Can carbon capture technology help address the climate crisis?

It’s been over 250 years since industrialisation saw fossil fuels adopted as a form of mass energy production, and yet they still account for almost 85% of the world’s energy mix. As a result of continuing to burn coal, oil and natural gas, levels of carbon dioxide in the atmosphere have increased to their highest concentration for over 650,000 years. This has happened at an alarming rate and, if left unchecked, will cause global temperatures to rise even more dramatically, crossing irreversible ‘tipping points’ that will have disastrous consequences for all life on earth.

NASA Earth Observatory Image source for Blue-grey landscape seen from space, with locations of coal mines and an airport marked

Scientists have long understood the link between greenhouse gases and rising global temperatures, but only recently has the urgency of the issue been brought into full public focus. Popular media, in particular, has made a significant impact, connecting us to the natural world like never before. Documentaries such as the BBC’s Planet Earth II and National Geographic's Before the Flood have provided immediacy to an issue that can be difficult to communicate conceptually, especially when it comes to the creeping effects of climate change. With the help of celebrity figures such as Leonardo DiCaprio and Greta Thunberg, and the growth of climate protest movements, global warming has never been such a hot topic.  

Science Museum Group Collection Image source for 3 magazines with headlines 'global warming', 'be afraid, be very afraid' and 'how to win the war on global warming'

As public pressure grows, governments around the world have committed to a raft of new pledges, including the 2015 Paris Agreement (an agreement to limit planetary warming to below 2 degrees from pre-industrial levels). Along with this shift in policy, steady advances have also been made technologically, and 2020 was a boom year for renewable energy growth. 

Even so, the global economy remains heavily reliant on fossil fuels. The world needs to adopt more sustainable sources of energy, as well as tackle existing sources of emissions, in order to mitigate the worst effects of the climate crisis. One avenue of research that seeks to tackle this problem is carbon capture and storage.

Pioneered by the scientist Klaus Lackner, the ‘mechanical tree’ concept offers a visually striking approach to direct air capture. Inspired by their organic counterparts, mechanical trees use specially coated resin ‘leaves’ that can passively absorb carbon dioxide from the air. As the air passes over the leaves, the carbon dioxide binds with a special carbonate to form a bicarbonate powder (a bit like baking soda). After around 20 minutes, the metal limbs of the tree are then retracted into a water tank below, where the leaves release the carbon dioxide for extraction, before the process starts again.

Although Lackner and his team are already working on the second generation of their capture technology, the journey to this point has been a long and difficult one, with the idea first proposed back in 1992. As with any experimental technology, it required a fair amount of improvisation to get going, and at one stage a beer fridge was required for the team’s testing site in the Arizona to prevent the computing equipment from melting under the heat of the sun! Electronic and plumbing issues continued to plague the early designs, earning the machine the (somewhat) affectionate nickname ‘Cranky’. 

Despite these early challenges, the mechanical tree concept is now being rolled out across the world. When at scale, these ‘carbon farms’ would be capable of absorbing up to 4 million tonnes of CO2 each year. To match the billions of tonnes of emissions produced every year, however, we would require these 21st century technological forests to become a much more common sight in our landscapes, just as wind turbines have become.

Carbon Collect

DAC solutions such as these only make up part of the global carbon capture solution, however. Whilst these 'trees' may be many times more efficient at capturing carbon than their natural counterparts, they do not bring with them the same benefits in terms of habitats and biodiversity for local wildlife. Additionally, they only work to remove carbon dioxide that has already been released into the air, doing nothing to reduce the huge quantities of emissions still being produced by factories and the energy industry. To tackle this issue, other carbon capture and carbon reduction methods will need to be adopted. 

One way to approach this problem is by using various chemical solvents and filters. For example, it’s now possible to retrofit carbon capture devices onto the exhaust flues of factories and power stations, with chemicals binding to carbon emissions in a similar way to the carbonates used in the mechanical tree. The resulting material can then be separated and treated before the solvent is refreshed and reused. This technique has the advantages of being adaptable to current technologies, keeping costs low and making carbon reduction a more attractive option. 

There are concerns about the principles of carbon capture, including the potential for it to justify ongoing fossil fuel use and to reduce our sense of urgency about the need to transition to more sustainable energy sources. Certainly carbon capture should only be seen as one of a suite of technological solutions to the immediate climate crisis, working alongside longer-term schemes to massively reduce the use of fossil fuels across industry, eventually eliminating their use completely.