Zhu Hongli has come up with a waste preventing, waste recycling container material. Photo by Ruby Wallau/Northeastern University.
A smart researcher at Northeastern University in Boston has discovered that although sugar has a poor reputation, health-wise, it could bring significant advantages to disposable food containers. By James Teo.
Boston, USA. January 2021. Hongli Zhu, an assistant professor of mechanical and industrial engineering at Northeastern University has a young son. Surprisingly, his predilection for sweet treats led indirectly to a breakthrough in disposable container manufacture.
“I have a 4-year-old son, and he eats a lot of candy,” says Zhu. Being a diligent mother, she reads through the ingredients in the sweet things he eats, to make sure there is nothing too toxic in the mix. Top of the list in most treats was sugar. As she read the list on each wrapper, a thought lodged. “I realised that sugar is a natural, mass-produced material with no synthetic chemicals,” she says. “What if I collected the pulp by-product of sugarcane production and used it to create a sustainable alternative to plastic that was used in containers?”
Zhu, who arrived in the US from China in 2007, was already aware of the widespread and wasteful use of single-use plastics as food containers in supermarkets and restaurants. “”Yes, the material is cheap and convenient, but most of the containers are not biodegradable,” she notes. According to the US Environmental Protection Agency, 27 million tonnes of plastic were diverted to landfills in 2018.
The new material is strong, waterproof, yet composts down in only 60 days. Photo by Ruby Wallau/Northeastern University
As an expert in wood chemistry, she was already looking at wood pulp for use in recyclable materials, but wood demands new plantations, so she started looking at existing source materials – and sugar started to look more attractive every time she looked.
As a raw resource, sugar is very inefficient. Although sugar cane grows fast and dense, it only contains around 10% sugar. This is squeezed out of the woody, straw-like material that holds it, called bagasse. So about 90% of the harvested material is not used; most often the surplus bagasse is burned. Around 200million tonnes of sugar cane was harvested in 2018, meaning 180 millions of tonnes of fibrous bagasse was probably incinerated. Even though bagasse is often used to power sugar factory boilers, that’s still a big resource wasted.
The big problem with bagasse is that although safe to consume and naturally biodegradable, it has short and weak fibre structure. That means that when it gets wet the short fibres separate and it leaks all over the place. No good at all for containers that need to be durable and pliable as well as liquid-proof. Zhu’s breakthrough idea was to mix the abundant bagasse with another natural, plentiful fibre that brought long, strong and waterproof fibres into the mix – bamboo.
Northeastern University is fast establishing a reputation as the US’s greenest and most innovative sustainability-aware educational establishment. Photo courtesy Northeastern University.
“The result (of the compound) is a completely natural and biodegradable material that is sufficiently durable to be moulded into containers strong enough to hold food and liquids,” says the report from Northeastern. “And even better, since bagasse and bamboo fibres are made up of similar underlying chemicals (cellulose, hemicellulose, and lignin), the material doesn’t require any additional processing to separate different components, unlike some other options.”
The result is a sustainable, compostable, and inexpensive material that’s durable enough to serve as tableware, and that better still, that biodegrades without any special requirements or equipment within 60 days.
“We buried a sample of the material and checked it every 10 days,” says Zhu. “The material began breaking down after about 30 days and disintegrated almost completely after 60 days. That is a huge improvement over currently available compostable containers, some of which require specialised industrial equipment and high temperatures to actually decompose,” she adds.
Since her research was published, Zhu has filed for a patent and is working on commercialising the product, and has already had requests from sugar production companies excited about putting waste bagasse byproduct to good use.
“Our end goal is to tackle the plastic pollution problem,” Zhu says. “That’s why I’m very passionate about this material.”