Eggshell absorbers

Engineers at Ohio State University have found a novel use for discarded chicken eggshells. The patented process that they have developed uses eggshells to soak up carbon dioxide from a reaction that produces hydrogen fuel.

L.S. Fan, Prof of chemical and biomolecular engineering at Ohio State, said that he and former Ohio State doctoral student, Mahesh Iyer, hit upon the idea when they were trying to improve a method of hydrogen production called the water-gas-shift reaction. With this method, fossil fuels such as coal are gasified to produce carbon monoxide gas, which then combines with water to produce carbon dioxide and hydrogen.

‘The key to making pure hydrogen is separating out the carbon dioxide,’ Fan said. ‘To do it very economically, we needed a new way of thinking, a new process scheme.’

That brought them to the eggshells, which mostly consist of calcium carbonate – one of nature’s most absorbent materials. With heat processing, calcium carbonate becomes calcium oxide, which will then absorb any acidic gas, such as carbon dioxide.

In the laboratory, Fan and his colleagues demonstrated that ground-up eggshells could be used in the water-gas-shift reaction. The calcium carbonate in the eggshells captures 78 percent of carbon dioxide by weight, Fan explained. That, they claim, makes it the most effective carbon dioxide absorber ever tested.

Before they could grind up the egg shell, the engineers needed to remove the collagen-containing membrane that clings to the inside, so they developed an organic acid to do the job. About 10 percent of the membrane consists of collagen, and, once extracted, can be used in the food or pharmaceuticals industry.

‘Our technology can help the egg industry to dispose of its waste, and at the same time convert the waste to a useful product,’ Fan said.

The university plans to license the technology for further development.