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Basalt columns by the ocean in Northern Ireland.

Basalt columns are natural pillars made of hardened lava, caused by the contraction of volcanic rock as it cools. Northern Ireland.

Credit: Alexander Hafemann / Getty Images

Enhanced Weathering

Call to action:

Accelerate the breakdown of silicate minerals to improve crop productivity, reverse ocean acidification, and permanently absorb carbon from the atmosphere.

Volcanic minerals called silicates are highly abundant on Earth. As they erode slowly over time, a process called weathering, they pull carbon dioxide from the atmosphere through a series of chemical reactions. This process can be enhanced by action, such as crushing the rocks mechanically, which exposes more surface area to the atmosphere. Crushed silicates have many benefits. Spread on agricultural fields, they can boost soil health and plant fertility, improving crop yields. Applied to oceans, they can reverse acidification and reduce algal blooms. Enhanced weathering has the potential for large-scale carbon dioxide removal. It faces challenges, however, including the high energy demands of pulverizing rocks and understanding the full impacts of adding silicates to soils and oceans under real-world conditions. With careful attention to mining practices, energy sources, and environmental impacts, enhanced weathering could be a key regenerative solution.

Action Items

Individuals

Learn about the potential of enhanced weathering. Enhanced weathering involves pulverizing silicate rocks and spreading them over the ground or over water. The idea has origins in the traditional practices of several agricultural societies and in the sciences in the 1800s when German agronomist Julius Hensel discovered he could increase the productivity of his garden with rock dust that he called “stone meal.” The idea of using crushed silicates to trap carbon dioxide was first proposed in 1990, but it did not take off until 2006 when it was identified as a potential large-scale climate solution.

Learn about challenges to the implementation of enhanced weathering. There are several hurdles to overcome in order for enhanced weathering to be scaled up and implemented as a key climate solution.

  • Energy. It takes a lot of energy to crush rocks. The energy required for rock-milling machines and transportation is still mostly dependent on fossil fuels. Renewable energy is needed to maximize the climate benefits of enhanced weathering, particularly with basalt, which requires a higher tonnage of material to draw down the same amount of carbon as olivine.
  • Quantity. Sequestering a ton of atmospheric carbon with enhanced weathering requires 1.6–3.7 tons of silicates, requiring large amounts of minerals in order to draw down meaningful amounts of carbon. Mining at this scale might cause environmental degradation if not done carefully. Recycling mine waste is an option, with the added benefit of removing troublesome waste from mine sites.
  • Cost. It is expensive to crush and transport enormous quantities of rock, especially at smaller grain sizes.
  • Safety. Silicates contain elements such as chromium and nickel, which can surpass safe levels when applied to an agricultural field or coastal waters in large quantities. Stringent safeguards and careful monitoring are needed to prevent harm to consumers and marine organisms.
  • Scientific uncertainty. The long-term effects of applying crushed silicates to soils and oceans are uncertain. Coastal enhanced weathering involves deploying sand-size particles and letting the power of ocean waves finish breaking down and dissolving the silicates. However, more evidence is needed to prove this strategy works and wouldn’t harm marine life.

Buy rock dust. Pulverized silicate rocks are often marketed as rock dust for use in gardens or orchards. Rock dust can boost productivity by providing nutrients such as phosphorous, potassium, magnesium, and calcium to depleted soils. Rock dust is generally considered acceptable for organic use, but it might depend on the source of the silicates. Rock dust is sold in small enough quantities to allow gardeners to experiment with different types for different crops.

  • Rock dust is popular and aggressively marketed, but its benefits are sometimes overhyped, as this video explains. It is not a substitute for organic compost. Get to know the pros and cons of rock dust. See the Compost Nexus for more information.
  • Various types of carbon-absorbing pulverized rock can be purchased online. Consider buying from local operations, sellers that mill with renewable energy, or rock flour made from mining by-products, all good strategies for maximizing net carbon drawdown.

