Imagine being able to suck the carbon dioxide (CO2) that is causing climate change right out of the atmosphere. That is the promise of Direct Air Capture (DAC) technologies. It is an emerging technology that is just moving to the commercialization stage.
The
Intergovernmental Panel on Climate Change (IPCC) has concluded that Carbon Dioxide Removal (CDR) to counterbalance carbon dioxide (CO2) and other greenhouse gas emissions is an essential element of scenarios that limit warming to below 2 degrees Celcius by 2100. CDR refers to removing CO2 from the atmosphere and durably storing it in geological, terrestrial, or ocean reservoirs, or in products. It excludes Carbon Capture and Storage (CCS) and Carbon Capture and Utilisation (CCU) applied to fossil fuel based CO2 unless such CO2 is directly captured from ambient air. See OWOE Topic:
What is carbon capture and storage (CCS)? for more information about CCS. The reason for the narrow definition is that the IPCC scenarios are predicated on significantly reducing or eliminating fossil fuel based emissions, and in addition, reducing the amount of CO2 that has already been released into the atmosphere.
Technologies that extract CO2 directly from the atmosphere work by pulling air into a mechanical system which, through a series of chemical reactions, extracts the CO2 (see Figure 1). Two technological approaches are currently being used:
- Solid DAC (S-DAC) is based on solid adsorbents operating at ambient to low pre?under a vacuum) and medium temperature (80-120 degreesC). The first commercial S-DAC facility was built by Climeworks in Hinwil, Switzerland (see Figure 2) that proved the technology. In September 2021, Climeworks began operation of their Orca facility in Iceland, the world's largest direct air capture and storage plant, with a capture capacity of 4000 tonnes per year.
- Liquid DAC (L-DAC) relies on an aqueous basic solution (such as potassium hydroxide), which releases the captured CO2 through a series of units operating at high temperature (between 300 and 900 degrees C).
The CO2 can be permanently stored in deep geological formations, or used directly, for example, in food processing or combined with hydrogen to produce synthetic fuels.
Figure 3 shows a plot of greenhouse gas emissions from the
UN Environment Emissions Gap Report 2017 that shows how a "business-as-usual" approach to climate change will need both significant emissions mitigation (e.g., replacement of fossil fuels with renewable energy) and negative CO2 emissions (e.g., DAC implementation) in order to maintain global warming below 2 degrees C. This indicates a need to remove about 5 giga-tonnes of CO2 per year by 2050, increasing to 20 giga-tonnes by 2100.
Recent US legislation, including the
Inflation Reduction Act of 2022, that has earmarked funds for development of DAC technology as well as increased tax credits, along with the growing number of
large corporations setting net-zero emission goals and seeking high-quality carbon removal credits, have created an opportunity to build a viable business in the US. And technicological advancements have created the opportunity for scaling up DAC technology and reducing development costs.
As of Septeber 2022, there were 18?DAC plants operating worldwide, capturing almost 0.01?million tonnes CO2/year. The
first commercial DAC facility in the United States, built by Heirloom Carbon Technologies in Tracy, California, became operational in November 2023 with capacity to capture up to 1,000 tons of CO2 per year. In May 2024 the
world's largest DAC plant, Mammoth, operated by Swiss company Climeworks (see Figure 4), began operating in Iceland with initial capacity to remove 6,000 tons per year, with full capacity planned at 36,000 tons per year.
1PointFive is in the process of developing the largest direct air capture facility in the world, called DAC1, which is expected to come online in mid-2025 and achieve an anticipated capture capacity of one million tonnes of CO2 each year when fully operational. And in September 2022 Los Angeles-based Carbon Capture Inc. and Texas-based Frontier Carbon Solutions announced their
Project Bison is scheduled to officially begin operations in Wyoming in 2024 and is expected to start removing about 12,000 tons of CO2 each year, scaling up to 5 million tons per year by 2030.
Another approach being investigated for carbon capture includes using seaweed to capture atmospheric carbon via photosynthesis and sinking it to the ocean floor, which is believed will sequester the carbon for 1,000 years. The company
Running Tide conducted field testing in 2021 to evaluate the performance of their carbon-sinking solution and conduct research, impact analysis and optimization. Running Tide is looking to increase the amount of carbon it sinks by tenfold, helping them reach their goal of sinking a megaton of carbon by 2025.
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