
Classification
Worthwhile
Updated Date

Use Fossil Fuels with Carbon Capture & Storage

Sector
Electricity
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Peatland
Coming Soon
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Description for Social and Search
The Use Fossil Fuels with Carbon Capture & Storage solution is coming soon.
Solution in Action
Speed of Action
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Use
Solution Title
Fossil Fuels with Carbon Capture & Storage
Classification
Not Recommended
Updated Date

Advance Cultivated Meat

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Fried chicken sandwich
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Summary

Cultivated meat is produced from a sample of animal cells, rather than by slaughtering animals. This technology shows promise for reducing emissions from animal agriculture, but its climate impact depends on the energy source used during production. Research and development are still in early stages, and whether the products can scale depends on continued investments, consumer approval, technological growth, and regulatory acceptance. While cultivated meat shows potential, evidence about its emissions reduction potential is limited, and the high costs of production may restrain its scalability. Based on our assessment, we will “Keep Watching” this potential solution.

Description for Social and Search
Cultivated meat is produced from a sample of animal cells, rather than by slaughtering animals. This technology shows promise for reducing emissions from animal agriculture, but its climate impact depends on the energy source used during production.
Overview

What is our assessment?

Based on our analysis, cultivated meat is promising in its ability to reduce emissions from meat production, but the impact on a large scale remains unclear. Based on our assessment, we will “Keep Watching” this potential solution.

Plausible Could it work? Yes
Ready Is it ready? Yes
Evidence Are there data to evaluate it? Limited
Effective Does it consistently work? Yes
Impact Is it big enough to matter? ?
Risk Is it risky or harmful? No
Cost Is it cheap? No

What is it?

Cultivated meat (also called lab-grown or cultured meat) is a cellular agriculture product that, when used to replace meat from livestock, can reduce emissions. Cultivated meat is developed through bioengineering. Its production uses sample cells from an animal, in addition to a medium that supports cell growth in a bioreactor. Energy is required to produce the ingredients for the growth medium and to run the bioreactor (e.g., for temperature control, the mixing processes, aeration).

Does it work? 

Since the development of cultivated meat is still in its infancy, there is limited evidence on its emissions savings potential from large-scale production. Preliminary estimates differ by an order of magnitude, depending on the energy source used in the lab environment. Using fossil energy sources, emissions generated from the production of one kilogram of cultivated meat could reach 25 kilograms CO₂‑eq. If renewable energy is used, emissions could be about two kilograms CO₂‑eq per kilogram of cultivated meat. By comparison, producing a kilogram of beef from livestock generates 80–100 kilograms CO₂‑eq, on average. Almost half of those emissions from livestock beef are in the form of methane. Producing pig meat and poultry meat generates about 12 kilograms and 10 kilograms of CO₂‑eq, respectively. Based on these estimates, cultivated meat could substantially reduce the emissions of beef. Compared to pork and chicken, however, its emissions depend on the source of energy used during production.

Why are we excited?

The cultivated meat industry is fairly new but growing rapidly. The first cell-cultivated meat product was developed in 2013. In 2024, there were 155 companies involved in the industry, located across six continents, mostly based in the United States, Israel, the United Kingdom, and Singapore. Agriculture is responsible for about 22% of global GHG emissions, and raising livestock, especially beef, is particularly emissions-intensive. Therefore, cultivated meat has great potential to reduce related emissions as demand for meat continues to grow across the world. Cultivated meat enables the production of a large amount of meat from a single stem cell. This means that far fewer animals will be needed for meat production. Cultivated meat is also more efficient at converting feed into meat than chickens, which reduces emissions associated with feed production and demand for land.

Why are we concerned?

