Heirloom

The Warehouse That Eats the Sky

In a nondescript industrial building in Tracy, California, trays of white powder sit in the open air. Within three days, that powder - calcium oxide derived from limestone - absorbs CO2 directly from the atmosphere, becomes calcium carbonate, and gets fed into an electric kiln. The kiln releases concentrated CO2, which gets pumped underground or locked into concrete. The powder resets and starts again.

This is Heirloom Carbon's commercial facility - the first of its kind in the United States. It's not a science experiment. It's a factory. And it's already fulfilling purchase orders from Microsoft, Stripe, Shopify, JP Morgan, and a growing list of corporations that have learned the difference between "carbon neutral" (often meaningless) and carbon removal (definitively not).

Heirloom's current facility captures roughly 1,000 metric tons of CO2 per year - a number that sounds modest until you consider that all 18 DAC facilities operating globally capture about 10,000 tons combined. And Heirloom's next facilities in Louisiana would handle 320,000 tons annually.

The Problem Nobody Wanted to Solve

Carbon dioxide stays in the atmosphere for hundreds to thousands of years. Cutting emissions - however necessary - does nothing about the roughly 2.5 trillion tons already up there. The IPCC has been saying since 2018 that reaching 1.5C requires not just emissions reductions but active removal of historical CO2. The conversation about that second part has been, to put it charitably, slow.

Direct air capture - pulling CO2 directly from ambient air - has existed as a concept since the 1990s. The problem has always been cost. The two most developed technologies before Heirloom used synthetic chemical sorbents and proprietary contactors, which are energy-intensive and expensive to manufacture. Climeworks' Mammoth plant in Iceland costs roughly $1,000 per metric ton. The market needs something closer to $100.

Heirloom looked at the periodic table and found their answer sitting in limestone quarries across the planet.

From a PhD Thesis to a Commercial Plant

The company begins, somewhat unusually, in academic literature. Noah McQueen's doctoral research at the University of Pennsylvania under Jennifer Wilcox - one of the field's leading researchers - described a process for using calcium oxide to absorb atmospheric CO2. It wasn't just theory. The thermodynamics were sound. The feedstock was abundant and cheap. The energy requirements were manageable with renewable power. What it needed was someone who wanted to build a company around it.

That someone was Shashank Samala. A second-time founder who had previously co-founded Tempo Automation and worked at Square, Samala had spent time at Carbon180 as an Entrepreneur in Residence, learning the carbon removal space. He had also grown up in Southeast India and watched climate change affect agriculture and water security in ways that most Silicon Valley founders encounter only in research papers.

Together with co-founder Zack Bloom, they incorporated Heirloom in 2020. Breakthrough Energy Ventures, Bill Gates' climate fund, backed their initial development. The Series A, announced in March 2022, brought in $53 million - one of the largest investments in new carbon removal technologies at the time.

The Technology: Geology at Manufacturing Speed

The process Heirloom runs is called enhanced mineral weathering - specifically, accelerated carbonation of calcium oxide. Here is the short version. Limestone (calcium carbonate) is heated to release CO2, producing calcium oxide. That calcium oxide is spread across large trays and left outdoors. Over three days, it reacts with CO2 in ambient air and reverts to calcium carbonate. The trays go back into the kiln, releasing concentrated CO2 for permanent storage. Repeat.

In nature, this cycle takes geological time. Heirloom does it in three days and runs it in continuous loops. The limestone feedstock is essentially free by industrial standards. The energy requirement is heat, which renewable electricity can provide. The CO2 output is concentrated enough to inject underground or pass to storage partners.

Their partnership with CarbonCure Technologies adds another dimension: in February 2024, Heirloom demonstrated the world's first permanent storage of atmospheric CO2 inside concrete. The CO2 gets injected into fresh concrete during mixing, where it mineralizes and gets locked into the structure permanently. The buildings being built today could, in principle, be made of yesterday's CO2.

