Carbon capture: artificial trees suck CO2 from the air
Fewer trees means less clean air for us to breathe. But geophysicist Klaus Lackner explains that artificial trees can help repair the damage from deforestation.
August 04, 2011
Article at a glance
- Trees are not able to balance current CO2 emissions
- Klaus Lackner has studied the science of CO2 capture by trees
- This knowledge has been implemented in a carbon capture mechanism
- The project is still small scale but commercial applications are being identified
It took billions of years to create trees. These giant plants have long been a close ally to us, helping to keep the balance of CO2 in the air and in return generate oxygen, which is so vital to life. Now, trees are under siege, through deforestation, wildfires and pollution. At the same time we need trees more than ever to control rising emissions. In this interview, Geophysicist Klaus Lackner from Columbia University explains how he wants to address this imbalance.
Allianz Knowledge: CO2 capture systems that look like trees? Aren’t real trees doing their job?
Klaus Lackner: They do their job. But their job is not to clean up after our CO2 emissions and they are not really designed to do that for two reasons: One is that a tree spends most of its effort converting that CO2 into biomass; the other is that it is biomass which you still have to store.
If you wanted to collect all the CO2 we produce by using biomass growth, which could be trees or corn, you would roughly be talking about using all the agricultural land available globally.
How would an artificial tree capture carbon dioxide?
Like a tree it would stand exposed to the wind and artificial surfaces like leaves would take the CO2 out of the air. Since we are not doing photosynthesis these artificial leaves can be in the shade and so we can pack them more tightly than real leaves, but not so tightly that they hinder the air flow.
What would this device look like?
The design we are sort of favoring right now looks like a large box with filters like straws or fibers through which the air travels.
So if the air coming into the box has 400 parts per million (ppm) of CO2, the air coming out will have maybe 300ppm or even 200ppm. We are not trying to remove all the CO2 because our goal is to collect CO2, not to make CO2-free air.
How much CO2 is enough for you to capture?
If we end up at around 280ppm it won’t be too bad because the levels were 280ppm during pre-industrial times. We are right now above 390ppm and going up every year. So we could capture a substantial amount of CO2.
If you ask where we ultimately want to stop that becomes a political question. And I think we do not know the answer. The climate change models are good enough to tell us there is substantial risk but I don’t think they are really good enough to tell us whether 350ppm or 450ppm is safe.
My personal view is it doesn’t matter that much because I would argue 450ppm is now nearly impossible to maintain. It seems to me we have to figure out how to get to a zero-carbon economy. The question is do we have fifty years to accomplish this goal or do we have 10 years or are we already too late.
That’s why you develop air capture systems. But how would you store CO2?
That’s an important question. Unlike carbon capture and storage (CCS), with air capture it doesn’t matter where you take the CO2 out. You can emit emissions in New York and I can capture it in Australia. But as long as you use fossil energy for every ton of carbon coming out of the ground another ton of carbon will have to go back into the ground.
One way of doing this is to inject the CO2 underground, like the Norwegians are doing in the Sleipner gasfield off the Norwegian coast. They are putting a million tons of CO2 away per year 800 meters below the seafloor.
Another option is to make mineral carbonates, what I have been working on since the 1990s. That means we lock CO2 back into the rock through a geochemical process. Basically that’s what nature does; it balances the CO2 level in the air by exhaling carbon out of the earth and absorbing it back into the ground over a cycle of about one hundred thousand years. We just try to accelerate this process.
Is air capture something that’s ready to be commercialized?
No, we are still small scale. My goal at the university is working with students to understand the basic science. But I am actually involved with a private company originally known as GRT now called Kilimanjaro Energy. They are in the process of building small prototypes. Their job is to seek commercial applications for that.
Which markets would you target?
To get an air capture business started the idea is to find small markets which need CO2 to run businesses, for example dry ice producers, greenhouses, algae ponds and enhanced oil recovery.
These industries pay more than you would ever expect to get from a carbon trading market which is associated with climate change. Enhanced oil recovery alone uses some 40 million tons a year in the US to push oil out of the ground. I think we can get into the game at around 200 dollars per ton of CO2 and drop the price from there.
So the interesting thing about the air capture which I think differs from power plant CO2 capture is that it could very well have a strong economic incentive to start with. These markets don’t come close to the 30 billion tons of CO2 we have to capture in order to make the world carbon neutral, but it is the place to learn.