Plastic is everywhere. Our society cannot do without it: plastics have numerous advantages, are extremely versatile, and 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 energy-intensive production of plastics and their incineration release large amounts of CO2 into the atmosphere, making plastic products a major contributor to climate change.
One way out would be to rely on sustainable production methods, such as the circular economy, in which as much plastic as possible is recycled. Then the main raw material for plastic products would no longer be crude oil but shredded plastic waste. But is it even possible to tweak the plastics economy to absolute sustainability? Yes, it is, shows a new study led by André Bardow, Professor of Energy and Process Systems Engineering 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.
Massively increased recycling rate needed
The scientists looked at the complete value chains of the 14 most common types of plastics, including polyethylene, polypropylene and polyvinyl chloride. These 14 bulk plastics account for 90 percent of the plastic products manufactured worldwide. In their study, 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 over the long term without depleting the Earth’s resources.
The study finds that circular plastics are feasible within planetary boundaries. This would require at least 74 percent of the plastic to be recycled. By way of comparison, only around 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 would have to be improved. Specifically, plastics recycling would have to become as efficient as other chemical processes already are today. As things currently stand, not all plastics can be recycled. In the case of polyurethanes used as foams, for example, recycling has yet to be established – a question Professor Bardow is also addressing.
For the remaining 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 (known as carbon capture and utilisation or CCU), and on the other hand, from biomass. “Recycling alone won’t do it; we need all three pillars,” Bardow says.
