Unexpected items in the bagging area: The truth about biodegradable bags

On 5th October 2015, the UK government put in place a law that requires large shops in England to charge 5p for all single-use plastic carrier bags.

Supermarkets, high street stores and out-of-town retailers with 250 or more employees had to abide by this rule, and smaller businesses were encouraged to join in on a voluntary basis in a bid to reduce the amount of single- use plastic being used in the UK retail industry.

Shoppers were also given the option to buy a thicker, reusable ‘bag for life’, with the idea being that you’d pay slightly more for one of these, and you would be able to use it over and over again until it wears out.

Five years on and the bag for life idea has also caused a boom in cotton tote bag sales. We’ve all got used to hoarding our tote bags in the designated kitchen cupboard and taking them out with us wherever we go. However, a new study has looked into just how eco-friendly tote bags and bags for life actually are, with some surprising results.

In 2018, the Ministry of Environment and Food of Denmark looked at the environmental impact of different types of carrier bags throughout their lives, including heavy-duty bags for life, paper bags and cotton tote bags.

It found that the production of some (not all) cotton tote bags was damaging to the ozone layer; caused by gases used to help transport the fossil fuels powering the pumps that water the cotton plants.

Going back to the thicker, sturdier bag for life that you can buy from most large retailers, research from the Environmental Investigation Agency (EIA) and Greenpeace in 2019 found that UK shoppers have somewhat of an addiction to bags for life.

Despite an 83% reduction in the use of conventional plastic bags, shoppers still bought bags for life at a similar rate. A whopping 1.5 billion were sold in the UK in 2019.

It turns out that sales of the sturdier bags increased by 26% in the UK in 2019, resulting in enough for 54 bags per household per year. Breaking this figure down, it seems shoppers are only using a ‘bags for life’ for around a week before getting a new one.

Biodegradable bags

At this point, you’re probably thinking, well surely the answer to all this is to just use biodegradable bags? And you’d be right. However, in 2015 a British marine biologist, Richard Thompson, was wondering how well these new biodegradable shopping bags actually were, so he collected a handful of different bags labelled at biodegradable and buried them in the garden of Plymouth University.

Three years later Thompson and his graduate students dug up the bags and to their surprise, not only had they all remained intact, but each one could carry almost five pounds of weight.

Speaking to National Geographic at the time, Thompson commented: “It did surprise me that after three years you can still carry shopping home in them. They didn’t have the same strength as they had when they were brand new. But they hadn’t degraded to any meaningful extent.”

Obviously this was only a three year experiment, and over a longer period of time the bags could very well degrade a lot more. But the point is that the general public has this idea that biodegradable bags are going to break down quickly and not cause harm to the environment.

If an animal got its head stuck in one of these biodegradable bags, it could theoretically still be hanging off its neck three years on.

There is some light at the end of the tunnel though. Scientists are working hard to come up with a biodegradable bag that doesn’t use plastic and is much better at breaking down.

First up, Japan’s largest manufacturer of shopping bags, Fukusuke Kogyo, has developed a plant-derived, marine biodegradable bag. Developed with researchers from Gunma University, the bags are made from sugarcane and corn resin.

Designed to carry over 17lbs of goods, if they end up in the sea, marine bacteria will break down more than 90% of the bag into water and carbon dioxide within 180 days.

Although they currently cost ten times more than conventional shopping bags, the company says there are already several firms considering buying them, with the bags set to go on sale as early as July 2020. If they are successful, perhaps they will make their way to the UK.

Going bananas

Japan isn’t the only country hard at work developing a new biodegradable bag that will actually do what it says on the tin. Researchers at the University of New South Wales have found a way to turn banana plantation waste into recyclable, biodegradable packaging.

Associate Professor Jayashree Arcot and Professor Martina Stenzel discovered that, in most cases, only 12% of the banana plant is actually used when harvesting the fruit, with the rest being discarded post-harvest.

“What makes the banana-growing business particularly wasteful compared to other fruit crops is the fact that the plant dies after each harvest,” Arcot told Packaging Europe.

“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 professors wondered whether these fleshy parts of the banana plant could be used to make carrier bags and packaging amongst other things, such as paper products and in the medical field for wound healing.

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

The researchers are urging the banana industry to get on board so that the pseudostem can become a realistic alternative to plastic bags and food packaging, saying 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,” explains Arcot.

And at the other end of the supply chain, Arcot says that if packaging manufacturers updated their machines to be able to fabricate the nano-cellulose film into bags and other packaging materials, then banana pseudostems stand a real chance of making packaging much more sustainable in the near future.

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