Direct Air Capture explained

What is Direct Air Capture?

Direct Air Capture (DAC) is a carbon removal technology that captures carbon dioxide directly from the atmosphere. Processes vary from supplier to supplier, but generally involve filtering carbon dioxide from the other components of the air—such as nitrogen and oxygen—so that the carbon dioxide can be permanently stored. Most often, the captured carbon dioxide is stored deep underground.

How does Direct Air Capture work?

While there are several different DAC technologies—which are covered below—in practice they follow the same broad process.

First, air from the atmosphere is pushed by fans into a chamber—called a contactor. Inside the contactor, the air is exposed to material (usually a sorbent or a solvent) which reacts with the carbon dioxide. As the air passes through the contactor, the carbon dioxide in the air binds to the reactive material. This leaves the other components of the air—such as nitrogen and oxygen—to pass back into the atmosphere.

Second, heat, pressure or chemical reactions are then used to separate the carbon dioxide from the reactive material—a process called recovery. This process breaks the chemical bonds between the carbon dioxide and the reactive material, leaving pure carbon dioxide behind.

Finally, this pure carbon dioxide is compressed for transportation and storage. One of the most common and widely studied storage methods involves injecting the captured carbon dioxide deep underground into geological formations—such as saline aquifers.

What are the advantages of Direct Air Capture?

High measurability

The amount of carbon dioxide removed from the atmosphere by DAC is directly measurable by monitoring the flow and concentration of captured carbon dioxide at the point of storage. This means that there is a high level of confidence in the amount of carbon dioxide being captured by a DAC project as well as its climate benefit.

High durability

When paired with permanent storage—such as sequestration in geological formations—DAC can effectively remove carbon dioxide from the atmosphere for thousands of years. These types of permanent storage also have a very low risk of the carbon dioxide returning to the atmosphere—a process called reversal.

Geographic flexibility

DAC projects can essentially be deployed anywhere in the world where there is sufficient access to low-carbon energy and the infrastructure and capacity needed to store the captured carbon dioxide. This flexibility allows DAC project developers to choose sites that will lead to the highest levels of efficiency for carbon capture.

Direct atmospheric carbon removal

As DAC removes carbon dioxide directly from the atmosphere there is an immediate benefit to the climate at the point of removal. This makes DAC one of the leading carbon capture technologies for rapid positive impacts on the climate.

Benefits from captured carbon dioxide

DAC can also have a number of additional benefits beyond immediate carbon removal. The captured carbon dioxide can be used to produce synthetic fuels, plastics or other chemicals—creating useful products without adding additional carbon dioxide to the atmosphere. The carbon dioxide captured by DAC can also be combined with renewable hydrogen to produce carbon-neutral fuels—which can be used by hard-to-decarbonize sectors like aviation and shipping.

What’s the difference between Direct Air Capture technologies?

There are currently several different DAC technologies at various levels of development and deployment. These technologies primarily differ on the material—or process—used to absorb carbon dioxide from the air.

The two most commonly deployed technologies are liquid solvent DAC (L-DAC) and solid sorbent DAC (S-DAC). As their names suggest, L-DAC uses a liquid solvent to absorb carbon dioxide while S-DAC uses porous solid materials. Other DAC technologies also use electricity, membranes or water to filter carbon dioxide from the air.

How much does Direct Air Capture cost?