Physicist and engineer Klaus Lackner makes artificial trees – but not the kind that decorate living rooms and lobbies. His artificial trees can capture carbon dioxide directly out of the air—and they’re 1,000 times more efficient than nature’s trees in doing so.
Millions of the trees could eventually generate “negative carbon emissions,” meaning they could take more carbon dioxide out of the air than we put in from fossil fuel emissions. That is what we need to reverse the course of climate change, he said. People on Earth generate 36 billion metric tons of CO2 each year and CO2 is a greenhouse gas that holds heat in the atmosphere.
Even if the world drastically cut carbon emissions today, it would take a very long time to return to a safe range because of the way CO2 accumulates, or “piles up” in the air, said Lackner, the director of the Center for Negative Carbon Emissions at Arizona State University.
Lackner developed the artificial trees to offset the already-high global carbon dioxide levels. These trees don’t look like natural trees – they don’t have leaves or branches. But they function in a similar way by absorbing carbon dioxide out of the atmosphere. Existing technology could recycle the captured carbon dioxide and use it to as a resource to make fuel, “closing the loop” of carbon emissions, he said.
“We can argue where to stop [carbon emissions], but that we will have to stop is unavoidable. The world cannot run ‘business-as-usual’ in energy, it has to figure out a better way. And at the same time, it’s not likely that it can do that overnight, so you do need to balance the carbon budget,” Lackner said.
Lackner’s trees are made from a special resin – a unique plastic that sponges up CO2 from the air in a chemical reaction. When the resin is dry, it “has an exceedingly high affinity to carbon dioxide” –in other words, it absorbs the C02. And when the resin is submerged in water, it releases the carbon dioxide, Lackner said.
“People say, ‘Why not just grow normal trees, natural trees, rather than those artificial trees?’ But I argue that’s like pulling a plow over using a tractor. You certainly can do it with a horse, but it’s not as efficient,” Lackner said. “Our trees are specialists for carbon dioxide collection, and they’re about 1,000 times faster [than natural trees].”
The first outdoor prototype has been on the roof at Arizona State University for about a year, Lackner told climate scientists at this fall’s annual Comer Abrupt Climate Change Conference in Wisconsin.
“It’s running essentially automatically, with a little bit of graduate student supervision,” he said.
One hundred million of Lackner’s units, each built to remove one metric ton {2,204 pounds} of C02 a day, would be needed to match the amount of carbon dioxide the world currently emits each year, Lackner said. Adding more units would begin to lower the 400 parts-per-million (ppm) of carbon dioxide already in the atmosphere, a level that is on the rise.
“If we had another 100 million [units], you could bring [carbon dioxide levels] down another 2 ppm, per year,” said Wallace Broecker, one of the world’s pioneering climate scientists. “If we just did that, we’d now have 200 million, one [million] matching what we’re producing, and another [million] taking some out. Then to go back to 350 ppm, it would take 50 years.”
Scientists consider 350 ppm of C02 a ceiling to keep climate change under control, according to many experts. Levels of the greenhouse gas started to rise above 300 ppm with the Industrial Revolution.
Lackner’s device demonstrates that carbon dioxide can be effectively captured from the atmosphere. But technology exists that could also turn that captured carbon dioxide back into liquid fuels, essentially reusing carbon emissions to generate new energy, Lackner said.
The concept is based on a process that was used in South Africa during the apartheid years. While under an embargo, South Africa “had no access to oil, and they showed that you can convert coal to liquid fuels, gasoline and diesel,” he said.
In this process, steam and coal are converted into carbon monoxide and hydrogen. Carbon monoxide and hydrogen can then be reacted to form any type of fuel – gasoline, diesel, methanol, dimethyl ether or alcohol, he said.
But instead of starting with coal, Lackner said, renewable electricity from wind or solar can be combined with captured carbon dioxide emissions and water to create carbon monoxide and hydrogen.
“Then we are right at the same spot they are to make fuels again,” he said. “The technologies exist. They’re not all that well developed, because nobody ever had good reason to do it, but certainly they exist, it’s not something we don’t know how to do,” he said.
Energy from solar or wind could drive the conversion, creating a way to store renewable energy from solar or wind power as gasoline for use in months with less sunshine or wind, Lackner said. This would “make it possible for the renewable energy to truly penetrate into the system,” he said.
In order for that to happen, Lackner believes volunteers must first commit to capturing carbon dioxide waste. Then eventually, more people will see the benefits, get on board, and regulations could be established.
“The problem is, [carbon dioxide] doesn’t hurt right away, it doesn’t smell, it’s invisible, and so it’s hard to convince people. People don’t realize that they put out 20 pounds of carbon dioxide every time they burn a gallon of gasoline, because it’s invisible,” he said.
“I think we’re playing with something we don’t understand and the easy way out is to not let [excess carbon emissions] happen,” Lackner said.
