New Way to turn Banana Pseudostem into Recyclable Food Packaging
Researchers at the UNSW Sydney have discovered a novel way to turn banana plantation waste into packaging material that is not only biodegradable, but also recyclable.
Converting Waste into Valuable Products
Associate Professor Jayashree Arcot and Professor Martina Stenzel were looking for ways to convert agricultural waste into something that could value add to the industry it came from while potentially solving problems for another.
A good contender was the banana growing industry which, according to A/Prof Arcot, produces large amounts of organic waste, with only 12% of the plant being used (the fruit) while the rest is discarded after harvest.
A/Prof Arcot and Prof Stenzel (UNSW School of Chemistry) wondered whether the pseudostems - basically the layered, fleshy trunk of the plant could be used in packaging, paper products, textiles and even medical applications such as wound healing and drug delivery.
Cellulose Extraction for Use in Packaging
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 per cent water, so the solid material reduces to about 10%. The pseudostem was chopped into pieces, dryed at very low temperatures in a drying oven, and then milled into a very fine powder.
The powder was then washed with a very soft chemical treatment. This isolates what nano-cellulose which is a material of high value with a whole range of applications. One of those applications that interested the researchers 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.
A/Prof Arcot said depending on the intended thickness, the material could be used in 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.”
A Biodegradable and Safe Material
A/Prof Arcot said she and Prof 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. One of the PhD students proved that the material can be recycled 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,” Professor 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,” adds Stenzel.
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,” Prof 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,” A/Prof Arcot added.
Realistic Alternative to Food Packaging
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,” Prof 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,” Prof Stenzel said.
A/Prof 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.”