Scientists from the University of Leicester have developed a proprietary process that transforms the shells into a material that can be added to polypropylene (PP), polyethylene and PET as a filler while still allowing the plastic to retain the necessary barrier properties.
The technique involves separating the protein and calcium carbonate elements of the shells and drying them into powder-like flour, William Wise, a post-doctoral research associate at the university’s green chemistry unit, told FoodProductionDaily.com.
“Currently we have been able to mix this substance to a range of plastics up to a level of 30% - but we believe this has the potential to increase to up to 50%,” he added. “It’s taking a waste product and making into something useful.”
Comparable barrier properties
The researcher said the current technique involved compression moulding the material but that the higher filler levels would be achieved once the team had developed an extrusion process.
Potential uses for the plastics that were being examined were food packaging – including plastic egg boxes, as well as general packaging.
“We will need to do all the safety tests on material for food packaging but we are confident at this stage there will be no problems with them exhibiting bacterial stability and remaining sterile throughout the process,” said Wise.
The filler-added materials had also demonstrated comparable barrier properties to conventional plastics, he added.
“We have left a sample soaking in water for one month and there has been no sign of disintegration,” said Wise.
The researcher explained the process has been carried out at laboratory level but that the group was about to scale up thanks to a £20,000 (€24,000) grant from Food and Drink iNet, an organisation part-funded by the European Regional Development Fund (ERDF).
Commercial partnerships
This cash injection will allow the scientists to develop a pilot-scale plant and develop and validate the sterility pre-treatment, as well as the post-treatment process to convert the eggshell into a starch-based plastic.
It will also permit the team to test the mechanical properties, including the strength of the new material and make a variety of materials to optimise the eggshell loading and particle size.
“The work completed up to now is a stepping stone but we believe we are onto something important,” said Wise. “We are interested in exploring options with any commercial partners as the project develops.”
Cash benefit for food processors
As well as providing a sustainable material to augment plastic packaging, the initiative could also result in savings for food manufacturers that use large quantities of eggs.
Wise said the plan was to collaborate with small and medium-sized egg-related companies in the region to supply the egg shells.
“To be viable we will need vast quantities of eggs shells that can realistically only be supplied from an industrial user,” he said. “The process involves recycling egg shell that would otherwise go to landfill. Apart from the recycling angle, it also represents a cost saving for food manufacturers in terms of landfill tax, which is likely to increase in the future.”
A Leicester-base hard-boiled egg and mayonnaise manufacturer Just Egg said it uses around 1.3m eggs every week and spends around £30,000 a year sending about 480 tonnes of shells to landfill for disposal.