Plastic bottles holding 2.3 litres are least harmful to the planet

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plastic bottles

Plastic bottles are a significant source of plastic waste

M. Timothy O’Keefe/Alamy

Using plastic bottles that contain the most liquid for the lowest packaging weight could help reduce plastic waste.

Plastic pollution is a huge problem for the world, with much plastic waste reaching the oceans where it can affect marine life.

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In recognition of this, many researchers are developing strategies to tackle the plastic waste problem. Now, Rafael Becerril-Arreola at the University of South Carolina and his colleagues have come up with a relatively simple method to make a difference: change the plastic packaging size to maximise capacity for a given weight of plastic.

“We realised we could establish a relationship between supermarket beverage sales and plastic waste,” says Becerril-Arreola. “I saw the opportunity to create an impact, and I took it.”

Becerril-Arreola and his team focused on polyethylene terephthalate (PET), the most common material in plastic bottles. They weighed 187 empty bottles of different sizes from bestselling drink brands to determine the weight of plastic required to produce a bottle of a given capacity. They also compared this against PET waste and drink sales in Minnesota between 2009 and 2013, as the state government there reliably collects waste statistics and its bottled drink consumption is close to the US national average.

The researchers found that the most efficient bottles – those with the greatest capacity relative to the weight of plastic used to make the bottle – had a volume between 0.5 and 2.9 litres. Bottles of this size are typically brought for on-the-go use or social gatherings. Bottles that were smaller (under 0.4 litres) and larger (over 3 litres) used more plastic in relation to each bottle’s capacity.

The highest efficiency was seen with bottles with a volume of 2.3 litres. The data from Minnesota supported this: PET waste was lower during periods when, for reasons that were unclear, the proportion of bottles of approximately 2.3 litres sold was unusually high. In contrast, during periods in which unusually high proportions of smaller bottles were sold, waste seemed to increase.

The team then calculated what could happen if there were a shift in sales in the US towards bottles with a volume nearer 2.3 litres using the national data on PET waste. Becerril-Arreola says that PET generates around 815,000 tons of waste each year in the US, and that a 20 per cent shift to bottles closer to 2.3 litres in size could reduce that waste by around 10,000 tons a year.

Becerril-Arreola says he hopes these findings encourage consumers to switch to more efficient bottles to help reduce plastic waste. “It’s going to be tricky,” he says. “It’s a matter of awareness. We cannot expect corporations to make plastic bottles more efficient themselves.”

Journal reference: Scientific Reports, DOI: 10.1038/s41598-021-82983-x

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