CO2 Sequestration at Frontier: Assessing the Potential for Climate Change Challenges and Implications for Soil Chemical Composition and Fertilization

Stripe, Alphabet, Shopify, and a slew of other companies plan to spend more than $57 million cumulatively to fight climate change by spreading crushed rock over farmland.

The companies hope that alkaline rocks will absorb CO2 from the air when they break down. This happens when rain, wind and waves wash away the rocks. The process of trapping CO2 is not assisted.

There are limited options for companies with negative emissions. Frontier’s purchases are essentially down payments on ideas that are still in their infancy—generally too hard to verify or too expensive, or both, to attract a significant customer base. At Frontier and at other places, we’re trying to evaluate whether the field is on a trajectory to get to climate-relevant scale. The group begins with small pre- purchases meant to help promising startup, and then moves on to bigger agreements for larger amounts of carbon that can be used to meet emissions goals.

The hard part is knowing how much carbon dioxide has been safely stored. The company says it does this by taking soil samples, monitoring the chemical composition of the soil as a way to judge how much CO2 was removed. It is a process that was created from research at Yale University.

The process can be expedited if people grinding basalt into gravel or dust. Doing so and then splaying the crushed rock out across a swath of land increases surface area and exposes it to more ambient carbon dioxide to absorb.

Farmers can spread basalt for free to manage the pH balance of the soil if they use it. The carbon dioxide that is trapped in the air as a bicarbonate is produced by the basalt. Eventually, the bicarbonate moves through groundwater out to the sea where Lithos expects it to be stored for at least 10,000 years or longer.

It’s crucial to get this part right, not only to assure that companies are getting what they pay for but also to show that they’re actually combating climate change

Data shared by the company in a pre-print study essentially show “an absolute maximum estimate of what can be, and the reality unfortunately is much more complicated,” he added. Namely, there’s a risk of overestimating how much carbon dioxide has been sequestered when not fully accounting for how fertilizers in the soil affect the process.

Frontier: A $57.1 million boost on basalt dust to turn enhanced weathering into a viable carbon dioxide mitigation solution for agriculture and coastal areas

Enhanced weathering can have potential side effects to try to avoid. Flooding a particular area with too much bicarbonate is one issue that could affect the ecosystems. The environmental footprint of mining, crushing, and transporting rock need to be taken into consideration, too. Lithos uses waste material from quarries to minimize those kinds of impacts. Dust shouldn’t get airborne and affect air quality at farms.

“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.

The concern among environmental advocates is that companies pay to take carbon dioxide out of the atmosphere instead of focusing on trying to reduce fossil fuel emissions.

On Thursday, Yap’s startup, Lithos Carbon, got a $57.1 million boost for its attempt to turn basalt dust into a viable climate solution. Frontier is a benefit corporation backed by a consortia of companies that are trying to finance promising approaches to CDR. Lithos says it will use the funds to soak up 154,000 tons of CO2 by 2028, by sprinkling basalt dust on thousands of acres of US farmland. The average US car emits about 4 tons of CO2 each year.

This $57.1 million offtake agreement for enhanced weathering is the first of its kind, according to Frontier. That’s supposed to cover the costs of sequestering more than 154,000 tons of CO2 by 2028, equivalent to taking about 34,000 cars off the road for a year. Breaking down to roughly $370 per ton of CO2 removed, it’s still costly but notably cheaper than new industrial plants being built to filter the greenhouse gas out of the air for around $600 a ton.

That accounting trick has been easier to prove out on paper than in practice. Many companies would have once turned to buying carbon offsets from activities like protecting forests that would otherwise be felled. But some have been trying to move away from those scandal-plagued and often short-lived approaches and into more durable techniques for carbon removal.

One of the larger deals is the Lithos purchase. It charges $370 per ton for carbon removal, but only 25 percent of the cost is for field monitoring and modeling to verify carbon is being sequestered away from the atmosphere for the long term. Frontier believes that there is a path for Lithos to remove CO2 for less than 100 per ton, and at a rate of approximately half a billion tons per year.

The strategy has the benefit of piggy-backing on things that humans already do, Yap says. That’s in contrast with techniques like direct air capture, which involves building industrial plants that suck out carbon from the atmosphere. It is easy to measure carbon taken out of the air, but critics say removing enough carbon will be difficult because of the resources required.