DACCS

DACCS

Carbon removal technology

What you need to know about DACCS

How direct air capture and storage works

Despite having major implications for climate change by trapping heat via the greenhouse effect, CO₂ is actually a relatively small percentage of the overall makeup of the atmosphere — about 0.04%. That means to remove CO₂ from a given quantity of atmospheric air often requires large amounts of air to be collected — often using fans. That air is channeled through machines where a series of chemical processes remove the CO₂ to yield a pure, compressed gas, liquid, or solid carbonate that can then be stored or used.

Here’s more detail on the steps:

  1. CO2 capture: Large fans draw in ambient air into machines, where chemical filters or sorbents capture CO2 molecules while allowing the rest of the air to be released back into the atmosphere.
  2. Separation: Once the filters are saturated, the CO₂ is released from them using heat or another process. The almost pure CO₂ is then captured and compressed.
  3. Sequestration: The captured CO₂ is safely stored, typically by injecting it into geological formations. Alternatively, it can be used to produce durable materials like concrete.

Direct Air Capture (DAC) technologies usually perform the first two steps only, and the sequestration is often performed by specialized partners. If a DAC solution is used for the purpose of using the captured CO₂ in a method that will re-release the carbon, the process is not considered to be DACCS or even a method of carbon removal.

Why is DACCS important for climate change?

DACCS has become increasingly a key focus for scientists, project developers, governments, and corporations. There are three main reasons why:

  1. Some emissions are extremely difficult or costly to eliminate, particularly from sectors like agriculture, aviation, and heavy industry.
  2. We’ve already emitted enough CO₂ to exceed safe atmospheric levels. Current levels exceed 400 ppm and continue rising.
  3. We’re likely to overshoot climate targets — at least temporarily. Most pathways to limiting warming to 1.5°C rely on removing 5-10 gigatonnes of CO₂ annually by 2050.

The IPCC and major climate models now include significant carbon removal in their scenarios for meeting Paris Agreement goals. While emissions reduction remains the primary priority, carbon removal has become a necessary complement — not a replacement — for aggressive decarbonization efforts.

DACCS complements other natural and hybrid carbon removal methods by offering a highly durable and measurable solution. Unlike nature-based projects, which are susceptible to risks like wildfires or deforestation, DACCS projects can ensure the permanence of CO₂ storage for thousands of years.

Important considerations for DACCS projects

DACCS and PSC The major difference between DACCS and Point Source Capture (PSC) solutions is that PSC is implemented directly within industrial processes that emit carbon, capturing it at the emissions source.

DACCS and EOR Some DACCS projects use the captured CO₂ for Enhanced Oil Recovery (EOR). While using captured CO₂ could mitigate some of the total net carbon emissions of an oil well, it directly supports the release of greenhouse gas emissions.

DACCS and utilization If the CO₂ captured through DAC is used in processes that eventually release it back into the atmospheres, the process does not qualify for carbon removal since it does not sequester the captured carbon.

Carbon credits and DACCS

DACCS carbon credits are considered premium due to their high durability and integrity. These credits provide:

  1. Permanence - CO₂ storage through DACCS is designed to be irreversible.
  2. Certainty - The closed system with direct measurements allows for precise monitoring and verification of carbon removal amounts.
  3. Scalability - Experts estimate that DACCS could remove up to 5 gigatonnes of CO₂ per year by 2050 when heavily commercialized.

Although DACCS credits are currently more expensive than those from nature-based solutions, their long-term impact and reliability make them a critical component of global carbon removal strategies.

The history and future of DACCS

The concept of DACCS as a solution for climate change emerged in the late 1990’s, but the technology gained momentum in the 2010s. Despite several barriers to the large-scale deployment of DACCS, like reducing both the cost and energy use per tonne of carbon, the technology is rapidly gaining ground.

Today, both policymakers and private investors are prioritizing research and development for DACCS. The U.S. Department of Energy (DOE) launched the Carbon Negative Shot initiative, which includes a $3.5 billion investment in DAC hubs, aiming to capture at least 1 million metric tonnes of CO₂ annually.

Energy use in DACCS

One of the major challenges facing DACCS is the energy use required to power existing technology. In particular, energy is required for three discrete processes:

  1. Regeneration Energy: Breaking CO₂-sorbent bonds requires significant heat.
  2. Fan Power: Moving large volumes of air through contactors requires substantial electricity.
  3. Compression: Compressing captured CO₂ for transport/storage needs additional energy.

Current estimates range from 5–10 gigajoules per tonne of CO₂ captured.

The durability of DACCS

The effectiveness of DACCS depends on the durability of its storage solutions. Geological storage, such as injecting CO₂ into deep rock formations, is highly secure with minimal risk of leakage.

Benefits and Risks

Benefits

Risks