What is our assessment?

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. 

What is it?

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). 

Does it work?

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). 

Why are we excited?

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). 

Why are we concerned?

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 durability and 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). 

What is our assessment?

Based on our analysis, Improve Steel Production using H₂-DRI-EAF powered by clean electricity has the potential to significantly reduce emissions. However, while the individual technologies for H₂-DRI-EAF are mature and their combined use has been piloted, the process has not yet been adopted in a meaningful way. We will “Keep Watching” this solution, but it is not ready for widespread adoption.

What is it?

Currently, making steel from iron ore relies heavily on coal and other fossil fuels to provide heat and reducing agents (chemicals that remove oxygen from iron ore). Improve Steel Production refers to using electric heat and hydrogen produced by electrolysis to reduce the iron ore (H₂-DRI) and electric arc furnaces (EAF) to melt the resulting iron and alloy it with carbon to make steel. The solution also requires the electricity used in these processes to include significant renewable energy or other low-carbon generation. The output is varying grades of steel with different degrees of hardness and brittleness determined by slight variations in carbon content. This solution does not include processes that rely on bioenergy or CCS, since the emissions from burning bioenergy contribute to climate change and CCS is not an effective climate solution.  

Does it work?

Replacing fossil fuels in steelmaking with H₂-DRI-EAF that uses electrolytic hydrogen and where all electricity comes from relatively clean sources results in significantly reduced emissions. Steel made today using fossil fuels for heat and as a reducing agent results in an estimated 1.8 t CO₂‑eq /t of steel. By contrast, steel made using H₂-DRI-EAF and low-carbon electricity would generate an estimated 0.12 t CO₂‑eq /t of steel and is a more energy-efficient process. EAF furnaces are already very common in steelmaking and for recycling existing steel, but are rarely combined with H₂-DRI. Although H₂-DRI was first used on an industrial scale in 2001, that plant was shut down for economic and political reasons, and economics remain a barrier. Finally, technologies to make industrial hydrogen from electricity are mature, but most hydrogen produced today is made from fossil fuels and is carbon-intensive. Active research is exploring other technologies that could become important for improving steel production in the future, most notably aqueous or molten oxide electrolysis, both of which use electricity to directly remove oxygen from iron ore, and can be combined with EAF to make steel.  

Why are we excited?

Steelmaking is classified as a hard-to-abate industry, and H₂-DRI-EAF powered by clean electricity is considered one of the best strategies for cutting emissions in this sector. The Net Zero Industry project forecasts that under an emissions-neutral steel scenario by 2050, roughly 40% of global steel production could depend on H₂-DRI-EAF, with the remainder consisting of recycled steel (47%), steelmaking with CCS (11%), or technologies not yet defined (2%). The impact is potentially significant, given that steelmaking accounted for an estimated 3.7 Gt of CO₂‑eq in 2019. Improved steelmaking has the additional benefit of reducing air and land pollution, as burning coal releases fine particulate matter, heavy metals, and other pollutants. In China, steel production is the largest industrial source of air pollution. As demand for steel is expected to increase up to 30% by 2050 due to demand from India and other low- and middle-income countries, it is critical that new and existing production shift to cleaner, lower-emission technologies, and that policies supporting this shift be implemented.  

Why are we concerned?

While proposed low-emission steel projects have attracted significant attention from the press, many have since been canceled or put on hold. As of 2025, we could find references to only a few pilot facilities producing improved steel as we have defined it here. The entire H₂-DRI-EAF process is considered to be at the large-scale prototype demonstration stage. However, contributing technologies such as electrolytic hydrogen production and EAF are more mature, and H₂-DRI was first used on an industrial scale in 2001. The higher cost of making low-emission steel is a significant barrier to industrial adoption and consumer demand. Electricity accounts for nearly half the cost of producing low-emission steel from iron ore. To increase adoption, improved steel facilities need to be located in areas that can readily supply both iron ore and abundant low-carbon, low-cost electricity. In areas such as China, where the electricity grid still relies heavily on fossil fuels, transitioning to H₂-DRI-EAF risks increasing emissions unless dedicated renewables are integrated into the project. To move this solution forward, new policies are needed to create an international market for low-emission steel. Meanwhile, existing steelmaking facilities typically have lifetimes of 25–40 years, which increases the likelihood of stranded assets or continued reliance on fossil fuels by 2050. Under its Sustainable Development Scenario, the International Energy Agency (IEA) projects that, by 2050, only 12% of cumulative direct emissions reductions in steelmaking will be due to electrification and the use of hydrogen (the IEA considered emissions from electricity to be indirect). Reducing demand for steel, incremental efficiency gains, and CCS are expected to make up the bulk of cumulative direct emissions reductions, according to the IEA projections.

