Wojciech Lipiński, Dr. Sc.Techn, said at the National Meeting & Exposition of the American Chemical Society (ACS) of recycling carbon dioxide (CO2), “It may seem like trying to put the genie back into the bottle. But it already has been proven with laboratory scale equipment. The process uses three of the worlds most abundant and inexpensive resources. Sunlight is the energy source and carbon dioxide and water are the raw materials.”

The search for ways to use the megatons of industrial carbon dioxide emission has led to a process system for converting that “major greenhouse gas” back into a fuel that released it in the first place.

Solar CO2 Capture Process Graph.  Image Credit: Solar Energy Lab, University of Minnesota.  Click image for the largest view.

Solar CO2 Capture Process Graph. Image Credit: Solar Energy Lab, University of Minnesota. Click image for the largest view.

Additionally Lipiński also discussed another project that could be part of a process system using inexpensive calcium oxide, made from ordinary limestone, to capture CO2 before it leaves the smokestacks of coal-fired electric power stations. The CO2 reacts with calcium oxide, forming calcium carbonate, the same material in blackboard chalk, some calcium dietary supplements and some antacids. The calcium carbonate then goes into a reactor that removes the CO2 and regenerates the calcium oxide for another encounter with the CO2.

Both processes use highly concentrated sunlight as the energy source. The test facility built at the University of Minnesota by Lipiński and his colleague Jane Davidson, Ph.D., is a high-flux solar simulator consisting of seven 6,500-watt light bulbs and mirrors that focus the light into a spot about 2 inches in diameter. Temperatures in that spot can reach 3,600º F, which is far higher than the melting point of iron.

In a smokestack process system the solar heat would remove the carbon dioxide from calcium carbonate and regenerate the calcium oxide. In the “genie-out-of-the-bottle” CO2 process, that heat fosters breakdown of carbon dioxide and water to form carbon monoxide and hydrogen, the two components of “synthesis gas” or “syngas.”

The name for syngas comes from its time-tested use – for more than a century – in making or synthesizing other products. Syngas can be converted into synthetic hydrocarbons, for instance, gasoline, diesel and jet fuel or aviation kerosene. Jet fuel is already industrially produced in significant quantities from syngas obtained from coal and natural gas.

Lipiński and his colleagues are developing prototype reactors to demonstrate syngas production from water and captured carbon dioxide in the solar simulator. A full-scale commercial facility would use a field of mirrors to focus sunlight onto a central reactor, similar to the emerging concentrated solar power, or CSP, facilities that now use heat from sunlight to produce electricity.

Lipiński noted that the sunlight-to-synfuels technology could be the basis of “carbon-neutral” energy production, in which CO2 is reused, with the same amount released into the air from burning of fossil fuels removed and put back into synfuels. With their similarity in composition to conventional fuels and long history of use, synfuels made with the solar process also would not require a new infrastructure.

In a closed loop system the CO2 could be used over and over again endlessly.  If the sunlight energy source can be made to work in a cost effective manner the idea could get some legs.

Another point that isn’t considered is the ordinary limestone supply is considerable.  While no one so far has put the latest technology to numbers ordinary limestone isn’t expensive, making CO2 collection something, well, everyone could do if the technology could scale up economically.

As far fetched as that sounds the tempering comes from the heat units needed.  Lipiński and his colleagues have the germ of a great idea, but the 45,500 watts at their disposal in the lab focused to a 2” diameter doesn’t easily transfer into something we could use to work up a paper napkin scenario.  Nor is there a rate discussed.  It’s an idea in need of more data.

That and the making of the syngas and converting it to fuel aren’t addressed from a cost or facility cost.

We’ll be keeping an eye out for more progress at Minnesota.  The idea has a certain charm; using CO2 over and over again does offer the global warming folks a hint of a way to reduce the CO2 emissions.  On the other hand, a massive CO2 reduction effort would put anthropological CO2 reduction in direct competition to the planet’s plant life ecosystem.

It’s not as simple as it seems.


1 Comment so far

  1. www.mama2punto0.cl on November 11, 2013 12:12 AM

    Hi there! This article couldn’t be written much better!
    Reading through this article reminds me of my previous roommate!

    He always kept preaching about this. I will forward this article to him.
    Fairly certain he’ll have a great read. Thank you for

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