Coffee waste to help produce biodegradable plastics

LOUISA TANG Today Online 11 Dec 17;

SINGAPORE — One day, the waste generated from the cup of coffee you are drinking from the hawker centre could be used to make more eco-friendly plastic bags, thanks to a team of Nanyang Polytechnic (NYP) scientists.

Dr Henry Leung, a senior lecturer and senior specialist at NYP’s School of Chemical and Life Sciences, has found a more sustainable way to turn coffee waste into biodegradable plastic.

“This adds value to the coffee waste that hawkers usually just throw away, creating environmental issues,” Dr Leung told reporters at a media briefing on Monday (Dec 11).

Incinerating coffee waste consumes large amounts of energy and it also requires large storage areas. In 2011, 7 million tonnes of coffee waste was generated globally.

In the method used by the NYP team, water and bacteria are first added to the coffee waste. The blend found in Singapore coffee shops, termed “Nanyang coffee”, is traditionally roasted with butter and sugar, which provide natural nutrients for the bacteria to grow.

The mixture is then allowed to sit for seven to 10 days. When the bacteria consumes the coffee waste and multiplies rapidly, it produces a chemical that scientists extract — specifically, a biopolymer called PHA. This chemical can then be used to produce biodegradable plastic.

The team decided to use the Cupriavidus necator bacteria because it is the “easiest to handle” among the common PHA-producing bacteria, Dr Leung explained. It can also work at room temperature and does not need fancy temperature controls, which will use more energy.

At first, the researchers were disappointed with the purity of the PHA yield when using the bacteria, Dr Leung disclosed. For example, from 100g of coffee waste, they were able to get 0.5g to 2.5g of pure PHA.

When using the typical heavy solvents to extract the PHA, they could only achieve 30 per cent purity, and produced organic waste in the process as well.

They then switched to using environment-friendly and more soluble organic solvents in the form of acetone and an alkaline chemical solvent. These do not produce more waste, and are also 50 per cent cheaper than heavy solvents.

However, the team ran into another problem: These eco-friendly solvents normally do not produce as much yield as their heavy counterparts.

So they decided to genetically modify the bacteria and managed to counteract the problem, ending up with a purity yield of more than 50 per cent. Out of 100g of coffee waste, they can now get roughly 1g to 3g of pure PHA.

PHA is more beneficial to the environment because they take a shorter time to decompose and release fewer toxic compounds in the process, compared with the traditional polyvinyl chloride (PVC) used in plastic products. PVC is the world’s third-most widely produced synthetic plastic polymer.

Dr Leung said that the team has completed its laboratory experiments, which began in 2013. They are now looking for industrial partners — such as plastic manufacturers — to expand the project, and are looking to commercialise the process in three to five years.

Similar projects using coffee waste have been conducted in other countries such as Hong Kong and South Korea, but Dr Leung said that only one company in Australia is doing it on a commercial scale.

“The big dream is that, one day, far in the future, we won’t need to use PVC at all to make plastic products,” he added.

Poly scientists find cheaper way to make greener plastics
Coffee-eating bacteria can help cut the cost of making biodegradable plastics by half
Jose Hong Straits Times 12 Dec 17;

Scientists in Singapore have found a process that can potentially produce biodegradable plastics at half the cost and in a manner that is less harmful to the environment.

While promising, it is still early days for the project, which may come to fruition only in three to five years, said Dr Henry Leung, leader of the research team from Nanyang Polytechnic, yesterday.

The breakthrough in making "greener" plastics involves using new bacteria and solvents like acetone.

The bacteria, Cupriavidus necator, eat nutrients in coffee waste and store them as a chemical called polyhydroxyalkanoate (PHA).

When the solvent is added, the bacteria die and release the PHA, which is used for making plastics that are environmentally friendly, said Dr Leung, 42, a senior specialist in pharmacology and toxicology and a senior lecturer at the polytechnic's school of chemical and life sciences.

The PHA helps degrade plastics more swiftly, he added.

This will lead to fewer plastic products such as bottles and bags clogging waterways and being eaten by animals, such as sea turtles and birds.


One day, these degradable products could even replace microbeads in personal care products.

DR HENRY LEUNG, leader of the research team from Nanyang Polytechnic, on the harmful spheres found in facial washes.

He also said such degradable products could one day replace microbeads in personal care products. Microbeads are tiny plastic balls found in beauty products like exfoliating facial washes.

When washed out to sea from drains, these can kill marine life and be harmful to people.

The making of PHA also pollutes the environment because the solvents typically used, like hexane, are more pollutive than acetone.

But the current process of producing PHA is very pricey, with 1g of PHA being sold at $28,000, said Dr Leung. He estimates his method of producing PHA would cost about half as much.

The way coffee is produced in Singapore also helps to save on costs, Dr Leung said.

"Coffee beans are roasted with sugar and butter, and these are enough to give the bacteria energy to produce PHA," he added.

His efforts join the growing global push for better ways to make plastics. For instance, they can be made from plant starch, which can degrade harmlessly and quickly. However, such sustainable plastics make up only 10 per cent of the whole plastics market, reported a Nature news article last year.

As team member Alvin Teo, 49, a senior lecturer in molecular biotechnology, said: "The project is in a very exploratory stage. It's up to industry players to see how far we can take this."

The next step for the team is to find business partners such as coffee companies and plastic manufacturers, as well as partner other researchers to improve the process and get it ready for the market, added Dr Leung.