Trash-to-glass investigatıons
Engineers extract pure minerals from rotten food
Colorado School of Mines engineers have found an alternative to digging into mountains for minerals: mining the minerals from food waste.
They’ve turned putrid banana peels, eggshells and rice husks into crystal-clear glass.
Now they’re investigating what other muck may yield.
In a lab here, they rigged up a cooking system that starts at a fridge, where students delightedly donate garbage.
This garbage is ground in blenders, dried, then pounded into fine white powder containing pure minerals, such as silica and oxides, that typically are mined using heavy diggers and toxic chemicals. An oven heated to 3,000 degrees melts the silica powder into a molten red substance that when poured into molds morphs to glass.
TheU.S. government has registered a provisional patent.
And materials engineer Ivan Cor- nejo and his crew are calculating just howmuch greenhouse gas-producing food and agricultural waste worldwide could be diverted from landfills.
Beyond that potential to address climate change, they also envision a revolution that would redefine mining to include a variety of new sources of minerals. No longer would the Earth’s crust have to be cut to meet growing global demands for silica to make glass and other ingredients essential to industrial growth.
“These mines are mostly open-pit mines all over the world. Silica is coming from Brazil and China,” Cornejo said. “There’s no reason to continue mining, destroying the environment, when we can findmany of thematerialswe need fromwaste.”
Cornejo comes from Corning Inc., where he helped develop Gorilla Glass, used on about 1 billion smartphones and other high-performance products.
His food waste-to-glass investigations began earlier this year when he heard a radio report about people trying to decide whether to destroy a forest to reach a deposit of calcium carbonate beneath it. He and engineer Ivar Reimanis and postdoctoral researcher Subramanian Ramalingam started analyzing food waste to identify minerals.
In May, they set up their system at the school’s Center for Advanced Ceramics, substituting cheap alumina crucibles for the $10,000 platinum kind they prefer. They wear goggles, protective jackets and face shields, handling red-hot liquid with tongs as it cools to gold, white and, eventually, clear glass.
The team hypothesizes that volumes of food waste worldwide may be sufficient to sustain the booming global demand for glass — requiring 36 million tons of silica.
“I mean, this was rotten garbage,” Cornejo said of a 60-gram piece of clear glass. The banana, rice husk and eggshells weighed 240 grams before cooking.
Mines’ students are intrigued, jockeying to work in the lab. New waste is offered for testing — peanut shells, coffee grounds, avocado seeds.
Next on the agenda is cataloging minerals that could be mined from cafeteria, feedlot and farmwaste. The engineers also are seeking federal and industry funding for measuring the composition of the various glasses they produce.
“This opens a newway of thinking about foodwaste,” Cornejo said. “You allow people to eat what they have to eat. Then you use their waste to make unique materials.”