Frontier has established offtake agreements with CarbonRun, a Canadian company that employs river liming, a proven method for river de-acidification, to facilitate carbon removal. Frontier’s buyers will invest $25.4 million to permanently eliminate 55,442 tons of CO₂ from multiple sites between 2025 and 2029, beginning with projects in Nova Scotia, Canada. This marks the first carbon removal offtake utilising river liming.
Frontier, an advanced market commitment aimed at purchasing over $1 billion worth of permanent carbon removal from 2022 to 2030, was initiated by companies such as Stripe, Alphabet, Shopify, Meta, and McKinsey.
The river liming process involves adding crushed limestone (alkalinity) to acidified rivers to mitigate the damage caused by acid rain, a method that has effectively addressed acid rain issues in Scandinavia. However, rising costs have led to a decline in the practice, forcing many regions to reduce or halt river liming efforts. CarbonRun has found that the addition of limestone also enhances rivers’ natural capacity to absorb CO₂ from the atmosphere. The carbon present in the air and land combines with the limestone to create bicarbonate, which eventually flows to the ocean for permanent storage.
The Frontier offtake concentrates on rivers impacted by pollution and climate change, where river liming provides both carbon removal and ecological advantages, including the restoration of salmon and shellfish populations. Expanding river liming to pH-neutral rivers could potentially scale this method to gigaton levels. To support this, Stripe is providing an additional $1 million research and development grant to CarbonRun to further explore the potential of river liming for carbon removal and ecosystem benefits in neutral pH rivers.
River liming represents a new carbon removal strategy that has received limited attention and financial backing thus far. This offtake will enable the necessary data collection to assess how quickly limestone dissolves and the safe quantities that can be added to various types of rivers. This approach is part of a wider initiative for carbon removal through ocean deacidification. To aid buyers in responsibly evaluating these methods, a marine carbon removal buyer’s guide has been created.
Nan Ransohoff, Head of Frontier said, “River liming for carbon removal is cheap, scalable, and measurable. And yet it’s underexplored and underfunded relative to its potential. Moreover, CarbonRun’s work will help establish the foundation for more rigorous evaluation and measurement of aquatic approaches to carbon removal more broadly.”
Luke Connell, Cofounder and CEO, CarbonRun said, “Beyond removing tons of CO₂, this offtake will enable us to do the research on river liming’s potential in different kinds of rivers. Those findings will make the difference between a pathway that is promising into one we can potentially deploy safely and at scale, putting it on the map as a serious contender for gigaton-scale carbon removal.”
Frontier has facilitated purchases on behalf of founding members such as Stripe, Alphabet, Shopify, and McKinsey Sustainability, as well as Autodesk, H&M Group, JPMorgan Chase, Workday, and Salesforce. Other companies, including Aledade, Canva, Match Group, Samsara, SKIMS, Skyscanner, Wise, and Zendesk, have also made purchases through Watershed’s partnership with Frontier.
