Cheap, scalable carbon capture could restore rivers

Originally developed to combat acid rain, the technology has the potential to remove large amounts of carbon dioxide from the atmosphere, while simultaneously reducing ocean acidification, restoring rivers and increasing biodiversity and fish populations.

Decarbonization is an incredibly difficult and costly challenge for some sectors, so significant carbon capture efforts will certainly be needed as humanity fights to limit the most devastating effects of climate change.

While huge direct air capture plants like Wyoming’s Project Bison and Iceland’s Mammoth Factory will no doubt play a role, Canadian company CarbonRun is one of several proposing ocean-based solutions.

The United Nations describes Earth’s oceans as “the world’s greatest ally against climate change,” and they already absorb about 25 percent of humanity’s carbon emissions and 90 percent of the excess heat generated by these emissions. But this mechanism can’t last for long: Ocean acidification combined with rapidly rising sea temperatures is significantly reducing the ocean’s ability to absorb and sequester carbon.

CarbonRun aims to significantly increase ocean water’s carbon capture capacity while simultaneously helping to repair damaged river ecosystems and normalize pH balance.

The technology involved is surprisingly simple: huge limestone-crushing “dozer” silos draw in river water, add alkaline limestone powder and pump it back into the river.

This is a proven technique for restoring rivers that have been made uninhabitable by acid rain, by using alkaline substances to return the river’s pH to a neutral level, allowing fish and other organisms to return.

But limestone, also known as calcium carbonate, also reacts directly with carbon dioxide in the water, turning it into stable bicarbonate that sinks to the bottom, trapping the carbon there almost permanently, allowing the water to absorb more carbon dioxide from the atmosphere.

Admittedly, a huge amount of limestone is required – about two tonnes of limestone for every tonne of carbon you want to clean – but CarbonRun says there are more than enough acid-depleted river systems around the world that could make a big contribution to global CO2 reductions.

The company claims that simply deploying its system in large acidic river systems “could reduce 10-15% of the carbon dioxide needed to meet projected global demand by 2050,” which would undoubtedly be a trajectory-changing contribution.

Of course, there are practical problems: they need a cheap source of limestone as close as possible to the site, as well as a transportation and logistics solution that doesn’t generate huge carbon emissions of its own. They need to convince local residents in various areas that filling their broken rivers with rock dust won’t just make things worse. To make matters worse, they need to meet local regulations and get the local government officials on board.

And if they want to apply the same ideas to the ocean itself, they’ll need to prove they actually work in this much more chaotic environment. The New York Times details some of the trials and tribulations facing a group trying to scale up this form of geoengineering at an ocean scale, by having ships secrete alkaline chemicals as they travel across the ocean.

But CarbonRun has considerable backing. For example, Frontier, a group that includes Google parent Alphabet, Meta, Stripe, and Shopify, is committing $25 million to a pilot project that is expected to capture about 55,442 tonnes of CO2 by 2029.

According to my back-of-the-envelope estimate, this equates to a modest capture cost of around $450 per ton, but it’s still a big improvement over direct air capture, which currently captures CO2 at a rate of about $1,200 per ton and aims to reach levels of $400-600 by 2030.

For reference, the World Economic Forum says the price of carbon capture needs to fall below $200 for the technology to be adopted at scale.

According to Frontier, this limestone powder solution could get to that level fairly quickly. “CarbonRun has a credible near-term trajectory to under $100 per ton,” Frontier’s “The Case for CarbonRun” reads, adding: “Limestone is widely available and inexpensive. The limestone dozer is a simple, inexpensive, proven technology that minimizes R&D costs. It is easy to operate and can be largely automated, keeping labor costs down.”

Carbon Run

A technology with so many potential benefits on a local and global scale is rare, but the clear economic feasibility of this solution, combined with a range of exciting benefits for local ecosystems and biodiversity, certainly makes it very promising.

We look forward to hearing more about this and similar efforts.

Source: CarbonRun via The New York Times