Branching out to help solve climate change

Scientists mimic trees to provide another potential solution to growing CO2 emissions

Artist’s rendering of unit to remove CO2 from air. Any such machine must be able to run passively, “like a tree standing in the wind”, says Prof Klaus S Lackner, who has designed a prototype.

Artist’s rendering of unit to remove CO2 from air. Any such machine must be able to run passively, “like a tree standing in the wind”, says Prof Klaus S Lackner, who has designed a prototype.

 

Artificial plants are one of this reporter’s biggest pet hates. Sitting in the waiting room of a dentist’s surgery, a fake fern strategically positioned in the corner of the room catches your eye. Rather than having the desired effect of providing some semblance of life in an otherwise sterile place, the plastic plant makes one feel even further removed from nature.

It’s not that surprising really, when you consider the process of manufacturing cheap, plastic house ferns generates harmful CO2, the same unwanted byproduct that could have been offset by planting the real thing in the first place.

But mimicking plants and trees in other ways might just represent another small solution to the man-made climate change dilemma.

Prof Klaus S Lackner, from the Centre for Negative Carbon Emissions (CNCE) in Arizona State University, has been trying to make artificial trees in his lab for years. His, however, won’t end up in the dentist’s waiting room. Lackner’s trees neither look nor smell like the real thing. Rather they mimic their basic function: the capture of air-born carbon dioxide for its practical application in other areas.

Lackner has been studying different ways CO2, released by the burning of fossil fuels, might be collected for most of his career.

Collected CO2 can assist in the development of biofuels and synthetic fuels. It can be pumped into greenhouses to provide carbon-enriched air for agriculture. It can also be found in the production of a variety of materials, from cosmetics to cement.

CO2 is useful in its purest form too. It can, for example, be used to carbonate beverages or assist in enhanced oil recovery. It could even be buried in the ground only to one day be converted back into a fossil fuel.

Carbon sequestration

However, deliberate CO2 collection from the air for practical applications is a burgeoning business ecosystem. If and when someone can figure out how to do it efficiently, there are numerous ways to make a buck. “We are doing it here at the CNCE to help reverse the impact of climate change,” says Lackner.

The financial element

Since the 1990s, Lackner has been seeking out novel ways to collect CO2. “In the early 1990s I began trying to figure out how to rebalance the carbon budget,” he says. “I realised how important it was to look at CO2 emissions in a different light. We have nearly unlimited carbon resources but we need to figure out how to manage our environmental footprint.”

After decades of trial-and-error research, he and his colleague Allen Wright have come up with a small outdoor prototype based on a membrane which operates on an “anionic exchange resin that captures carbon dioxide when dry and releases it when moist”. This allows for the “passive capture and release” of carbon dioxide and a minimal amount of energy required to produce this stream of CO2 through the “frictional movement of membrane material from dry to moist environments”.

“Passive” is the operative word here. This prototype is significant because of the way in which it can collect CO2 without requiring significant energy itself to function.

Does the device look like a tree? “The look is an interesting question and is still up for debate,” he says. “Right now it is akin to a furnace filter with holes where air can flow through.”

The bottom line

While this may sound like a lot of money in the short term, one of the key drivers for Lackner has been finding ways to reduce expenses. He is acutely aware of how crucial running costs will be in eventually popularising the notion of carbon collection in this way. That’s why the device itself has been designed with such low energy requirements.

Running out of options

However, options are becoming increasingly limited. “We have ignored the problem for so long,” says Lackner. “We would have to build 100,000000 of our devices to solve the existing carbon footprint, which isn’t an ideal solution.

Stopping the rise in CO2 to dangerous levels will require a net zero carbon economy. “The Intergovernmental Panel on Climate Change suggests we are already on a trajectory that will reach levels of CO2 that pose serious risks to the environment and human well-being,” he says. “So stabilising the climate will require pulling CO2 back with a negative carbon technology that can address past emissions.”

“There is no question that combating climate change can be done affordably though,” he stresses. “What’s key is figuring out how to achieve efficient CO2 collection. Any collecting machine must be able to run passively, like a tree standing in the wind.”

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