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What is Direct Air Capture?
The Direct Air Capture technology extracts carbon dioxide directly from the atmosphere. It then stores the captured carbon dioxide in deep geological formations. Alternatively, we can even use the captured carbon dioxide, for example, in food processing or combine it with hydrogen to produce synthetic fuels.
Today, the industry mainly uses two technologies to capture CO2 from the atmosphere:
1. Liquid Direct Air Capture
2. Solid Direct Air Capture
In the liquid system, air passes through chemical solutions (e.g., a hydroxide solution). These chemical solutions remove the CO2. The system will reintegrate the chemicals back into the process through the application of high-temperature heat. It will return the rest of the air back to the environment.
Solid technology involves the use of solid filters. These filters chemically bind with carbon dioxide. For the filters to release the concentrated CO2, the competent personnel will heat the filters and place them under a vacuum. They then capture the CO2 and then either store it or use it.
Most large-scale industries use the captured carbon dioxide to produce synthetic fuel. The burning of synthetic fuel results in the release of carbon dioxide back into the atmosphere. However, as per the International Energy Agency (IEA), this does not create negative emissions. In fact, it could still generate climate benefits if, for example, synthetic fuel replaces conventional fuel.
A Key Option for Carbon Removal
Today, direct air capture is one of the few technologies available for carbon removal from the atmosphere. Economists and researchers predict that carbon removal will be key in the transition to a net-zero emissions world. In this world, the CO2 released into the atmosphere has to be equal to the CO2 removed by natural or man-made systems from the atmosphere. Certain sectors, such as heavy industries and aviation, are difficult to decarbonize. Carbon removal technologies like direct air capture can offset their emissions and support a rapid transition.
Other options available for carbon removal include nature-based solutions like afforestation and restoration of marine, terrestrial, and riverine habitats. It also includes measures to enhance land management practices to increase the carbon content of soils.
There are many benefits to adopting direct air capture as a carbon removal option. Some of them include its limited land and water footprint. The plants do not need any special location requirements. Therefore, we can build them on non-arable land, close to suitable storage. This eliminates the need for transporting CO2 all the way from the place of capture to the place of storage.
We also need to base the location of the plant on the energy source that will run the plant. The energy used to run the plant will determine how net-negative the system is. It is also a significant factor in determining the cost per tonne of CO2 captured. For example, renewable energy sources could fuel solid and liquid capture technologies, while waste recovery could power a solid direct air capture system.
Direct Air Capture Technology is Currently Expensive
Carbon dioxide in the atmosphere is much more dilute than, say, carbon emissions from a power station or a cement plant. Direct air capture technology is expensive because of the higher energy needed to remove this dilute CO2 from the atmosphere.
Costs and energy needs also vary according to the type of technology. The cost also depends on whether we’re going to geologically store the captured CO2 or we’re going to use it immediately at low pressure. We need to compress CO2 under very high pressure to inject it into geological formations. This need for compression under high pressures increases both the plant’s capital cost and operating expenses. Capital cost increases since we’d have to buy the compressor, and operating expenses increase due to the energy required to run the compressor.
As of now, direct air capture technologies have not been adopted on a large scale. Therefore, the capture cost estimates of CO2 are wide-ranging. In 2018, peer-reviewed research showed that we could achieve carbon capture costs of USD 94 per tonne to USD 232 per tonne, depending on the plant configuration, financial assumptions, and energy costs.
The public and private sectors are increasingly backing direct air capture. The voluntary market for CO2 removal based on direct air capture technologies has expanded. Companies like Microsoft, Shopify, and Stripe are purchasing direct air capture removal to offset their carbon emissions.
Some of these purchase agreements are hybrid. This means that the company purchasing the offsets financially supports the construction of the direct air capture plant that will eventually capture CO2 from the atmosphere. On a small scale, some direct air capture plants are offering individuals and businesses a paid subscription to have CO2 removed from the atmosphere and stored underground on their behalf.
Public funding has also increased for direct air capture deployment. In March 2021, the United States Department of Energy announced financing specifically for direct air capture of USD 24 million. These improved investments from the public and private sectors led to the announcement of several new projects in 2021. The United Kingdom announced the Storegga Dreamcatcher Project aimed at carbon removal. Chile announced the HIF Haru Oni eFuels Pilot Project. This project will produce synthetic fuels from electrolysis-based hydrogen, and CO2 captured from the atmosphere. By 2024, the Norsk e-Fuel AS consortium in Norway will produce up to 3 million liters of synthetic fuel from CO2 obtained by direct air capture.
Carbon removal technologies such as direct air capture are not an alternative to cutting emissions. It is wrong to even think of them as an excuse for delayed action. But they can play an important role in achieving climate goals. Direct air capture is highly effective in reducing the concentration of carbon dioxide in the atmosphere. All we need to do now is find a way to work around its high costs so that we can implement it on a large scale.
Dr. Emily Greenfield is a highly accomplished environmentalist with over 30 years of experience in writing, reviewing, and publishing content on various environmental topics. Hailing from the United States, she has dedicated her career to raising awareness about environmental issues and promoting sustainable practices.