Groups

Farmers

Incorporate silicate rock dust into farm soil. Carbon-absorbing minerals can benefit different types of crops. Precise numbers are highly particular to climate, soil conditions, crop type, and silicate source, but in general, the practice is thought to be most helpful for impoverished soil in the tropics.

Partner with scientists. Partnerships between the agriculture and research sectors are critical for understanding the impacts of enhanced weathering.

Scientists

Conduct research on enhanced weathering co-benefits, impacts, and potential scale. A major factor limiting interest in enhanced weathering is uncertainty about its potential impacts on agriculture and coastal ecosystems. More research is needed, particularly in the tropics, where enhanced weathering may be more impactful on depleted soils but where carbon benefits might not be as strong initially.

  • Establish enhanced weathering extension projects. Agriculture is a promising context for enhanced weathering, particularly given the potential for productivity upsides. However, more research is needed to establish when, where, and how much impact such additives could have, as some projects have found unexpected results or systems where enhanced weathering is counterproductive.
  • Improving ocean health by decreasing toxic algal blooms is an intriguing possibility. However, the idea is largely theoretical and requires additional research to prove that it works in practice.
  • More research is needed on the impact of enhanced weathering on local flora and fauna. Natural green sand beaches rich in olivine, such as Papakolea on the island of Hawaii, offer lessons as natural experiments.
  • One particular challenge that needs further research is on the impact that undissolved particles of silicates could have on stream and river health.
  • Using the energy of the ocean to break down silicates into their smallest grain sizes would save a huge amount of energy, but it’s not clear if and where it would be a viable approach and what impacts it would have on coastal species. Project Vesta is one group leading research in this area.

Share the science. Despite years of research, enhanced weathering is still off the radar as a climate solution. One of the most effective ways to get the word out on enhanced weathering is for scientists to engage with the public on the potential of enhanced weathering as a climate solution.

  • Scientists Grace Andrews and Mel Murphy gave interviews for videos on enhanced weathering that have collectively been viewed millions of times.

Companies

Invest in enhanced weathering pilot projects. Enhanced weathering initiatives are still in their infancy and need stable financial investments and partnerships to explore their full potential. Projects that boost crop productivity or reverse ocean acidification while durably reducing carbon in the atmosphere should be particularly attractive to companies who are bumping up against the limits of other ways they can reduce their greenhouse gas emissions.

Turn mine tailings into sequestered carbon. Some by-products of mining include minerals that can be used for enhanced weathering. Special attention is needed to make sure enhanced weathering projects are not leading to pollution, however, given that source rocks can contain harmful compounds, especially the metals chromium and nickel.

  • The mining company BHP is looking to speed up the natural carbon mineralization of its tailing pond at a nickel mine in Australia. The large amount of magnesium naturally binds with carbon dioxide and water. BHP believes they can enhance this process to entirely offset the greenhouse gas emissions of their operations at the mine.

Governance

Regulate enhanced weathering projects. Enhanced rock weathering is not without its risks, and clear rules are needed to ensure that communities and wildlife are not adversely impacted. Regulatory bodies, such as the EPA, need to establish clear limits for what mineral types can be used in different contexts, with mechanisms to prevent excessive application of toxic elements such as nickel and chromium, as well as rules for preventing clouding of local waterways with undissolved particles.

  • The US Department of Energy has signaled its interest in supporting research on enhanced weathering through a Request for Information about related research opportunities. Similar efforts from other agencies or similar entities in other countries would accelerate research on this topic.
  • Small-scale pilot projects often involve close coordination with a variety of government entities. Project Vesta has established a model to be followed through its work with local, state, and federal entities on an enhanced weathering project along a New York beach.
  • Government bodies that manage carbon permits, such as Australia’s Clean Energy Regulator, need to establish whether enhanced rock weathering projects can be included in their trading marketplaces. There need to be specific rules for application and monitoring since rates of carbon absorption through enhanced weathering projects can vary greatly.

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