Engineers have developed a recipe for making hydrogen fuel that uses a secret ingredient: pulverized eggshells. The technique could help scientists overcome some of the obstacles to powering more environmentally friendly cars.
Hydrogen has long been touted as the clean fuel of the future because the only waste product is water (ScienceNOW, 20 August). But hydrogen is hard to make. It doesn't exist naturally on Earth as a gas; most of it comes from the conversion of fossil fuels to gas, resulting in carbon monoxide. When combined with water, carbon monoxide yields hydrogen. But the process also creates carbon dioxide, which contributes to global warming.
That's where the eggshells come in. The shells are 95% calcium carbonate, a compound that, when heated, becomes calcium oxide, which can absorb acidic gases like CO2. In laboratory tests, Liang-Shih Fan, a chemical engineer at Ohio State University in Columbus and his former doctoral student, Mahesh Iyer found that ground up eggshells removed as much as 78% of the carbon dioxide made during the hydrogen-production process. The United States produces more than 200,000 kilograms of eggshell waste per year, notes Fan, which should make the approach more cost-effective. There's also the added benefit of reducing landfill waste.
Another perk: a thin membrane that sticks to the shells' insides. Researchers must remove this membrane before the shells can be ground, and because it's 10% collagen, it can be used to regenerate skin in burn victims or in cosmetic surgery. Fan and Iyer have patented a special acid that removes the membrane, as well as the new technology that allows eggshells to be used in hydrogen production.
Still, not everyone is convinced that eggshells are the future. "It's an intriguing idea, but I don't know how this could work at a large scale," says Joseph Romm, a physicist and author of several books on energy and the climate. Plus, he notes, the approach doesn't address the biggest problems with hydrogen fuel: extending the life of fuel cells and developing more compact hydrogen storage tanks on board vehicles. Daniel Sperling, director of the Institute of Transportation Studies at the University of California, Davis, is more optimistic. "As we focus our societal resources on replacing fossil energy, I am certain many new materials and techniques will be developed," he says. "This may be one of them."