Polyethylene terephthalate, better known as PET, is probably the plastic we encounter most often in our everyday lives. Along with textile and foil products, PET is particularly popular in the field of food packaging due to its resistance to fats and acids. PET can already boast about its good recycling record—yet another reason for its popularity.
However, transporting PET products to be recycled in other countries, such as China, creates ecological and economic stresses, and the process itself is also problematic. Even with efficient recycling, melting PET releases a large amount of carbon dioxide and toxic gases—meaning that there is a direct path from the fossil fuel precursors of the plastic to the carbon dioxide it emits. In addition, PET can only undergo a certain number of such recycling cycles. With each cycle, the material quality decreases and the plastic becomes increasingly yellow.
“Because of this, it’s necessary at some point to break down the material to recover the constituent components,” says Dr. Christian Sonnendecker from Leipzig University. Working with a team of researchers, Sonnendecker discovered the enzyme PHL7 in a compost pile at a cemetery in Leipzig. It’s proven to be incredibly potent: it was able to decompose 90 percent of a plastic fruit container in just 16 hours.
For more than a decade now, new discoveries have been providing a foretaste of the potential importance of enzymes for recycling. Enzymes are proteins that stimulate biochemical processes in cells. For instance, they can break down the waxy layer on the outside of plants, a type of natural polyester: an ability that effectively predestines them to be able to decompose PET.
“By recovering the basic building blocks of PET, we can create a permanent cycle and thus achieve independence from fossil raw materials.”
Is a revolution on the horizon? “Enzymatic recycling is still in its infancy,” Sonnendecker explains. “Around the world, research groups are working on preparing enzymes for use in the marketplace—particularly with regard to efficiency and cost-effectiveness.” Artificial intelligence has already been used to optimize enzymes. With all these innovations, it is hoped that the plastics market will change dramatically in the coming years.
“By recovering the basic building blocks of PET, we can create a permanent cycle.”
Without an effectively closed circular economy, the path of a plastic bottle inevitably can lead in just one direction—to a landfill, an incinerator or into the ocean. The need to establish closed-loop raw materials cycles seems inescapable.
“The circular economy also includes the life cycles of buildings, textiles and batteries,” says Katharina Istel, an expert on the circular economy at the Nature and Biodiversity Conservation Union Germany (NABU). She believes there’s another essential step before all of this: “First and foremost, a sustainable circular economy means avoiding waste, including disposable one-use products and fast fashion.”
So we’re facing a transition from a throwaway society to a system in which consumption and re-use are carbon neutral, sustainable and forward-looking. Strictly speaking, this means that the terms “consumption” and “waste” (or “trash”) are facing extinction.
The goal is to create the conditions for a functioning circular economy by the year 2050. The EU has designated different fields of action covering this topic—from the creation of a product to its utilization, the end of its useful life (end-of-life) and its recycling thereafter. The Packaging & Packaging Waste regulation was proposed in November 2022 as part of this action plan. Dr. Robert Hermann, who is the manager of the Business Unit for Green Energy and Sustainability at TÜV SÜD, sees an important message in this unambiguous legislation: “This regulation puts specific pressure on the EU member states, while leaving some room for interpretation through delegated acts.”
Over the long term, along with recyclability, other factors including repairability, durability, reusability and the labeling of various ingredients will play a role—and it must also be possible to present these comprehensibly in the form of a conformity assessment. The testing and verification process according to the TÜV SÜD standard for packaging recyclability is used for packaging made of materials such as plastics, paper, aluminum/ferrous metals and glass.
While we wait for industrially applicable enzymes for recycling PET, we must continue to work on our consumption habits—for instance bringing our own bags instead of using plastic bags from shops, or checking for reliable certifications on products. “It takes me twice as long to do my shopping as it did ten years ago,” Hermann says. “By now, though, I know what to reach for.”
