Catching CO2 on the Cheap

Klaus Lackner, the Ewing-Worzel Professor of Geophysics in the Department of Earth and Environmental Engineering at Columbia University “starred” in an article by CNN’s Hilary Whiteman last Monday. Being CNN, starred will have to do, sorry.  Nevertheless, One cannot fault Lackner, he’s been at his project since 1998.  As ideas go, merits aside, CO2 does have its uses – gathered cleaned and concentrated to pure form.  Lackner has a new gathering method that’s said to be much less expensive to operate.

Lackner is developing a structure that can capture atmospheric carbon dioxide 1,000 times faster than a real tree.  Whether the name is coming from Lackner or CNN, it’s now being called a “synthetic tree.”  This synthetic “tree” doesn’t need direct sunlight, water, a trunk, or branches to function, as it looks more like a cylinder.  No shady spot here, unless you add a porch.  Each synthetic tree would absorb one ton of carbon dioxide per day, eliminating an amount of CO2 approximate to that produced by 20 U.S. cars.  But the catch is – each unit is said to cost only about $30,000 to build.

That would be 365 tons of CO2 annually for a sunk investment of $30K.  Whoa, the algae folks and everyone else needing CO2 in high concentrations had better have a look.  Lackner told CNN the synthetic tree is highly efficient for its size.  He and his colleagues have developed an (ab)sorbent that is “close to the ideal,” in that it uses a relatively small amount of energy to release the CO2 and is not prohibitively expensive.  Lackner says, “By the time we make liquid CO2 we have spent approximately 50 kilojoules [of electricity] per mole of CO2.”  That makes the biggest cost at the back-end of the collector, primarily the technology used to release the CO2 from the (ab)sorbent.  I am curious to know, just what does it cost to yield CO2 in gas form?

Somehow, Lackner and CNN’s reporter Hilary Whiteman come upon this analogy to explain efficiency.  – Not to worry, the sense of the collector will become apparent. – When compared, for example, to a modern power-generating wind turbine, Lackner says, “If you give me one of those big windmills which have those big areas through which the rotor moves — how much CO2 could I avoid? And if I had an equally sized CO2 collector — how much CO2 can I collect? It turns out the collector is several hundred times better than the windmill.”

The meat of the collector importance becomes apparent when Lackner says, “By the time we make liquid CO2 we have spent approximately 50 kilojoules [of electricity] per mole of CO2.” Compare that, Lackner said, to the average power plant in the U.S., which produces one mole of CO2 with every 230 kilojoules of electricity. In other words, if we simply plugged our device in to the power grid to satisfy its energy needs, for every roughly 1000 kilograms of carbon dioxide we collect we would re-emit 200, so 800 we can chalk up as having been successful.”  Environmentalist logic can be fun, huh?

So, in real world terms, after using a fuel and selling the energy one could spend about 20% of the energy production to recover the CO2 in saleable form.  Having watched this area without any posts to the blog as of yet, this is a number that finally makes some sense.  CO2 is fuel, remember, it can feed algae, be reformed back into synthetic fuels and a wealth of other products.  What we haven’t seen are numbers that score prices of captured CO2 for such uses.

But that’s what needs done.  $30K per 365 annual tons plus the cost of the electricity to clean the CO2 out of the (ab)sorbent for ready to reuse CO2 in liquid form has to have some market power.  Time will tell what a gas form of supply might be priced.

Lackner is targeting carbon that’s already in the air, so the technology is not being developed as an alternative to the carbon capture and storage methods currently being tested for large-scale use on coal-fired power stations. That means that the collectors could be in the very best places where CO2 can be put to use.

This may seem a little far “out there.”  But recycling CO2 is an essential part of the future whether or not the media and political class catch on.  There are great swaths of the world suitable for growing CO2 consuming plants for fuel products that would benefit greatly from an added CO2 supply.  One of the main products from processing biomatter is CO2, so when cheap enough, CO2 can be a direct route to synthetic fuels.

That may be a bit far out there for many, but cheap CO2 is really exciting here.

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