What is Direct Air Capture (DAC)?

Direct Air Capture, often abbreviated as DAC, is a technology designed to remove carbon dioxide directly from the ambient air.

Unlike traditional carbon capture that focuses on the concentrated streams of gas coming out of industrial smokestacks, DAC units can theoretically be placed anywhere.

They act as industrial scale filters for the atmosphere.

For a founder looking at the climate tech space, DAC represents a category of hardware known as engineered removals.

It is distinct from nature based solutions like planting trees because it uses mechanical and chemical engineering to achieve the same goal at a much faster rate and with a smaller land footprint.

In a startup context, DAC is currently one of the most capital intensive and technically challenging fields to enter.

It requires a deep understanding of thermodynamics, fluid dynamics, and chemical engineering.

There are two primary methods currently being used to pull carbon from the sky.

The first method is liquid DAC.

In this system, air is passed through a chemical solution, often a strong base like potassium hydroxide.

The carbon dioxide reacts with the liquid and is trapped as a salt.

That liquid is then processed through several more steps to release the pure carbon dioxide and recycle the original chemicals.

This process usually requires high heat, often around 900 degrees Celsius, which is a major engineering hurdle for startups trying to maintain a low carbon footprint.

The second method is solid DAC.

This involves solid sorbent filters that chemically bind with carbon dioxide.

When these filters are full, they are heated or placed under a vacuum to release the concentrated gas.

Solid systems usually operate at lower temperatures, which makes them easier to power with waste heat or renewable energy.

As a founder, choosing between these two paths defines your entire supply chain and your energy requirements.

It is vital to distinguish DAC from point source carbon capture and storage (CCS).

Point source capture happens at the site of emission, such as a coal plant or a cement factory.

Because the concentration of carbon dioxide in a smokestack is very high, it is much easier and cheaper to capture.

Direct Air Capture deals with ambient air, where the concentration of carbon dioxide is only about 0.04 percent.

Imagine trying to find a few specific grains of blue sand in a giant bucket of white sand.

That is the challenge of DAC.

Because the concentration is so low, you have to move massive amounts of air through your machines.

This is why DAC is currently much more expensive per ton of carbon captured than point source methods.

However, DAC is unique because it can address legacy emissions and emissions from sources that are hard to capture, like airplanes or cars.

It is a tool for cleaning up the existing atmosphere rather than just preventing new pollution.

If you are building a DAC startup, your primary product is usually a carbon removal credit.

Companies that cannot fully eliminate their own emissions pay DAC operators to remove an equivalent amount of carbon from the air.

There is also the option of carbon utilization, often called CCU.

In this scenario, the captured carbon is used as a raw material for other products.

• Synthetic aviation fuels
• Carbonated beverages
• Building materials like concrete
• Manufacturing polymers and plastics

Selling the carbon as a physical product can provide immediate revenue while the carbon credit markets mature.

However, the cost of capture must drop significantly for these products to be price competitive.

Currently, capturing a ton of carbon via DAC can cost anywhere from 500 to 1,000 dollars.

The industry goal is to reach 100 dollars per ton.

Reaching that goal requires massive improvements in material science and energy efficiency.

One of the biggest hurdles for any DAC founder is the energy penalty.

It takes energy to run the fans that move the air.

It takes even more energy to heat the chemicals to release the captured carbon.

If the energy you use comes from fossil fuels, you might end up emitting more carbon than you capture.

This means DAC startups must be strategically located near abundant, cheap, and clean energy sources.

Geothermal, nuclear, or dedicated solar arrays are often the only viable options.

Scaling these systems also presents a massive manufacturing challenge.

You are essentially building large scale chemical plants that need to be modular and reliable.

Maintenance costs can be high because the sorbents and chemicals degrade over time and must be replaced.

There are several questions that the industry has not yet fully answered.

How will the global policy landscape change to support high cost removals?

Will customers be willing to pay a premium for permanent removals compared to cheaper, less permanent options like forestry?

We also do not know which chemical pathways will prove to be the most durable over decades of operation.

As a founder, you have to decide if you are going to be a technology provider or a plant operator.

Are you building the machines and selling them, or are you building the projects and selling the credits?

Both paths have very different capital requirements and risk profiles.

The permanence of the storage is another area of active research.

Once the carbon is captured, it must be pumped underground into rock formations where it can turn into mineral.

This requires partnerships with geologists and oil and gas service companies who understand the subsurface.

Building a DAC company is a long term play that requires a decade of patience and significant technical grit.

It is not a typical software startup path.

It is a fundamental piece of the puzzle for a net zero future, but it remains one of the hardest businesses to build from the ground up.