Concerns about cultivated meat include scalability, cost, and consumer acceptance. Because cultivated meat is still an emerging area of food science, the cost of production may be prohibitive at a large scale. Although cell culture is routinely performed in industrial and academic labs, creating the culture medium for mass-market production at competitive prices will require innovations and significant cost reductions. There are still many unknowns about the commercial potential of cultivated meat and whether consumers will accept the products. In 2024, companies began to move from research labs to larger facilities to start producing meat for consumers. There are only two countries that allow the sale of cultivated meat: Singapore and the United States. Within the United States, about one-third of adults find the concept of cultivated meat appealing, and only about 17% would be likely to purchase it, according to a poll conducted on behalf of the Good Food Institute. However, even substituting a fraction of the beef consumed in the United States with cultivated meat could have an important impact on reducing emissions. Cultivated meat is a novel food and may require consumer education and producer transparency on production methods and safeguards in order to become more widely accepted.

Solution in Action

Congressional Research Service of the United States (2023). Cell-Cultivated Meat: An Overview Link to source: https://www.congress.gov/crs-product/R47697

Garrison, G. L., et al. (2022). How much will large-scale production of cell-cultured meat cost?. Journal of Agriculture and Food Research, 10: 100358. Link to source: https://doi.org/10.1016/j.jafr.2022.100358

Good Food Institute (2025). 2024 State of the Industry report: Cultivated meat, seafood, and ingredients. Link to source: https://gfi.org/resource/cultivated-meat-seafood-and-ingredients-state-of-the-industry/

Good Food Institute (2024). Consumer snapshot: Cultivated meat in the U.S. Link to source: https://gfi.org/wp-content/uploads/2025/01/Consumer-snapshot-cultivated-meat-in-the-US.pdf

Good Food Institute (2020). An analysis of culture medium costs and production volumes for cultivated meat Link to source: https://gfi.org/resource/analyzing-cell-culture-medium-costs/

Gursel, I. et al. (2022). Review and analysis of studies on sustainability of cultured meat. Wageningen Food & Biobased Research. Link to source: https://edepot.wur.nl/563404

Mendly-Zambo, Z., et al. (2021). Dairy 3.0: cellular agriculture and the future of milk. Food, Culture & Society, 24(5), 675–693. Link to source: https://doi.org/10.1080/15528014.2021.1888411

MIT Technology Review (2023). Here’s what we know about lab-grown meat and climate change. Link to source: https://www.technologyreview.com/2023/07/03/1075809/lab-grown-meat-climate-change/

J. Poore, & T. Nemecek (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360, 987-992. Link to source: https://doi.org/10.1126/science.aaq0216

Risner, D., et al. (2023) Environmental impacts of cultured meat: A cradle-to-gate life cycle assessment. bioRxiv, 2023.04.21.537778; doi: Link to source: https://doi.org/10.1101/2023.04.21.537778

Sinke, P., et al. (2023). Ex-ante life cycle assessment of commercial-scale cultivated meat production in 2030. Int J Life Cycle Assess, 28, 234–254 Link to source: https://doi.org/10.1007/s11367-022-02128-8

Treich, N. (2021). Cultured Meat: Promises and Challenges. Environ Resource Econ, 79, 33–61 Link to source: https://doi.org/10.1007/s10640-021-00551-3

Tuomisto HL, et al. (2022) Prospective life cycle assessment of a bioprocess design for cultured meat production in hollow fiber bioreactors. Science of the Total Environment, 851:158051

World Bank (2024) Recipe for a Livable Planet: Achieving Net Zero Emissions in the Agrifood System Link to source: https://openknowledge.worldbank.org/entities/publication/406c71a3-c13f-49cd-8f3f-a071715858fb

Xu X, Sharma P, Shu S et al (2021) Global greenhouse gas emissions from animal-based foods are twice those of plant-based foods. Nature Food, 2:724–732 Link to source: https://doi.org/10.1038/s43016-021-00358-x 

Credits

Lead Fellow

  • Emily Cassidy

Internal Reviewers

  • Eric Toensmeier
  • Paul West, Ph.D.
  • Christina Swanson, Ph.D.
Speed of Action
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Action Word
Advance
Solution Title
Cultivated Meat
Classification
Keep Watching
Updated Date

