Environmentally friendly energy discovered in wood biochar
A wood biochar supercapacitor may seem like a burnt piece of wood in a small plastic container at first glance; however, these little devices could be the future of environmentally friendly energy.
For the past two years, Junhua Jiang, senior research engineer, and a team of researchers at the University’s Illinois Sustainable Technology Center have been studying wood biochar supercapacitors as an electrochemical source of power.
“Supercapacitors are ideal for applications needing instant power and can even provide constant power — like batteries, but at lower cost,” he said.
Supercapacitors are traditionally used in low-power devices such as PC cards, photographic flashes, flashlights or portable media players, Jiang said.
Nancy Holm, assistant director for sponsored research at the Center, oversaw the Hazardous Waste Research Fund, which provided funding for Jiang’s project. She has coordinated the Illinois Biochar Group for the past three years.
“We research ways to use materials and make other ways of producing energy so that we don’t have to use things like coal which can produce hazardous waste,” Holm said.
Jiang and his team have studied Red Cedar wood biochar supercapacitors in particular. They found that these function much more efficiently than the commercial types of supercapacitors.
“There’s a lot of interest in biochar because it’s got some interesting properties,” Holm said.
The properties of wood biochar supercapacitors are what allow them to be more environmentally friendly than those supercapacitors commonly used today. Supercapacitors function by capturing and releasing ions through a porous network.
However, activated-carbon supercapacitors, the type of supercapacitors used most often nowadays, must undergo complicated methods to get this porous network, Jiang said.
“Expensive and corrosive chemicals are often used to prepare the activated carbon used in supercapacitors, giving the electrodes the physical and chemical properties they need to function well,” Jiang said.
These chemicals can have negative environmental impacts.
Wood biochar supercapacitors have a natural porous network that can be used as an electrode surface, so there is no need for such complex techniques. The wood used comes from forest waste like burned trunks, branches or even saw dusts. Wood biochar is also activated with mild nitric acid, which, when washed away with ash, creates a beneficial byproduct that can be used as fertilizer.
The contrast in environmental costs and benefits is dramatic, said Jiang. He estimates that activated-carbon costs about $5,000 per ton while wood-biochar can be as low as $100 per ton.
Jiang foresees many potential future uses of wood biochar supercapacitors, they will be “very useful in solar and wind-power energy storage and distribution, transportation and electronics,” he said.
He also says it is possible that wood biochar will be useful in areas besides energy storage, such as water purification and desalination techniques.
Wei Zheng, a senior researcher at the center, elaborated on the future of biochar. He studies biochar as a means of soil improvement. Because Illinois is a largely agricultural state, he said, much of the nutrients are removed from the soil. When biochar is added to the soil, it improves soil quality and eliminates the need for harmful chemical fertilizers.
At this point, it is still in the lab stages and needs further research in order to become a commercialized product that can compete with current capacitors on the market.
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