Can 'mechanical trees' absorb greenhouse gases from the air?

New technology may take a decade or two to achieve a breakthrough, but if there is an economic appeal, things can go quickly.

Mechanical trees that suck CO2 out of the atmosphere

The US Department of Energy has a new goal of increasing direct carbon dioxide capture, a technology that uses chemical reactions to capture this gas directly from the air.

In an interview with The Daily Beast, Klaus Lackner, Professor of Engineering and Director of the Center for Negative Carbon Emissions at Arizona State University, spoke about this technology, what is meant by direct carbon removal, and why it is necessary.

End carbon and climate stabilization

Lackner said that carbon builds up in the environment and that nature takes thousands of years to remove, and that the world is moving towards much higher concentrations of carbon dioxide that far exceed anything humans have experienced, and humanity cannot tolerate the increasing amounts of excess carbon that floats in the environment, so it must be disposed of.

He added that two centuries of burning fossil fuels have caused more carbon dioxide, a powerful greenhouse gas, to be pumped into the atmosphere than nature can remove. When this gas accumulates, it traps excess heat near the Earth's surface, causing global warming.

Now there is so much carbon dioxide in the atmosphere that most scenarios show that ending emissions alone will not be enough to stabilize the climate, so humanity must also remove carbon dioxide from the air directly.

Lackner explained that not all emissions come from large sources, such as power plants or factories, as carbon dioxide can be captured when it exits. So there is a need to deal with the other half of emissions; From cars and planes and taking a hot bath while the gas furnace is expelling carbon dioxide, this means taking the carbon dioxide out of the air.

Mechanical tree method

Because carbon dioxide mixes quickly in the air, it doesn't matter where it is removed anywhere in the world, and how it is stored is also important. Storing carbon dioxide for 60 or 100 years is not good enough. If all that carbon returns to the environment 100 years from now, all we have to do is take care of ourselves, and our grandchildren will have to find out again. Meanwhile, the world's energy consumption is growing at about 2% annually.

Lackner explained his laboratory's method for capturing gas from the air directly, and it is called the "mechanical trees" method, saying that it is long vertical columns of disks covered with chemical resin, about 5 feet in diameter (one and a half meters), and the disks are separated by about two inches (5 centimeters). , Like a pile of records.

As the air blows, the surfaces of the tablets absorb the carbon dioxide, and after 20 minutes or so the tablets are full, sinking into a barrel at the bottom. Then, water and steam are sent to release carbon dioxide in a closed environment.

By using moisture, about half of the energy consumption can be avoided, and renewable energy is used for the rest. This requires water and dry air, so it will not be ideal everywhere, but there are also other ways.

And about storing carbon dioxide and the possibility of the world getting rid of it permanently, Lackner said that this is possible by taking advantage of the fact that it is acid and that some rocks are basic. When carbon dioxide reacts with calcium-rich minerals, it forms a solid carbonate. With carbon dioxide mineralization, an almost unlimited amount of carbon can be stored permanently.

The need for a regulatory framework

Lackner stated that the Department of Energy has set a new goal of reducing CO2 removal costs to $100 per ton and expanding it rapidly within a decade. "But after neglecting technology for 30 years, we can't just say that there are companies that know how to do it and all we have to do is push it forward. We have to assume that this is a nascent technology."

He noted that Climeworks is the largest company to directly capture carbon dioxide and sell it at about $500 to $1,000 per ton. He described it as too expensive, when the world could do it at $50 a ton.

He explained that the United States consumes approximately 7 million tons of commercial carbon dioxide annually; Soft drinks, fire extinguishers, and granaries, which you use to control explosive grain powder, average $60 to $150. So, "under $100, you have a market."

He stressed that what the world really needs is a regulatory framework that says we demand the removal of carbon dioxide, and then the market will move from capturing kilotons of carbon dioxide today to capturing gigatonnes of it. He added that he sees a world moving away from fossil fuels, "perhaps incrementally, but has a mandate to capture and store all the CO2 over the long term."

Carbon Sequestration Certificate

He said his recommendation that the carbon when it leaves the Earth should be combined with equal removal; “If you produce one ton of carbon related to coal, oil or gas you need to get rid of one ton. It doesn’t have to be in the same ton, but there has to be a sequestration certificate confirming that it has been phased out, and it must last more than 100 year. And if all the carbon were documented from the moment it came out of the ground, it would be hard to deceive the system."

He noted that the big unknown is how hard it will be to get industry and society to decarbonise, adding that it is encouraging to see companies like Microsoft and Stripe buying carbon credits and decarbonization certificates and willing to pay somewhat higher prices.

He concluded by saying that the new technology may take a decade or two to achieve a breakthrough, but if there is an economic attraction, things can go quickly, noting that the first commercial aircraft were available in 1951, and by 1965 they were everywhere.