Mobilize Green Hydrogen for Aviation and Trucking

Cluster
Fuel Switching
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A graphic of a clear bubble in the form of a molecule with a green background
Coming Soon
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Summary

Green hydrogen is an emissions-free fuel produced by using renewable electricity to split water into hydrogen and oxygen. For aviation and long-haul trucking, green hydrogen can be used either directly in fuel cells or combusted in modified engines, offering a potential pathway to deep emissions reductions. It generates no CO₂ at the point of use, and when produced with clean power, life-cycle emissions can be near zero. However, green hydrogen faces major barriers in terms of energy intensity, infrastructure needs, cost, and vehicle redesign. We will “Keep Watching” Mobilize Green Hydrogen for Aviation and Trucking due to its high potential impact, even though it is not yet ready for widespread deployment.

Description for Social and Search
Green hydrogen is an emissions-free fuel produced by using renewable electricity to split water into hydrogen and oxygen. For aviation and long-haul trucking, green hydrogen can be used either directly in fuel cells or combusted in modified engines, offering a potential pathway to deep emissions reductions.
Overview

What is our assessment?

Based on our analysis, green hydrogen holds long-term potential in sectors that are difficult to decarbonize, particularly long-haul aviation and freight trucking. It is technologically feasible, but currently hampered by high costs, severe infrastructure gaps, and limited commercial readiness. While it is unlikely to be deployed at scale this decade, we will “Keep Watching” green hydrogen as innovation and policy evolve

Plausible Could it work? Yes
Ready Is it ready? No
Evidence Are there data to evaluate it? Yes
Effective Does it consistently work? Yes
Impact Is it big enough to matter? Yes
Risk Is it risky or harmful? No
Cost Is it cheap? No

What is it?

Green hydrogen is a clean, emissions-free liquid fuel produced through electrolysis powered by renewable energy that can replace fossil fuels in some transportation sectors. Unlike hydrogen from fossil fuels (gray or blue hydrogen), green hydrogen generates no CO₂ emissions during production. For transportation, green hydrogen can be used in two main ways: (1) in fuel cell electric vehicles (FCEVs) to generate electricity onboard and power electric motors, or (2) combusted in specially designed hydrogen combustion engines or turbines. For aviation, liquid hydrogen may fuel aircraft engines directly, be used to produce synthetic jet fuels, or power fuel cell airplanes. For long-haul trucking, hydrogen can replace diesel by powering fuel cell trucks, which offer long range and fast refueling.

Does it work?

Green hydrogen is being produced and used in pilot projects and select transportation initiatives globally. Hydrogen combustion engines and fuel cells are currently in use and have been shown to reduce emissions compared to fossil fuels. For aviation, aircraft manufacturers, such as Airbus, have hydrogen-powered planes in development, with test flights expected by 2030, but it could be several decades before they are put into commercial use. In heavy-duty trucking, several major automakers, including Toyota and Hyundai, have already commercialized hydrogen trucks in limited markets, such as China and Japan.

Why are we excited?

Green hydrogen is one of the few near-zero-emission fuels with the potential to decarbonize aviation and long-haul trucking, where battery-electric solutions currently face range and weight constraints. If produced using abundant, low-cost renewables, green hydrogen could significantly cut emissions in sectors responsible for nearly 15% of global transport emissions. In aviation, hydrogen-based fuels like e-kerosene could save around five million tons of CO₂ per year in Europe by 2030. In trucking, hydrogen fuel cell vehicles are beginning to roll out but remain a niche market. Looking ahead, hydrogen has strong potential: by 2050, it could meet up to 30% of energy demand in long-haul trucking and significantly reduce aviation emissions, particularly for short- and medium-haul flights, but it will have to compete with advances in battery-electric options. Hydrogen enables fast refueling and long range, making it a strong candidate for freight and intercity applications. Additionally, investment in green hydrogen infrastructure could unlock cross-sectoral benefits, supporting decarbonization of industry, power, and potentially heating. As electrolyzer costs fall and renewable power expands, the economics and emissions profile of green hydrogen are likely to improve.

