Remove CO2 directly from the air.

Plants do it all the time: it’s called photosynthesis [1]. They take in CO2 from the air, combine it with water, and use it to grow and produce oxygen [1]. Could we build a machine to suck CO2 from the air?

Some engineers are doing just that [e.g. 2,3,4,5,6]! They call it ‘Direct Air Capture’ (DAC) [13]. One company [3] claims that they will be able to do it for $94-232 per ton of CO2 [16]. Being optimistic and assuming $100 per ton, it would cost $3.7 trillion to remove the amount of CO2 that humans emitted in 2018 (about 37 billion tons [7]). That’s about 4% of global GDP [15]. Clearly we need to get the price down [8,18].

There are a few different methods of DAC [17]. We will explain the most mature one in simple terms: air is blown across a material that CO2 sticks to, whilst the rest of the air is blown out [16]. The CO2 is then collected and the material is re-used to capture the next load of CO2 [16]. Swipe for a diagram of the chemical reactions!

There are a few challenges [9,18]. For example, capturing CO2 from the air is inherently difficult because the concentration of CO2 is so low: only 400 out of every 1,000,000 molecules in the air are CO2 [18]. This means making the process cost-efficient is difficult [18].

Scientists and engineers have solved problems in the past that seemed previously unsolvable (electricity [20], the structure of DNA [21], the internet [22] etc.). A recent investment of $68 million into a DAC company [14], and partnerships between oil companies and teams working on DAC [10] suggests that people think this technology is promising. This is a sign that DAC will hopefully become more efficient and affordable, and could play a major role in reducing CO2 emissions [12]. However, some scientists argue that other methods of CO2 removal deserve more attention [18,19].









[8] See: Abstract

[9] See: Discussion



[13] See: CDR technologies and deployment levels in 1.5°C pathways



[16] - diagram inspired by this


[18] See: 12.2 Direct air capture of CO2





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