Atmospheric oxidation enhancement (AOE) of methane is a technology that injects highly reactive hydroxyl and chlorine radical aerosols into the air to accelerate the natural conversion of methane into CO₂. Methane is a greenhouse gas found naturally in the atmosphere, but human activities such as production and use of fossil fuels, landfilling waste, and increasing populations of ruminant animals have dramatically increased concentrations. Methane decays in the atmosphere in ~10 years but, because it is ~80 times stronger at trapping heat than CO₂ on a 20-year basis, actions to reduce its concentration more quickly have climate benefits.
AOE for methane removal is still in the early phases of research, and its ability to meaningfully and cost-effectively remove methane is questionable. In addition, there are other more practical, cost-effective, and proven technologies that can prevent methane emissions from entering the atmosphere (e.g., Improve Landfill Management, Manage Oil & Gas Methane and Manage Coal Mine Methane). And, this solution, which is designed to alter atmospheric chemistry, could have unintended consequences, present novel risks to Earth systems, and pose geopolitical, legal, and ethical challenges. Therefore, even though this solution addresses a potent GHG, it is “Not Recommended.”
Based on the potential for harmful impacts, the risks of using AOE to destroy atmospheric methane outweigh its uncertain benefits. Because of this, as well as the fact that there are other effective solutions to reduce methane emissions already available, this climate solution is “Not Recommended.”
| Plausible | Could it work? | Yes |
|---|---|---|
| Ready | Is it ready? | No |
| Evidence | Are there data to evaluate it? | No |
| Effective | Does it consistently work? | ? |
| Impact | Is it big enough to matter? | ? |
| Risk | Is it risky or harmful? | Yes |
| Cost | Is it cheap? | No |
AOE of methane is a technology designed to accelerate the natural decay of methane to CO₂ by increasing the concentration of hydroxyl and chlorine radicals in the air. In the presence of sunlight and oxygen, these molecules convert methane to CO₂. This solution aims to increase the atmospheric concentration of these molecules by injecting precursors, such as iron salts and hydrogen peroxide, into the air.
Methane is a potent greenhouse gas, more than 80 times stronger than CO₂ at trapping heat on a 20-year basis. Under natural conditions, it persists in the atmosphere for about 10 years before it converts into CO₂. Therefore, artificially accelerating methane conversion reduces its disproportionate warming impact.
There is evidence that the concentration of hydroxyl radicals affects the rate at which methane is converted into CO₂ in the atmosphere. However, research into AOE for methane removal is still in its early stages and limited to a few modeling and laboratory studies. There are currently no real-world examples of atmospheric methane removal. The effectiveness of the solution is unknown and uncertain. Based on current research, no one knows if it is possible to remove atmospheric methane at a meaningful scale in a safe and cost-effective manner.
Because methane is such a potent greenhouse gas, any actions to reduce its concentration in the atmosphere would be emergency brake solutions with immediate and disproportionate climate benefits. In addition, unlike direct air capture or carbon capture and storage, there is no need to capture or store the gas that the process produces.
AOE for methane removal is an untested technology designed to alter atmospheric chemistry that presents novel and potentially uncontrollable risks to Earth systems and ecosystem processes. Hydroxyl and chlorine radicals are highly reactive molecules, and they do not react solely with methane. When they react with other atmospheric constituents they can generate other, even stronger, climate pollutants such as nitrous oxide as well as other air pollutants such as PM2.5, carbon monoxide, nitrogen dioxide, and ground-level ozone, and they could deplete stratospheric ozone. Some proposed AOE methods, such as atmospheric injection of iron salt aerosols, create chlorine radicals. The chlorine- and iron-containing byproducts of these aerosols could adversely affect ocean chemistry and food webs when they are deposited on the ocean surface (see Deploy Ocean Fertilization).
Other serious concerns include technical feasibility, scalability, cost, monitoring, reporting and verification, and governance. For example, in order for methane in the atmosphere to be reduced at climate-relevant scales, the production of chlorine or hydroxyl radicals would need to be magnitudes greater than the current global production. Costs have not been estimated, but they would likely be high. New tools for monitoring atmospheric methane would need to be developed to quantify the amounts of methane removed for accurate accounting and verification. Similar to stratospheric aerosol injection, deployment of atmospheric methane removal could pose geopolitical, legal, and ethical challenges. In addition, it could distract from or delay action on other methane reduction approaches, such as managing oil and gas methane, managing coal mine methane, improving landfill management, and increasing centralized composting.
He, M., Jacob, D. J., Estrada, L. A., Varon, D. J., Sulprizio, M., Balasus, N., East, J. D., Penn, E., Pendergrass, D. C., Chen, Z., Mooring, T. A., Maasakkers, J. D., Brodrick, P. G., Frankenberg, C., Bowman, K. W., & Bruhwiler, L. (2026). Attributing 2019–2024 methane growth using TROPOMI satellite observations. Science Advances, 12(15), Article eadz9007. Link to source: https://doi.org/10.1126/sciadv.adz9007
Jackson, R. B., Abernethy, S., Canadell, J. G., Cargnello, M., Davis, S. J., Féron, S., Fuss, S., Heyer, A. J., Hong, C., Jones, C. D., Damon Matthews, H., O’Connor, F. M., Pisciotta, M., Rhoda, H. M., de Richter, R., Solomon, E. I., Wilcox, J. L., & Zickfeld, K. (2021). Atmospheric methane removal: A research agenda. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 379(2210), Article 20200454. Link to source: https://doi.org/10.1098/rsta.2020.0454
Lackner, K. S. (2020). Practical constraints on atmospheric methane removal. Nature Sustainability, 3(5), Article 357. Link to source: https://doi.org/10.1038/s41893-020-0496-7
Lebling, K., & Harasaki, H. (2025). 5 things to know about atmospheric methane removal [Insights]. World Resources Institute. Link to source: https://www.wri.org/insights/atmospheric-methane-removal
Li, Q., Meidan, D., Hess, P., Añel, J. A., Cuevas, C. A., Doney, S., Fernandez, R. P., van Herpen, M., Höglund-Isaksson, L., Johnson, M. S., Kinnison, D. E., Lamarque, J-F., Röckmann, T., Mahowald, N. M., & Saiz-Lopez, A. (2023). Global environmental implications of atmospheric methane removal through chlorine-mediated chemistry-climate interactions. Nature Communications, 14(1), Article 4045. Link to source: https://www.nature.com/articles/s41467-023-39794-7
Lindsey, R. (2025, May 21). Climate change: Atmospheric carbon dioxide. National Oceanic and Atmospheric Administration. Link to source: https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide
Liu, Y., Yao, X., Zhou, L., Ming, T., Li, W., & de Richter, R. (2024). Removal of atmospheric methane by increasing hydroxyl radicals via a water vapor enhancement strategy. Atmosphere, 15(9), Article 1046. Link to source: https://www.mdpi.com/2073-4433/15/9/1046
