NUS engineers turn pineapple leaves into cheap aerogels which can preserve food & treat wastewater


Ashley Tan | September 09, 2020, 03:49 PM

Engineers from the National University of Singapore (NUS) have devised a way to transform pineapple leaves into useful and economical "eco-aerogels".

Pineapples are a common tropical fruit rich in vitamins, enzymes and antioxidants.

However, even if some people insist on putting it on pizza, the fruits' leaves are often left to rot or are burned after harvests.

To eliminate this waste stream, the research team from NUS Mechanical Engineering, helmed by Associate Professor Duong Hai-Minh, came up with a way to make use of pineapple leaves.

The process involves shredding and blending the leaf fibres, mixing with water and some non-toxic chemicals, aging, freezing and freeze-drying.

The result is a light and biodegradable eco-aerogel. These eco-aerogels are highly versatile, and can be combined with various chemicals to serve different functions.

Food preservation

These eco-aerogels, when modified with certain compounds like activated carbon powder, can help preserve fruits and vegetables.

The aerogels are then able to absorb ethylene gas — also known as a "fruit-ripening hormone" and which effectively triggers the ripening process in these fruits and vegetables like bananas, mangoes, papayas, tomatoes and potatoes.

The team's lab experiments show that the modified eco-aerogels can absorb six times more ethylenes then commercial absorbents, thus delaying the rotting process by at least 14 days.

Banana with a block of eco-aerogel modified with activated carbon vs. banana without. Photo from NUSLife / YouTube

“Vast quantities of fresh agricultural produce are discarded due to inadequate post-harvest storage and processing facilities, as well as inefficient or disrupted transportation systems," Professor Nhan Phan-Thien from the research team said.

The eco-aerogels therefore serve as a nifty solution to reduce spoilage.

Wastewater treatment

The eco-aerogels can be used in treating wastewater as well.

When coated in a chemical called diethylenetriamine (DETA), they can remove four times more nickel ions in industrial wastewater than conventional methods.

Applying different chemical coatings on the eco-aerogel can allow it to extract different types of heavy metals from wastewater.

Heavy metals are some of the most common and persistent pollutants in wastewater which can lead to environmental and human health impacts.

According to Duong, the treatment process is "simple, cheaper and does not generate secondary waste".

Cheap and cost-efficient

The eco-aerogels are rather cost-efficient too.

Making a sheet of aerogel one square metre in area and one centimetre thick costs less than S$10. When it reaches the market, a sheet of aerogel at such a size can be sold between S$30 and S$50.

The NUS team's process of making the eco-aerogels, which currently takes about 12 hours, is also 18 times faster than conventional methods used to manufacture commercial aerogels.

The eco-aerogels can also be reused, further minimising waste.

At the moment, the team of nine has filed a patent for the production of the eco-aerogels made from pineapple leaf fibres.

Duong (centre) with his team. Photo from NUS

They have plans to work with an industry partner to scale up and commercialise the technology as well.

There are still areas for improvement though.

The team is looking at identifying ways to efficiently recover heavy metals from the eco-aerogels after absorption during wastewater treatment, and is also conducting studies to develop techniques to produce eco-aerogels as a roll with unlimited length.

You can see NUS's video here.


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Top photo from NUS