Why are we concerned?

Despite its promise, green hydrogen for transport faces significant technical, economic, and logistical hurdles. Electrolysis is energy-intensive, and green hydrogen production is still expensive (US$300–600/t CO₂ avoided for trucking and US$500–1500/t CO₂ for aviation), making it much more costly than diesel or jet fuel but comparable to sustainable aviation fuel today. It is also less energy-dense by volume than other fuels, requiring complex transportation and storage (especially for aviation, where cryogenic tanks are needed) and limiting payload capacity. In addition to producing contrails, hydrogen leakage, though not a GHG, can contribute to indirect global warming effects. There are also safety concerns related to flammability and explosiveness, and a complete overhaul of transportation and refueling infrastructure is needed for both aviation and trucking. Green hydrogen requires entirely new infrastructure for production, storage, and distribution, including refueling stations for trucks and specialized handling systems for liquid or compressed hydrogen at each airport the airplane uses. The absence of this infrastructure creates a major barrier to adoption in aviation and long-haul trucking, where fuel logistics, safety standards, and scale are critical for commercial viability. Hydrogen remains a niche fuel due to its low energy density per volume, the need for cryogenic storage in aviation, limited refueling infrastructure, and high cost. While technically viable, major deployment for aviation and trucking is still nascent. Without a clear business case or strong policy incentives, uptake will remain limited in the near term.

Solution in Action

Clean Hydrogen Partnership. (2020). Hydrogen-powered aviation. Link to source: https://www.clean-hydrogen.europa.eu/media/publications/hydrogen-powered-aviation_en

Clean Hydrogen Partnership. (2020). Study on Fuel Cells Hydrogen Trucks. Link to source: https://www.clean-hydrogen.europa.eu/media/publications/study-fuel-cells-hydrogen-trucks_en

Galimova, T., Fasihi, M., Bogdanov, D., & Breyer, C. (2023). Impact of international transportation chains on cost of green e-hydrogen: Global cost of hydrogen and consequences for Germany and Finland. Applied Energy, 347, 121369. Link to source: https://doi.org/10.1016/j.apenergy.2023.121369

IEA. (2019). The Future of Hydrogen – Analysis. IEA. Link to source: https://www.iea.org/reports/the-future-of-hydrogen

IPCC. (2022). IPCC Sixth Assessment Report Working Group III: Mitigation of Climate Change, Chapter 10: Transport. Retrieved May 28, 2025, from Link to source: https://www.ipcc.ch/report/ar6/wg3/chapter/chapter-10/

IRENA. (2022). Green Hydrogen for Industry: A Guide to Policy Making. Link to source: https://www.irena.org/publications/2022/Mar/Green-Hydrogen-for-Industry

Li, Y., & Taghizadeh-Hesary, F. (2022). The economic feasibility of green hydrogen and fuel cell electric vehicles for road transport in China. Energy Policy, 160, 112703. Link to source: https://doi.org/10.1016/j.enpol.2021.112703

McKinsey. (2023). Global Energy Perspective 2023: Hydrogen outlook. Link to source: https://www.mckinsey.com/industries/oil-and-gas/our-insights/global-energy-perspective-2023-hydrogen-outlook 

Credits

Lead Fellow

  • Heather Jones, Ph.D.