Ming, T., Li, W., Yuan, Q., Davies, P., de Richter, R., Peng, C., Deng, Q., Yuan, Y., Caillol, S., & Zhou, N. (2022). Perspectives on removal of atmospheric methane. Advances in Applied Energy, 5, Article 100085. Link to source: https://doi.org/10.1016/j.adapen.2022.100085
Nisbet-Jones, P. B. R., Fernandez, J. M., Fisher, R. E., France, J. L., Lowry, D., Waltham, D. A., Woolley Maisch, C. A., & Nisbet, E. G. (2022). Is the destruction or removal of atmospheric methane a worthwhile option? Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 380(2215), Article 20210108. Link to source: https://doi.org/10.1098/rsta.2021.0108
Pennacchio, L., Mikkelsen, M. K., Krogsbøll, M., van Herpen, M., & Johnson, M. S. (2024). Physical and practical constraints on atmospheric methane removal technologies. Environmental Research Letters, 19(10), Article 104058. Link to source: https://doi.org/10.1088/1748-9326/ad7041
Spark Climate Solutions. (n.d.-a). Atmospheric methane removal. Retrieved March 3, 2026, from Link to source: https://www.sparkclimate.org/methane-removal/home
Spark Climate Solutions. (n.d.-b). Approaches to atmospheric methane removal. Retrieved March 3, 2026, from Link to source: https://www.sparkclimate.org/methane-removal/primer/approaches
van Herpen, M. M. J. W., Li, Q., Saiz-Lopez, A., Liisberg, J. B., Röckmann, T., Cuevas, C. A., Fernandez, R. P., Mak, J. E., Mahowald, N. M., Hess, P., Meidan, D., Stuut, J.-B. W., & Johnson, M. S. (2023). Photocatalytic chlorine atom production on mineral dust–sea spray aerosols over the North Atlantic. Proceedings of the National Academy of Sciences, 120(31), Article e2303974120, Link to source: https://doi.org/10.1073/pnas.2303974120
Wang, J., & He, Q. P. (2023). Methane removal from air: Challenges and opportunities. Methane, 2(4), 404–414. Link to source: https://doi.org/10.3390/methane2040027
Lead Fellow:
Internal Reviewers:
Photocatalytic methane-oxidizing coatings applied to roofs and other surfaces exposed to air can convert methane molecules that contact the surface into CO₂. The concentration of methane in the air is low, less than 2 ppm but, because methane is ~80 times better at trapping heat than CO₂ on a 20-year basis, actions to quickly reduce its concentration have outsized climate benefits. Several photocatalytic compounds can be incorporated into thin coatings such as paint and applied to a variety of surfaces. However, significant advances are needed in photocatalytic surface coatings’ chemical conversion efficiency and resistance to weathering. Methane removal using this method is also limited by the area of the coated surface and the rate at which methane molecules contact it; models suggest that the area of coated surfaces needed to achieve a meaningful climate impact would be infeasibly large. More practical, cost-effective, and proven technologies are available to prevent methane emissions from entering the atmosphere from high-emitting industries. However, methane is a potent GHG and deployment of methane-oxidizing coatings on existing structures could be minimally disruptive and targeted at areas with elevated methane concentrations. Given these caveats, we will “Keep Watching” this solution.
Based on our assessment, removing methane from the air using photocatalytic methane-oxidizing surface coatings is plausible, but its effectiveness and potential climate impact are currently limited by technological and practical uncertainties. However, because methane is such potent GHG, we will “Keep Watching” this solution.
| Plausible | Could it work? | Yes |
|---|---|---|
| Ready | Is it ready? | No |
| Evidence | Are there data to evaluate it? | Limited |
| Effective | Does it consistently work? | ? |
| Impact | Is it big enough to matter? | ? |
| Risk | Is it risky or harmful? | No |
| Cost | Is it cheap? | ? |
This solution aims to remove methane from the air by coating large surfaces that contact air, such as buildings and wind turbine blades, with photocatalytic chemicals that convert methane to CO₂ on contact (Jackson et al., 2021; Lebling & Harasaki, 2025). Methane-oxidizing coatings use sunlight to drive the chemical reaction and rely on natural air movement to bring methane in the air into contact with the coated surface (Abernethy & Jackson, 2024).
Methane is a potent but short-lived greenhouse gas, more than 80 times stronger than CO₂ at trapping heat on a 20-year basis (IPCC, 2023). Actions that accelerate methane conversion to CO₂ would reduce its disproportionate warming impact (Jackson et al., 2019). Several photocatalytic compounds, such as titanium dioxide, can convert methane into CO₂ and can be incorporated into thin coatings such as paint and applied to a variety of surfaces. However, the chemical reaction to convert methane to CO₂ is not 100% efficient and, because the atmospheric concentration of methane is so low (~2 ppm compared to 430 ppm for CO₂ ), the amount of methane removed is limited by the area of the coated surface and the rate at which methane molecules contact it (Abernethy & Jackson, 2024; Pennacchio et al., 2024). Research into using methane-oxidizing coatings is still in its early stages and limited to a few modeling and laboratory studies. Modeling estimates suggest that the area of coated surfaces needed to achieve a meaningful climate impact would be impractically large (Pennacchio et al., 2024).
Because methane is such a potent GHG, actions that reduce its concentration in the atmosphere have immediate climate benefits. Unlike direct air capture or carbon capture and storage, there is no need to capture or store any gases because the goal is to oxidize methane to CO₂ (Ming et al., 2022). Using a chemical treatment that can be incorporated into coating materials such as paint is minimally invasive or disruptive. In addition, because the solution relies on natural air movement rather than fans, its energy demands and operating costs are low. The effectiveness of this solution could be enhanced if it were deployed in areas with habitually elevated methane concentrations, such as cattle, waste management, oil and gas facilities, and rice paddies (Nisbet-Jones et al., 2021).
Significant advances in the methane removal efficiency of photocatalytic surface coatings are needed for this solution to be effective, scalable, and practical (Lebling & Harasaki, 2025). Other unknowns include the lifespan of the photocatalytic coatings on different types of surfaces and under different environmental and weather conditions (Lei et al., 2025; Liu et al., 2023). Costs are unknown due to these limitations, and could be high relative to other more targeted methane reduction solutions such as managing oil and gas methane, managing coal mine methane, improving landfill management, and increasing centralized composting. New tools for monitoring and measuring changes in the low concentrations of atmospheric methane will need to be developed to quantify the amounts of methane removed for accurate accounting and verification. Finally, some researchers argue that use of photocatalytic coatings to neutralize potent GHGs would be more effectively and impactfully directed at longer-lived climate pollutants such as nitrous oxide (Lackner, 2020).
