ClimateTicker

Heirloom Carbon

71Credible Contributor· Provisional
0 followersCarbon removal·Brisbane, CA, USA·Founded 2020
www.heirloomcarbon.com

US DAC company that accelerates the natural carbon mineralisation of limestone from years to days, with its first commercial facility in California and a second announced in Louisiana.

71/100
Credible Contributor· Provisional

ClimateTicker Green Score · how it's calculated

Greenwashing risk: lowData confidence: medium

Why it's on ClimateTicker

Heirloom Carbon operates America's first commercial DAC facility using an accelerated limestone mineralization process that genuinely removes CO2 from the atmosphere and stores it permanently — either underground or in concrete. The core technology is scientifically credible and independently monitored, but the company remains early-stage with only ~1,000 tonne/year operational capacity and a far larger 300,000 tonne/year pipeline still under development. Investors should credit the real mitigation impact while discounting aspirational billion-ton targets that are years and billions of dollars away.

mitigationHeirloom sells permanent carbon dioxide removal credits — currently priced at $600–$1,000 per tonne — to corporate buyers such as Microsoft, Stripe, Meta, JPMorgan, and Shopify, and is scaling capacity via DOE-backed Project Cypress in Louisiana to drive down costs through economies of scale.

Commitments & Certifications

other: DOE Project Cypress Award — Federal oversight with go/no-go phase reviews ↗other: Third-party credit monitoring (claimed, verifier not publicly named) ↗

Controversy & Greenwashing Watch

lowUnquantified lifecycle emissions from limestone calcination kiln

Heirloom's process requires heating limestone to ~900°C to release CO2 before re-carbonation; while the company claims 100% renewable energy powers facilities, no independently published full lifecycle net-removal accounting (including kiln Scope 1/2 emissions and embodied carbon) has been found, creating a transparency gap that could affect claimed net-removal per credit.source ↗

lowProject Cypress funding uncertainty under Trump administration review

The Project Cypress DOE funding went largely quiet during a broad federal spending review in late 2024–early 2025, with project developers keeping public statements minimal; DOE clearance was subsequently confirmed in April 2026, but this episode highlights political/funding risk for federally dependent scale-up.source ↗

lowBillion-ton 2035 target lacks credible pathway

Heirloom's stated goal of removing 1 billion tonnes of CO2 by 2035 is not backed by any published science-based target, phased milestone plan, or independent validation — representing a significant gap between marketing ambition and verified roadmap.source ↗

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