The Proof: Who's Paying and Why

The customers tell the story better than any press release. Microsoft has committed to 315,000 metric tons of CO2 removal from Heirloom - enough to fill roughly 23,000 Olympic swimming pools with CO2. Stripe, one of the earliest and most rigorous buyers in the voluntary carbon market, has purchased from Heirloom. So have JP Morgan, Shopify, Meta, McKinsey, H&M, and Autodesk.

These are not companies known for fuzzy accounting. Stripe in particular helped develop the Frontier Climate framework, which requires carbon removal purchases to be permanent, measurable, and additional. Heirloom's removals are third-party monitored and verifiable. The CO2 doesn't come back.

The investor list is equally pointed. Breakthrough Energy Ventures, Lowercarbon Capital, Future Positive - these are climate-specific funds that have turned away hundreds of pitches. Returning investors doubling down at Series B (as Lowercarbon, Ahren, Breakthrough, and Carbon Direct all did) is a meaningful signal. New investors include Japan Airlines, Mitsubishi Corporation, Mitsui & Co., and Siemens Financial Services - a set of corporate partners that suggests the global infrastructure buildout is beginning to get serious.

Funding History

What They've Actually Done

• Opened America's first commercial Direct Air Capture facility in Tracy, California (November 2023)
• First US facility to capture, permanently sequester, and fulfill commercial CO2 removal orders
• World's first permanent storage of atmospheric CO2 in concrete (February 2024)
• Selected for U.S. Department of Energy's Project Cypress DAC Hub program
• Named to Fast Company's Most Innovative Companies 2024
• Named to TIME's America's Top GreenTech Companies
• Raised $354M+ across Series A and Series B
• Announced $475M Louisiana investment for North America's second DAC facility
• Built Tracy facility entirely with union labor (UA Local 442, IBEW 595)
• Refuses oil major investment on principle - unusual and consistent

The Billion-Ton Bet

Heirloom's stated goal is to remove 1 billion metric tons of CO2 from the atmosphere by 2035. To put that in context: global CO2 emissions currently run around 37 billion tons per year. One billion tons is approximately what 220 million cars produce in a year. It's a large number. Getting there from 1,000 tons today requires a scale-up of roughly one million times in twelve years.

The company isn't shy about how audacious this is. Their bet is that the cost curve for limestone-based DAC will follow the pattern set by solar panels, lithium-ion batteries, and wind turbines: a technology that looks impossibly expensive in its early years becomes cheap at scale because the underlying inputs (limestone, electricity, land) are abundant and the manufacturing process improves with repetition.

The Louisiana facilities will test this thesis at a scale that actually matters. Combined, they would have roughly 32 times more capacity than all currently operating DAC facilities globally. That's either the beginning of an industry or a very expensive learning experience. Heirloom is betting on the former.

Why It Matters Tomorrow

The voluntary carbon market has a credibility problem that has been well-documented. Offset schemes based on forestry, avoided emissions, or vague sustainability promises have repeatedly failed to deliver what was sold. The market is slowly, grudgingly, learning to distinguish between offsets that reduce emissions and removals that actually extract existing CO2 - and within removals, between temporary storage (biomass that can burn, forests that can die) and permanent storage (underground or in concrete).

Heirloom is positioning itself at the intersection of that shift: permanent, measurable, verifiable, and eventually cheap enough to work at scale. Their refusal to take oil major investment - while competitors like Carbon Engineering were acquired by Occidental Petroleum - is a differentiating stance in a market where greenwashing is endemic.

There is also the employment story. Heirloom has built its facilities with union labor and structured community governance around new facilities in Louisiana - a region that has historically been on the receiving end of energy infrastructure without much of the economic benefit. Whether this holds as the company scales is a legitimate question. But the stated intent is deliberate and specific.

Watch & Learn

Interviews, facility tours, and technology explainers from the Heirloom team.