Abernethy, S., & Jackson, R. B. (2024). Atmospheric methane removal may reduce climate risks. Environmental Research Letters, 19(5), Article 051001. Link to source: https://iopscience.iop.org/article/10.1088/1748-9326/ad3b22/pdf
Intergovernmental Panel On Climate Change. (2023). Climate change 2022 – Impacts, adaptation and vulnerability: Working Group II contribution to the sixth assessment report of the Intergovernmental Panel on Climate Change (1st ed.). Cambridge University Press. Link to source: https://doi.org/10.1017/9781009325844
Jackson, R. B., Solomon, E. I., Canadell, J. G., Cargnello, M., & Field, C. B. (2019). Methane removal and atmospheric restoration. Nature Sustainability, 2(6), 436–438. Link to source: https://par.nsf.gov/servlets/purl/10142837
Jackson, R. B., Abernethy, S., Canadell, J. G., Cargnello, M., Davis, S. J., Féron, S., Fuss, S., Heyer, A. J., Hong, C., Jones, C. D., Damon Matthews, H., O’Connor, F. M., Pisciotta, M., Rhoda, H. M., de Richter, R., Solomon, E. I., Wilcox, J. L., & Zickfeld, K. (2021). Atmospheric methane removal: A research agenda. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 379(2210), Article 20200454. Link to source: https://doi.org/10.1098/rsta.2020.0454
Lackner, K. S. (2020). Practical constraints on atmospheric methane removal. Nature Sustainability, 3(5), 357–357. Link to source: https://doi.org/10.1038/s41893-020-0496-7
Lebling, K., & Harasaki, H. (2025). 5 things to know about atmospheric methane removal. World Resources Institute. Link to source: https://www.wri.org/insights/atmospheric-methane-removal
Lei, Y., Sala, X., García-Antón, J., & Muñoz, J. (2025). A review on photocatalytic methane conversion systems: from fundamental mechanisms to the emerging role of ferroelectric materials. Journal of Materials Chemistry A, 13(18), 12712–12745. Link to source: https://pubs.rsc.org/ta/article/13/18/12712/875561/A-review-on-photocatalytic-methane-conversion
Liu, Z., Xu, B., Jiang, Y. J., Zhou, Y., Sun, X., Wang, Y., & Zhu, W. (2023). Photocatalytic conversion of methane: current state of the art, challenges, and future perspectives. ACS Environmental Au, 3(5), 252–276. Link to source: https://pmc.ncbi.nlm.nih.gov/articles/PMC10515711/#sec1
Ming, T., Li, W., Yuan, Q., Davies, P., de Richter, R., Peng, C., Deng, Q., Yuan, Y., Caillol, S., & Zhou, N. (2022). Perspectives on removal of atmospheric methane. Advances in Applied Energy, 5, Article 100085. Link to source: https://doi.org/10.1016/j.adapen.2022.100085
Nisbet-Jones, P. B. R., Fernandez, J. M., Fisher, R. E., France, J. L., Lowry, D., Waltham, D. A., Woolley Maisch, C. A., & Nisbet, E. G. (2021). Is the destruction or removal of atmospheric methane a worthwhile option? Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 380(2215), Article 20210108. Link to source: https://doi.org/10.1098/rsta.2021.0108
Pennacchio, L., Mikkelsen, M. K., Krogsbøll, M., van Herpen, M., & Johnson, M. S. (2024). Physical and practical constraints on atmospheric methane removal technologies. Environmental Research Letters, 19(10), Article 104058. Link to source: https://doi.org/10.1088/1748-9326/ad7041
Wang, J., & He, Q. P. (2023). Methane removal from air: Challenges and opportunities. Methane, 2(4), 404–414. Link to source: https://doi.org/10.3390/methane2040027
Nitrous oxide removal involves treating agricultural fields with photocatalytic chemicals that convert nitrous oxide into oxygen and nitrogen. Nitrous oxide is a GHG that persists in the atmosphere for more than 100 years and is ~270 times stronger than CO₂ at trapping heat, so removing it from the atmosphere has large climate benefits.
Nitrous oxide removal is still in the early phases of research, most of the limited data are from laboratory studies, and the effectiveness and feasibility of this climate solution is unknown. Research on one of the most studied nitrous oxide photocatalysts, titanium dioxide, has indicated benefits for crop yields and resilience at low application rates but some risk of adverse effects at high application rates. There are also concerns about health, food safety, and environmental impacts. Tools and GHG accounting methods and standards for measuring and reporting nitrous oxide removal need to be further developed. In addition, other ways to reduce nitrous oxide emissions from agriculture and industry are more practical, cost-effective and readily used. Despite these limitations, because this solution addresses such a potent GHG, we will “Keep Watching” it.
Nitrous oxide removal technology is at a very early stage of development. Other available technologies and practices can effectively reduce nitrous oxide emissions. However, because this solution aims to remove such a potent GHG from the atmosphere, we will “Keep Watching” it.
| Plausible | Could it work? | Yes |
|---|---|---|
| Ready | Is it ready? | No |
| Evidence | Are there data to evaluate it? | Limited |
| Effective | Does it consistently work? | ? |
| Impact | Is it big enough to matter? | ? |
| Risk | Is it risky or harmful? | ? |
| Cost | Is it cheap? | ? |
Nitrous oxide removal is a technology that uses photocatalytic chemicals to convert nitrous oxide, a GHG that has 270 times more warming potential than CO₂ and persists in the atmosphere for more than 100 years, into gaseous nitrogen and oxygen.
Nitrous oxide is found naturally in the atmosphere, but 40% of emissions come from human activities, and human-caused emissions have increased more than 30% during the past four decades. Most anthropogenic contributions are from fertilizers applied to croplands and other farming activities, while the rest are from fossil fuel use, industrial activities, and waste and wastewater.
This solution involves spraying a chemical photocatalyst onto agricultural fields. When the photocatalyst is exposed to sunlight and nitrous oxide, it drives a chemical reaction that decomposes nitrous oxide into gaseous nitrogen and oxygen.
Research into atmospheric nitrous oxide removal is still in its early stages. The concentration of nitrous oxide in the atmosphere is very low, so nitrous oxide removal would likely be implemented in agricultural areas where fertilizer use locally elevates atmospheric concentrations. Laboratory testing has shown that nitrous oxide can be converted into nitrogen and oxygen using light energy and photocatalysts. However, the effectiveness of the solution in practice is uncertain because few experiments have been conducted in real-world settings. The single field study that applied titanium dioxide to a field crop did report a measurable reduction in nitrous oxide emissions. However, there is no evidence that this technology can remove atmospheric nitrous oxide at a meaningful scale.
Because nitrous oxide is such a potent GHG, reducing its concentration in the atmosphere could have a disproportionately beneficial climate impact. In addition, unlike direct air capture or carbon capture and storage, there is no need to capture or store any gases because the nitrous oxide breaks down into gases that have no climate impact. Also, titanium dioxide application to crops is being researched as a method for improving crop resilience.
Serious concerns include technical feasibility, environmental risk (including environmental and food safety), scalability, cost, and monitoring, reporting, and verification. While there is currently very little research on the real-world use of photocatalysts to destroy atmospheric nitrous oxide, ongoing research on the application of nanoparticles of titanium dioxide to crops to enhance productivity and resilience to stress suggests that high concentrations of titanium dioxide can have adverse effects. Furthermore, these nanoparticles are not approved for direct food consumption, and their fate and environmental impacts are poorly understood.
Tools, methods, and standards need to be developed to quantify nitrous oxide removal for accurate accounting and verification. Costs are unknown. Finally, numerous other approaches for reducing human-caused nitrous oxide emissions exist, including improving nutrient management, rice production, manure management, and industrial processes, as well as reducing fossil-fuel use for power generation and transportation and increasing use of centralized composting.
