Frontier has secured offtake agreements with CarbonRun, a Canadian company that employs river liming—a proven method of river de-acidification—to achieve carbon removal.
Frontier buyers will invest $25.4 million to permanently eliminate 55,442 tons of CO₂ from 2025 to 2029 across multiple sites, beginning with initiatives in Nova Scotia, Canada. This marks the first carbon removal offtake agreement utilizing river liming.
River liming involves adding crushed limestone (alkalinity) to acidified rivers to mitigate the effects of acid rain. This technique has effectively addressed acid rain issues in Scandinavia. Still, rising costs have led to a decline in its use, forcing many regions to reduce or halt their river liming efforts.
CarbonRun has found that limestone helps restore river acidity and enhances the rivers’ capacity to absorb CO₂ from the atmosphere.
When atmospheric and land-based carbon enters the rivers, it reacts with the limestone to form bicarbonate, which then travels to the open ocean for permanent storage.
The Frontier offtake targets rivers affected by pollution and climate change, where river liming provides both carbon removal and ecological benefits, such as the restoration of salmon and shellfish populations.
By expanding river liming efforts to pH-neutral rivers, this method has the potential to scale up to gigaton levels. To support this, Stripe is providing an additional $1 million in research and development funding to CarbonRun to explore the efficacy of river liming in neutral pH environments for carbon removal and ecosystem enhancement.
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.”
She added, Moreover, CarbonRun’s work will help establish the foundation for more rigorous evaluation and measurement of aquatic approaches to carbon removal more broadly.”
According to the statement by Frontier, CarbonRun’s approach is compelling for several reasons:
1. Cost-Effective Solution: With limestone being widely available and inexpensive, CarbonRun is on track to achieve costs below $100 per ton. The use of simple, automated limestone dosers keeps research and development expenses low and minimizes labor costs.
2. Straightforward Measurement: The method allows for direct measurement of water chemistry upstream and downstream of treatment sites, enabling accurate assessment of CO₂ removal without relying on emerging scientific models.
3.Established Practice: River and lake liming, initially developed as a conservation technique, has effectively addressed acid rain issues, improving river health and salmon stocks. This established practice means scaling up doesn’t require new engineering solutions.
4. Expert Team: CarbonRun boasts a unique combination of expertise in both river liming for carbon removal and river ecology, particularly in salmon rehabilitation.
5. Strong Community Engagement: The company has garnered support from local governments, First Nations, and environmental organizations. Their best-in-class community benefits plan actively involves local stakeholders in site selection, project design, and data sharing, facilitating rapid scaling.
