What if plastic waste could be turned into something useful? That dream may soon become a reality, as scientists have found a way to turn plastic into acetic acid using sunlight. Plastics and microplastics have been found everywhere from waterways to remote ecosystems to the bodies of humans and animals. Worldwide plastic usage has also continued to increase over the past 60 years. But this new method would mark a uniquely environmentally friendly way of dealing with plastic pollution.
Sunny solutions
Scientists have created a “sustainable, highly efficient” method to “upcycle plastics to value-added acetic acid,” which is the main component of vinegar, said a study published in the journal Advanced Energy Materials. The process is a “bio-inspired cascade photocatalysis using iron atoms embedded in carbon nitride,” said a release about the study. It is similar to “how certain types of fungi break down organic matter using enzymes.”
“Our goal was to solve the plastic pollution challenge by converting microplastic waste into high-value products using sunlight,” said Dr. Yimin Wu, a professor of mechanical and mechatronics engineering at the University of Waterloo who guided the study, in the release. When the photocatalyst is exposed to sunlight, it triggers two back-to-back chemical reactions. The first one “breaks plastic down into smaller molecules,” and the second “converts those molecules into acetic acid,” said Earth.com. The reaction also takes place in water, “making it particularly relevant for addressing plastic pollution in aquatic environments,” said the release.
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The other benefit is that the system works on a variety of plastic types. Acetic acid could be produced from “common plastic wastes, including PVC, PP, PE and PET,” and remained “effective across mixed plastic compositions,” said the release. This makes it a valuable tool for real-world waste streams where different plastics are all mixed together.
Acidic answers
Global plastic use has grown from 20 megatons (Mt) in 1966 to 460 Mt in 2019, according to the Center for Sustainable Systems at the University of Michigan. It is expected to reach 1,231 Mt by 2060. Unfortunately, there is no great way to deal with plastic waste. The majority of it ends up in landfills, where it stays for thousands of years. It can also get stuck in the ecosystem or in waterways. Some can be incinerated, but that releases chemicals and smoke into the atmosphere. Recycling is another option, but not all types of plastic can be recycled, and many current processes require the use of fossil fuels.
This newly discovered alternative “allows abundant and free solar energy to break down plastic pollution without adding extra carbon dioxide to the atmosphere,” Wu said. In addition, while acetic acid is used to make vinegar, it also has several other uses and a “global annual demand of approximately 18 million tons,” said The Engineer. The material is “widely used across the chemicals sector and also has some energy applications.” The study’s findings also “point to new possibilities for addressing microplastics directly,” as the “process degrades plastics at the chemical level,” which “could help prevent the accumulation of microplastics in water systems,” said the release. The technology is still in the laboratory phase.