Bueno-Alejo, C. J., Khambhati, Y. K., & Papadopoulos, A. (2025). Photocatalytic removal of N2O in cropped fields using R-Leaf. Applied Catalysis O: Open, 201, Article 207032. Link to source: https://doi.org/10.1016/j.apcato.2025.207032
Carbon Registry. (n.d.). Atmospheric nitrous oxide (N2O) destruction using photocatalysts. International Carbon Registry. Retrieved May 7, 2026, from https://www.carbonregistry.com/methodologies/m-icr-011
Ma, H., Li, Y., Wang, C., Li, Y., & Zhang, X. (2025). TiO2-based photocatalysts for removal of low-concentration NOx contamination. Catalysts, 15(2), Article 103. Link to source: https://doi.org/10.3390/catal15020103
Olaifa, O., Alimard, P., Itskou, I., Eisner, F., Petit, C., Díez-González, S., & Kafizas, A. (2025). Purifying the air with photocatalysis: Developing bismuth oxybromide/ copper phthalocyanine composite photocatalyst filters with enhanced activity for NOx removal. ChemPhotoChem, 9(6), Article e202400346. Link to source: https://doi.org/10.1002/cptc.202400346
Rehman, M., Salam, A., Ulhassan, Z., Ali, B., Haider, Z., Ahmad, I., Yasin, M. U., Javaid, M. H., Yang, C., Fayyaz, M., & Gan, Y. (2025). Titanium dioxide nanoparticles TiO2 NPs in crop stress management: Mechanisms, applications, and abiotic stress mitigation. Plant Nano Biology, 14, Article 100207. Link to source: https://doi.org/10.1016/j.plana.2025.100207
Schödel, S. (2024). Nitrous oxide—The underestimated greenhouse gas [Fact sheet]. German Environment Agency. Link to source: https://www.umweltbundesamt.de/en/publikationen/nitrous-oxide-the-underestimated-greenhouse-gas
Thiagarajan, V., & Ramasubbu, S. (2021). Fate and behaviour of TiO2 nanoparticles in the soil: Their impact on staple food crops. Water, Air, & Soil Pollution, 232(7), Article 274. Link to source: https://doi.org/10.1007/s11270-021-05219-8
Tian, H., Xu, R., Canadell, J. G., Thompson, R. L., Winiwarter, W., Suntharalingam, P., Davidson, E. A., Ciais, P., Jackson, R. B., Janssens-Maenhout, G., Prather, M. J., Regnier, P., Pan, N., Pan, S., Peters, G. P., Shi, H., Tubiello, F. N., Zaehle, S., Zhou, F., … Yao, Y. (2020). A comprehensive quantification of global nitrous oxide sources and sinks. Nature, 586(7828), 248–256. Link to source: https://doi.org/10.1038/s41586-020-2780-0
United Nations Environment Programme, & Food and Agriculture Organization of the United Nations. (2024). Global nitrous oxide assessment [Report]. Link to source: https://doi.org/10.59117/20.500.11822/46562
U.S. Environmental Protection Agency. (2026). Nitrous oxide emissions. Link to source: https://www.epa.gov/ghgemissions/nitrous-oxide-emissions
Verra. (n.d.). Methodology for using photocatalysts to remove atmospheric nitrous oxide. Retrieved April 28, 2026, from Link to source: https://verra.org/methodologies/methodology-for-using-photocatalysts-to-remove-atmospheric-nitrous-oxide/
Xue, T., Li, J., Chen, L., Li, K., Hua, Y., Yang, Y., & Dong, F. (2024). Photocatalytic NOx removal and recovery: Progress, challenges and future perspectives. Chemical Science, 15(24), 9026–9046. Link to source: https://doi.org/10.1039/D4SC01891E
Lead Fellow:
Internal Reviewers:
Biomass burial involves storing plant biomass, such as logs, woody debris, agricultural and forestry residues, and engineered bio-blocks, under conditions that prevent GHG-releasing decay – underground, above ground, or at ground level. Applications range from simple wood vaults buried underground to blocks of dried, compressed plant biomass sealed in impermeable barriers. Wood preservation and engineered storage systems provide evidence that biogenic carbon can be stored for >100 years when protected from decomposition. Early studies suggest meaningful storage potential, low cost, and scalability using existing technologies. However, field validation of durability is limited, permanence is uncertain, and effectiveness depends on moisture control and feedstock sourcing. Based on this assessment, we classify Bury Biomass as a solution to “Keep Watching.”
Burying biomass offers promise for long-lasting storage of already-captured biogenic carbon and could meaningfully scale using existing technologies and low-cost plant biomass. However, little is known about real-world performance over long time scales, effectiveness depends on storage conditions, and land use impacts remain uncertain. As a result, we will “Keep Watching” Bury Biomass 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? | ? |
| Impact | Is it big enough to matter? | Yes |
| Risk | Is it risky or harmful? | No |
| Cost | Is it cheap? | Yes |
Biomass burial stockpiles plant matter in conditions that limit decomposition so the stored carbon cannot return to the atmosphere (Amelse, 2025). Approaches include simple terrestrial burial (wood vaults) and treated methods (bio-block encapsulation), with typical feedstocks of logs, forestry and agricultural residues, and other processed or unprocessed plant matter.
Wood vaulting buries unprocessed, low-value woody biomass in clay-dense or powdery mineral soil, away from groundwater, while controlling conditions that could promote decay (Mohr, 2024). Mohr (2024) describes these vaults as “a layer cake of trees, gaps filled with dirt, and more trees stacked on top, finished off with a [layer] of topsoil.” Oxygen, water, and methane (biological activity) among the factors that are monitored.
Bio-blocks are a more engineered form of biomass burial with added barriers that may improve durability. Plant residues are dried to moisture levels low enough to prevent rotting driven by microorganisms, mechanically compressed into dense blocks, and encased inside nonpolluting, multilayered barriers that keep out water and oxygen (Crotty et al., 2026; Yablonovitch & Deckman, 2023; Zeng et al., 2023). The barriers often combine nontoxic geomembranes made of high-density or linear low-density polyethylene liners, compacted clay layers, and polymeric sealants (Yablonovitch & Deckman, 2023). Once packaged, bio-blocks are buried in designated sites designed to keep the material dry and sealed for long-term carbon storage (Amelse, 2025).
These approaches do not make carbon inert, but “lock” it into the organic matter.
Biomass burial is a physically plausible means to durably store carbon captured by plants. Microbes cannot sustain metabolism when water activity is below 0.60, preventing biomass decomposition in dry, oxygen-deprived storage (Crotty et al., 2026; Yablonovitch & Deckman, 2023). Biomass burial’s net climate benefit depends on processing emissions, biomass type and source, site characteristics, and whether the buried biomass remains dry and intact. Effectiveness is supported by peer-reviewed studies, concept papers, life-cycle analyses, and reactor studies (Crotty et al., 2026; Johnson et al., 2025; Wang et al., 2011; Ximenes et al., 2019), with the strongest support for wood vaulting, engineered dry biomass storage, and landfill-style wood preservation (Crotty et al., 2026; Yablonovitch & Deckman, 2023; Zeng & Hausmann, 2022). A 3,775-year-old wood sample found 2 meters below ground had near-perfect preservation, with less than 5% of its carbon lost due to decay (Zeng et al., 2024). Other assessments by the Intergovernmental Panel on Climate Change (IPCC) suggest wood biomass burial could retain 99.9% of stored CO₂‑eq over a century (Gooding, 2023), and another study found anoxic biomass burial was more carbon-efficient than decomposition, pile burning, or biochar production (Clayton et al., 2026).
Despite this, biomass burial is not yet a mature carbon storage strategy. It has little real-world validation beyond concept, operating guidance, and early implementation (Crotty et al., 2026; Zeng et al., 2023), requiring further study of decay and storage controls (Clayton et al., 2026). Currently, only a handful of companies use proprietary “bio-block” or “carbon-stiffened brick” methods to sequester atmospheric carbon (Scafidi & Denvir, 2026).
Biomass burial is an inexpensive form of durable carbon storage that could be scaled up toward globally meaningful sequestration of atmospheric CO₂ (>0.1 Gt CO₂ /yr). According to one study, terrestrial photosynthesis removes six times more CO₂ each year than fossil-fuel burning emits (Zeng et al., 2024). Since most of that carbon would return to the atmosphere through biomass decomposition, storing some long term in designated sites is a major opportunity. A study in the United States estimated that about 415 Mt CO₂‑eq/yr is available for wood harvesting and storage from coarse woody debris (Hausmann et al., 2024). Broader wood-vaulting studies project gigaton-scale climate impacts, with wood burial having a theoretical ceiling of 37 ± 18 Gt CO₂‑eq/yr, a level far above any sustainable deployment, supported by an estimated ~238 Gt CO₂‑eq contained in coarse woody debris currently accumulated on forest floors worldwide (Zeng, 2008; Zeng & Hausmann, 2022; Zeng et al., 2024). Furthermore, drying and compacting biomass into bio-blocks is mechanically and practically straightforward with existing technologies. Cost is favorable for wood burial including bio-blocks, ranging from US$10–50/t CO₂ stored in most studies to as high as US$100/t CO₂ (Allen, 2025; Mohr, 2024; Johnson et al., 2025; Zeng & Hausmann, 2022), but this is based on estimates rather than commercialized outcomes. Biomass burial also provides simple, high verifiability.
