the path to carbon negative plastic

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Researchers chart a path to carbon-negative plastic

A new study shows this feat is possible, but will require more than recycling or a price on carbon
December 13, 2022

If current trends and policies continue, global plastic demand will double by 2050 and triple by 2100, with similar increases in greenhouse gas emissions, according to a new study. But careful policy and planning could reduce plastic’s environmental impact and in fact turn the material into a form of long-term carbon storage.

Plastics currently account for a larger proportion of global greenhouse gas emissions than does aviation, but there has been little research on how different climate policy and socioeconomic development pathways might shape the climate impact of plastics in the coming decades. Nor have plastics been integrated into the models that inform the work of the Intergovernmental Panel on Climate Change (IPCC).

That’s a glaring oversight because the stakes are high. “Plastics have a significant impact on the climate which will further increase if we don’t drastically change the way we produce and use plastics and treat plastic waste,” says study team member Paul Stegmann, a sustainability researcher at the Netherlands Organisation for Applied Scientific Research in Utrecht.

Stegmann and his colleagues used a new computer model to analyze three possible scenarios for reining in greenhouse gas emissions from the plastics industry. The model traces the entire life cycle of plastics and assesses the climate impact of different source materials, or feedstocks; production processes and sources of energy; and waste management strategies.

Each strategy for making the plastics industry more sustainable comes with its own benefits and tradeoffs, the researchers report in the journal Nature.

Putting a globally uniform price on carbon to keep warming under 2 °C would drive a switch to renewable energy throughout the economy, reducing greenhouse gas emissions associated with plastics production along with everything else. But while carbon pricing is necessary to make the plastics industry more sustainable, it’s not sufficient, the researchers found.

With carbon pricing alone, recycling would increase somewhat, but chemical recycling—an advanced form of recycling that has the potential to produce higher-quality recycled plastics and keep them in circulation for longer—would decrease, because it requires a lot of energy. Less plastic waste would be burned for energy, which causes carbon emissions, and more would be sent to the landfill, which doesn’t.

 

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“Initially, I was surprised how much the model liked landfilling when applying a CO2 price,” Stegmann says. “But it makes sense, as it is cheap and barely has emissions if plastics are properly disposed in managed sanitary landfills.” But there are problems with landfilling too, Stegmann emphasizes, and in this scenario more and more new plastics would continue to be produced, most of them made from fossil fuels.

The second scenario, which emphasizes recycling to create what researchers call a circular economy, could reduce resource consumption and emissions from the plastics industry. “Circular economy strategies have a particularly strong emission mitigation potential in the short and medium term (up to 2050),” Stegmann says.

Yet even massive efforts to improve recycling technologies and roll them out around the world can’t achieve a fully circular plastic economy, the researchers found: there simply won’t be enough plastics headed to recycling centers to meet demand, as long as the demand for plastics keeps growing. So efforts to stabilize demand for plastics will be necessary too.

Finally, the researchers’ third scenario suggests that subsidizing the production of plant-based plastics, in combination with increased recycling, could even turn plastics into a long-term carbon sink. “Plants take up CO2 while growing and that CO2 is then stored in plastics that we then should keep in use for a long time”—either by recycling it endlessly or in long-lived products such as building materials, Stegmann explains.

The negative emissions could be significant: the equivalent of up to 275 billion tons of carbon dioxide pulled out of the air between 2020 and 2100, the researchers calculated. Achieving that would require substantial changes to plastics production, waste management, and the energy system as a whole—so the findings may be best read as a sketch of what’s theoretically possible for the plastics sector.

Even so, there may be yet other strategies that could further improve the sustainability of plastics. Stegmann and his collaborators aim to investigate the impacts of reducing plastic demand, sharing plastic items, and keeping them in use for longer, he says.

Source: Stegmann P. et al.  “Plastic futures and their CO2 emissions.” Nature 2022.

Image: ©Anthropocene Magazine.

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