Researchers from the University of New South Wales have developed a way to turn banana plantation waste into biodegradable and recyclable packaging.
Associate Professor Jayashree Arcot and Professor Martina Stenzel from UNSW’s School of Chemical Engineering were looking at ways to convert agricultural waste into something that could value add to the industry it came from.
Arcot said the banana growing industry was a “good contender” because only 12 per cent of the plant is used (the bananas) while the rest is discarded after harvest. It is more wasteful compared to other crops because the plant dies after each harvest. But that makes the industry more attractive as its cellulose content is high quality and the plant is an annual, Arcot said.
“We were particularly interested in the pseudostems – basically the layered, fleshy trunk of the plant which is cut down after each harvest and mostly discarded on the field. Some of it is used for textiles, some as compost, but other than that, it’s a huge waste.”
The pair researched whether the pseudostem could be a valuable source of cellulose, which could be used in packaging, paper products, textiles and medical applications for wound healing and drug delivery.
Working with pseudostem material from the Royal Botanic Garden Sydney, Arcot and Stenzel worked on extracting cellulose to test its suitability as a packaging alternative.
Arcot said: “The pseudostem is 90 per cent water, so the solid material ends up reducing down to about 10 per cent. We bring the pseudostem into the lab and chop it into pieces, dry it at very low temperatures in a drying oven, and then mill it into a very fine powder.”
The powder is then washed with a chemical treatment which isolates the nano-cellulose, a high value material with a range of applications. Once processed, the material has a consistency similar to baking paper.
Non-toxic, no contamination, biodegradable
Stenzel said: “One of those applications that interested us greatly was packaging, particularly single-use food packaging where so much ends up in landfill.”
Arcot said the material can take a number of different formats in food packaging, depending on the intended thickness. At the moment it could be used to make a shopping bag.
“Depending on how we pour the material and how thick we make it, we could make the trays that you see for meat and fruit. Except of course, instead of being foam, it is a material that is completely non-toxic, biodegradable and recyclable.”
Arcot and Stenzel confirmed in tests that the material breaks down organically after putting ‘films’ of the cellulose material in soil for six months. The results showed that the sheets of cellulose were well on the way to disintegrating in the soil samples.
“The material is also recyclable. One of our PhD students proved that we can recycle this for three times without any change in properties,” Arcot said.
Tests with food have proved that it poses no contamination risks.
Stenzel said: “We tested the material with food samples to see whether there was any leaching into the cells. We didn’t see any of that. I also tested it on mammalian cells, cancer cells, T-cells and it’s all non-toxic to them. So if the T-cells are happy – because they’re usually sensitive to anything that’s toxic – then it’s very benign.”
The team have also looked at cotton and rice growing industries, extracting cellulose from both waste cotton gathered from cotton gins and rice paddy husks.
Call for industry and supply chain buy-in
“In theory you can get nano-cellulose from every plant, it’s just that some plants are better than others in that they have higher cellulose content,” Stenzel said.
For the banana pseudostem to be a realistic alternative to plastic bags and food packaging, it would make sense for the banana industry to start the processing of the pseudostems into powder which they could then sell to packaging suppliers.
“If the banana industry can come on board, and they say to their farmers or growers that there’s a lot of value in using those pseudostems to make into a powder which you could then sell, that's a much better option for them as well as for us,” Arcot said.
And at the other end of the supply chain, if packaging manufacturers updated their machines to be able to fabricate the nano-cellulose film into bags and other food packaging materials, then banana pseudostems stand a real chance of making food packaging much more sustainable.
“What we’re really wanting at this stage is an industry partner who can look into how this could be upscaled and how cheap we can make it,” Stenzel said.
Arcot agreed. “I think the packaging companies would be more willing to have a go at this material, if they knew the material was available readily.”