Packaging made from banana plants an ‘a-peeling’ alternative

Packaging made from banana plants an ‘a-peeling’ alternative

December 3, 2019
Marcia González

Biodegradable ‘plastic’ bags made out of banana plants might sounds a bit… bananas, but a couple of University of New South Wales researchers in Australia have found a way to do it, and it could solve two industrial waste problems in one

Two researchers at University of New South Wales Sydney (UNSW) have discovered a novel way to turn banana plantation waste into packaging material that is not only biodegradable, but also recyclable.

Associate Professor Jayashree Arcot and Professor Martina Stenzel were looking for ways to convert agricultural waste into something that could add value to the industry it came from while potentially solving problems for another.

A good contender was the banana-growing industry which, according to Associate Professor Arcot, produces large amounts of organic waste, with only 12% of the plant being used (the fruit) while the rest is discarded after harvest. “What makes the banana-growing business particularly wasteful compared to other fruit crops is the fact that the plant dies after each harvest,” said Arcot, UNSW School of Chemical Engineering. “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.”

Arcot and Stenzel (UNSW School of Chemistry) wondered whether the pseudostems would be valuable sources of cellulose – an important structural component of plant cell walls – that could be used in packaging, paper products, textiles and even medical applications such as wound healing and drug delivery.

Using a reliable supply of pseudostem material from banana plants grown at the Royal Botanic Garden Sydney, the duo set to work in extracting cellulose to test its suitability as a packaging alternative.

“The pseudostem is 90% water, so the solid material ends up reducing down to about 10%,” Arcot explained. “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.”

“We then take this powder and wash it with a very soft chemical treatment,” continued Stenzel. “This isolates what we call nano-cellulose which is a material of high value with a whole range of applications. One of those applications that interested us greatly was packaging, particularly single-use food packaging where so much ends up in landfill.”

When processed, the material has a consistency similar to baking paper.

Arcot said depending on the intended thickness, the material could be used in a number of different formats in food packaging. “There are some options at this point – we could make a shopping bag, for example,” she said.

“Or 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 said she and Stenzel have 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,” Arcot revealed. “One of our PhD students proved that we can recycle this for three times without any change in properties.”

Tests with food have proved that it poses no contamination risks.

“We tested the material with food samples to see whether there was any leaching into the cells,” Stenzel said. “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.”

Other uses of agricultural waste that the duo have looked at are in the cotton industry and rice growing industry – they have extracted cellulose from both waste cotton gathered from cotton gins and rice paddy husks.

“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.

“What makes bananas so attractive in addition to the quality of the cellulose content is the fact that they are an annual plant,” Arcot said.

The researchers say that 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.

Plastic Free World Conference & Expo 2020 will take place at Cologne Messe, Germany, on Tuesday 16 June and Wednesday 17 June. To register for this highly focused, solutions-driven event, please click here. For sponsorship and exhibition opportunities, please email peter@trans-globalevents.com

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