Scientists research use of eggshells, food waste in tires

Eggshells may be part of the next phase of sustainable manufacturing practices for the tire and rubber product industry.

WOOSTER, Ohio — Eggshells and other food waste may be the next phase of sustainable manufacturing practices for the tire and rubber product industry, as a replacement for carbon black.

Scientists at the Ohio Agricultural Research and Development Center (OARDC) at the Ohio State University-Wooster Campus are conducting research into eggshells and tomato peels as locally sourced and naturally occurring substitutes for carbon black.

So far the results are very encouraging, according to Katrina Cornish, Ohio research scholar and endowed chair in bio-emergent materials at Ohio State's College of Food, Agricultural and Environmental Services (CFAES).

Ms. Cornish, who also directs OARDC research into dandelions as a source of natural rubber, said her research into carbon black alternatives began in 2010, the year she arrived at the university.

Local sourcing is very important to the carbon black alternative project, according to Ms. Cornish.

"In Ohio, we serve the public, and Ohio is big in agriculture and food processing," she said.

• This story appeared in the June 5 print edition of Tire Business

Using eggshells and tomato peels as substitutes for carbon black offers three potential benefits, according to Ms. Cornish:

  • Reducing petroleum dependency;

  • Increasing sustainability in the manufacture of tires and rubber products; and

  • Keeping food waste out of landfills.

The research at OARDC concentrates on using food waste as a partial, not total, replacement for carbon black, according to Ms. Cornish.

Experimentation in eggshells involves research into macro-, micro- and nano-sized grind, she said.

Photo provided

Cornish

Nano-sized pieces could replace carbon black 100 percent in guayule rubber, she said. (Ms. Cornish also is an expert in guayule rubber, thanks to her previous research both at the U.S. Department of Agriculture's Agricultural Research Service and at Yulex Corp.)

However, nano-sized grind in guayule rubber would be prohibitively expensive, Ms. Cornish said.

Micro-sized grind as a partial replacement in various rubbers is a more viable option, she said.

In any case, the OARDC researchers have their work cut out for them, according to Ms. Cornish.

"We have to match what carbon black can do or exceed it," she said.

In some blends, eggshells and tomato peels can improve rubber properties slightly, such as elongation and softness, depending on what the application calls for, according to Ms. Cornish.

One effect of using eggshells as a partial carbon black replacement is a change in the color of the rubber, according to Ms. Cornish.

Carbon black represents about 30 percent of a tire by weight, and it is responsible for the traditional black color of a tire, she said.

Photo provided

Sample of an alternative rubber source.

For the past four or five years, the OARDC has worked with Michael Foods Inc., a Minnetonka, Minn.-based producer of egg, potato and frozen food products, as a supplier of eggshells, according to Jonathan A. Merkle, vice president of science and technology and chief science officer for Michael Foods.

According to Mr. Merkle, the U.S. egg processing industry generates about 140,000 metric tons of eggshells annually, which is only a small fraction of the eggshells produced around the world.

Eggshells already have a number of productive uses, including soil amendments and as a mineral source for both animals and humans, Mr. Merkle said.

But eggshells used as a reinforcing ingredient of rubber have the potential for making them a high-demand product, he said.

"Even at parity of cost, the use of eggshells in rubber polymers decreases the dependence on carbon black, which is produced under strict environmental standards," Mr. Merkle said.

OARDC uses Michael Foods as a direct supplier of eggshells, according to Ms. Cornish. "It makes sense, rather than going through a third party," she said.

Photo provided

A variety of rubber composites, derived from alternative sources such as food waste, could one day lead to a replacement for carbon black.

One of the companies that is investigating eggshells as an ingredient in rubber formulations is Ford Motor Co., which has been conducting research since the beginning of 2016, according to Janice L. Tardiff, an elastomer materials technical expert for the auto maker.

Although Ford is conducting its own research, it was Ms. Cornish who introduced Ford to the use of eggshells as a filler, according to Ms. Tardiff.

"Our team is looking at natural rubber part applications, such as hood/door stops and suspension mounts," Ms. Tardiff said of Ford's eggshell research.

Eggshells are compatible with both Hevea and guayule rubber, and they do not degrade when exposed to the heat cycles normally observed in auto parts, according to Ms. Tardiff.

They also are easy to manage, because no drying is necessary and they can be used with or without membranes, she said.

Ford also looked at tomato peels as a partial replacement for carbon blackbut decided to concentrate on eggshells, Ms. Tardiff said.

OARDC also is starting to test eggshells as a partial replacement for silica, according to Ms. Cornish.

"We could be quite close to commercialization," she said.

Meanwhile, Ms. Tardiff estimated that Ford could start using eggshells in auto parts within four years.

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