Engineers at UNSW Sydney have unveiled a breakthrough process to produce graphene, the so-called “wonder material”, using discarded peanut shells, offering a cheaper, cleaner, and faster method for mass production.
Graphene has been hailed as one of the world’s most extraordinary materials thanks to its unique combination of strength, flexibility, and conductivity.
“Graphene is famous for being one of the thinnest, strongest and most conductive materials known to science,” said Professor Guan Yeoh, who led the research team.
“It is made up of a single layer of carbon atoms arranged in a hexagonal lattice, but is hundreds of times stronger than steel, conducts electricity and heat better than copper and is almost completely transparent.”
That combination makes graphene useful in everything from batteries and solar panels to flexible electronics, supercapacitors, and high-speed transistors.
However, conventional graphene production relies on chemical- and energy-intensive methods that are expensive and environmentally taxing.
To overcome these challenges, Professor Yeoh’s team at UNSW Sydney has developed a method to produce high-quality graphene from a surprising source: peanut shells.
“There are about 55 million tonnes of peanut crops produced globally every year, yet most of the waste from the shell is either discarded or recycled into low-value applications that don’t maximise their full potential,” said Prof. Yeoh.
“What we have shown in this work is that basic peanut shells can be turned into high-quality graphene, using much lower energy than is currently required and therefore at a lower cost.
“We also do not need to use any chemicals, so there is an added environmental benefit.”
The team’s breakthrough lies in leveraging lignin — a carbon-rich polymer abundant in peanut shells.
By grinding the shells and subjecting them to a two-stage heating process, the researchers could rapidly convert them into graphene.
First, the shells are heated to about 500 degrees Celsius to form a carbon-rich ‘char’.
Next, flash joule heating blasts the material to roughly 3000 degrees Celsius within milliseconds, rearranging the carbon atoms into graphene sheets.
Unlike industrial methods that rely on carbon black from fossil fuels, UNSW’s process uses only the peanut-shell-derived char, drastically reducing environmental impact.
The entire process takes just 10 minutes and consumes far less energy, with calculations showing a production cost as low as US$1.30 per kilogram of graphene.
“What we identified in the experiments was that the most important aspect in terms of producing high-quality graphene was the pre-treatment or precursor engineering done to the peanut shells before the flash joule heating,” said Prof. Yeoh.
“That process is vital to remove the impurities and give us the best carbon-rich material to help ensure there are minimal defects in the final graphene and that it is indeed just a single layer of atoms.”
Although current production volumes are still small, the researchers believe the process could be commercially viable within three to four years.
More broadly, the team plans to test other organic waste sources (such as coffee grounds or banana peels) for similar results.
“We’ve used peanuts as a test case, but the key ingredient to this process is the lignin which is present in many different plants,” said Prof. Yeoh.
“What we have done is really highlighted its potential for use in large-scale biomass-to-graphene manufacturing.”
Their findings were published in the Chemical Engineering Journal Advances.
