Can Dusting Cropland With Crushed Up Volcanic Rock Ease Climate Change?

A truck spreads crushed basalt rock over a Brazilian
farm field. The idea is supposed to combat climate
change by running weathered rock into the oceans
where it is stored out of the atmosphere so 
that it can't affect global temperatures. 

 Across big stretches agricultural land in southern Brazil, a company called Tereradot is spreading dust made of crushed volcanic rock all over the place. 

It's not some odd form of fertilizer. It's even weirder: It's an effort to combat climate change. 

As the Washington Post explains: 

"As rain percolates throughout the soil, chemical reactions pull carbon from the air and convert it into bicarbonate ions that eventually wash into the ocean, where the carbon remains stored."

Spreading the dust greatly accelerates a process that usually takes thousands or even millions of years to complete. 

WaPo goes on:

"The technique, known as ''enhanced rock weathering' is emerging as a promising approach to lock away carbon on a massive scale. Some researchers estimate the method has the potential to sequester billions of tons of carbon, helping slow global climate trends. 

Other major projects are underway across the globe and have collectively raised over a quarter billion dollars."

Rock weathering is a natural, but slow process in which rock breaks down, gets washed into rivers and eventually the ocean, which stores the carbon in the water, out of the atmosphere. When temperatures are high, the weathering speeds up. But not nearly enough to combat climate change. 

Enter a company called Terradot to greatly accelerating that slow process. They take basalt, which weathers easily, and crush up until it's the texture of baby powder. That increases its surface area. The rock is then spread out on the ground in hot, humid places so the pace of the weathering is maximized. 

Most of Terradot's work is happening in Brazil. Much of the cropland has naturally acidic soils, but the crushed up basalt balances that acidity, helping with crop yields.

Brazil has a lot of basalt quarries, as the rock is used in construction. Grinding and crushing the rock for construction leaves a lot of pieces of waste basalt. Terradot buys that waste, turns it into dust and spreads it on fields for their climate change control efforts. 

The powdered basalt is free for farmers. Terradot bears the cost of shipping and spreading the rock dust.  

As cool as it sounds, this idea is no slam dunk against climate change.  How accurately can anyone measure how much this process removes from the atmosphere. Is it cost effective? And scaling up the enhanced rock weathering all over the world is a logistical nightmare. 

Scientists want to see more data to determine whether the basalt dust gets rid of as much atmospheric carbon as startups like Terradot claim.