Biomass burial has several limitations as a viable climate solution, including possible concerns from large-scale deployment. Dry biomass storage systems fail if the barrier is breached and internal humidity rises enough to restart microbial activity and anoxic digestion of biomass, forming and leaking methane (Crotty et al., 2026; Johnson et al., 2025). This reversibility concern is highest for feedstocks with larger degradable fractions, such as agricultural residues, and lower for coarse woody debris (Crotty et al., 2026; Ximenes et al., 2019). Therefore, the durability of this type of carbon storage depends on sealing requirements, site selection, and gas monitoring (Zeng et al., 2023).
Burying plant matter from forest floors can lead to forest nutrient depletion, habitat removal, and biomass diversion from better climate uses (Burns, 2025; Mohr, 2024). Permanence concerns include uncertain long-term barrier integrity (Crotty et al., 2026), the need for decades’ worth of monitoring to ensure stored carbon doesn’t leak (Crotty et al., 2026; Zeng et al., 2023), and potential soil-carbon release from excavating deep burial pits (Johnson et al., 2025; Zeng et al., 2023). For biomass burial to sustainably store carbon, the feedstocks are ideally sourced from low-conflict waste streams in limited amounts, protect soil health, and are evaluated for land use changes (Denvir & Leslie-Bole, 2025).
Allen, M. (2025, June 3). Bury it, don’t burn it: Turning biomass waste into a carbon solution. Physics World. Link to source: https://physicsworld.com/a/bury-it-dont-burn-it-turning-biomass-waste-into-a-carbon-solution/
Amelse, J. A. (2025). Terrestrial storage of biomass (biomass burial): A natural, carbon-efficient, and low-cost method for removing CO2 from air. Applied Sciences, 15(4), Article 2183. https://doi.org/10.3390/app15042183
Burns, W. (2025, June 3). Woody biomass burial. Illuminem. Link to source: https://illuminem.com/illuminemvoices/woody-biomass-burial
Clayton, L. K., Wyckoff, A. S., & Crotty, S. M. (2026). Near-term, geospatial opportunity for biomass carbon storage to address the wildfire and climate crises. Science Advances, 12(35), Article eaee6185. Link to source: https://doi.org/10.1126/sciadv.aee6185
Crotty, S. M., Reiners, P. W., Clayton, L. K., Young, E., Jones, A., Cregger, M. A., Starace, A. K., & Harman-Ware, A. E. (2026). Nonenergy biomass carbon removal and storage (BiCRS): Assessing durability of nongaseous carbon products across terrestrial storage fates. Chemical Reviews, 126(8), 4375–4404. https://doi.org/10.1021/acs.chemrev.5c00618
Denvir, A., & Leslie-Bole, H. (2025). Biomass can fight climate change, but only if you do it right [Explainer]. World Resources Institute. Link to source: https://www.wri.org/insights/sustainable-biomass-carbon-removal
Gooding, J. L. (2023). Geologic perspective for carbon sequestration by woody biomass burial. Science and Technology for Energy Transition, 78, Article 17. https://doi.org/10.2516/stet/2023014
Hausmann, H., Cai, Q., & Zeng, N. (2024). Quantification of biomass availability for wood harvesting and storage in the continental United States with a carbon cycle model. Carbon Balance and Management, 19(1), Article 34. https://doi.org/10.1186/s13021-024-00270-4
Johnson, D., Voorhis, J., & Porder, S. (2025). Life cycle emissions associated with vault storage of wood cleared for fire management in the Western United States. Carbon Balance and Management, 20(1), Article 26. https://doi.org/10.1186/s13021-025-00309-0
Mohr, K. (2024, July 23). ‘Wood vaulting’: A simple climate solution you’ve probably never heard of. Grist. Link to source: https://grist.org/solutions/wood-vaulting-carbon-storage-solution/
Scafidi, A. I., & Denvir, A. (2026). Companies are finding new ways to use waste and fight climate change [Vignette]. World Resources Institute. Link to source: https://www.wri.org/insights/biomass-carbon-removal-storage-companies-fight-climate-change
Wang, X., Padgett, J. M., De la Cruz, F. B., & Barlaz, M. A. (2011). Wood biodegradation in laboratory-scale landfills. Environmental Science & Technology, 45(16), 6864–6871. https://doi.org/10.1021/es201241g
Ximenes, F. A., Björdal, C., Kathuria, A., Barlaz, M. A., & Cowie, A. L. (2019). Improving understanding of carbon storage in wood in landfills: Evidence from reactor studies. Waste Management, 85, 341–350. https://doi.org/10.1016/j.wasman.2019.01.004
Yablonovitch, E., & Deckman, H. W. (2023). Scalable, economical, and stable sequestration of agricultural fixed carbon. Proceedings of the National Academy of Sciences, 120(16), Article e2217695120. https://doi.org/10.1073/pnas.2217695120
Zeng, N. (2008). Carbon sequestration via wood burial. Carbon Balance and Management, 3(1), Article 1. https://doi.org/10.1186/1750-0680-3-1
Zeng, N., & Hausmann, H. (2022). Wood vault: Remove atmospheric CO2 with trees, store wood for carbon sequestration for now and as biomass, bioenergy and carbon reserve for the future. Carbon Balance and Management, 17(1), Article 2. https://doi.org/10.1186/s13021-022-00202-0
Zeng, N., Sanchez, D., Belmont, E., & Hausmann, H. (2023). Implementation guidance for wood harvesting and storage [Preprint]. arXiv. Link to source: https://doi.org/10.48550/arXiv.2309.06529
Zeng, N., Zhao, X., Poisson, G., Clifford, B., Liu, Y., Liu, H., Meng, T., Picard, L., Zeng-Mariotti, E., Zaitchik, B., & Hu, L. (2024). 3775-year-old wood burial supports “wood vaulting” as a durable carbon removal method. Science, 385(6716), 1454–1459. https://doi.org/10.1126/science.adm8133
Nina-Francesca Farac, Ph.D.
Sarah Gleeson, Ph.D.
Christina Swanson, Ph.D.
Direct air capture (DAC) is an industrial process that captures CO₂ from the air and then injects it deep underground for permanent, geologic storage. This process is energy-intensive. Therefore, DAC can only be effective for net carbon removal if it does not generate high levels of emissions during the process. This requires that DAC be powered by zero- or low-carbon energy sources and that the captured carbon is permanently stored rather than used for emission-generating applications. Unlike the situation for many other carbon removal methods, the amounts of CO₂ captured and stored using DAC can be reliably measured, which is an advantage in the carbon marketplace. However, the effectiveness of DAC has been extremely low so far. DAC is also expensive, up to US$1,000/t CO₂ removed and stored. Substantial funding to support DAC development has come from fossil-fuel interests or their government proxies, which view carbon capture as a strategy to extend society’s use of fossil fuels. Therefore, there is a risk that DAC could be used to delay or avoid emissions reductions and perpetuate or even expand fossil-fuel production and use. Based on this risk, as well as the functional and financial challenges for scaling this technology to remove globally meaningful amounts of CO₂, we conclude that DAC is “Not Recommended” as a climate solution.
Based on the difficulty of capturing low concentrations of CO₂ from the air and the associated technological, energy consumption, and financial challenges facing DAC, it is unlikely that this climate technology can be scaled up to remove globally meaningful amounts of CO₂. Furthermore, based on the current financial and policy support for DAC from fossil-fuel interests, there is a clear risk that the technology will be used to enable and perpetuate the production and use of fossil fuels, which is antithetical to solving the climate crisis. Therefore, we conclude that deployment of DAC is “Not Recommended” as a climate solution.
| Plausible | Could it work? | Yes |
|---|---|---|
| Ready | Is it ready? | No |
| 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? | Yes |
| Cost | Is it cheap? | No |
DAC is a suite of engineered technologies that remove CO₂ directly from the atmosphere, concentrate it, and then inject it underground for permanent storage. CO₂ is captured from the atmosphere by moving large volumes of air, usually with large fans, past a reactive material that selectively binds CO₂, either a solid sorbent (referred to as solid-DAC or S-DAC) or a liquid solvent (referred to as liquid-DAC or L-DAC). The captured CO₂ is recovered from the reactive material by applying heat, pressure, or chemical reactions, and collected and compressed for transportation and storage. The concentrated CO₂ is then injected deep underground into geological formations, such as saline aquifers or basalt formations, where it can be permanently stored.
