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Dr Elliot Chang cofounder and CTO Eion
Dr. Elliot Chang, cofounder and CTO, Eion. Image credit: AgFunder

Enhanced rock weathering startup Eion predicts dramatic growth as DOE pumps $35m into CO2 removal

October 18, 2023

[Disclosure: AgFunderNews’ parent company AgFunder is an investor in Eion]

Eion—a startup with a patented approach to measuring carbon dioxide removed through enhanced rock weathering on farmland—is scaling up aggressively in 2024 as more players commit to buying carbon credits generated by the process.

Rather than applying ag lime (pulverized limestone or calcium carbonate) to farmland to reduce soil acidity, Berkeley-based Eion supplies farmers (via partners such as Southern Ag) with a 1:1 replacement: crushed olivine, a mineral mined in Norway by its partner and investor Sibelco.

Rain and soil acidity dissolve the olivine, which increases soil pH, improves soil health, and absorbs CO2 from the atmosphere. Ultimately, it ends up in rivers and makes its way to the ocean, permanently sequestering carbon. Application levels will vary but are typically around one ton per acre.

Founded by Dr. Elliot Chang (CTO) and Adam Wolf (CEO) in 2020, Eion calculates the carbon dioxide removed from the atmosphere through its mineral weathering process by measuring trace elements in the soil (‘soil fingerprinting’) such as magnesium and nickel.

Eion takes soil samples before the olivine is applied and monitors changes in the soil over time to quantify weathering and the CO2 removed in the process. Typically, 40-70% of the mineral dissolves six to nine months after application, going down to zero after one to four years, when it can be reapplied.

While it makes a small margin on selling the crushed olivine “at cost parity with ag lime or below,” Eion generates revenue by selling carbon credits to companies looking to offset their emissions, says Chang. “We are a carbon dioxide removal company with rigorous verification.”

Although it is initially supplying farmers with olivine, Eion’s approach can be deployed with any silicate rock, says Chang, who is now talking to other players in the enhanced rock weathering (ERW) space about licensing his patented measurement technology to generate another potential revenue stream.

Carbon credits: ‘The important thing in this market is can you remove it and can you prove it?’

While Eion’s business model relies on selling carbon credits, some of which have recently been deemed ‘worthless,’ the devil is in the detail, says Chang.

“The important thing in this market is can you remove it and can you prove it, so you can generate those credits in a reputable and consistent way, so forestry credits have been problematic.

“However, we’ve seen growing interest in enhanced rock weathering, in large part because we can quantify carbon removal,” adds Chang, who was speaking to AgFunderNews after the Department of Energy (DOE) said it would spend $35 million on carbon dioxide removal credits from firms using technologies such as ERW or direct carbon capture (see below).

“The fact that the government is now stepping in and saying it will purchase carbon dioxide removal credits is also an indication of the rapid maturation of the market. And what’s exciting is that enhanced rock weathering and Eion’s technology is lower cost and readily scalable, unlike some carbon capture technologies.”

A paper recently published in the peer-reviewed journal Global Change Biology and co-authored by Chang, researchers from the University of Illinois at Urbana-Champaign, and the Leverhulme Center for Climate Change Mitigation, found that silicate rock application to farmland significantly increased the amount of carbon captured in soybeans, corn, and miscanthus, he says.

“Beyond carbon capture, our findings spotlighted increased yields, particularly in miscanthus—a crucial benefit to our farmer partners. This paper is an important step for Eion, as it represents the first peer-reviewed, accepted direct measurement-based method for quantifying ERW carbon dioxide removal under multi-year, field scale conditions.”

Watch Dr. Chang’s interview with AgFunderNews from March 2023:

Navigating the carbon offset market

So how does the carbon credit system work?

“In the voluntary carbon market (VCM), which many believe will evolve into a much larger compliance-driven market, you submit your methodology and then international verification bodies will come in, validate your approach, and you can generate credits,” he explains.

While the temptation for corporations buying carbon credits might be to pick the cheapest option, they are now facing far more scrutiny, which is prompting interest in credits from firms such as Eion that can provide far more robust documentation to support its ISO-compliant methodology, he says.

There is also growing interest in carbon insetting, whereby buyers purchase credits from companies that are removing carbon dioxide from the industry in which the buyer operates. As an example, where Eion’s enhanced rock weathering removes carbon dioxide from cornfields, an airline using corn-derived ethanol in its aviation fuel can say it is ‘insetting’ if it purchases Eion’s credits.

Trust and transparency

Eion—which now has a team of 15—is currently working with multiple buyers of credits, says Chang.

“A tech company called Stripe was our first customer, and in 2021 they pre-purchased 500 metric tons [worth of carbon credits] from Eion because they really liked what we are doing. We’re also working with other companies interested in buying our credits directly.”

Another route to market is via online marketplaces whereby firms such as Eion list their carbon credits, enabling buyers to compare different options and purchase through a registry that also serves as a public ledger showing that carbon credits have been issued and sold, he explains.

“The above are not mutually exclusive, so once you have a solid, trustworthy registry [direct] buyers might for example require Eion to post that we have issued credits to them on a registry so they can show the world that they bought those credits in a transparent manner.”

Asked about pricing, he says: “Certainly our hope is to have carbon credits from enhanced rock weathering that are as affordable as possible. You see prices anywhere from $100-$500 [per credit, which is the equivalent of one ton of carbon removed], which is still lower than credits for direct air capture, which is about $1,000, but we’re scaling much faster.

“We’re shooting for a more affordable, less than $200-300 price point, for enhanced crop weathering, but funding from catalytic buyers [of these kinds of credits] should help us get there. In a couple of years we should very reasonably hit that price point.”

Dramatic growth

On the upstream side of the business, Eion is predicting dramatic growth next year, says Chang,

“Our first trial was 41 acres, and in 2024 we’re shooting for thousands to tens of thousands of metric tons of application in the Midwest and Southeast combined. And so if you are applying one ton per acre, that’s a lot of land, which is super exciting.”

“With the [$12 million series A] raise last year and the DoE demonstrating its willingness to purchase $35 million in carbon credits from a variety of carbon removal companies, I’m confident that we’re on an accelerated trajectory and probably a couple of years ahead of other companies in this space.”


As part of its new CDR (carbon dioxide removal) Purchase Pilot Prize, the US Department of Energy will provide up to $35 million in cash awards in the form of offtake agreements from the federal government in four carbon dioxide removal pathways:

  • Direct air capture with storage
  • Biomass with carbon removal and storage
  • Enhanced weathering and mineralization
  • Planned or managed carbon sinks

The prize asks applicants to develop carbon dioxide purchase agreements through a pilot project delivering third-party verified carbon dioxide removal. Private entities (for-profits and nonprofits) and academic institutions who meet requirements are eligible to apply. Up to 10 teams will be chosen as grand prize winners, with each team receiving a purchase award prize of up to $3 million.

“The prize represents the first time the United States federal government will purchase high-quality carbon removal credits from commercial-scale activities,” says Brad Crabtree, assistant secretary of fossil energy and carbon management. “It will define how to evaluate success for carbon dioxide removal technologies and how purchase contracts can advance innovation, all while addressing environmental, climate, and community priorities.”

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