An a-peeling alternative: Australian researchers convert banana waste into super-sustainable bags and trays

03 Dec 2019 --- Two researchers from The University of New South Wales (UNSW Sydney), Australia, have discovered a novel way to turn banana plantation waste into packaging material that is both biodegradable and recyclable. Tapping into the “particularly wasteful” banana-growing business, Associate Professor Jayashree Arcot and Professor Martina Stenzel converted banana waste into a non-toxic material that can be shaped into bags, trays and other packaging types. The researchers believe that with the right industry partner, the material has the commercialization potential to supply the industry with sustainable packaging that reduces agricultural waste.

The researchers 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 Arcot, produces large amounts of organic waste, with only 12 percent 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,” notes Arcot of the 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.”

Banana pseudostem is dried, powdered and placed in alkaline solution to extract the cellulose, which is then processed into films of varying thicknesses.Arcot and Stenzel 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 percent water, so the solid material ends up reducing down to about 10 percent,” Arcot explains. “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,” Stenzel continues. “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.”

Biodegradable, recyclable and non-toxic
When processed, the material has a consistency similar to baking paper. Arcot notes that, depending on the intended thickness, the material could be used in several different formats in food packaging. “There are some options at this point, we could make a shopping bag, for example.”

“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.”

Tests have confirmed 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 adds.Associate Professor Jayashree Arcot, Professor Martina Stenzel and researcher Kehao Huang in the lab (Source: Richard Freeman, UNSW).

Tests with food have also proved that the material poses no contamination risks, the researchers affirm. “We tested the material with food samples to see whether there was any leaching into the cells,” says Stenzel. “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 toxic – then it’s very benign.”

Banana waste: An untapped revenue stream
Other uses of agricultural waste that the duo has 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 continues.

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

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 advises.

Meanwhile, 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, the researchers say.

Banana-growing produces large amounts of organic waste, with only 12 percent of the plant (the fruit) being used.“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 says.

“I think the packaging companies would be more willing to have a go at this material, if they knew the material was available readily,” Arcot agrees.

The weird and wonderful
Rising demand for more environmentally-responsible consumer products is driving innovation in biodegradable and compostable packaging solutions. Public concern for the environmental impact of everyday packaging materials – particularly plastics – has intensified, creating market opportunities for creative, forward-thinking and sometimes entirely unusual biodegradable/compostable packaging.

Also in Australia, a start-up recently developed a biodegradable alternative to plastic food packaging produced from the chitin and cellulose contained in crustacean skeletons. Meanwhile, UK designer Lucy Hughes created MarinaTex, a bioplastic made from fish waste that is biodegradable and resource-efficient.

Similar to the UNSW Sydney research, Simone Caronni, Pietro Gaeli and Paolo Stefano Gentile, three product designers from NABA University in Milan, created cone-shaped fries packaging from discarded potato peels. Also, Dutch design graduate Don Kwaning created a bio-based packaging material from the pith of a cosmopolitan and typically unwanted weed called soft rush, and Roza Janusz, a graduate of the School of Form in Poznan, Poland, reimagined packaging with SCOBY: an organic and sustainable material which can be eaten or composted after use.

By Joshua Poole