Turning banana waste into food packaging

UNSW

RESEARCHERS at the University of New South Wales, Australia, have developed a process to turn banana plantation waste into a nanocellulose film that could have applications in food packaging.

Jayashree Arcot, Associate Professor of Chemical Engineering, and Martina Stenzel, Co-director of the Centre for Advanced Macromolecular Design at UNSW, wanted to use agricultural waste as a feedstock for other products and decided to use the banana plant. The fruit only comprises 12% of the plant and the rest is usually discarded after the fruit is harvested.

“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. “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.”

They used pseudostems from plants grown at The Royal Botanic Garden Sydney to extract cellulose, the structural component in plant cell walls. Solid material makes up around 10% of the pseudostem with the rest being water. “In theory you can get nanocellulose from every plant, it’s just that some plants are better than others in that they have higher cellulose content,” said Stenzel.

The pseudostem is chopped and then dried at low temperatures in a drying oven, before being milled into a very fine powder. It is then placed in an alkaline solution to extract nanocellulose which is then made into a film.

“Nanocellulose [is] a material of high value with a whole range of applications,” said Stenzel. “One of those applications that interested us greatly was packaging, particularly single-use food packaging where so much ends up in landfill.”

Speaking on a podcast for The Royal Botanic Garden Sydney, Stenzel explained that the fibres of nanocellulose are tiny compared to ordinary cellulose, and have a large surface area, which is what makes them attractive for so many applications.

The nanocellulose film can have different applications depending on the thickness. It could be used as shopping bags or as food packaging such as the trays used for fresh food. The new material is recyclable, biodegradable, and non-toxic. The researchers tested its biodegradability by putting it in soil for six months and showed that it was disintegrating. They also tested its recyclability and it was recycled three times without a change in properties. There are also no contamination risks with food.

“We tested the material with food samples to see whether there was any leaching into the cells,” said 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 that’s toxic – then it’s very benign.”

Arcot explained on the podcast that that process is currently only at lab-scale, and that once they scale it up they will need help from industry as universities can only take it so far. “I think the packaging companies would be more willing to have a go at this material, if they knew the material was available readily,” said Arcot.

“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,” said Stenzel.

The researchers suggested the that the supply chain could be adapted to make use of the banana production waste. This would work best if the banana industry could start processing the pseudostems into powder which could then be sold to packaging suppliers, and if packaging manufacturers updated their equipment to be able to use the nanocellulose film.