Suck CO2 (out of the atmosphere)!

In the last post, we established that at this juncture, reducing GHG emissions is not enough to arrest the increase in Earth’s temperature; the existing CO₂ in the atmosphere needs to be sucked out to achieve a ‘net-zero’/ ‘net-negative’ emissions state. 

It’s simple math. 

Let’s understand Carbon Dioxide Removal (CDR) 

CDR (a rather self explanatory term), understandably, is the most widely and urgently needed tool to mitigate climate change. Think of CDR solutions like gigantic vacuum cleaners, which, can broadly be categorized as:

• Nature based - using natural resources, largely forests and soil;

• Technology based - using tech innovations in conjunction with nature.

Now, if you remember bits of science from school, you may recall this sing-song law:

Matter can neither be created nor destroyed, it can only change form.

This means that the CO₂ sucked by the gigantic vacuum cleaners won’t vanish, pretty much like the dirt sucked by your house vacuum cleaner, which is simply displaced from your house surfaces to the solitary confinement of your mean machine, then to a dustbin and eventually to a place far out of your sight.

Hence, the removed CO₂ needs to be stored somewhere safe - in geological formations (like rocks), in trees & soil, in the ocean, or in products (like concrete) - so that it doesn’t escape back into the atmosphere. This process of storage is known as carbon sequestration. Interestingly, forests, soil and oceans are the largest naturally occurring carbon storage systems, thereby, earning their fame as carbon sinks.

Digging a little deeper, allow me to give you a sneak peek into the currently understood variety of CDR solutions.    

Source: World Resources Institute

Note: The natural vs. technological categorization shown above is illustrative, not definitive and will vary depending on how approaches are applied

If the visual above felt like too much information, take it easy! You don’t really need to know it all. Let me pick a few super interesting solutions and tell you what they entail. In case you want to read about all of them, do so here and here. 

Tech based

Direct Air Capture (DAC)

This is one of the most talked about recent technologies...because a lot of hopes are pinned on it.

In this process, large structures are used to quite literally suck CO₂ from the ambient air and bury it underground or in rocks or in products like concrete. These structures are powered largely by renewable energy. 

However, given the capital intensive nature of this solution, it is extremely expensive at the moment - $600 to $800 per tonne of CO₂ removed! The goal is to bring this cost below $100 to make it feasible for deployment by corporations and governments at large¹.

What a DAC facility could look like

Having said this, there are a few companies which have already begun work in this space. Climeworks, a Swiss co., has built a facility called Orca in Iceland which resembles a congregation of large transistor radios. 

Heirloom and CarbonCure, American and Canadian cos. respectively, recently successfully piloted DAC with carbon sequestration in concrete - pretty cool! They say that even if the structures created with this concrete were to be demolished, the stored CO₂ won’t escape. Read about how they did it.

Nature based

Biochar

Source: Nicole Kelner

This solution leverages the unutilized plant waste (biomass) like crop residues, waste wood and other agri/organic waste by putting them through an oxygen-less heating process (pyrolysis) to create a charcoal like substance (with a high carbon content)  which is a top-notch soil additive and a permanent carbon sequestration medium. And the best part is that the byproducts of this process prove to be great ingredients for biofuels and generation of energy which can in turn power the pyrolysis process.

So you think you’ve figured out CO₂ capture now…

BUT  

CO₂ removal is not the same as CO₂ capture!

Whaaaaaa….

(you’re not alone; a lot of publications also mess up the two but I don’t want YOU to repeat their gross mistake)

To put it simply,

Source: Nicole Kelner

CDR undoes the misdeeds of the past, i.e. it removes legacy emissions, whereas,

Carbon Capture and Utilization/Storage (CCUS) prevents the misdeed from happening, i.e. doesn’t let active/new CO₂ emissions reach the atmosphere in the first place.

CDR enables negative CO₂ emissions; CCUS helps neutralize those emissions at best.

Source: The State of CDR

PS: Solar geoengineering (manipulating climate by reflecting more sunlight back into space) is also a potential CDR solution but scientists don’t know much about its real world effects yet. However, a startup, Make Sunsets, recently went ahead (recklessly?) and released reflective sulphur particles from a site in Mexico to run this experiment.

PPS: The next post is going to be a super special one - it’s the first anniversary of my Antarctica expedition next week! So I’m gonna take a small detour and take you through my Antarctic journey - stay tuned.

1. Climate finance is a separate mammoth topic which we’ll deal with in a separate post