Are used tires and bacon grease the fuel of the future?

9/13/2017

Used tires have many opportunities for a second life after the rubber meets the road, so to speak. They can be ground into pavement or playground cover, and even used to tread shoes.

Soon, they may help power diesel engines too, thanks to a team of researchers from Oak Ridge National Laboratory.

A disposal problem, a solution

Old tires present complicated waste disposal problems. They are large and hollow and take up a lot of space in landfills. When left to nature, they turn into breeding grounds for mosquitoes and other pests.

The United States generates nearly 300 million scrap tires per year. Globally, it’s more like 2 billion, and each scrap tire contains about 35 grams of carbon.

ORNL lead scientist Parans Paranthaman, Carbon and Composites group leader Amit Naskar, and graduate research fellow Zachary Hood have found a way to extract that carbon and use it to make biodiesel.

“We are functionalizing the carbon in these tires and using it as a catalyst, converting waste cooking oil into a biofuel,” Paranthaman said.

First, the researchers grind up the tires and soak the pieces in an acid treatment that increases the amount of carbon available by about 15 percent. Then they pour the pieces into a ceramic boat and heat them 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, powder-like carbon behind.

Used cooking oil plays role

Then, the team uses the carbon powder to catalyze a reaction between methanol and another common waste product: used cooking oil.

The Environmental Protection Agency estimates 3 billion gallons of cooking oil is wasted each year. That amount could generate enough biofuel to power 400,000 trucks to go 2,000 miles, according to Paranthaman.

The researchers first began experimenting with leftover oil Paranthaman’s wife collected when she made dinner. The process works with used canola, vegetable or soybean oils and even animal fats.

“This is not corn or anything diverted from the food chain,” Paranthaman said, referring to ethanol-based biofuel manufacturing, which has been the subject of ethical and economic debates. “This is a waste biosource, and it is unlimited.”

Cooking oil is also the cheapest oil available. Fast food restaurants use and throw out gallons of it, and few biodiesel manufacturers are able to exploit the resource because of its high free-fatty acid content.

Hood said 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. Some companies work around that by adding sulfuric acid, but it is ultimately more expensive and can corrode equipment.

“So to avert that, we and many other groups have been trying to make these kinds of solid acid catalysts,” Hood said.

Step toward large-scale biofuel production

Paranthaman said the team’s research is a big step toward large-scale biofuel production and addresses two major sustainability issues at once: waste and energy production.

The process is still patent-pending. To make it a norm for biodiesel production, the group will have to work with a major supply chain. Several companies are already courting the team to license the product as part of the Department of Energy’s technology transfer program.

The team expects to license it in the next four to six months. The company that gets the license will be responsible for continuing to develop it and bring it to the commercial market, paying royalties to the Energy Department in return.

Source: Knoxville News Sentinel, by BRITTANY CROCKER

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