Enhanced Rock Weathering

Who thought breaking rocks could have such upside

When rain falls it “grabs” carbon dioxide molecules on the way down to Earth. If, by chance, it lands on volcanic rock the carbon dioxide will be captured. This process is called “Rock Weathering.” It’s okay. It’s not great. It needs significant rain, it needs volcanic rock, and it’s slow. REALLY slow. Like millions of years to make a difference slow.

But. There’s good news.

If you crush the rock then the process speeds up quite a bit, this is called “Enchanted Rock Weathering.” The crushed up rock increases surface area thus more ambient carbon dioxide can be captured. Once captured, the crushed rock ends, eventually, in groundwater and oceans where carbon would be stored for up to 100,000 years. Enhanced Rock Weathering is still being tested, but a recent experiment in California’s Sacramento Valley yielded positive results.

Crushed metabasalt and olivine were spread over 5 acres of fallowed cornfield in the midst of the area’s drought. Measurements indicate the enhanced weathering stored 0.15 tons of carbon dioxide per hectare (2.47 acres) compared to plots without crushed rock, if this amount of carbon was removed across just California cropland, it would be like removing over 300K gas-using cars off the road every year.

There are questions and further testing is needed. How will different environments perform, how much faith can be put into the measurements of removed CO2 (it’s not easy to determine given existing tools) are examples of this. There are concerns too! Flooding any particular area with too much bicarbonate is one issue, since that could have its own effects on ecosystems. The environmental footprint of the crushing process, if there’s a potential air quality worry.

But this is good stuff. It also fits into a larger potential schema of geo-hacking that not only captures carbon/carbon dioxide but reconstitutes it into soil to increase fertility and plant growth via bio-char¹ and other goodies.

There’s momentum too. Recently a group of companies including Alphabet and Stripe have invested $50mm to support further tests and roll-outs via Frontier, a carbon removal initiative.

“Enhanced weathering has the potential to get to very large scale at relatively low costs in a pretty short amount of time,” says Nan Ransohoff, head of Frontier.

1. Warning: Jonathan Franzen alert!