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Researchers Develop Process to Recover Eggshell Waste for Alternative Uses

IN THIS ISSUE Gaining New Ground on Biodiesel Conversion Efficiency The Economics of Biofuels Georgia Tech Students Study Biodiesel Production Using Algae High School Student Produces Homemade Biodiesel Using Restaurant Fryer Oil Defining Strategies to Control Storm Water Runoff from Poultry Processing Facilities Researchers Develop Process to Recover Eggshell Waste for Alternative Uses A Look at the Department of Homeland Security’s Chemical Facility Anti-Terrorism Standard and Its Impact on Poultry Processors and Growers Changing Environmental and Energy Climate Creates New Opportunities for Electric Boilers and Water Heaters Bringing the Research Lab to the Classroom

Georgia Tech researchers have successfully developed a novel separation technology and built a pilot-scale separation facility to recover calcium carbonate from eggshells for commercial use. The project, funded by Georgia’s Traditional Industries Program for Food Processing, is in the final year of a multi-year effort focused on developing an alternative to landfills that extracts value-added byproducts from eggshell waste. More than 37 million pounds of eggshells are landfilled each year in the state.

Dr. Jeffery Hsieh and his research team run tests on the pilot-scale system located at ADF in Social Circle, Ga.

“We are seeking to find an environmentally better solution to disposing of eggshells by recovering the calcium carbonate and membrane from the eggshell waste and using them in some other applications,” says Jeffery Hsieh, project director.

According to Hsieh, the end customer has interest in the calcium carbonate from eggshells because it is sustainable and can be used as a partial substitute for mined calcium carbonate, which is used in paper and plastic manufacturing. For example, the calcium carbonate can be used as a component in ink jet paper coatings or compounded into plastics to reduce the use of petroleum-based products.

Working with industrial partner, American Dehydrated Foods (ADF), the research team constructed a pilot-scale separation facility at ADF’s egg processing plant in Social Circle, Ga. The pilot-scale system can process 500 pounds of eggshells per day, thus allowing researchers to generate greater volumes of calcium carbonate for use in product testing and to evaluate the system’s design under actual process conditions.

The pilot unit, explains Hsieh, has a series of washing stations that subject the eggshells to severe agitation in order to separate the membrane from the calcium carbonate. The eggshells are first ground into small pieces that are then fed through the system counter to the flow of water. This countercurrent path helps to separate the membrane from the calcium carbonate. The membrane is lighter than water and floats out, whereas the calcium carbonate falls through to the bottom.

The recovered calcium carbonate is the focus of current research. “The ultimate goal is to have a calcium carbonate that is clean, or in other words, has no biologic activity, with a very low level of membrane still attached,” notes Hsieh. The membrane has to be at low levels, he says, so that subsequent grinding of the calcium carbonate is not impaired. To date, the research team has been able to make a clean calcium carbonate and reduce the amount of membrane. But, Hsieh says, the membrane still has to be reduced more.

Researchers are now exploring methods to further reduce the amount of remaining membrane. “We have shown that the amount of membrane can be reduced to slightly below a 2 percent level with only mechanical separation,” says Hsieh. The team has decided on evaluating three different approaches to further reduce the membrane: (1) use the lower levels of membrane without further purification; this may be possible, but will require higher levels of energy to grind the particles fine enough to be used along with conventional calcium carbonate; (2) use chemicals to extract the membrane; and (3) chemically recover the calcium carbonate as calcium oxide and then possibly convert it back into calcium carbonate in a subsequent step if a completely pure product is required. “This is technically a feasible approach, but adds extra cost and complexity to the program,” notes Hsieh.

Interest in the project remains strong among industrial collaborators. In addition to ADF, four others are actively working with the research team. EvCo Research, a supplier of coating and wet end treatment chemicals to the paper industry, is interested in using the calcium carbonate in its ink jet coating products and is spearheading commercialization efforts with the other partners. Imerys, a Georgia-based mineral processor, is assisting in the processing of the calcium carbonate so that it can be usable for various end-use applications. Heritage Plastics, a plastics compounder and processor with a location in Villa Rica, Ga., is considering the use of the recovered calcium carbonate in place of conventional calcium carbonate in plastics. The final partner is a package supplier to the fast food industry that has expressed interest in potentially using the plastics processed by Heritage.

Hsieh says ultimately the project should yield significant environmental benefits. “The successful conclusion of the project will provide the poultry industry with an environmentally better solution than landfilling eggshells. In addition, the calcium carbonate will be used to replace petroleum-based plastics, reducing America’s dependence on foreign oil feedstocks.”