The Paris Agreement is an accord signed into by 196 parties with the aim of reducing the world’s carbon emission to a level where the global temperature rise is below 2°C relative to pre-industrial levels. In order to achieve this the reduction, carbon emissions need to be cut substantially, something countries are doing by swapping to renewable energy and pushing the EV agenda.

But to achieve the ambitious goals of the agreement existing carbon dioxide in the atmosphere also needs to removed. A process that isn’t talked about much.

Planting trees is just one option

One way of removing carbon dioxide is to plant trees which convert carbon to wood. A nice idea, but reforestation would have to happen on a massive scale which is unlikely due to our rapid urbanization. The other method involves big machines and experimental technologies.

The results of this method so far seem to show this might be the answer to removing carbon dioxide from the atmosphere. David Keith is the co-founder of Carbon Engineering, a firm that is developing the technology that can extract carbon dioxide.

His company has been slowly perfecting its technology for nine years and has been so successful Bill Gates has invested in it. The Carbon Engineering team have recently published a paper in the journal Joule which explains the science behind their system.

Four stages of carbon dioxide removal

Essentially removing carbon dioxide happens in four stages all inside a massive carbon dioxide removal plant that Carbon Engineering has developed. The main part of the plant looks a little bit like a bank of air conditioners.

First up, air is sucked into the machine using fans, the air is channeled into a honeycombed plastic slab called a contactor, here carbon dioxide reacts with aqueous potassium hydroxide. The result is a solution of potassium carbonate, this is then filtered and exposed to a slurry of calcium hydroxide.

This process produces potassium hydroxide which is then sent back to the contractor to be recycled and used in the first step. At the same moment, the calcium carbonate pellets which are also produced at this stage are moved to a receptacle called a calciner.

The pellets are heated to 900°C to release pure carbon-dioxide gas ready for capture, and calcium oxide. The final step involves piping the calcium oxide to a “slaker”, where it is dissolved in water to form calcium hydroxide, which is reused in the second step.

Old idea given fresh legs

While it sounds complicated the idea is actually 20 years old, having first been invented by a researcher called Klaus Lackner.

Dr. Keith patented the Carbon Engineering method in 2015.

Carbon Engineering has had a test contactor running for three years now and it manages to extract a tonne of carbon dioxide each and every day from the atmosphere. The latest paper from Dr. Keith and his team delves into the nuts and bolts of how much this carbon extraction would cost and look like at a massive scale.

They have estimated that a scaled up system could capture a tonne of the greenhouse gas for between $94 and $232. This isn’t cheap but it isn’t expensive in the scheme of things either and Dr. Keith has said he is confident the price will be lowered along with the further development of the machine.

Next step is convincing world's leaders this is the sort of technology they need to be investing in to secure the future of our planet.