Extracting Carbon Dioxide from the air: a futile endeavour or the new frontier in the fight against climate change?

By Mariusz Bogacki, Researcher and Science Communicator, Edinburgh

Among the natural greenhouse gasses in existence on our planet, carbon dioxide (CO2) is considered as the most important. CO2 absorbs and radiates heat in order to stabilise the Earth’s temperature – without it we would be living in freezing temperatures! However, increases in greenhouse gasses caused by industrialisation have tipped the Earth’s energy budget out of balance, trapping additional heat and raising the planet’s average temperature. Each year we put more carbon dioxide into the atmosphere than natural processes can remove, which means the net global amount of carbon dioxide rises. The more we overshoot what natural processes remove, the faster the annual growth rate. This is what scientists call global warming and what environmentalist around the world are trying to manage.

As decreasing the amount of greenhouse gasses emission caused by transport and industrial plants around the world appears increasingly difficult, some companies are calling for a different resolution: to suck it out of the atmosphere using Direct Air Capture (DAC) technology.

DAC extracts CO2 directly from the atmosphere in order to store it permanently in deep geological formations or recycle it to produce synthetic fuels. The capture, or extraction, happens with the use of giant fans that draw in air, along with the CO2. Carbon dioxide is then bonded with sorbents, chemicals used to absorb liquids or gasses. When the sorbent is saturated, it is heated to 80—100C to release the captured CO2 which can then be stored and repurposed.

There are around 20 different DAC plants worldwide today, capturing and recycling the CO2 in variety of ways. ClimeWorks in Iceland captures and buries CO2 in mineral form at a rate of 4,000 tonnes a year. Carbon Engineering, due to start operating the world’s biggest DAC facility in Texas (USA) promises to capture up to 1m tonnes of CO2 per year and convert it to produce synthetic liquid fuels. Global Thermostat is planning on installing millions of small units of its DAC systems in cities and industrial parks worldwide, harnessing waste heat to draw down carbon pollution.

While proponents of the technology argue that it is another important tool in combating the climate crisis, critics point out to the high levels of energy required to produce and maintain DAC components and industrial plants. However, costs and energy needs vary according to the type of technology and whether the captured CO2 is going to be geologically stored or used immediately at low pressure.

It appears that the jury is still out as DAC systems are still in their early days of development. Getting the costs down and scaling up the technology will ultimately determine its potential and feasibility. Let’s remember similar arguments were used to discredit the viability of solar panels and other green energy solutions. Perhaps the most important take away from this new endeavour is that it pushes new technological solutions in our shared efforts to control global warming.