Humans are now emitting over 30 billion tons of CO2 each year into the atmosphere

Global action to reduce CO2 emissions has been slow to develop. But in many places people are now installing wind turbines and solar panels – which produce energy without emitting CO2 – and are focussing on energy efficiency as ways to reduce emissions. Others are developing technologies that can capture CO2 from the smoke stacks of power plants and industrial facilities to store it back underground.
But what if there were a way to capture CO2 straight from the atmosphere itself, in order to compensate for and reduce our overall emissions?
In fact, there is. People have “scrubbed” CO2 from the air in space-ships and submarines for decades now to maintain the health and safety of the people on board. But those systems are far too small, specialized, and expensive to be used at industrial scale. I work at a company called Carbon Engineering, one of several trying to take this concept and apply it at large scale to help make a dent in cutting emissions. We call the concept of capturing CO2 right from the atmosphere around us “direct air capture”, or DAC. The DAC technology we are developing would look like a large factory, except instead of releasing CO2, it would process large amounts of air and remove the CO2 from it, for subsequent use or storage.

People have “scrubbed” CO2 from the air in space-ships and submarines for decades

In principle, there are several ways to remove CO2 from air. Air could be cooled until CO2 freezes out and can be collected, but this would require far too much energy to be practical. One could develop specialized solid materials that absorb CO2 the same way a sponge absorbs water. In fact, some of our competitors are pursuing this approach, but it’s challenging to take new materials from the lab and apply them at industrial scale. Our method involves using liquid solutions that have an affinity for CO2 in order to scrub it from air that passes through a device we call an “air contactor”. We think this approach shows the most near-term promise, since there is significant industrial experience in “wet scrubbing” within other large-scale industries.

The first step in our process to capture atmospheric CO2 occurs in the air contactor. It works a lot like a cooling tower, to pull air through small flow channels, that are wetted with our capture chemical. As the air passes through the contactor, CO2 is preferentially absorbed, until air comes out the back end slightly more humid, and with 80% less CO2, than when it went in. The scrubbed CO2 ends up in our liquid solution, which we then circulate to our “regeneration facility” for further processing. Regeneration involves a few chemical reactions that occur in mixed tanks and a high temperature kiln. It extracts pure CO2 from our solution, and remakes the original capture chemical, so that it can be re-used to scrub more CO2. By the end of our process, we have a pure stream of compressed, liquefied CO2, that can be used for industrial purposes or stored underground.
By injecting and storing atmospheric CO2 underground, we can offset emissions that occur somewhere else in the world, the climatic benefit is the same as if those emissions never happened. Alternately, by using the CO2 we capture, we can create low-carbon or even carbon-neutral fuels. These fuels would be exactly the same as those burned by vehicles and airplanes today, but would contribute much less (or not at all) to the CO2 concentration in our atmosphere that causes climate change. This might be one of few ways to sustainably power the transportation sector in the future.

DAC offers a compelling proposition, but there are challenges too. To make a meaningful impact on emissions, DAC facilities would have to be large, and thus costly. In fact, DAC is slightly more expensive at reducing emissions than some other options such as installing wind turbines or implementing policies that help people use less energy. It’s also more challenging than capturing emissions from smokestacks, but can help us control the emissions that don’t originate from big factories and power plants. Further, DAC is not ready to deploy yet, proponents like ourselves are still developing and demonstrating the technology. Lastly, DAC alone cannot solve the climate problem, we need other options and solutions too. Those of us in the field like to think of Direct Air Capture as a complement to other technologies; an option that can be used along-side others like wind power and energy efficiency.

Those of us in the field like to think of Direct Air Capture as a complement to other technologies

This year, we are working away at demonstrating and marketing our direct air capture system. Within the year, we’ll be performing small-scale air capture – 1 to 2 tons of CO2 per day – with our demonstration plant. We think this brings DAC closer to reality, and offers policy makers another tool to consider as we all ramp up efforts to reduce CO2 emissions and avoid dangerous climate change.