Carbon Capture & Storage (CCS) vs Direct Air Capture (DAC)

Carbon Capture and Storage

Carbon capture and storage is focused on emission points like factories and other industrial devices. Its main goal is to reduce the carbon emissions of these point sources, and as such, it is a preventative measure rather than proactive like direct air capture [4].

CCS is a three step process. First, "the CO2 is seperated from other gases produced in industrial processes, such as those at coal and natural gas-fired power generation plants or steel or cement factories [11]".

Second, the resulting carbon dioxide is "compressed and transported via pipelines, road transport or ships to a site for storage [11]". Lastly, it is "injected into rock formations deep underground for permanent storage [11]".

Rather than store the carbon, a similar process is CCUS - Carbon Capture, Utilization and Storage - which involves re-using carbon (utilizing it) in "industrial processes by converting it into, for example, plastics, concrete, or biofuel [11]".

Direct Air Capture (and Storage)

Direct air capture isn’t stuck to one location, nor does it require an emission point - it takes carbon out of the ambient air using a filter. ”DACS is carbon negative, while fossil CCS achieves carbon neutrality at best [4]”.

Companies like Climeworks and Carbon Engineering are on the forefront of this new technology. "Both companies argue [DACS] can play its role, alongside a net-zero industry transition, in both reducing and removing carbon dioxide emissions from the atmosphere [10]".

Their technologies are very similar - both start off with fans drawing in air, but "Climeworks captures carbon dioxide on the surface of a 'highly selective filter material' [10]", with the collector raising the temperature and releasing "high-purity, high-concentration CO2 [10]".

Carbon Engineering, on the other hand, uses a "potassium hydroxide solution to bind with the CO2 molecules drawn in in by the fans [10]", going through checmical changes that again results in pure gaseous CO2.

For both technologies, the resulting filtered air is released into the atmosphere, and the captured carbon dioxide is either sent to be stored or reused [10], similar to comparable CCS technologies.

Similarities

After the carbon is captured, the differences are null; the carbon is still captured and sequestered deep underground Both CCS and DAC are scalable, and have much more efficient land use compared to natural sequestration techniques [4]. Utilizing both of these technologies in unison, as well as natural sequestration, will be imperative for slowing climate change.