Internal Reviewers

  • Heather McDiarmid, Ph.D.
  • Christina Swanson, Ph.D.
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Action Word
Mobilize
Solution Title
Green Hydrogen for Aviation and Trucking
Classification
Keep Watching
Updated Date

Deploy Sustainable Aviation Fuel

Cluster
Fuel Switching
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Airline jet engine
Coming Soon
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Summary

Sustainable aviation fuel (SAF) is a low-carbon alternative to conventional jet fuel. It is made from renewable feedstocks, including waste oils, agricultural residues, and renewable electricity. SAF can substantially reduce life-cycle GHG emissions and is already in use in commercial flights at low blending levels. Advantages include its compatibility with existing aircraft and fueling infrastructure, its potential to reduce emissions for long-haul aviation, and its ability to reduce emissions from organic waste streams. Disadvantages include limited feedstock availability, high costs, variable climate benefits depending on production methods, and challenges in scaling up supply to meet global demand. Based on our assessment, we will “Keep Watching” this potential solution.

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The Deploy Sustainable Aviation Fuel solution is coming soon.
Overview

What is our assessment?

Based on our analysis, sustainable aviation fuel (SAF) is a promising climate mitigation solution for reducing emissions in the aviation sector, particularly for long-haul flights where few alternatives exist. However, it is not yet cost-effective and faces significant challenges to scaling production due to severe feedstock restraints, land use pressure, and the need to meet robust sustainability standards. Based on our assessment, we will “Keep Watching” this potential solution.

Plausible Could it work? Yes
Ready Is it ready? Yes
Evidence Are there data to evaluate it? Yes
Effective Does it consistently work? Yes
Impact Is it big enough to matter? Yes
Risk Is it risky or harmful? No
Cost Is it cheap? No

What is it?

Sustainable aviation fuel (SAF) is a low-carbon alternative to conventional jet fuel that reduces life-cycle greenhouse gas emissions from fuel production by using only non-petroleum feedstocks such as waste oils, agricultural residues, and municipal solid waste. It is usually produced using renewable electricity and captured CO₂. SAF is produced through chemical processes that convert these feedstocks into fuels that meet the same technical standards as fossil-based jet fuel, allowing them to be blended and used in existing aircraft engines and fueling infrastructure without modification. All SAFs approved by ASTM International, the body that sets fuel standards for aviation, are certified only for use in blends. No SAF is yet certified for 100% use in commercial aircraft (also known as “neat SAF”) for passenger flights.

Does it work?

The basic idea of sustainable aviation fuel is technologically sound and supported by decades of research into low-carbon fuel alternatives for aviation. Multiple SAF production pathways – such as hydroprocessed esters and fatty acids (HEFA), Fischer-Tropsch synthesis (FT), and alcohol-to-jet (ATJ) – have been approved by international aviation standards bodies, and several have been demonstrated at commercial scale. Real-world use of SAF is already underway: over 450,000 commercial flights have flown using SAF blends as of early 2025. SAF is currently being supplied at major airports in Europe, the United States, and Asia, with dozens of airlines integrating SAF into operations or entering offtake agreements. While current production remains limited (less than 0.5% of global jet fuel supply), government mandates, tax credits, and airline demand are driving the need for rapid scale-up. SAF is considered one of the most evidence-backed and immediately deployable climate solutions for reducing aviation emissions.

Why are we excited?

Sustainable aviation fuel offers several compelling advantages that make it a potential pathway for reducing aviation emissions. By reducing emissions 60-70% per ton compared to jet fuel, SAF could potentially avoid 0.1–0.2 Gt CO₂/yr by 2050. It can also reduce contrails. SAF can be used in existing aircraft and fueling systems without requiring new infrastructure or major redesigns. This makes it one of the few ready-to-deploy solutions for long-haul and international flights, which are difficult to electrify or replace. SAF production from waste oils and residues can also deliver benefits such as reduced methane emissions from organic waste streams and improved waste management. SAF offers a potentially scalable, technically feasible route to emissions reductions in a sector with few alternatives. Growing policy support, rising carbon prices, and airline demand are accelerating development. 

Why are we concerned?

