Plastics in the circular economy

Bio-plastic bottles will soon fill the shelves. (Credit: Unsplash, Giuseppe Famiani)

Replacing single-use plastics with recyclable bio-plastics will stop the planet from drowning in waste

An ocean of plastic. That is the picture painted in our minds when we imagine the estimated eight million tonnes of plastic waste entering our marine ecosystems every year. Such an unmanageable volume of plastic has devastating environmental consequences that are only just starting to become apparent.

Despite our reliance on plastic products, there is a way to curb the amount of plastic waste we produce. In a new study published in Current Opinion in Green and Sustainable Chemistry, researchers at the City University of Hong Kong make the case for a circular plastics economy. The idea is for bio-plastic products made from natural materials, such as food waste, to be recycled at low cost and without producing waste to form new products.

“Plastics need to be produced and re-used in a sustainable way,” says Dr Guneet Kaur, co-author of the study. “To be sustainable, processes should not just be environmentally friendly and socially acceptable – but also economically viable and even profitable.”

In a circular economy, there is no waste. The concept looks beyond the traditional industrial mantra of “take, make, dispose” and instead creates an industrial system with the environment in mind. It is an idea that has been championed by the European Union for years.

After looking at the work of several EU-funded projects on food and agricultural waste, the Hong Kong-based team examined the ways in which food waste can be converted into plastic in a biorefinery. They used the work of research groups around the world, including their own lab, to illustrate that inexpensive and renewable sugars can be used to produce high-value plastics.

“Bio-plastics have come a long way in recent years,” says project lead Dr Carol Sze Ki Lin. “A joint venture of global companies that includes Coca-Cola is about to open a manufacturing plant for bio-plastic bottles in Belgium. It will have the capacity to produce 50,000 tonnes of bio-based polyethylene furanoate (PEF) a year.”

PEF is a bio-based and recyclable polymer that is projected to replace conventional petroleum-based polyethylene terephthalate (PET) because of its superior properties that make it suitable for a wider range of applications. Dr Lin adds, “The global market for bio-plastics is estimated to reach 30.8 billion dollars by 2020 – and PEF, which has not reached its full market potential yet – is expected to hold a large share of the market.”

Key to the success of a circular plastics economy is waste management – and this comes through recyclability, not biodegradability. A recyclable product means that material is retained in the recirculation loop; it can be re-made into new value-added products. If it can biodegrade, a valuable resource is removed which could impact profitability.

Although PEF products can be successfully recycled into other usable products, it is no more biodegradable than petroleum-based PET. With the correct protocols in place to ensure recycling, PEF bioplastics are an ideal entrant to the circular plastic economy. Dr Lin’s team hopes to contribute to this and is improving the production of bio-sugar from restaurant waste.

Kaur, G. et al.: "Recent trends in green and sustainable chemistry & waste valorisation: Rethinking plastics in a circular economy,Current Opinion in Green and Sustainable Chemistry (2017)