We've known about the effects of climate change for decades now, but the past few years (and even months) have been particularly revealing. This past year, for instance, we've seen arctic sea ice levels reach an historic low, while the United States has experienced its worst wildfire season on record (not to mention all the new temperature records). In these desperate times we may have to call upon desperate measures, including any number of proposed geoengineering projects. But as Gaia Vince of BBC Future recently pointed out, the solution may simply involve the improvement of an existing "carbon capture" technology: The humble tree.
Indeed, plants are nature's way of pulling carbon dioxide from the atmosphere. Subsequently, many ecologists have suggested that we simply plant more trees and other foliage. But as Vince notes, there are limits to such plans, including the high demand for agricultural space.
Instead, Vince points to the work of Klaus Lackner, director of the Lenfest Center for Sustainable Energy at Columbia University, who has designed an artificial tree that absorbs CO2 from the air using "leaves" that are 1,000 times more efficient than the real thing — but at the same time does not require exposure to sunlight.
The leaves look like sheets of papery plastic and are coated in a resin that contains sodium carbonate, which pulls carbon dioxide out of the air and stores it as a bicarbonate (baking soda) on the leaf. To remove the carbon dioxide, the leaves are rinsed in water vapour and can dry naturally in the wind, soaking up more carbon dioxide.
Lackner calculates that his tree can remove one tonne of carbon dioxide a day. Ten million of these trees could remove 3.6 billion tonnes of carbon dioxide a year – equivalent to about 10% of our global annual carbon dioxide emissions. "Our total emissions could be removed with 100 million trees," he says, "whereas we would need 1,000 times that in real trees to have the same effect."
As for what should be done with the resulting stores of CO2, Lackner suggests that it be converted into liquid fuels to power vehicles. And indeed, carbon dioxide produces carbon monoxide and hydrogen when it reacts with water — a solution known as syngas on account of its ability to be converted into hydrocarbon fuels like methanol or diesel. Again, Vince writes:
We have the technology to suck carbon dioxide out of the air – and keep it out – but whether it is economically viable is a different question. Lackner says his trees would do the job for around $200 per tonne of removed carbon dioxide, dropping to $30 a tonne as the project is scaled up. At that price – which has been criticised as wildly optimistic (the American Physical Society's most optimistic calculations for direct air capture are $600 per tonne of carbon dioxide removed, although the UK's Met Office is more favourable) – it starts to make economic sense for oil companies who would pay in the region of $100 per tonne to use the gas in enhanced oil recovery.
As Vince correctly points out, Lackner's plan is indeed very expensive. But that said, it is a plan — and one that sounds rather elegant. In terms of the costs, that will have to be offset against the prospect of doing nothing.
Be sure to read all of Gaia Vince's article as she goes over more of the details.
Image via Shutterstock.com/angelo lano. Inset image via.