aid: heirloom
name: Heirloom
description: >-
  Heirloom Carbon Technologies, Inc. is a San Francisco Bay Area direct air capture (DAC)
  company that removes carbon dioxide from the atmosphere by accelerating the natural
  mineralization of limestone. Heirloom spreads calcium oxide on vertical trays where it
  re-absorbs atmospheric CO2 in days rather than years, then uses electric kilns to release
  the captured CO2 for permanent geologic or in-concrete storage. The company opened the
  first commercial DAC facility in the United States, sells permanent carbon removal credits
  to individuals, businesses and enterprises, and has signed offtake agreements with
  Microsoft, Frontier, United's Sustainable Flight Fund and CarbonCure. It is an industrial
  climate-technology company; it does not operate a public developer program or API.
image: https://cdn.prod.website-files.com/639c8f646dc35afd81aeebc2/651aee726de0080273ee5ad9_Heirloom_SocialShare.jpg
url: https://raw.githubusercontent.com/api-evangelist/heirloom/refs/heads/main/apis.yml
x-type: company
x-source: harvest:secondary-market
x-tier: stub
x-tier-reason: harvest
specificationVersion: '0.20'
created: '2026-08-22'
modified: '2026-08-22'
tags:
- Company
- Carbon Removal
- Direct Air Capture
- Climate Technology
- Carbon Credits
- Sustainability
- Energy
- Climate
apis: []
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: DomainSecurity
  url: security/heirloom-domain-security.yml
- type: Website
  url: https://www.heirloomcarbon.com/
- type: Blog
  url: https://www.heirloomcarbon.com/news
- type: Support
  url: https://www.heirloomcarbon.com/contact-us
- type: Pricing
  url: https://www.heirloomcarbon.com/remove-co2
- type: TermsOfService
  url: https://www.heirloomcarbon.com/terms
- type: PrivacyPolicy
  url: https://www.heirloomcarbon.com/privacy
- type: SecondaryMarket
  url: https://www.hiive.com/securities/heirloom-stock
x-enrichment:
  date: '2026-08-22'
  status: minimal
  artifacts_added: 3
  pass: local-v1
x-coverage:
  state: none
  reason: not-a-software-company
  detail: >-
    Heirloom Carbon Technologies is an industrial direct air capture company that sells
    permanent CO2 removal credits through a Webflow storefront; its 46-URL sitemap contains
    no developer, docs or API page, no api./docs./developer./app./portal. subdomain resolves
    in DNS, and every /openapi.json, /llms.txt, /graphql and /.well-known/* path 404s on both
    www and apex.
  evidence:
  - url: https://www.heirloomcarbon.com/sitemap.xml
    status: 200
  - url: https://www.heirloomcarbon.com/openapi.json
    status: 404
  - url: https://www.heirloomcarbon.com/llms.txt
    status: 404
  - url: https://www.heirloomcarbon.com/.well-known/agent-card.json
    status: 404
  - url: https://heirloomcarbon.com/.well-known/security.txt
    status: 404
  checked: '2026-08-22'