Heirloom Carbon

Heirloom is one of the few DAC companies with a running commercial plant, a federal anchor program, and a blue-chip buyer list — the trifecta the sector mostly promises and rarely assembles. Its limestone-looping approach accelerates the natural weathering of cheap, abundant crushed limestone so it reabsorbs atmospheric CO2 in days rather than years, then heats the carbonate to release a concentrated stream and regenerates the limestone to capture again. Using limestone as the sorbent sidesteps the expensive proprietary chemicals rival DAC designs depend on, and the process runs at lower thermal demand than high-temperature liquid-solvent systems. Heirloom operates North America's first commercial DAC facility in Tracy, California, and is the technology partner on Project Cypress, the DOE-backed Louisiana regional DAC hub eligible for up to $600M in federal funding. In June 2024 it committed to two facilities in northwest Louisiana at the Port of Caddo-Bossier near Shreveport, with the first phase scaling toward 100,000 tonnes per year — a step change from demonstration volumes. It has raised over $200M including a $150M Series B (December 2024, Future Positive and Lowercarbon Capital), and its offtake roster — Microsoft, Stripe, Shopify, United Airlines — is exactly the set of durability-focused buyers with the willingness to pay today's premium prices. Heirloom sits at the intersection of the two forces that could carry DAC to scale: government demonstration dollars and corporate net-zero demand.

DAC remains the most expensive removal pathway per tonne, and Heirloom's economics still depend on capture costs falling by a factor no one has yet demonstrated at commercial scale — the Tracy plant proves the chemistry, not the price. The scale gap is stark: the Louisiana phase-one target of ~100,000 tonnes per year does not begin operations until 2027, and even that is a rounding error against the megatonne volumes DAC must reach to matter, each increment demanding fresh nine-figure capital. Heirloom's federal leg is a double-edged one — Project Cypress money flows through DOE's demonstration office, and the entire U.S. DAC-hub program is exposed to the political and budgetary risk of an administration less committed to climate spending, with the promised $600M only partly obligated. Limestone looping still requires substantial heat to calcine the carbonate; the clean-energy sourcing that makes the removal genuinely additive adds cost and siting complexity. And the buyer base, while prestigious, is thin and concentrated in a handful of voluntary purchasers whose willingness to pay $500-plus per tonne is a function of ESG budgets that soften in downturns. Competitors — Climeworks, 1PointFive, and a dozen newer entrants — are chasing the same DOE dollars and the same buyers. Heirloom's lead is real, but it is a lead in a race whose finish line (cost-competitive, policy-durable, gigatonne DAC) remains years and billions away.