The technique, developed at the University of New South Wales (UNSW) in Sydney, takes the pseudostems of the banana plant and converts the waste into nanocellulose, which can then be used as a feedstock to create bioplastics. According to the researchers, the actual fruit of the banana tree makes up just 12 per cent of the plant, with the rest discarded as waste. This makes the crop an enticing target for alternative uses, both to reduce waste and provide a solid supply of raw materials for industrial production of bioplastics.
“What makes the banana growing business particularly wasteful compared to other fruit crops is the fact that the plant dies after each harvest,” said Associate Professor Jayashree 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.
“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.”
Using a reliable supply of pseudostem material from banana plants grown at the Royal Botanic Garden Sydney, the UNSW team set to work extracting cellulose to test its suitability as a packaging alternative. When processed, the material has a consistency similar to baking paper and 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,” said Arcot. “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.
“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.”