Despite its promise, sustainable aviation fuel faces significant limitations, risks, and challenges that could constrain its impact and scalability. First, supply is a critical constraint. Due to limited feedstock availability, SAF is highly unlikely to be able to meet the ambitious 2050 goals set by ICAO, ReFuelEU Aviation, and other industry organizations, associations, and governmental institutions. This means that SAF must be combined with other strategies, like demand reduction and new aircraft technologies, to achieve full decarbonization. There are also major ecological and social risks, including competition for land and feedstocks that could displace food production or degrade ecosystems, as well as unequal access to the benefits of SAF deployment. Scaling synthetic SAF (e-fuels) requires vast amounts of clean electricity, water, and CO₂ – raising concerns about resource use and trade-offs with other sectors. Another major concern is cost. Current SAF prices are substantially higher than fossil jet fuel, ranging from US$300 to over US$1,500 per t CO₂ avoided, depending on the pathway. Without strong policy support, this cost premium poses a barrier to widespread adoption. Additionally, life-cycle emissions reductions vary widely depending on the feedstock and production pathway. While some SAFs (e.g., e-fuels using renewable electricity) can achieve near-zero emissions, others, especially those using food crops or poorly regulated waste streams, may deliver modest or uncertain climate benefits. Measurement, reporting, and verification of actual emissions reductions can be complex, especially when land-use change, indirect emissions, or supply chain impacts are involved. SAF combustion still contributes to climate impacts from contrails (albeit reduced compared to jet fuel), nitrogen oxides, and soot.

Solution in Action

Alternative Fuels Data Center. (n.d.). Sustainable Aviation Fuel. Link to source: https://afdc.energy.gov/fuels/sustainable-aviation-fuel

Bardon, P., & Massol, O. (2025). Decarbonizing aviation with sustainable aviation fuels: Myths and realities of the roadmaps to net zero by 2050. Renewable and Sustainable Energy Reviews, 211, 115279. Link to source: https://doi.org/10.1016/j.rser.2024.115279

Boyles, H. (2022). Climate-Tech to Watch: Sustainable Aviation Fuel. Link to source: https://itif.org/publications/2022/10/17/climate-tech-to-watch-sustainable-aviation-fuel

Buchholz, N., Fehrm, B., Kaestner, L., Uhrenbacher, S., & Vesco, M. (2023). Study: How To Accelerate Aviation’s CO2 Reduction | Aviation Week Network. Link to source: https://aviationweek.com/air-transport/aircraft-propulsion/study-how-accelerate-aviations-co2-reduction 

Bullerdiek, N., Neuling, U., & Kaltschmitt, M. (2021). A GHG reduction obligation for sustainable aviation fuels (SAF) in the EU and in Germany. Journal of Air Transport Management, 92, 102020. Link to source: https://doi.org/10.1016/j.jairtraman.2021.102020

EASA. (2025). Sustainable Aviation Fuels | EASA. Link to source: https://www.easa.europa.eu/en/domains/environment/eaer/sustainable-aviation-fuels

European Commission. (n.d.). ReFuelEU Aviation. ReFuelEU Aviation - European Commission. Link to source: https://transport.ec.europa.eu/transport-modes/air/environment/refueleu-aviation_en 

ICAO. (n.d.). LTAG Costs and Investments. ICAO. Link to source: https://www.icao.int/environmental-protection/LTAG/Pages/LTAG-and-Fuels.aspx

ICAO. (n.d.). Sustainable Aviation Fuels. Link to source: https://www.icao.int/environmental-protection/pages/SAF.aspx

IEA. (2025). Aviation. IEA. Link to source: https://www.iea.org/energy-system/transport/aviation

IATA. (2024). IATA - Disappointingly Slow Growth in SAF Production. Link to source: https://www.iata.org/en/pressroom/2024-releases/2024-12-10-03/

IATA. (2025). IATA Releases SAF Accounting and Reporting Methodology. Link to source: https://www.iata.org/en/pressroom/2025-releases/2025-01-31-01/