What is our assessment?

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. 

What is it?

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. 

Does it work?

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. 

Why are we excited?

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.

Why are we concerned?

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. 

What is our assessment?

Reduced grazing intensity can temporarily reduce soil degradation and erosion. However, SOC outcomes depend on a number of factors, such as climate zone, land use history, soil properties, and grass type. Therefore, until stronger, long-term evidence is available to guide more effective implementation, we will Keep Watching this solution.

What is it?

Reducing grazing intensity refers to lowering ruminant livestock stocking rates or shortening grazing duration to reduce pressure on grazing lands. As a climate solution, it is intended to remove carbon from the atmosphere by increasing SOC through enhanced plant productivity, root inputs, and soil stability. Grazing intensity is typically classified as heavy, moderate, or light, based on the proportion of forage removed per unit time.

Does it work?

In general, while heavy grazing reduces SOC, the effects of grazing intensity on SOC recovery varies with climate zones, grass types, soil properties, and prior land use. Increases in SOC under reduced grazing intensity are largely limited to wetter regions, often with high annual rainfall. In arid and semi-arid regions, which represent a major share of global grazing land, reduced grazing intensity often results in neutral or negative SOC responses. A global review and meta-analysis that normalized SOC to 30 cm depth found that even grazing below carrying capacity was associated with an overall decline in SOC, with gains limited to lower-intensity grazing conditions in specific climate zones.

Why are we excited?

Reducing grazing intensity provides ecological benefits. This usually involves reducing the number of ruminant livestock on a farm, which in turn reduces the farm’s methane emissions, land-use pressure, and threats to biodiversity–at least in isolation. It can reduce soil degradation, erosion, and vegetation loss. It is already practiced in many contexts and requires no new technology or infrastructure, making it easy and relatively low cost as a climate intervention, though not necessarily cost-neutral for ruminant livestock producers.

Why are we concerned?

Several limitations, risks, and trade-offs are associated with reducing grazing intensity as a carbon removal strategy.

First, even low-intensity grazing can prevent ecosystem recovery when pastures are seeded with, or invaded by, aggressive grasses that suppress native plants, prevent tree regrowth where ecologically appropriate, and lock landscapes into lower-biodiversity, grass-dominated states.

Second, SOC gains are limited, slow, and reversible. Soil organic carbon is a finite sink that approaches saturation within decades and can be lost through drought, warming, fire, or management changes. SOC accumulation through reduced grazing intensity has been shown to be a temporary and fragile form of carbon storage. 

Third, SOC gains are difficult to measure and verify. Many studies lack baseline SOC measurements, adequate controls, sufficient duration, and/or adequate soil-depth sampling, making it difficult to attribute carbon gains to grazing intensity. To show an increase in SOC from reduced grazing intensity, an ideal experiment would adopt a before-and-after control intervention at a commercial scale and follow SOC changes for 5–10 years.

Fourth, while reducing grazing intensity compares favorably with alternative grazing when it reduces total stocking numbers, it is still less durable and certain as a carbon removal strategy than protecting intact ecosystems, restoring degraded grasslands, or restoring forests where ecologically appropriate. 

Fifth, reducing grazing intensity often lowers herd sizes, but under rising global beef demand this can simply shift production elsewhere. This underscores the value of improving diets and shifting food system infrastructure away from ruminant consumption rather than simply altering ruminant production practices.

Overall, reducing grazing intensity can reduce some local damage from heavier grazing, but in climate-favorable regions especially, the stronger opportunity is often restoring ecosystems or producing higher-yielding plant-based foods.