Changing plastic’s life cycle from linear to circular
With plastic being an incredibly sturdy, durable, and one of the most versatile materials around, the rate at which it is produced has increased significantly over the last couple of decades. However, due to the limited possibilities for recycling and the fact that plastic can take up to a thousand years to decompose, the processing of plastic has become one of the biggest environmental challenges that we are currently facing and plastic waste has been a massive problem for many years now. Most of the plastic that is produced is quickly discarded and ends up in incinerators, landfills, or in our oceans – Greenpeace reported that 12 million tonnes of plastic enter our oceans every year. Only a small portion of plastics – less than a quarter of what is produced – is recycled, but this is a costly and energy-intensive process, and even these plastics have a linear lifecycle and eventually become unusable.
In order to divert plastic from the oceans and landfills, a more efficient method of recycling is required. With the recycling processes that are currently in use, the already small portion of plastic that is recycled significantly declines in its quality in the recycling process, and the resulting product is hardly ever used in high quality products after being recycled. This is due to the many different chemical additives that most plastics contain to give it its characteristics such as the texture, colour, and shape. After disassembling the polymers that the plastic is built up from, these additives are still attached to the plastic’s monomers with immutable bonds. At the recycling plant, these monomers, with their particular set of additives still attached, end up in a large mixture with different monomers, each with varying sets of additives that determined the qualities of the original product. Because of this large mixture of monomers with countless different chemical additives, it becomes extremely difficult to predict the qualities that the end-product will inherit from the original material. As a result, Science Daily explains, the recycled plastic is usually subject to a decrease in quality and performance.
As a result, (recycled) plastics have never had a circular life-cycle. That is, until last week when a new research by a team of researchers at the U.S. Department of Energy’s Berkeley Lab, published in Nature Chemistry, introduced a new kind of plastic that can be recycled in closed-loop life cycles. This new material, called poly(diketoenamine) or PDK, contains reversible instead of immutable bonds that, when dunked in a highly acidic solution, allow the plastic to be broken down into its original monomers. Additionally, when disassembled into monomers, the PDKs can be freed of any chemical additives in this acidic solution. These “purified” monomers can in turn be reassembled into polymers, creating new, high quality plastics, thereby allowing them to be fully recycled and be turned into new plastics that don’t necessarily inherit the features of the original material. In short, any plastic product can be turned into any other plastic product.
The idea to approach plastic recycling at a molecular level is not completely new and it has been attempted in the past. In the execution of comparable methods, researchers ran into issues with the retrieval of the monomers of “regular plastics” due to irreversible bonds in the polymers, making this process a difficult and costly endeavour. Here, with the relative ease with which the original monomers can be recovered and the fact that this process can be repeated over and over again, PDKs offer an exceptional to provide a plastic with a circular life-cycle with a minimal environmental impact.