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L. S. Fan
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The eggshell plays a critical role.
"The key to making pure hydrogen is separating out the carbon dioxide,"
Fan said. "In order to do it very economically, we needed a new way of
thinking, a new process scheme."
That brought them to eggshells, which mostly consist of calcium
carbonate - one of nature's most absorbent materials. It is a common
ingredient in calcium supplements and antacids. 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. Iyer
performed those early experiments; recent graduate Theresa Vonder Haar
also worked on the project for her bachelor's degree honors thesis.
Calcium carbonate - a key ingredient in the
eggshells - captures 78 percent of carbon dioxide by weight, Fan
explained. That means, given equal amounts of carbon dioxide and
eggshell, the eggshell would absorb 78 percent of the carbon dioxide.
That makes it the most effective carbon dioxide absorber ever tested.
Energy experts believe that hydrogen may become an important power
source in the future, most notably in the form of fuel cells. But
first, researchers must develop affordable ways to produce large
quantities of hydrogen - and that means finding ways to deal with the
byproducts of chemical reactions that produce the gas.
According to the United States Department of Agriculture, the country
produced nearly 91 billion eggs in 2006. That equates to about 455,000
tons of shell per year that could potentially be used in hydrogen
production.
Still, Fan said, even if all that shell were utilized, it would only
provide a portion of what the United States would need to seriously
pursue a hydrogen economy.
"Eggshell alone may not be adequate to produce hydrogen for the whole
country, but at least we can use eggshell in a better way compared to
dumping it as organic waste in landfills, where companies have to pay
up to $40 dollars per ton disposal cost," he said.
Before they could grind up the egg shell, the engineers needed to
remove the collagen-containing membrane that clings to the inside;
they developed an organic acid that does the job. About 10 percent of
the membrane consists of collagen, which sells for about $ 1000/gram.
This collagen, once extracted, can be used in food or pharmaceuticals,
or for medical treatments. Doctors use collagen to help burn victims
regenerate skin; it's also used in cosmetic surgery.
"We like that 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.
"And in the long term, we're demonstrating that carbon-based fuel
sources, like coal or biomass, can be efficiently converted to
hydrogen and liquid fuel. The goal is an energy conversion system that
uses a dependable fossil energy source, but at the same time has very
little environmental impact."
Fan is currently working with a major egg company to produce large
quantities of the eggshell granules for testing. The university plans
to license the technology for further development.
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