Direct air capture (DAC) functions on the premise that carbon dioxide (CO2) can be captured from the atmosphere after it has been created rather than at the sources of emission. The sources of CO2 that have been produced by human social and industrial activity are transportation, factories, power plants, concrete production … and the list goes on.
Direct air capture involves a multi-step process:
1. Large fans mounted on the sides cooling towers pull in atmospheric ‘air’ which is then forced through filters that can be either liquid (potassium hydroxide) or solid metallic organic frames. The filters are designed so that clean air passes through them to be discharged back to atmosphere while the CO2 is entrapped by the filtration media.
2. Once the CO2 has been captured by the filtration medium, it can then be removed using steam, electricity, or heat … or combinations of all three energy modes.
3. After removal from the filtration stage, the CO2 is then compressed into a liquid state so that it can be pumped underground for storage.
4. After compression to a liquid, CO2 is typically stored up underground at depths of around 1 mile or more in ancient ocean beds consisting of porous sand.
At the time of writing, there is just one operational DAC plant worldwide. It is located in Iceland and operated by a company called Climeworks. This facility has the capacity to remove up to 40,000 metric tons of per year. Closer to home, Occidental Petroleum in Texas is constructing a DAC facility with a CO2 capture capacity of 500,000 tons per year, and the Deep Sky company in Canada with corporate offices in Montreal are planning a similar sized plant to the one in Texas. Because the DAC capture procedure consumes vast amounts of energy, locating a plant in Quebec where almost all the electricity is generated by hydroelectricity makes sense.
Storage capacity
Storage capacity for CO2 should not be a problem. Scientists estimate that there is sufficient storage space underground in Western Canada alone to store all of the CO2 emissions produced by human activities since the beginning of the Industrial Revolution in Britain in the late 1700’s. The two key criteria for storage are: •Renewable energy infrastructure •Underground porous storage space
Holdbacks
Cost will be a major factor. DAC is currently discredited by naysayers and corporations that have a vested economic interest in preserving the status quo. But this has been the naysayer’s position on every revolutionary technology that has been introduced throughout the history of industry. A typical DAC plant with a 500,000 metric ton CO2 removal capacity per year has a projected cost of between $700K and $1B in today’s money. However, by most economists’ reckoning, much the upfront costs can be offset by what is spent on current CO2 containment technologies.
Energy factors will also have to be reckoned with whether classified as green or not-so-green by source. A commercial DAC plant with the 500,000 metric ton capacity we cited earlier will consume around 200,000 to 300,000 megawatts. It sounds formidable until we compare this the operating energy requirements of a typical oil refinery which are almost identical. And there are hundreds of oil refineries worldwide!
Conclusions
Like petroleum extraction and refining, a skilled workforce will be required. However, there already exists an abundant supply of skilled energy workers in geographic areas such as Texas and Alberta. It helps that the skills required to remove carbon-base liquids and gases from ground, are not so different those required to put back under the ground.