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Our role -

When it comes to saving the planet, reducing CO2 emissions is a good place to start. We should all be using public transport and eating local, seasonal produce wherever possible.

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Paris Agreement -

Unfortunately, however, evidence suggests that this will not be enough if we are to achieve the Paris Agreement goal of limiting global warming to 1.5°C by 2100.

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IPCC -

According to the Intergovernmental Panel on Climate Change (IPCC), this will require "large-scale deployment of carbon dioxide removal measures.”

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"Large-scale deployment" -

When the IPCC says "large-scale deployment," they really do mean large-scale: we are talking about many millions of tonnes, or gigatonnes, every year.

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DAC -

That is where direct air capture (DAC) technology comes in. A device that removes carbon dioxide from the atmosphere may sound like wishful thinking, but it is in fact possible.

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Carbon Engineering -

Against the backdrop of snowy mountains in Squamish, British Columbia sits a prototype DAC plant built by a company called Carbon Engineering.

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Prototype plant -

The prototype plant is about the size of a barn, and when it starts up in September 2021 it will begin to capture a tonne of CO2 from the air every year.

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Big plans -

Of course, this doesn’t even put a dent in the amount of CO2 that needs to be extracted globally, and Carbon Engineering’s plans for a larger plant in Texas are underway.

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DAC technology -

Larger plants will be necessary if real progress is to be made, but for the time being the barn-size plant is standard when it comes to DAC technology.

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Extracting CO2 -

The science behind DAC technology is fairly simple. There are various accepted methods of extracting CO2 from the atmosphere, but the Carbon Engineering process is as follows.

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The process -

Fans are used to draw the CO2-containing air across a filter that is drenched in potassium hydroxide solution, which is known in the industry as "potash."

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The process -

The potash absorbs the CO2, forming a liquid that is then piped into another chamber. Once in the chamber, the liquid is mixed with calcium hydroxide (or "builder’s lime").

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The process -

The lime extracts the dissolved CO2 from the liquid, producing small limestone flakes, which are then sieved off and heated in a third chamber until they decompose.

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The process -

When they decompose, the flakes give off pure CO2, which is then caught and stored. At each stage, the waste materials are recycled back into the process.

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The need for DAC technology -

As CO2 emissions continue to rise, experts are concerned that we will be unable to meet the 2100 climate target without the introduction of DAC on a large scale.

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Expert opinion -

According to Ajay Gambhir, a senior researcher at the Imperial College Grantham Institute for Climate Change, “it's highly unlikely we can meet the Paris Agreements without it."

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DAC emerges as a top option -

The IPCC has presented some models that do not include DAC, but realistically these other models just look a lot less promising in terms of feasibility.

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The 'competition' -

According to Gambhir, these are “extremely ambitious” in terms of their assumptions about advances in energy efficiency and people’s readiness to change the way they behave.

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Alternatives -

Of course, there are other ways to remove CO2 from the air. Easily the most popular and fashionable of these other options is to plant new forests.

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The problem with trees -

However, planting trees is slow and ultimately doesn’t help that much; trees eventually die and release their carbon back into the atmosphere (unless they are burnt in a closed system).

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A huge task -

It is looking, then, like DAC is the best option. However, the task of removing sufficient volumes of CO2 from the air using this technology is simply huge.

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Some 30,000 plants -

According one Ghambir, we would need to build 30,000 large-scale plants just to keep up with current emissions. That’s more than three for every coal-fired power station in the world.

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DAC -

With each plant costing up to US$500 million just to set up, we’re looking at the modest sum of $15 trillion! The question as to who will fit the bill for this project is a big one.

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Elon Musk -

Billionaire entrepreneur Elon Musk recently pledged US$100 million to help develop DAC technologies, and companies such as Microsoft and United Airlines have invested billions of dollars.

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Investors not really interested -

In general, however, investor interest in DAC is low. The technology, however, does produce one important commodity, for which there is a clear market: compressed CO2.

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The fossil fuel industry -

One of the key customers is (somewhat ironically) the fossil fuel industry: CO2 is good for pressuring near-empty reservoirs to squeeze out any remaining oil.

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Remaining questions -

However, investment needs to be scaled up massively and the question as to how still stands. Some experts also worry about the effect of mitigation deterrence.

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Mitigation deterrence -

Indeed, some experts believe that if DAC technology is introduced on a large scale, people will use it as an excuse to carry on living in a non-carbon conscious way.

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The risk -

They worry that we may invest all the time and money into setting up a network of DAC plants, just to end up in a worse position than when we started.

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Conclusions -

To quote Ghambir: "We need to rapidly reduce emissions in the near-term, but at the same time, determinedly develop DAC to work out for sure if it's going to be there for us in the future."

Sources: (BBC) (Climate-KIC)

See also: The dairy industry and climate change

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