"Energy remains the low-hanging fruit in this space, and so it doesn’t make sense to prioritize bio-based plastics just yet," Daniel Posen, who was based at Carnegie Mellon University, US, at the time of the study, told environmentalresearchweb.

The researchers estimate that renewable feedstocks such as corn-based biopolymers could slash greenhouse-gas emissions by 16 million tonnes, but this is currently an expensive option.

Both strategies – switching to renewable power and replacing fossil-fuel-derived feedstocks with biopolymers – push up industry costs, by around $10–$200 per tonne of plastic for renewable power and $200–$3000 per tonne of plastic for biopolymers.

However, the study shouldn't be viewed as being bad news for bio-based plastics, the researchers believe. These plastics’ time will come once the industry has maximized the benefits of adopting renewable energy to power its production.

Other factors may also come into play, such as any increase in the price of fossil fuels, which could make conventional plastics more expensive than bio-based ones. And there’s also future demand to consider.

Energy substitution alone may not be enough to reduce greenhouse emissions in the plastics industry over the longer term. Assuming a 1–3% growth in per capita plastics consumption, the team projects that the associated greenhouse-gas emissions would return to current levels by around 2040.

So feedstock substitution pathways such as the use of advanced biopolymers in place of fossil fuel-based materials will need to be developed alongside switching to low-carbon energy across the chemical industry.

The team reported the findings in Environmental Research Letters (ERL).

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