Driftwood collected from rivers could be recycled for use in future electric car batteries.
The remains of trees provide many benefits to ecosystems in rivers and oceans, but driftwood is a nuisance for dam operators. For example, each year 1300 tonnes of wood have to be pulled out of a section of the Rh么ne river near the the G茅nissiat hydroelectric plant in France so as not to interfere with it, says Abdullah Qatarneh, formerly at the IHE Delft Institute for Water Education in the Netherlands.
The wood is usually burned or ends up in landfills, but Qatarneh and his colleagues have found that they make an excellent raw material for a form of carbon used in a battery technology that is being considered for use in electric cars.
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The researchers treated driftwood with a process called hydrothermal carbonisation, which involves submerging it in water and subjecting it to pressure and 200掳C heat until it turns into a carbon-rich solid called hydrochar.
They then baked the hydrochar at 1400掳C until it turned into a material called hard carbon and tested its performance in sodium-ion batteries, which use it as their anode material. The batteries performed well, 聽on 27 April.
Electric vehicles generally run on lithium-ion batteries at the moment, but lithium is expensive and can be environmentally damaging to mine. Sodium-ion batteries are seen by some as a better alternative, but hard carbon for these batteries is currently produced using fossil fuels.
Driftwood could be a better option 鈥� the wood of the G茅nussiat dam alone could produce enough anode material for several thousand electric cars each year, says Qatarneh.
For this to happen, large-scale installations will have to be developed for the hydrothermal carbonisation step, something that Qatarneh is now working on. 鈥淚t is not a fully mature technology,鈥� he says.
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