Volume 17 | Number 2 | Summer 2005 | Environmental Issue

Georgia Tech Researchers Partner with Industry to Study Alternative Uses for Eggshell Waste

Researchers have developed a lab unit that successfully separates nearly 100 percent of the calcium carbonate from the membrane in eggshell waste using a water/air mixture.

Each year in Georgia alone, more than 37 million pounds of eggshells are directed to landfills. Such a large amount of waste is both an environmental (rotting shells generate malodors and attract pests) and economical (companies pay upward of $100,000 annually to depose of the eggshells) problem. With many landfills nearing capacity, Georgia Tech researchers recently undertook an effort to develop an alternative to landfills that extracts value-added byproducts from eggshell waste. The study is being funded by Georgia’s Traditional Industries Program for Food Processing.

“For years some of these eggshells have been converted by the rendering industry into animal feed supplements. And these same eggshells also have components of value to the papermaking, pharmaceutical, and biochemistry industries,” explains Jeff Hsieh, a professor in the Georgia Tech School of Chemical and Biomolecular Engineering and the study’s principal investigator. Hsieh and his research team are concentrating their efforts on using the main component, calcium carbonate (CaCO3), in papermaking applications.

According to Hsieh, the eggshells are approximately 95 percent calcium carbonate and 4.5 percent membrane. The calcium carbonate in the eggshells, he says, can be a substitute for mined minerals used to improve brightness, opacity, and strength in paper. It can also potentially be used to improve the appearance of the paper, making it easier to print on and smoother, more opaque, and brighter when used as a coating. The eggshell membrane, on the other hand, contains 10 percent collagen, which can possibly be used as a raw material in the manufacture of amino acids. The remainder of the membrane can be used as an additive for animal feed.

A key problem, however, is how to completely separate the calcium carbonate from the membrane in an economically and environmentally sound method. Over the past year, Hsieh and his team have taken the initial steps to solve the problem.

The research team has developed a lab unit that successfully separates the calcium carbonate from the membrane by using a water/air mixture. The unit first grinds the eggshells; then the ground eggshells are mixed with water. The mixture of the eggshell powder and the water is put into a countercurrent column with a water/air mixture pumped up from the bottom. The water and air separate the membrane from the calcium carbonate with the carbonate falling to the bottom and the membrane floating off the top, resulting in a collection of both products.

The team field tested the unit at American Dehydrated Foods, Inc.’s (a leader in the processing of underutilized agricultural raw materials into superior value-added products) plant in Social Circle, Ga. During the test, the unit successfully separated nearly 100 percent of the calcium carbonate from the membrane.

Having successfully separated the calcium carbonate from the membrane, the research team, together with EvCo Research, LLC, has just begun to evaluate the use of the calcium carbonate as pigment in paper coating formulations. EvCo, a supplier of coating and wet end treatment chemicals to the paper industry, has shown that some of its coating chemicals can be used in inkjet printing formulations and give improved results.

“We are interested in determining whether coatings based on our chemistry and used with calcium carbonate from eggshells would offer some synergistic benefit for the inkjet printing application,” says John Kokoszka, vice president of EvCo.

“I have been impressed with the work done by Georgia Tech on the separation technology; it was felt by all before this project began that this would be an almost impossible task. However, Georgia Tech was able to bring together creativity and ingenuity to solve a difficult problem. Given the success that Georgia Tech has had with the separation, we look forward to equal progress on the use of this chemical with our technology in inkjet coating formulations,” adds Kokoszka.

Imerys, a Georgia-based mineral processor, is assisting in the processing of the calcium carbonate so that it can be usable for applications in the paper or other industries.

Hsieh says successful completion of this project will provide tangible benefits for both the poultry and paper industries. “This project will solve
a landfill problem for the poultry industry and recover eggshell waste destined for the landfill and transform it into a value-added product for the paper industry.”

“It is also a project that can provide a win-win situation for food and other industries by pulling the resources together from all parties. This will increase the chance of success by reducing everyone’s risk and investment during the current economic climate,” adds Hsieh.