The archive · Climate & Energy · Technical decision · 2020–2026
Heirloom's limestone DAC bet: America's first commercial plant, then $150M Series B
Heirloom uses limestone to pull CO2 from the air; Tracy became America's first commercial DAC plant, and a 2024 $150M Series B funds Louisiana hubs.
Heirloom Carbon Technologies
What the business is
Building direct air capture facilities that use limestone to pull carbon dioxide out of the atmosphere and permanently store or sequester it, selling verified removal credits.
Starting capital：$150M Series B (December 2024) led by Future Positive and Lowercarbon Capital
How it started
Founded in 2020 in San Francisco, Heirloom built its process around limestone's natural ability to absorb CO2, using heat, renewable electricity and a proprietary accelerator to speed the cycle from weeks to days. Early purchase agreements with Microsoft and Frontier (Stripe) created demand before the technology was cheap.
What happened
In November 2023 Heirloom unveiled its Tracy, California facility — America's first commercial direct air capture plant, rated at up to 1,000 tons of CO2 a year and running on renewable power, with CarbonCure permanently storing the CO2 in concrete. By June 2024 it had logged about 1,000 hours of operation and announced two Louisiana facilities storing CO2 in CapturePoint Class VI wells.
How it ended up
In December 2024, after a year of Tracy operations and the first funding allocation under the DOE's Direct Air Capture Hub program, Heirloom closed a $150M Series B led by Future Positive and Lowercarbon Capital, with Japan Airlines, Mitsubishi, Mitsui, MOL and Siemens among the participants. It is building a 17,000-ton-a-year facility in Shreveport (targeted operational in 2026) and a Project Cypress unit of up to 300,000 tons a year, targeting $200–300 per ton industry-wide by the early 2030s.
Background
Heirloom Carbon, founded in San Francisco in 2020, is betting that direct air capture can become cheap enough to matter commercially. Its technology uses crushed limestone: the rock absorbs CO2 from the air, the company accelerates the natural cycle, then heat releases the CO2 for permanent storage or use.
In November 2023 it unveiled its Tracy, California facility, described as America's first commercial DAC plant, rated at up to 1,000 tons of CO2 a year and powered by renewable energy, with CarbonCure permanently locking captured CO2 into concrete. Microsoft and Frontier were early buyers of its removal credits.
A year later Heirloom closed a $150M Series B led by Future Positive and Lowercarbon Capital, with airlines, trading houses and manufacturers — Japan Airlines, Mitsubishi, Mitsui, MOL and Siemens — participating. The company says today's $600–1,000 per ton industry cost must fall to $200–300 by the early 2030s, with $100 per ton the long-term target.
The capital funds two Louisiana facilities: a 17,000-ton-a-year plant targeted to open in 2026 and a Project Cypress hub unit of up to 300,000 tons a year, both storing CO2 in Class VI wells operated with CapturePoint. The bet — that policy support and scale can make DAC a real business — is still being tested.
What has to be true
- Limestone is cheap and everywhere, so the cost curve starts near $10 a ton of absorbent instead of specialty solvents.
- Early contracts with Microsoft and Frontier created revenue and credibility before the plant reached scale.
- 45Q tax credits and DOE hub funding, including Project Cypress's up to $600M, de-risked the first megaton-scale builds.
- Corporate investors from airlines and trading houses signal buyers that see DAC as one of the few options for their emissions.
What can be applied
If the incumbent chemistry is already cheap, build on it: Heirloom started from limestone, the cheapest CO2 absorbent, and used early buyer commitments to fund the cost-down path to $100 per ton.
Aftermath
As of September 2026, Tracy remains the first commercial DAC facility in the US, running at about 1,000 tons of CO2 a year while Heirloom builds toward megaton scale in Louisiana: the first facility (17,000 tons/year) targets 2026 and the Project Cypress unit (up to 300,000 tons/year, 100,000 in phase one) targets 2027, storing CO2 in CapturePoint Class VI wells. The $150M Series B funds automation and process improvements; the company sees profitability at $200–300 per ton. Industry prices remain near $600–1,000 per ton today, so the cost-curve bet is unresolved.
Sources
- A Look at America's First Direct Air Capture Facility
- Heirloom Integrates Direct Air Capture in Northwest Louisiana
- Heirloom Carbon raises $150M to remove CO2 from the air using rocks
- As we conclude this pivotal year, we remain committed to removing billions of tons of carbon dioxide from the air
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