The technology and chemistry for the selective capture of CO₂ from air are effective, although the CO₂ capture efficiency varies with the reactive material and other factors. A variety of solid and liquid reactive materials have been developed, along with material-specific processes for recovering captured CO₂ and regenerating the sorbents. This process is very energy-intensive and, for liquid-DAC, water-intensive. To capture and recover 1 t CO₂, solid-DAC uses about 1,100 kWh, while liquid-DAC uses about 2,500 kWh and consumes as much as 7 t of water. Most of the energy for DAC (70–90%) is used to generate heat for recovery of the captured CO₂ and regeneration of the sorbent material. Liquid-DAC requires temperatures up to about 900 °C (1,652 °F), while solid-DAC requires temperatures of only about 100 °C (212 °F). Because the process is so energy intensive, DAC achieves net carbon removal – capturing and sequestering more CO₂ than it emits – only if it is powered by zero or low-carbon energy sources and/or uses waste heat. For example, recent reporting showed that the amount of CO₂ captured and stored by Climeworks, the largest commercial DAC company currently in operation, was insufficient to offset the facility’s operational GHG emissions. CO₂ captured by a DAC facility can also be used for other purposes, such as enhanced oil recovery or production of algae biofuels. However, life cycle analyses conducted by the National Energy Technology Laboratory show that these pathways do not result in net carbon removal due to the emissions from production and/or use of these other products. Therefore, in addition to its requirements for zero or low-carbon energy, DAC can only be an effective method for net carbon removal if the CO₂ it captures is permanently stored deep underground. With appropriate pre-injection site selection, geologic testing, and post-injection monitoring, underground storage of CO₂ is safe and effectively permanent.
Unlike some other carbon removal technologies and practices, a DAC facility has a relatively small footprint and can be located anywhere there is sufficient low-carbon energy and infrastructure and capacity to transport or store captured CO₂. In addition, the amount of CO₂ removed from the atmosphere can be directly measured by monitoring the flow and concentration of captured CO₂ at the point of storage. Compared to many other carbon removal approaches, this method provides a higher level of confidence in the amount of CO₂ being removed for investors and carbon credit purchasers. The geological sequestration of captured CO₂ has high permanence, effectively removing CO₂ from the atmosphere for thousands of years with a low risk of reversal. There are numerous research and pilot projects underway to improve CO₂ capture efficiency, reduce energy use, and reduce costs, which may improve the effectiveness and cost of this technology.
The concentration of CO₂ in the atmosphere is small, currently about 420 parts per million, or about 0.04%. This means that a DAC facility must process huge amounts of air – more than 1,600 t by one estimate – and consume more energy than a typical U.S. household uses in a month to capture 1 t CO₂. Scaled up to remove a globally meaningful amount of CO₂ (>0.1 Gt CO₂ /yr), DAC would consume more energy than the annual energy consumption of 10 million U.S. households. In addition, removing and storing CO₂ using DAC is very expensive, costing up to US$1,000/t CO₂ stored. This is more than twice the cost per t for all other commercially available carbon removal technologies and practices.
For these reasons, the technical and financial feasibility of scaling DAC to remove globally meaningful amounts of CO₂ from the atmosphere is low. Despite these challenges, as of September 2025, more than 30 companies have sold more than 2.4 million t of future carbon removal credits. However, less than 1,300 t CO₂ has actually been removed so far – or only 0.05% of these promised credits. To put this in perspective, despite spending billions of dollars, DAC has removed about as much CO₂ as would be saved by keeping 250-300 cars off the road for a single year.
There is also an opportunity cost for DAC. Even if a DAC facility is powered by solar, wind, geothermal, or nuclear energy, that carbon-free energy could have been used to displace coal- and gas-powered electricity instead, reducing emissions by far more than a DAC facility can capture and store. Similarly, the large amounts of public and private sector funding going to DAC could be more cost-effective and carbon-effective if used for other, more effective actions to cut emissions or remove CO₂. There is also the risk that DAC will be used to delay or avoid emissions reduction actions or for greenwashing by fossil fuel companies and other emitters. Substantial amounts of the funding supporting the development of DAC are coming from fossil fuel companies, which have publicly stated that they view carbon capture as a strategy to extend society’s use of fossil fuels. Finally, unlike most other emissions reduction or carbon removal actions, DAC provides no obvious other benefits to nature or human well-being.
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Producing biochar is the process of taking organic matter such as crop residues, animal manure, and forest residues and converting it into a charcoal-like substance known as biochar. Producing biochar removes carbon from the atmosphere by transforming carbon absorbed by plants and animals and into a highly stable form, preventing it from quickly returning to the atmosphere (Belmont & Sanchez, 2025). Biochar can be used as a soil amendment, a replacement for certain construction materials, or for filtration or pollution remediation. This solution focuses on large-scale production of biochar for soil application.
Biochar is a charcoal-like substance that is mainly produced by burning organic matter in an oxygen-deficient environment, a process called pyrolysis (Spears, 2018; Figure 1). Biochar production converts the carbon in the organic matter into a stable form that is not readily released into the atmosphere.
This solution considers producing biochar from agricultural (crop residue, manure) or industrial (forest residue) waste feedstocks. It does not include using purpose-grown plants, edible portions of food or feed crops, or other non-waste feedstocks, which could compete for land use and reduce the climate benefits. We focused on biochar facilities that process 1,000 or more metric tons of waste per year (Amonette et al., 2021). We included both pyrolysis and gasification in our analysis; however, the proportion of carbon that is turned into biochar can differ between processes (NorthX, 2025). We excluded hydrothermal processing of wet biomass that produces hydrochar from our analysis because the carbon storage properties differ from those of typical biochar (Lehmann & Joseph, 2015).
Co-products such as bio-oil or syngas can be produced during biochar production and used as energy or sold. Using biochar can have climate benefits in addition to storing carbon, such as avoiding the production of methane from waste (Afshar & Mofatteh, 2024) and enhancing soil carbon sequestration in certain soil types (Yang et al., 2025). This solution focuses only on the carbon sequestered in biochar. We do not quantify potential avoided waste emissions, reduced energy use from co-products, or any enhanced sequestration after soil application.
Figure 1. Example of a biochar production process. The conversion of 100% of biomass carbon to 50% biochar is specific to the pyrolysis process and can vary with different temperatures and methods used.
Source: International Biochar Initiative. (n.d.). Why Biochar. Retrieved 6 March 2026.
This solution focuses on biochar use as a soil additive in soils where it can improve soil organic matter as well as help retain water and nutrients. The carbon permanence of biochar can range from hundreds to thousands of years when applied to soil (Belmont & Sanchez, 2025). Biochar also can be used in filtration or remediation applications or as a filler material in building materials such as asphalt or concrete (Amonette et al., 2022).
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Aman, A. M. N., Selvarajoo, A., Lau, T. L., & Chen, W.-H. (2022). Biochar as cement replacement to enhance concrete composite properties: A review. Energies, 15(20), Article 7662. Link to source: https://doi.org/10.3390/en15207662
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Jason Lam
Ruthie Burrows, Ph.D.
James Gerber, Ph.D.
Daniel Jasper
Megan Matthews, Ph.D.
Alex Sweeney
Amanda D. Smith, Ph.D.
