Bagasse – A biodegradable alternative to plastic cups

Sugar Cane stalks

Origins of bagasse

Sugar cane is a tall perennial grass of the genus Saccharum, used in the production of sugar. Growing to 6 metres in height, it’s fibrous stalks are rich in sucrose. Only 10% is sugar, the remaining pulp, is called bagasse.

Production of bagasse

Almost 1.85 billion tonnes of sugar cane is cultivated in the world annually, which means there’s a lot of bagasse left. Currently most bagasse waste is used to fuel local generators so not wasted entirely. But a researcher, Dr. Zhu (Julie) Hongli at Northeastern University in Boston believes bagasse could be put to much better use – making recyclable cups.

Short fibre resilience

Bagasse take away food containers already exist (just go to Amazon and you’ll see plenty being sold there), but none are to hold water. The short fibres of bagasse don’t overlap sufficiently to give resilience, causing the structure to fail when wet. In technical parlance – not having ‘good wet mechanical strength’.

Bamboo to the rescue

Dr Zhu needed to find a substance that had long fibre and bamboo fit the bill perfectly. As a bonus, bamboo is a hardy grass that grows quickly, in abundance and degrades readily. (see: many benefits of bamboo)

When bamboo was blended with bagasse, the result had a strong interweaving of short and long fibres. Additionally when a hot moulding process was used to shape the containers, the heat mobilised some of the lignin in the fibres. This had dual effects of acting as an adhesive bond between fibres and also retaining it’s water repelling features.

When tested with boiling water, it remained intact for a couple of hours (which is not as long as plastic, but for practical purposes this was long enough). When buried in the ground, the container decomposed completely to its elements within 3 – 6 months.

Bagasse cup biodegrading over time
Bagasse-bamboo cup biodegrading over time

The Economics

Dr Zhu estimates that this bagasse-bamboo cup, with scaled up production, would cost half the amount of current biodegradable cups and only slightly more than a plastic. As a bonus, the production of this type of material emits 97% and 65% less CO2 when compared to plastic or paper/ biodegradable cups.

Food for thought

In the UK, close to 2.5 billion coffee cups are thrown away annually. In the US, Starbucks alone is responsible for nearly 4 billion cups. Most of these ‘paper’ cups are technically recyclable but end up in landfill.

The process of recycling itself is wasteful so finding an ecological solution that can perform dually better surely has to be the way forward. Bagasse could be it – I’ll drink a glass of refreshing sugar cane juice to that!

references:

Matter, Liu, Luan, and Li et al.: “Biodegradable, Hygienic, and Compostable Tableware from Hybrid Sugarcane and Bamboo Fibers as Plastic Alternative”

Hugh Fearnley-Whittingstall Slams Coffee Companies Over ‘Recyclable’ Cups

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