It’s odd to work every day developing an industry we wish didn’t have to exist. But that’s exactly what we’re doing. Each morning, we wake up and consider the different ways to pull carbon dioxide from the atmosphere—and the technical and economic feasibility of those methods.

One of the most promising approaches is direct air capture (DAC), a suite of technologies that use materials such as specially engineered sorbents or limestone rocks to suck already-emitted CO2 from the atmosphere. Pairing this technology with permanent storage locks that carbon away so it no longer contributes to warming.

Some experts argue DAC is distracting from the need to quickly and rapidly decarbonize every sector of our economy. Thirty years ago, we would have agreed with them.

But over the last three decades, we’ve released half of all the CO2 emitted since 1750 and we continue to emit over 35 billion tons of the gas each year. Carbon removal will be required to pull us back from the brink of climate disaster.

Under best-case emissions reductions scenarios, we’ll still need to remove six to 10 billion tons of already-emitted CO2 per year to keep warming below 1.5°C and to compensate for hard-to-abate emissions from industries like agriculture and aviation.

We’ve backed ourselves into a corner—we need to stop emitting CO2 and take it out of the atmosphere.

Deploying DAC at the scale needed to meaningfully address climate change will only be possible if the technologies are economically viable. In the industry, $100 per ton of CO2 removed from the atmosphere is widely considered the threshold for economic viability.

Some DAC systems currently report costs near $1,000 per ton of CO2 removed. This price tag is well above both the threshold and the cost of many other kinds of decarbonization, like replacing emissions-intensive coal plants with renewable electricity.

Operating a DAC system involves many costs, including equipment, materials and labor. One of the largest cost drivers, however, is the energy required to pull CO2 from the atmosphere. Theoretically, the minimum amount of energy required to remove one metric ton of CO2 from the air is 125 kilowatt hours (kWh), about the same amount of energy as it takes to power a 50-watt light bulb for the better part of a year.

No DAC technology is 100% efficient (meaning the technology uses the same amount of energy as the minimum 125 kWh to pull carbon from the air). But a system with 10% efficiency is possible. Many energy sources today are much more efficient; wind turbines, for example, can be 30 to 45% efficient.

At 10% efficiency, the expected amount of energy required to remove a ton of CO2 is 1,250 kWh. If we assume an electricity price of roughly $0.045/kWh—consistent with average U.S. renewable electricity prices in the third quarter of 2022—the minimum cost to remove one ton of CO2 is $56. That’s at today’s price, which does not factor in the predicted continued decline in the cost of renewable energy.

With declining electricity costs, reasonable carbon removal costs are more than possible.

The math (and existing literature) suggests the cost of DAC could drop from today’s prices by a factor of 10. Industry precedent also supports this assertion. For example, in 1976, solar photovoltaic modules cost over $106 per watt. In 2019, the cost dropped to around $0.4/W. This more than 99% drop is one of many examples.

With every ton of CO2 we remove from the atmosphere, we are learning how to do it even better. Many factors will determine how cost changes as the technology scales: investing in research and development, implementing manufacturing improvements and achieving economies of scale.

If the time comes when greenhouse gas emissions have been reduced to zero and enough CO2 has been pulled from the atmosphere to restore balance to our climate, we’ll happily cheer as DAC technologies are relegated to the history books.

Until then, direct air capture will be a key part of saving our planet.

Editor’s note: Heirloom’s investors include Breakthrough Energy Ventures, a program of Breakthrough Energy, which also supports Cipher.