Emily Cassidy
We estimated that 1 metric ton of biochar produced and incorporated into soil will remove 0.84 t CO₂‑eq (0.82 t CO₂‑eq , 20-yr), after subtracting production emissions (Table 1). This assumes the primary feedstock is agricultural waste and forestry residue. Due to very limited direct production emissions data, we estimated that any carbon not stabilized in biochar is emitted as CO₂ or methane.
Producing and using biochar may have various additional benefits after application in different soil types (Yang et al., 2025). Afshar & Mofatteh (2024) found biochar applied to soils can reduce the production of methane from rice paddies, and Kabir et al. (2023) observed decreased nitrous oxide emissions from some soils treated with biochar. Because these additional benefits of biochar are context specific, our analysis of effectiveness in reducing GHGs focused only on the amount of carbon sequestered with biochar.
Biochar's carbon sequestration potential depends in part on the feedstock used, because carbon content varies with type of organic waste. Woolf et al. (2021) examined several globally abundant feedstocks and found that the carbon content of biochar can also vary depending on how the biochar is produced, ranging from 10–81% of the carbon found in the dry mass feedstocks.
Table 1. Effectiveness at sequestering carbon.
Unit: t CO₂‑eq /t biochar, 100-yr basis
| 25th percentile | 0.81 |
| Mean | 0.63 |
| Median (50th percentile) | 0.84 |
| 75th percentile | 1.30 |
To sequester 1 t CO₂‑eq with biochar, a biochar production facility will have an initial cost of around US$200/t biochar, an operating cost of roughly US$510/t biochar, and revenue of US$120/t biochar. However, these values do not include potential costs for applying biochar to soils. Globally, the net cost of producing and using biochar is roughly US$190/t biochar, based on literature estimates of abatement costs. Table 2 shows the cost per unit climate impact, based on net cost.
Our cost data only include revenue from the sale of biochar for soil amendment and do not include revenue from increased crop yield, carbon credit systems, or other by-products such as the thermal energy, syngas or bio-oils, which can be used to reduce energy costs or sold as fuel (Amonette et al., 2021). We found limited capital cost and revenue data; many sources (Buss et al., 2022; British Columbia Centre for Innovation & Clean Energy [CICE] & Deloitte, 2023; Fuss et al., 2018; IPCC, 2018; Liang & Chen, 2025; Russel et al., 2025) focused on the overall costs of biochar production. Operating costs include labor, feedstocks, transportation, and application of biochar, and can vary significantly (Liang & Chen, 2025; Shackley et al., 2014; Xiao et al, 2019). Xiao et al. (2019) found that it is possible to achieve low-cost biochar production at small scales. Some facilities may have a feedstock cost near zero with local organic waste, while others may have a high cost due to transportation and processing (International Renewable Energy Agency [IRENA], 2018).
We considered the baseline scenario where biomass is left to naturally decompose or is collected and processed for conventional disposal. We assumed baseline initial costs, operational costs, and revenue to be 0.
Table 2. Cost per unit climate impact.
Unit: 2023 US$/t CO₂‑eq , 100-yr basis
| Median | 230 |
The processes and technologies for producing biochar are mature, and we were unable to find literature suggesting the costs to implement these solutions will fall in the future (The Institute for Carbon Removal, 2020). Even if technology costs drop over time, competition for feedstocks with bioenergy producers or composters could also increase production costs.
Speed of action refers to how quickly a climate solution physically affects the atmosphere after it is deployed. This is different from speed of deployment, which is the pace at which solutions are adopted.
At Project Drawdown, we define the speed of action for each climate solution as emergency brake, gradual, or delayed.
Producing biochar is a GRADUAL climate solution. It has a steady, linear impact on the atmosphere.
Biochar properties may vary depending on the feedstock and production process. The carbon content of biochar can range from 10–81% of the carbon found in the feedstock (Woolf et al., 2021). Production processes also affect what co-products are produced: Slow pyrolysis generates more biochar, while fast pyrolysis boosts bio-oil production, and producing biochar with gasification will have syngas as the largest output (Afshar & Mofatteh, 2024).
While strong evidence suggests that biochar sequesters carbon for hundreds to thousands of years, some uncertainties about permanence remain. Short-duration experiments have shown carbon loss over years or decades due to exposure to oxygen, water, and ultraviolet light, but these might not reflect real-world soil and environmental factors (Belmont & Sanchez, 2025). There is also evidence that co-application of biochar with nitrogen fertilizer can mitigate methane emissions in rice paddies (Baek et al., 2025).
We estimated that 380,000 t of biochar were produced in 2023 (Table 3).
We found only one source for current global annual production of biochar (International Biochar Initiative, 2024). These data were based on voluntary surveys of biochar producers with more than 1,000 respondents in 2023; we assumed it is an underestimate because it likely doesn’t include all biochar production facilities.
Table 3. Current adoption level (2023).
Unit: t biochar produced and added to soil/yr
| 25th percentile | 370,000 |
| Mean | 380,000 |
| Median (50th percentile) | 380,000 |
| 75th percentile | 400,000 |
We were only able to find adoption trend data for 2013, 2014, 2015, 2021, and 2023, all from the International Biochar Initiative (2014, 2015, 2016, 2024). These data rely on voluntary surveys; the source noted that some companies did not respond to the survey every year and that some biochar producers did not respond to the survey.
These adoption data show that biochar production has increased over time; however, it’s not clear whether this is due to increasing biochar production or increasing response rates from producers.
Producing biochar has an estimated adoption ceiling of 1.3 billion t/yr (Table 4) based on reports from Energy Transition Commission (2022), Fuss et al. (2018), International Biochar Initiative (2024), IPCC (2022), Lehmann et al. (2021), Lenton (2010), NorthX, (2025), Smith et al. (2019), and Woolf et al. (2010).
The adoption ceiling for biochar is often stated in terms of CO₂‑eq/yr removed. To convert this into metric tons of biochar we used the value of 1.9 t CO₂‑eq removed per mewtric ton of biochar produced given by the International Biochar Initiative (2024). In practice, the amount of carbon sequestered will depend on the feedstock used as well as the method used for producing biochar.
We based our analysis on the current level of organic waste produced by agriculture and industry. Many projections (Energy Transition Commission, 2022; Fuss et al., 2018; International Biochar Initiative, 2024; IPCC 2022; Lehmann et al., 2021; Lenton, 2010; NorthX, 2025; Smith et al., 2019; Woolf et al., 2010) show the technical potential of biochar production using all available waste biomass from agriculture or industry feedstocks. If biochar production is increased, we would expect to see more waste feedstocks used for biochar and less available for other climate solutions that use organic waste feedstocks.
Table 4. Adoption ceiling.
Unit: t biochar produced and added to soil/yr
| 25th percentile | 530,000,000 |
| Mean | 1,100,000,000 |
| Median (50th percentile) | 1,300,000,000 |
| 75th percentile | 1,600,000,000 |
Biochar production depends on the source and volume of feedstock. We estimate an achievable adoption of 160–570 Mt of biochar (Table 5). The low value was based on the projected biochar ceiling from Griscom et al. (2017), which excludes avoided emissions and partially accounts for restrictions in biomass availability. The high value aligns with IPCC (2022)’s estimate for the mitigation potential of biochar based on a US$100/t CO₂‑eq carbon price. The US$100/t CO₂‑eq carbon price is an indicator that biochar production will require economic support for widespread adoption and assumes that achievable biochar production is constrained more by economics than by biomass availability.
Large-scale biochar production will likely be limited by biomass competition with other climate solutions. Many sources do not specify how they calculated the amount of biomass available for biochar production, making it difficult to determine where achievable adoption would fall between the current adoption and the full technical adoption ceiling. We have chosen to be conservative for the high achievable adoption to reduce the chance of biochar production being restricted by feedstock constraints.
Table 5. Range of achievable adoption levels.
