Summary Reader Response (Draft 3)

The Levy (2022) article that is posted on The University of Texas at Austin news site, titled “Plastic-eating Enzyme Could Eliminate Billions of Tons of Landfill Waste'', revealed to the readers that researchers at The University of Texas at Austin have developed an enzyme variant that can accelerate the degradation of environmentally harmful plastics in hours or days instead of centuries. The article also stated that the researchers mainly focused on polyethylene terephthalate (PET), a polymer most commonly found in consumer packaging and certain fibers and textiles. This enzyme variant is able to disintegrate the plastic into smaller parts (depolymerization) and then put it back together (repolymerization) which begins the upcycling process. Lavars (2022) mentioned that plastic-eating enzymes were first created in 2016, and among the factors that have hindered the application of this plastic-eating enzyme are its inability to function at low temperatures and different pH ranges, its inability to treat untreated plastic waste directly, and its slow reaction times. However, the Levy (2022) article claimed that this new and improved enzyme variant is proven to be superior in breaking down PET plastics more efficiently. Most of today’s plastic waste ends up in the landfill. This enzyme has the potential to remove waste from landfills and green high-waste industries, which would be a significant contribution to the cleanup of landfills and greening of high-waste industries.

Plastic-eating enzyme recycling could result in a more sustainable approach than traditional recycling methods in terms of fitting into a circular economy and have greater environmental and health benefits.

When traditional recycling methods such as mechanical recycling and chemical recycling are compared to the enzymatic conversion of plastics, traditional recycling methods are incompatible with a circular economy due to the inability to upcycle plastics, whereas plastic-eating enzymes not only fit into a circular economy but also provide new opportunities for upcycling. According to (Zhu et al., 2021b), plastic substrates can be depolymerized by enzyme biocatalysis into oligomers and monomers, which can then be reprocessed into new plastic products or refined into new value-added chemicals in a circular economy. In this case, plastics would be reused indefinitely and eliminate reliance on fossil fuels resources. For years, mechanical recycling has been used to recycle plastic waste on a large scale. The process involves a series of steps: sorting, washing, grinding, and extruding plastics into raw materials for reuse. It usually is a downcycling process since the quality of the reprocessed plastic material will significantly degrade and the end product will be of lower value and eventually results in lower quality plastic that is discarded in landfills hence unfit in the circular economy (Mechanical Recycling, n.d.). The same goes for chemical recycling, which is generally burned as fuel, and very little plastic waste actually becomes new plastic, even when technology is advanced. As a result, chemical recycling, as opposed to recycling with plastic-eating enzymes, has no place in a circular economy.

When compared to traditional recycling methods, recycling with plastic-eating enzymes is more environmentally friendly. According to Chemical Recycling: Distraction, Not Solution (2020), used plastic is broken down using a combination of heat, pressure, depleted oxygen, catalysts, and/or solvents to produce fuel or new plastic in chemical plastic recycling. Plastic, which contains a wide range of toxicants, releases more toxicants when heated. Toxins enter the environment via air emissions and toxic residues, especially when products and by-products are burned. Toxins include benzene, toluene, formaldehyde, vinyl chloride, hydrogen cyanide, PBDEs, PAHs, and high-temperature tars. Chemical Recycling: Distraction, Not Solution (2020) also stated that chemical recycling directly emits greenhouse gasses, and that chemical recycling also perpetuates the extraction of fossil fuels for plastic manufacturing, thereby exacerbating climate change. In contrast, the plastic-eating enzyme recycling method demonstrates superior degradation of PET plastic at low temperatures ranging from 30 to 50 °C (86 to 122 °F), a range of pH levels, and pressure. It is capable of breaking down plastic in as little as 24 hours and almost completely degrades 51 different untreated PET products within a week in some experiments (Lavars, 2022). Because the enzyme can quickly degrade post-consumer plastic waste with minimal heating, it is both environmentally friendly and time-saving.

Despite the plastic-eating enzyme being a more sustainable approach compared to traditional recycling methods. It would not be the solution to plastic problems but only put a dent on them as it does not break down plastic as readily as many had hoped. According to research (Cobongela, 2021), polyester, polyamides (PA), and polyurethanes (PU) are among the plastics that are hydrolyzable by most enzymes reported so far. Because non-hydrolyzable plastics are extremely resistant to biological cleavage, there are only a few reports on enzymes that degrade them. This shows that many enzymes only work for specific kinds of plastic, and much of our trash may contain a bad mixture of several types and layers of plastic (Temming, 2021). Also, often enzymes only can work under specific conditions such as ambient temperature. Despite enzymatic plastic degradation being a more environmentally friendly method of recycling plastic waste, it has remained a topic to be explored further with a major improvement.  However, research has been done by scientists that using genetic engineering could create bacteria capable of producing more efficient plastic-degrading enzymes. These genetically modified bacteria may be able to more thoroughly break down plastics as well as break down other types of plastic (Cooper, 2022).

To summarize, enzymatic plastic recycling is a more environmentally friendly, circular economy-friendly alternative to traditional recycling methods. It has the potential to be an excellent tool for combating the problem of plastic pollution in the near future if more research into plastic-eating enzymes is conducted. While these chemical machines can help with plastic recycling, reducing the amount of plastic used in the first place is a much simpler and likely less expensive solution to our plastic pollution problem.

References

Chemical Recycling: Distraction, Not Solution (pp. 1–8). (2020). GAIA. https://www.no-burn.org/wp-content/uploads/2021/11/CR-Briefing_June-2020.pdf

Cobongela, S. Z. Z. (2021). Enzymes Involved in Plastic Degradation. Degradation of Plastics, 95–110. https://doi.org/10.21741/9781644901335-4

Lavars, N. (2022, April 28). Fast-acting enzyme breaks down plastics in as little as 24 hours. New Atlas. https://newatlas.com/environment/fast-acting-enzyme-plastics-24-hours/

Levy, N. (2022). Plastic-eating Enzyme Could Eliminate Billions of Tons of Landfill Waste. [online] UT News. Available at: https://news.utexas.edu/2022/04/27/plastic-eating-enzyme-could-eliminate-billions-of-tons-of-landfill-waste/.

Malewar, A. (2022, April 28). Plastic-eating enzymes can break down plastics in as little as 24 hours. Inceptive Mind. https://www.inceptivemind.com/plastic-eating-enzymes-break-down-plastics-24-hours/24446/

Mechanical Recycling. (n.d.). Circular Economy Asia. https://www.circulareconomyasia.org/mechanical-recycling/

Temming, M. (2021, March 16). Chemists are reimagining recycling to keep plastics out of landfills. Endplasticwaste.org. https://endplasticwaste.org/en/our-stories/chemists-are-reimagining-recycling

Zhu, B., Wang, D., & Wei, N. (2021b). Enzyme Discovery and Engineering for Sustainable Plastic Recycling. Trends in Biotechnology, 40(1). https://doi.org/10.1016/j.tibtech.2021.02.008