How powdered rock could help slow climate change

Across six continents, farmers are experimenting with a technique called enhanced rock weathering, which aims to improve degraded soils and help combat climate change. This method takes advantage of Earth’s natural carbon cycle, using volcanic rock to trap atmospheric CO2 and moderate temperatures over geologic time.

Enhanced rock weathering has gained attention as a potential climate solution, with researchers studying ways to accelerate the process. Grinding volcanic rock into powder increases the surface area available for trapping CO2, and proponents typically target cropland for easy access and multiple crop benefits.

The Intergovernmental Panel on Climate Change (IPCC) has identified carbon dioxide removal technologies as key to meeting climate goals, with the need to remove 100 billion to 1,000 billion metric tons of carbon dioxide by the end of the century. Enhanced rock weathering could contribute significantly to this quantity, potentially removing up to 215 billion tons over the next 75 years, according to computer simulations.

Despite its potential, enhanced rock weathering faces challenges, including concerns about potential environmental contamination, the difficulty of measuring and verifying carbon removal, and the risk of shunting resources away from established priorities like preserving forests. However, given the urgent need to address climate change, the sensible course is to embrace all climate solutions, including newcomers like enhanced rock weathering.

Enhanced rock weathering works by trapping carbon dioxide in bicarbonate ions, which are formed when carbonic acid rains down on volcanic rock. The bicarbonate eventually flows into the ocean, where it can be used by marine life to form shells and skeletons.

Many enhanced rock weathering companies are already operating, focusing on cropland and offering soil amendments for free in exchange for carbon credits. Some companies are also exploring the possibility of spreading rock dust on beaches and ocean waters.

Enhanced rock weathering has multiple advantages over other forms of carbon dioxide removal, including energy savings, compatibility with existing land uses, and the potential to complement regenerative agriculture techniques. However, long-term risks, such as heavy metal accumulation in soils, remain uncertain. Accurate measurement and verification of carbon removal are also essential for enabling companies to sell carbon credits.

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