Last updated: June 14, 2012 1:45 pm
U of A research team probes charging powers of eggshells
Eggshell membranes identified as potential future green and efficient power source
EDMONTON (CUP) — Chicken eggs could become a new energy resource, according to a research team at the University of Alberta.
Although eggshells are usually considered a waste product, the David Mitlin research group at the U of A believes they can be used to charge future electronic devices in minutes, or even seconds, instead of hours.
Aided by a discovery grant from the Natural Sciences and Engineering Research Council (NSERC), the group has developed an eggshell “membrane” — a macroporous carbon film to charge supercapacitors far more quickly than normal batteries.
Post-doctoral member Zhi Li has been spearheading the egg shell membrane idea, and describes the ease by which he transformed his food waste into a useful engineered material.
“I just tried a normal egg that I bought from Costco,” Li said. He added that he has long been an avid admirer of the biochemistry of egg shell membranes and their inherent structures.
After Li washes and removes the hard shell with acid, the membrane is ready for processing at high activation temperatures.
“I carbonize it, [which] makes it into carbon fibre [with] nitrogen on the surface,” he explained. “It is a pretty cool structure.”
The high percentage of nitrogen in eggshell membranes is a core advantage of high capacitance. The higher the energy and power density promoted by a material, the more ideal it becomes for use in supercapacitors.
“Nitrogen reacts with electrolytes and stores more energy,” Li said. “With nitrogen in our eggshells, compared to traditional carbon materials which have oxygen groups, we have 1.5 to two times more energy.”
Li believes eggshell membrane supercapacitors have huge potential for a number of industries.
“Electrical vehicles need to charge and discharge quickly, [and] a battery simply cannot give the necessary energy,” he said. “Egg shell [membranes] have a very unique structure, and their cheapness and functionality allow for broader application.”
Aside from structural and biochemical composition, eggshell membranes are ideal because of their abundance and ease of preparation. In addition, the source and processing of eggshell membranes are organic and environmentally friendly, a factor that could set it apart should the demand for such technology ever increase.
“In general I use very few chemicals to get a useful eggshell membrane," said Li. "The process is pretty green.”
“There [are] definitely enough egg shells — more than I can imagine. The cooking industry uses processed eggs, but they just use the liquid egg. They separate the liquid from the egg and just throw the shell away.”
Perhaps the most overlooked property of the eggshell membrane is its durability over time. This may indicate that it is not only efficient, but sustainable in its usage, according to Li.
“I don’t want to say it lasts forever, but its life cycle is up to 10,000 cycles — which for normal use could be up to a couple of years.”
Li believes his eggshell research will encourage others to look into applications of natural systems and materials for solving future engineering problems. Although he used chicken eggs, it is possible that other eggs have the same potential.
“Every single natural material has an advantage and disadvantage, and you have to integrate them into a system to eliminate the disadvantages [and] emphasize the advantages,” he said. “This is especially true of egg shell membranes.”