By Thomas Kent, Local Journalism Initiative Reporter, Woolwich Observer
December 31, 2025
Researchers at the University of Guelph are investigating whether a locally mined mineral could help Ontario farmers improve soil health while capturing carbon from the atmosphere.
Supported by the Ontario Agri-Food Innovation Alliance, Dr. Rafael Santos, a chemical engineer at U of G’s College of Engineering, is leading research on using wollastonite (a white calcium silicate mineral mined near Kingston) as a soil amendment that could improve crop yields and lower greenhouse gas emissions.
“Wollastonite is an interesting mineral,” Santos said. “Its needle-shaped particles are aerodynamic, stay in place and spread well when applied to soil.”
Traditionally, farmers use limestone to adjust soil pH because many Ontario soils naturally become more acidic from crop removal, fertilizer use, and other factors. However, limestone can break down when exposed to air during application and release carbon, depending on weather conditions.
Wollastonite, by contrast, is highly reactive and capable of capturing carbon dioxide through a process known as enhanced rock weathering.
Enhanced rock weathering is increasingly studied as a nature-based climate solution. The process replicates natural geological weathering, in which crushed silicate rocks react with carbon dioxide and water to form stable carbon compounds that are stored in soils or eventually transported to the ocean.
This process can potentially remove carbon dioxide from the atmosphere at a scale similar to other negative-emissions technologies, while providing additional benefits for soil fertility and crop productivity.
To activate the process, wollastonite is crushed to increase its surface area, allowing it to react with water, soil microbes, and plant by-products. These interactions improve soil health while storing carbon over time.
Researchers have been testing the mineral at field plots at the Ontario Crops Research Centre–Simcoe, examining its effects on crop yield, plant growth, fertilizer efficiency, and carbon sequestration. The work is being carried out in collaboration with centre manager Torin Boyle, alongside U of G colleagues Dr. Emily Chiang, master’s students Ayda Amidi and Andrea Chacon, PhD graduate Dr. Francisco Araujo, and post-doctoral researcher Dr. Reza Khalidy.
“We’ve been able to show that crops are doing much better with wollastonite very clearly,” Santos said. “There are significant effects of better plant growth and improved soil health.”
According to the research team, soils treated with wollastonite consistently captured more carbon than untreated fields, with the highest levels observed where the mineral was applied over several consecutive years.
Most trials to date have focused on soybeans, which naturally acidify soil and accelerate the weathering process through microbial activity in their root nodules.
“We’ve found that wollastonite is reactive enough when you put it in the soil that you can see the effects after just one season,” Santos said.
The team is now working to measure carbon-capture rates more accurately and to develop reliable, cost-effective methods for detecting the products of weathering in soil and water.
Santos said the goal is to eventually give farmers a practical way to predict the benefits of applying wollastonite on their land.
Compared to limestone, Santos found that wollastonite can trap roughly twice as much carbon dioxide, significantly reducing the risk of emissions returning to the atmosphere. That potential has attracted interest from UNDO Carbon, a U.K.-based carbon-removal company now working with Ontario farmers.
In Ontario, UNDO covers the cost of purchasing and applying wollastonite in exchange for the carbon credits generated.
Carbon credits are issued when verified practices reduce or remove greenhouse gas emissions, with each credit typically representing one tonne of carbon dioxide.
In Canada and internationally, companies can purchase these credits to help meet climate targets, creating a potential new revenue stream for farmers who adopt approved carbon-removal practices.
The company partnered with Santos to provide scientific oversight for Ontario field trials and has also brought in University of Washington researcher Dr. Rebecca Neumann to add hydrological expertise to the Simcoe project.
“While we have a strong focus on investigating the use of enhanced rock weathering in Ontario, our research has also impacted the U.S., U.K. and beyond,” Santos said.
For Ontario farmers, Santos said the technology could offer multiple benefits beyond carbon sequestration.
“There are really interesting opportunities for Ontario farmers with wollastonite,” he said. “We are replacing limestone and might even be able to replace some fertilizer because of the plant health benefits – and then the climate benefits become so much bigger than just sequestration.”
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The Ontario Agri-Food Innovation Alliance, a partnership between the University of Guelph, the Government of Ontario and Agricultural Research and Innovation Ontario, funds the research. The Ontario Crops Research Centre is owned by ARIO and managed by U of G through the Alliance.
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