A fully sustainable plastics economy is possible — ScienceDaily

Plastic is everywhere. Our society cannot do without it: plastics have many advantages, they are extremely versatile, and they are also cost-effective. Today, plastics are mainly produced from crude oil. When the products reach the end of their life, they often end up in a waste incineration plant. The production and burning of energy-intensive plastic releases large amounts of CO2 into the atmosphere, making plastic products a major contributor to climate change.

One way out is to rely on sustainable production methods, such as the circular economy, where as much plastic as possible is recycled. Then the main raw material for plastic products would not be crude oil but shredded plastic waste. But is it even possible to change the plastics economy to full sustainability? Yes, it is, shows a new study led by André Bardow, Professor of Energy Engineering and Process Systems at ETH Zurich. Gonzalo Guillén Gosálbez, Professor of Chemical Systems Engineering at ETH Zurich, and researchers from RWTH Aachen University and the University of California, Santa Barbara collaborated on the study.

A greatly increased recycling rate is required

The scientists looked at the entire value chains of the 14 most common types of plastics, including polyethylene, polypropylene and polyvinyl chloride. These 14 major plastics account for 90 percent of the plastic products manufactured worldwide. In their studies, the researchers investigated for the first time whether it is possible for the plastics industry to respect planetary boundaries. These are a measure of comprehensive sustainability. They go beyond energy and climate issues to include, for example, impacts on land and water resources, ecosystems and biodiversity. In short: processes that adhere to planetary boundaries can be sustained in the long term without depleting Earth’s resources.

The study found that circular plastics are possible within planetary limits. At least 74 percent of the plastic would need to be recycled. By comparison, only about 15 percent is recycled in Europe today, and the rate is likely to be much lower in other regions of the world. In addition, the study finds that recycling processes need to be improved. Specifically, plastics recycling would have to be as efficient as other chemical processes are today. As things currently stand, not all plastic can be recycled. In the case of polyurethane used as foam, for example, recycling has yet to be established – a question that Professor Bardow is also asking.

For the maximum 26 percent of plastics, the carbon needed for production could be sourced using two other technologies, according to the study: on the one hand, CO2 captured from combustion processes or from the atmosphere (called carbon capture and utilization or CCU), and on the other hand, from biomass. “Recycling alone won’t do it; we need all three pillars,” says Bardow.

“Increasing the recycling rate to 74 percent worldwide is a very ambitious goal,” admits Bardow. Therefore, it is unlikely to be achieved by 2030, but 2050 is more realistic. Another challenge, however, is that more and more plastic products are now being manufactured year after year. If the current trend continues until 2050, improving recycling processes will not be enough, as planetary limits would still be exceeded in 2050.

This is why the authors of the study recommend addressing demand as well as assigning a different value to plastic. “Plastic is considered cheap, which was a blessing for a long time but is now a curse,” says Bardow. “Given their excellent properties, we should see plastic as the quality material it really is. That way, it would be okay for it to cost a little more, and to recycle it too.”

A more complete understanding of product stewardship

In the study, the scientists indicate that plastic products must be better aligned with the circular economy in the future. For this purpose, manufacturers should work more closely with recyclers. According to the authors of the study, it would be desirable if plastic manufacturers had a wider understanding of their responsibility: Nowadays, responsibility often ends when the product leaves the factory gates. The scientists, therefore, call for product stewardship to encompass the entire life cycle — including disposal and recycling — as a basis for optimizing the design of sustainable processes.

In any case, pushing recycling is the right way to go: since it has no serious disadvantages, it should be treated as a special case to change the economy towards sustainability. In many other areas, conflicting goals arise. Take, for example, the production of synthetic fuels, which are extremely energy intensive, or the use of biomass, which competes with food production. Plastic recycling, on the other hand, does not lead to such a conflict of goals. “Recycling efforts should be boosted whenever possible,” says Bardow. “As a good rule of thumb: Recycling more plastic always leads to more sustainability.”

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