Unit: t biochar produced and added to soil/yr
| Current adoption | 380,000 |
| Achievable – low | 160,000,000 |
| Achievable – high | 570,000,000 |
| Adoption ceiling | 1,300,000,000 |
Producing and using biochar has the potential to sequester a large amount of carbon emissions. While biochar currently sequesters 0 Gt CO₂‑eq/yr, we estimated 0.13–0.47 Gt CO₂‑eq/yr on a 100-yr basis (0.13–0.46 Gt CO₂‑eq/yr, 20-yr) could be sequestered (Table 6). The economics of building, operating, and maintaining biochar production facilities, along with biomass feedstock availability, will greatly affect how biochar production and use grows in the future.
Producing biochar requires the use of biomass as a feedstock. Multiple climate solutions require biomass, and projected demand across solutions greatly exceeds supply. The deforestation that would be required to meet demand would produce emissions far greater than any mitigation gains from full deployment of these solutions (Searchinger, 2024). In addition to deforestation, there would also be costs and emissions incurred to transport biomass from where it is produced to where it can be processed and used. Thus, the estimated climate impacts presented here are only possible if feedstocks are prioritized for this solution. If feedstocks are instead prioritized for other climate solutions (see Interactions for examples), adoption and impact will be lower for this solution. It is not possible to set all biomass-dependent solutions to high adoption levels, add up their impacts, and determine an accurate combined emissions impact.
Table 6. Climate impact at different levels of adoption.
Unit: Gt CO₂‑eq/yr, 100-yr basis
| Current adoption | 0.00 |
| Achievable – low | 0.13 |
| Achievable – high | 0.47 |
| Adoption ceiling | 1.10 |
When used as a soil amendment, biochar has been found to increase soil health and yields of a variety of staple crops (Agegnehu et al., 2016; Kabir et al., 2023; Yang et al., 2025).
Producing biochar can benefit health by mitigating the impacts of crop residue burning. Poor air quality from crop residue burning is harmful to health and can lead to premature mortality, especially in Southeast Asia, where residue burning is more common (Lan et al. 2022). Air pollution from burning crop residue has been linked to eye irritation, headaches, nausea, skin irritation, allergies, respiratory infections, increased risk of lung cancer, and reduced lung function (Gupta, 2019; Huang et al., 2022; Raza et al., 2022).
Using biochar can reduce nutrient-rich runoff from manure that can lead to eutrophication and hypoxic zones in aquatic ecosystems (Bijay-Singh & Craswell, 2021). Nitrogen pollution also harms terrestrial biodiversity through soil acidification and increases the productivity of fast-growing species, including invasives, which can outcompete native species (Porter et al., 2013).
By using crop residues instead of burning them, producing biochar can improve soils that would otherwise be degraded from crop residue burning (Bhuvaneshwari et al., 2019).
When used as a soil amendment, biochar has been found to increase soil quality (Agegnehu et al., 2016). Biochar can aid in nutrient retention, including nitrogen, phosphorus, and soil organic carbon, and can improve soil water content (Agegnehu et al., 2016; Kabir et al., 2023; Yang et al., 2025). Some benefits depend on soil type; for example, amending biochar to mineral soils can increase soil pH, organic matter, and nutrient availability, especially in sandy and acidic soils, but soils with high pH could see a reduction in micronutrient availability (Yang et al., 2025).
Amending soil with biochar can increase soil water content, which can improve plant growth (Agegnehu et al., 2016; Kabir et al., 2013).
Producing biochar can mitigate the use of manure on agriculture fields, which can improve water quality. Manure contains nutrients such as nitrogen and phosphorus as well as drug residues, heavy metals, and pathogens (Steinfeld et al., 2006). Manure can also leach into water sources when used as a fertilizer on croplands (Porter & Cox, 2020).
Producing biochar can benefit air quality by mitigating crop residue burning and the use of manure as fertilizer. Reducing the amount of manure applied as a fertilizer on croplands can improve air quality by reducing nitrogen and ammonia emissions associated with manure application (Grossi et al., 2019; Peterson et al., 2013; Steinfeld et al., 2006).
Crop residue burning is a major source of air pollution, including fine particulate matter, CO₂, and carbon monoxide, in South and Southeast Asia (Lan et al., 2022; Na Talang et al., 2024; Singh et al., 2021). Because fine particulate matter and black carbon make up a large part of the pollution, crop residue burning can lead to poor air quality far from agricultural fields (Kaskaoutis et al., 2014). Poor air quality associated with burning crop residues could be improved by instead producing biochar.
The environmental impact of high adoption of biochar application in soils is unknown. Feasibility, long-term mitigation potential, side effects, and trade-offs are uncertain. Resolving these uncertainties will require biochar application on different soil types, environments, and management conditions in real-world settings for long periods (Fuss et al., 2018; Belmont & Sanchez, 2025).
The application of biochar could potentially change the microbial composition of the soils or lower the ability of plants to defend against insects, pathogens, and environmental stresses (Viger et al., 2014). It also could darken the soil surface, altering the land surface radiation balance. Fine biochar particles could get released into the atmosphere during production, transportation, or handling, leading to poor air quality, disrupted local hydrological cycles, and potential health concerns (Genesio et al., 2016; Ravi et al., 2016). GHG emissions from producing biochar differ across scales and technologies. Strategies to minimize the potentially negative impacts of biochar will need to be developed in order to guarantee that biochar has an overall positive impact on global climate change.
Sayara & Sánchez (2021) observed reduced nitrogen emissions when biochar was added to compost.
Biochar production can compete with solutions that use biomass, specifically wood and crop residues, in other processes. Because the total projected demand for biomass for climate solutions exceeds the supply, not all of these solutions will be able to achieve their potential adoption. This solution competes with the following solutions for raw material:
t biochar produced and added to soil
CO₂
To preserve soil health and nutrient recovery, some agricultural and industrial forestry waste must be left on the land. If revenues from biochar production are very high, producers may be incentivized to convert additional land to grow crops for biochar. This could affect food security and soil health (CICE & Innovative Breakthrough Energy Technologies [IBET], 2023).
Pyrolytic production of biochar can generate heat and power. However, different processes produce different outputs, and it is important to understand the economic considerations for biochar production (Afshar & Mofatteh, 2024).
Biochar can be used to replace a small amount of cement in concrete production or incorporated into other building materials (Aman et al., 2022), but this limits its usage as a soil amendment and potential for enhanced soil carbon sequestration. However, using biochar in durable building materials stores carbon for multiple decades, while some agricultural applications could involve further combustion or decomposition of biochar and so release stored carbon back into the atmosphere within a few years.
Consensus of effectiveness in sequestering carbon: High
A wide variety of organic feedstocks can be used to produce biochar, mainly from the agricultural and industrial forestry sectors. Converting biomass into biochar using pyrolysis converts a portion of the carbon into a stable form, thereby slowing its release into the atmosphere. When biochar is used as a soil amendmen,t it improves soil fertility by retaining water and nutrients (Woolley & Hallowell, 2018).
The process used to create biochar can have varying efficiencies because the conversion of organic carbon in the feedstock to biochar can range from 30–55% with slow pyrolysis or be as low as 3% with regular combustion (Amonette et al., 2021). In addition, different biomass feedstocks contain different amounts of carbon, which will affect the carbon content of the biochar (Joseph et al., 2021).
Using biochar can also have additional benefits. Biochar can be used as filter material for remediation of soil or water pollution, an additive for composting or anaerobic digestion (Alayaki et al., 2025), or a supplement to concrete and other building materials, packaging, and bio-oils (Russell, 2025).
The results presented in this document summarize findings from 21 reviews and meta-analyses and 17 original studies reflecting current evidence from two countries (the United States and Canada) and from sources examining global biochar production. We recognize this limited geographic scope creates bias, and we hope this work inspires research and data sharing on this topic in underrepresented regions.
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