These compostable plastic bottles could replace boxed-wine packaging

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A new bioplastic bottle for wine packaging could replace boxed wine and protect its flavor. (Shutterstock)

Researchers have developed a prototype bioplastic bottle that could provide a more environmentally friendly way to enjoy a glass of vino.

Detailed in a study published May 15 in Polymer Testing, the compostable bioplastic bottle was designed as an alternative to bag-in-box and carton wine packages, which are not as sustainable as they may appear. The researchers tested different formulations to develop a sturdy bottle that protects the wine's flavor.

The popularity of bag-in-box and carton wines has seen an uptick in recent years, and this trend skyrocketed during the COVID-19 pandemic. A mix of cardboard, plastic and aluminum, this packaging is convenient because it's less fragile than glass. Boxed wine may also have a smaller carbon footprint than glass bottles because the transportation of these lighter packages produces less carbon dioxide emissions.

But there's an important downside to that box of pinot grigio or merlot.

"This packaging has a very high environmental impact because the multi-material solution is very difficult to recycle," said study lead author Clizia Aversa, a researcher in the department of engineering at Roma Tre University. 

The different layers must be separated to recycle them individually, which makes recycling "very complicated and expensive," she continued. This means that in practice, municipalities usually just send this type of waste to landfill.

"So we thought that a compostable material could be a good solution [to wine packaging] because this kind of material can go in the organic fraction of the waste collection," Aversa told The Academic Times. "Or if it is a home-compostable material, you could compost it directly at home."

Traditional plastics, made from non-renewable fossil fuels, take decades to break down. They often end up polluting oceans and fragmenting into microplastics, which are ubiquitous in soils, waterways and the atmosphere. Researchers have developed plastics that are designed to be recycled, but these materials won't likely be used for single-use items like food and drink containers.

Another alternative is biodegradable plastics, which break down much faster than traditional polymers. But some are made from fossil fuels and still produce potentially harmful microplastics

A biodegradable alternative to fossil fuel-based plastics is bioplastics, which are made from renewable sources such as sugarcane, cellulose or even fish oil.

Aversa and her colleagues sought to develop a compostable, bioplastic bottle for wine. 

"We're trying to customize to achieve the best compromise between oxygen barrier and mechanical properties of the bottle," she explained. "We need oxygen barrier because the product, the wine, is sensitive to oxidation; the flavor of the wine can be altered by the presence of oxygen." 

At the same time, she added, "The bottle should not be too fragile."

The team tested five formulations of bioplastic that differed in their composition of two commonly used bioplastics: polylactic acid, or PLA, and polybutylene succinate, or PBS. Because PLA is rigid, whereas PBS is more flexible, better mechanical properties can be achieved by combining the two materials, Aversa said. 

The formulations also had different levels of talc, a clay mineral that blocks oxygen from penetrating the bottles.

To make the bottles, the team first combined PLA, PBS and talc in a machine that melts and mixes the components to produce polymer granules. Inside a second machine, the granules are melted and the molten plastic is put into a mold. Air inflates the plastic inside the mold, which produces the final bottle shape.

The strength of the five different bottle formulations was tested with a drop test. The researchers dropped bottles filled with liquid from a height of 90 centimeters (almost 3 feet) and visually inspected them for signs of damage and leakage.

To see how well the bottles protected wine from oxygen, the team measured oxygen permeability in different temperatures and humidity levels. The researchers also tested whether the materials influenced the wine's flavor. The bottles were filled with wine, and after four weeks, a panel of expert wine-tasters sampled the contents.

The formulation with highest talc content, about 30%, blocked the most oxygen, but this bottle was also the most fragile, leaking after being dropped. When the talc content was reduced to about 18%, the bottles blocked only slightly less oxygen but were much less fragile, making this the best formulation of the five. The tasters found no change in the flavor of wine stored in this type of bottle for four weeks.  

In ongoing experiments, the researchers are testing the extended shelf-life of the top-performing bottle formulation to see how quality and flavor of the wine holds up after several months.  

According to Aversa, bioplastic bottles are unlikely to replace glass bottles for high-end wines, which can improve with age and are sometimes stored for decades. But for cheaper, quaffable wines, compostable bottles could be an alternative for boxes or bags. 

"Another application for this kind of bottle is, for example, in airplane travel," Aversa said. "Some companies serve wine in single-portion packaging, so it would be a solution to have them in plastic rather than glass for safety reasons — because obviously glass on a flight is pretty dangerous." 

According to Aversa, the bioplastic wine bottles would take around 12 weeks to degrade in industrial composting. It's unclear how long they would take to break down in a home composter, but the team is currently conducting these tests.

The study, "Design, manufacturing and preliminary assessment of the suitability of bioplastic bottles for wine packaging," published May 15 in Polymer Testing, was authored by C. Aversa, M. Barletta and E. Pizzi, Università degli Studi Roma Tre; A. Gisario, Sapienza Università degli Studi di Roma; R. Prati, Caviro SCA; and S. Vesco, Università degli Studi di Roma Tor Vergata.

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