Right now, cement production accounts for 5 to 6 percent of total man-made greenhouse gases. Producing lime, its key ingredient, uses an energy-intensive process that needs temperatures as high as 1,500 degrees Celsius, and that can only be obtained with fossil fuels. A new, rudimentary contraption at George Washington University does all that with solar power and without emitting carbon dioxide.
The team led by Stuart Licht used three Fresnel lenses to concentrate sunlight onto two different processes: one that heats up limestone and the other that produces electricity to perform electrolysis, that breaks the hot carbonate mixture and causes the lime to precipitate out of it, making it readily-collectible.
Around 60 percent of the carbon dioxide emissions from the production of cement is considered to be unavoidable. Licht’s team proved otherwise: they “hacked” the process to produce oxygen and carbon/carbon monoxide, which can be further recycled.
By mixing solid calcium carbonate with liquid lithium carbonate, and preheating the solution to 900 degrees Celsius, the scientists make up a liquid that acts like an electrolyte. The high temperature helps the entire electrolysis process to produce lime, which would be harder to collect at lower temperatures, because it would be more soluble.
However, the lime production system has to go a long way until it’s commercially-available. One of the roadblocks is that the energy (heat) has to be stored to counter the effects of the intermittent nature of solar power. Cited solutions include storing it in molten salts, just like it’s done in CSP (concentrated solar power) systems.
If it proves to work as advertised, this technology could offset up to 6 percent of our total greenhouse gas emissions, as I said earlier. What strikes me is that nobody had thought so far about making this contraption possible, and everyone is using expensive fossil fuels, when the Sun is readily available for anyone to use… weird or what?
On the other hand, it’s not uncommon for such inventions to create spin-offs that would later become industry leaders. We shall wait and see.