OAK RIDGE, Tenn. — Scientists have figured out how to turn the tiny amount of carbon in a scrap tire plus used cooking oil into biofuel that could power thousands of delivery trucks.
Both old items are considered waste now.
"We are functionalizing the carbon in these tires and using it as a catalyst, converting waste cooking oil into a biofuel," said Parans Paranthaman, lead scientist at Oak Ridge National Laboratory. Paranthaman; Amit Naskar, carbon and composites group leader; and Zachary Hood, a graduate research fellow, have found a way to extract that carbon.
The United States generates nearly 300 million scrap tires a year, tires that take up a lot of space in landfills and turn into mosquito breeding grounds when left unburied. Globally, the number of scrap tires is more like 2 billion, and each one contains about 35 grams — roughly 1.2 ounces — of carbon.
The federal Environmental Protection Agency estimates that U.S. hotels and restaurants alone generate about 3 billion gallons of cooking oil.
Most of it, too, ends up in landfills. But if that waste oil were used in biofuel, one truck would be able to go 800 million miles, driving coast to coast nearly 250,000 times.
To start the process, researchers grind up the tires and soak the pieces in an acid treatment that increases the amount of carbon available by about 15%. Then they pour the pieces into ceramic labware and heat the mixture in an oven at nearly 1,500 degrees Fahrenheit.
That baking process is short, but it burns off the tire rubber and leaves the black, powdered carbon behind.
Then the team uses the carbon powder to create a reaction between methanol, sometimes called wood alcohol, and the used cooking oil.
"This is not corn or anything diverted from the food chain," Paranthaman said. "This is a waste bio-source, and it is unlimited."
The researchers first began experimenting with leftover oil that Paranthaman's wife collected when she made dinner. The process works with used canola, vegetable or soybean oils and even animal fats.
Fast-food restaurants generally change the oil in their deep-fat fryers a couple of times a week, and few biodiesel manufacturers are able to exploit this resource because of its high free-fatty acid content.
That's because typical biodiesel processing uses lye, which turns into soap when it's combined with highly fatty oils in a reaction called saponification, Hood said. Some companies work around that by adding sulfuric acid to the oil, but that adds cost and can corrode equipment.
A patent on the process is still pending. Several companies already are courting the team to license the product as part of the Department of Energy's technology transfer program.
The team expects to license the technology in the next four to six months. The company that gets the license will be responsible for continuing to develop the process and bring it to the commercial market, paying royalties to the Energy Department on the profits.
Follow Brittany Crocker on Twitter: @BrittCrocker
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