A technique originally developed to combat acid rain has the potential to pull an enormous amount of carbon dioxide out of the atmosphere – while helping to deacidify oceans, restore rivers and boost biodiversity and fish populations.
Decarbonization is a brutally difficult and expensive challenge for some sectors – so bulk carbon capture initiatives will definitely be needed as humanity fights to keep the most devastating impacts of climate change at bay.
And while huge direct air capture plants like Project Bison in Wyoming and the Mammoth plant in Iceland can definitely play a part, Canadian company CarbonRun is one of several putting forth a solution that's based on the ocean.
The UN describes Earth's oceans as "the world's greatest ally against climate change," already absorbing some 25% of humanity's carbon emissions, as well as soaking up 90% of the excess heat these emissions are creating. But this mechanism can only help for so long; ocean acidification as well as dramatically rising sea temperatures are combining to significantly reduce the ocean's ability to absorb and sequester carbon.
CarbonRun's play is to supercharge the carbon-capturing ability of seawater, while simultaneously helping to rehabilitate damaged river ecosystems and re-balancing pH back toward normal.
The technology involved is remarkably simple: whopping big limestone rock-crushing 'doser' silos that draw river water through, add alkaline limestone powder and return it back into the river.
It's a technique that's already well proven in restoring rivers that have become uninhabitable to marine life due to acid rain; the alkaline material pushes the river's pH back towards neutral, and before long, the fish and other creatures return.
But limestone, also known as calcium carbonate, also reacts directly with carbon dioxide in the water, turning it into a stable bicarbonate that sinks to the bottom and keeps the carbon there more or less permanently, allowing the water to absorb more carbon dioxide from the atmosphere.
You do need rather a lot of limestone – about two tons per ton of carbon you wish to remediate – but CarbonRun says there are more than enough acid-degraded river systems around the world to make a significant contribution to global CO2 reduction.
Deploying its system on these large, acidified river systems alone, the company says it could "draw down 10-15% of the required carbon dioxide to meet the global need projected by 2050." That would certainly be a trajectory-altering contribution.
Of course, there are practicalities involved; you need cheap sources of limestone as close as possible to the site, as well as transport and logistics solutions that don't make too much CO2 in their own right. You need to convince locals in a variety of different regions that filling their poor broken river with rock dust won't just make things worse – and worse, you need to satisfy local regulations and get the idea past local government officials.
And if you want to apply the same idea to the oceans themselves, you need to prove it actually works in this far more chaotic environment; the New York Times details some of the trials and tribulations faced by groups trying to ramp this form of geoengineering up at the ocean scale, potentially by having ships secrete alkaline chemicals as they travel across the seas.
But CarbonRun has some pretty decent backing behind it. For example, Frontier, a group including Google parent company Alphabet, as well as Meta, Stripe and Shopify, is in to the tune of US$25 million, for a pilot project expected to capture some 55,442 tons of CO2 by 2029.
According to the back of my envelope here, that equates to a less-than-stellar cost of US$450-odd per ton captured. But that's still a huge improvement on the direct air capture business, which is currently pulling CO2 down at a rate of around US$1,200 per ton, with aspirations of reaching the US$400-$600 level by 2030.
For reference, the World Economic Forum says carbon capture prices will need to get below US$200 before the technology is likely to reach widespread adoption at scale.
According to Frontier, this limestone dust solution could hit that level reasonably rapidly: "CarbonRun has a credible, near-term trajectory to less than $100/ton," reads Frontier's "case for CarbonRun," going on to explain how: "Limestone is widely available and cheap. Limestone dosers are a simple, inexpensive and proven technology which makes R&D costs minimal. They’re easy to operate and can largely be automated, limiting labor costs."
It's rare to see a technology with so many potential benefits at the local and global scale, but this solution's apparent economic viability, combined with an impressive set of local ecological and biodiversity benefits, certainly looks very promising.
We look forward to hearing a lot more about this initiative and others like it.
Source: CarbonRun via New York Times