Michaga, M. F. R., Michailos, S., Hughes, K. J., Ingham, D., & Pourkashanian, M. (2021). 10—Techno-economic and life cycle assessment review of sustainable aviation fuel produced via biomass gasification. In R. C. Ray (Ed.), Sustainable Biofuels (pp. 269–303). Academic Press. Link to source: https://doi.org/10.1016/B978-0-12-820297-5.00012-8

O’Malley, J., & Baldino, C. (2024). Availability of biomass feedstocks in the European Union to meet the 2035 ReFuelEU Aviation SAF target. International Council on Clean Transportation. Link to source: https://theicct.org/publication/low-risk-biomass-feedstocks-eu-refueleu-aug24/

Prussi, M., Lee, U., Wang, M., Malina, R., Valin, H., Taheripour, F., Velarde, C., Staples, M. D., Lonza, L., & Hileman, J. I. (2021). CORSIA: The first internationally adopted approach to calculate life-cycle GHG emissions for aviation fuels. Renewable and Sustainable Energy Reviews, 150, 111398. Link to source: https://doi.org/10.1016/j.rser.2021.111398

Rojas-Michaga, M. F., Michailos, S., Cardozo, E., Akram, M., Hughes, K. J., Ingham, D., & Pourkashanian, M. (2023). Sustainable aviation fuel (SAF) production through power-to-liquid (PtL): A combined techno-economic and life cycle assessment. Energy Conversion and Management, 292, 117427. Link to source: https://doi.org/10.1016/j.enconman.2023.117427

Shahriar, M. F., & Khanal, A. (2022). The current techno-economic, environmental, policy status and perspectives of sustainable aviation fuel (SAF). Fuel, 325, 124905. Link to source: https://doi.org/10.1016/j.fuel.2022.124905 

Voigt, C., Kleine, J., Sauer, D., Moore, R. H., Bräuer, T., Le Clercq, P., Kaufmann, S., Scheibe, M., Jurkat-Witschas, T., Aigner, M., Bauder, U., Boose, Y., Borrmann, S., Crosbie, E., Diskin, G. S., DiGangi, J., Hahn, V., Heckl, C., Huber, F., … Anderson, B. E. (2021). Cleaner burning aviation fuels can reduce contrail cloudiness. Communications Earth & Environment, 2(1), 1–10. Link to source: https://doi.org/10.1038/s43247-021-00174-y

Watson, M. J., Machado, P. G., da Silva, A. V., Saltar, Y., Ribeiro, C. O., Nascimento, C. A. O., & Dowling, A. W. (2024). Sustainable aviation fuel technologies, costs, emissions, policies, and markets: A critical review. Journal of Cleaner Production, 449, 141472. Link to source: https://doi.org/10.1016/j.jclepro.2024.141472

World Economic Forum. (2021). Clean Skies for Tomorrow: Sustainable Aviation Fuels as a Pathway to Net-Zero Aviation. World Economic Forum. Link to source: https://www3.weforum.org/docs/WEF_Clean_Skies_Tomorrow_SAF_Analytics_2020.pdf

Yoo, E., Lee, U., & Wang, M. (2022). Life-Cycle Greenhouse Gas Emissions of Sustainable Aviation Fuel through a Net-Zero Carbon Biofuel Plant Design. ACS Sustainable Chemistry & Engineering, 10(27), 8725–8732. Link to source: https://doi.org/10.1021/acssuschemeng.2c00977

Zahid, I., Nazir, M. H., Chiang, K., Christo, F., & Ameen, M. (2024). Current outlook on sustainable feedstocks and processes for sustainable aviation fuel production. Current Opinion in Green and Sustainable Chemistry, 49, 100959. Link to source: https://doi.org/10.1016/j.cogsc.2024.100959 

Credits

Lead Fellow

  • Heather Jones, Ph.D.

Internal Reviewers

  • Christina Swanson, Ph.D.
  • Emily Cassidy
Speed of Action
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Action Word
Deploy
Solution Title
Sustainable Aviation Fuel
Classification
Keep Watching
Updated Date
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