Mining Waste Now Removes CO2 and Helps Farmers Grow Crops

What if the answer to pulling carbon from the sky was sitting in mining waste piles all along? Anglo American just proved it's possible with a simple but powerful idea that helps the planet and farmers at once.

The mining giant partnered with climate tech companies ZeroEx and Isometric to turn ferronickel slag into a carbon removal tool. Slag is the rocky waste left over from metal smelting, and millions of tons of it pile up each year with nowhere to go.

Their solution speeds up a natural process called rock weathering. When rain falls, it mixes with CO2 to form weak acid that slowly breaks down certain rocks. This reaction locks carbon away in stable forms or carries it to the ocean, where it stays trapped for thousands of years.

By crushing magnesium-rich slag and spreading it on farmland, the team multiplies the surface area for this reaction. More surface area means faster weathering and more CO2 pulled from the air. The crushed slag works double duty as fertilizer, adding magnesium back into depleted Brazilian soils.

Project Earthstone launched in Brazil in 2025 with robust monitoring technology from ZeroEx that cuts measurement costs dramatically. The partnership with Isometric ensures every carbon credit earned meets rigorous scientific standards, with full transparency and verification.

Farmers using the material see real benefits beyond helping the climate. The slag corrects soil pH and delivers magnesium, a nutrient most Brazilian farmland desperately needs. Healthier soil means better crop yields and stronger harvests.

Katie Fergusson, who leads studies and development for the project, says the trial aims to prove carbon credits can be generated at scale safely and responsibly. The approach transforms what was once a disposal problem into a valuable climate tool that creates revenue while supporting local agriculture.

The Ripple Effect

This breakthrough shows how industries can rethink their waste streams as resources. Mining operations worldwide generate similar slag that could be repurposed for carbon removal. If the model scales, millions of tons of industrial waste could become millions of tons of captured carbon.

The approach also creates a new income stream for mining companies while helping them meet climate commitments. Instead of buying carbon offsets from distant projects, they generate credits from materials they already produce. Farmers gain access to affordable soil amendments that boost productivity without depending on synthetic fertilizers.

The project proves climate solutions don't have to be expensive or complicated. Sometimes the best answers come from looking at old problems in new ways, turning what we throw away into what the world needs most.

One waste product is now removing carbon, enriching soil, and showing industries everywhere that their leftovers might be their greatest opportunity.