The Hot New Tech for Carbon Dioxide Removal: Rocks?

Many efforts to stop the planet from getting hotter focus on reducing emissions of greenhouse gases like carbon dioxide. As we’ve burned ever more fossil fuels, more and more of these heat-trapping gases have been piling up in our atmosphere for decades, so curbing those emissions is essential to prevent the planet from getting even hotter.

There’s no substitute for this work. But there’s much more we have to do. We have to adapt to face the climate impacts we’re already seeing. Increasingly, we’re also going to need a way to pull some of that CO₂ back out of the atmosphere and store it somewhere.

Trees can help, but they’re not a panacea; the same goes for technologies like direct air capture (DAC). But what about rocks? Enter “enhanced weathering.” Here’s the idea:

Starting tens of millions of years ago, what we now recognize as India and Asia collided, pushing up the Himalayas. Over time, amid the resulting erosion, particles of silicate minerals began tumbling into the surrounding plains and ocean. The thinking goes that since these minerals bind with carbon dioxide, atmospheric concentrations of CO₂ declined, helping usher in subsequent ice ages.

Enhanced weathering proposes we try something similar: crush up alkaline rocks like basalt, spread the particles in places like fields or the sea, and thus accelerate a naturally occurring process. (In theory, this could also help with the problem of ocean acidification.)

This is already a multimillion-dollar idea. However, even experts who consider it promising have questions about scalability. One concern: Where will the energy to crush and spread all those bits of rock come from? If the answer is renewables, those are renewable watts we can’t spend elsewhere—ideally to replace some of our current fossil fuel infrastructure.

– By Daniel Potter, with Anders Halverson. This newsletter draws on a pending update to our carbon dioxide removal class, which we’re retooling to discuss solutions like enhanced weathering.