In 2015, U.S. peanut farmers harvested more than 3.16 million tons of peanuts. It was one of their highest yields ever, roughly equivalent to the weight of three offshore gas drilling platforms, if each one stood more than 1,500-feet high.
That’s a lot of peanuts, but they’re eagerly consumed. What happens to all the peanut shells?
Some find their way into industrial applications, like plastics, building materials, even fuel. But there’s still a lot left over—by some estimates, enough to fill every cubic inch of the two largest skyscrapers in the U.S.
David Mitlin has landed on a solution: use the peanut shells to make batteries.
“High-power batteries,” he says, “that charge quickly.”
Mitlin is Professor and GE Chair in Oil and Gas Systems at Clarkson. He teaches, researches and publishes in both chemical & biomolecular and mechanical & aeronautical engineering. He’s made supercapacitors that can store tremendous amounts of energy, while accepting and delivering a charge much faster than batteries. His supercapacitors can handle more charging and discharging cycles than many mass-market rechargeable batteries.
What’s more, he’s made these supercapacitors from hemp bark.
“All well and good,” Mitlin says, “but these hemp supercapacitors performed just as well—if not better than—those made using graphene, which is a far more expensive material to produce.”
Recently, he and his research team used peanut shells to create a hybrid sodium ion capacitor (NIC), also called “super capattery,” which bridges the gap between conventional ion batteries and supercapacitors.
“While activated carbons per se are fairly straightforward to achieve,” he says, “their resultant electrochemical properties are unremarkable. The secret to creating carbons and ultimately devices with exemplary energy storage performance is to work backward.”
He starts with the targeted carbon structure for a given application and then tunes the synthesis methodology knowing the limitations and strengths of a given precursor. “If performed well,” he says, “the resultant carbons will not only be superior in performance but on par in cost to conventional activated carbon and graphite. That’s in the range of 20- to 85-dollars per kilogram.”
Now, it’s time to finalize a working prototype of his hybrid NIC and get it to market. Mitlin says his super capattery will have more than one edge against the competition. “Less expensive production translates to less expensive for consumers. We’re also keeping millions of tons of waste peanut shells from being dumped in landfills.”
Another advantage? Speed.
“These hybrid NICs can recharge in seconds,” he says. “There’s tremendous demand for inexpensive batteries, like these, that charge completely in less than a minute.”
These attributes—low cost, green and fast-charging—make Mitlin’s hybrid NIC an ideal battery to store energy from renewable sources.
“Renewables are only beginning to compete with traditional or fossil fuels,” Professor Sue Powers says. The interim director of Clarkson’s Institute for a Sustainable Environment has seen a sea change in the way people view renewable energy.
“Solar power is starting to come into its own,” she says, “especially in the American southwest and Hawaii. Wind power is still struggling, though, and the difference lies in the timing of energy production.”
Solar generates power when people use it most: during the day. Wind turbines produce most of their electricity at night.
“Most of us working on the issues of sustainable energy have looked to batteries as a way to store wind power for later use,” Powers says. “Cost has been a major stumbling block. But David Mitlin’s work has the potential to produce the hybrid NIC that renewables need.”
She sees the peanut shell super capattery as a way to clear one of the last hurdles between wide-spread, mainstream use of renewables.
“It could change the way we think about energy,” she says. “It could be the way we power so much in our daily lives, our homes, our cars and all the gadgets and devices we use. From power generation to battery production and energy consumption, the whole chain can be sustainable.”