What is Enhanced Weathering?
Enhanced Weathering (EW) is a carbon dioxide removal (CDR) technology that accelerates the Earth’s natural weathering process. Weathering is a well understood and thoroughly documented geological process that removes carbon dioxide from the atmosphere and durably stores it in the ocean for in excess of 10,000 years.
How does Enhanced Weathering work?
Natural weathering starts with carbon dioxide present in rainwater. The dissolution of carbon dioxide in rainwater creates carbonic acid. When rain falls, this acid reacts with minerals in rocks, forming stable bicarbonate ions. These bicarbonate ions are washed into rivers and eventually transported to the ocean, which durably stores the carbon dioxide for tens of thousands of years.
Under normal circumstances, this natural weathering process takes thousands—or millions—of years to impact the Earth’s climate. EW speeds up this process to turn weathering into a powerful tool that can benefit the climate now.
The EW process is straightforward. First, rocks that can react with the carbon dioxide in rainwater are crushed into a fine powder. Rocks and minerals like basalt or olivine are often used as feedstocks for this process. Crushing these feedstocks dramatically increases their surface area which means they can react more readily with the carbon dioxide in rainwater.
Next, the fine rock powder is spread on soil—typically on agricultural land—where it can also restore nutrients to the soil. When it rains, the rock powder reacts with the carbonic acid in the rainwater, forming stable bicarbonate ions. Over time these ions are washed into rivers and then out to the ocean where they are durably stored.
What are the advantages of Enhanced Weathering?
Rapid scalability
The systems and infrastructure needed for Enhanced Weathering—such as facilities to grind rocks into powder and spread it on fields—already exist and are often situated alongside industries, like agriculture, that have experience moving large amounts of materials. The process of spreading rock on agricultural land uses the same equipment and infrastructure as the existing practice of agricultural liming. This means that EW has a unique potential among CDR technologies to rapidly reach massive scale, without the need for major infrastructure investment.
High durability
The ocean is one of the most effective stores of carbon dioxide on Earth’s surface—containing approximately fifty times more carbon than the atmosphere. Carbon dioxide sequestered via EW within the ocean can be stored for tens of thousands of years and has a very low risk of returning to the atmosphere—a process called reversal.
Supporting agriculture
EW can have significant additional benefits when done on agricultural land—it boosts soil health, increases agricultural productivity and creates jobs in farming communities. The fine rock powder spread on farmland increases the amount of nutrients in the soil and acts as a fertilizer. This incentivizes farmers to take part in EW projects and can result in healthier and higher-yield crops.
How much does Enhanced Weathering cost?
Currently, EW has a wide range of costs, depending on the availability of suitable natural rocks and necessary infrastructure. Typically EW costs range between $150-$350 per tonne.
