An interesting possibility to get rid of our plastic waste
We have all heard of the growing problem of plastic wastes. Plastic can, over time, break down in the presence of ultraviolet light (UV). UV will degrade plastics. However, the product of the degradation will likely still be a toxic chemical. Ultimately, plastics will completely degrade but because plastics are a relatively new product, no one knows exactly how long it will take for a single plastic article to degrade to simple molecules. Some estimates are in the range of 500 to 1,000 years.
An additional problem with this scenario is that the plastic needs to be in the presence of UV. If it is in a landfill, it will not degrade. That was the case but recently, microbes have been identified as a potential source for “biodegradation” of plastics. Biodegradation is different from degradation in that unlike simple degradation which breaks pieces up into smaller and smaller pieces of the same material, biodegradation will convert the plastic into simple molecules bypassing the breaking into smaller particles phase.
In 2008, a young man in Canada identified that microbes can speed up the biodegradation, converting the equivalent of a plastic bag into simple molecules inside 3 months. But as the young man said, this would be best on an industrial scale because fermenting tanks would be necessary. But what about the plastics already in a landfill?
A Natural Solution, the Waxworm
Environmental Science and Technology published an article in 2014 that described the biodegradation of Polyethylene (PE) by bacterial strains from the guts of Waxworms. The study reported that between 6.1 and 10.7 % of a PE test film had degraded within 60 days.
In a 2015 report, a team identified that mealworms can consume polystyrene as a food source and not be harmed by the consumption. Roughly half of the polystyrene consumed was discharged as waste but the rest was converted to carbon dioxide through respiration. Additional work showed that the gut bacteria of the mealworms were the main heroes of this process. But just adding the bacteria to the plastic will not produce the same results, possibly due to the need for a controlled (warm and wet) environment evident in the mealworm’s gut.
The Use of Enzymes
In 2016, a team from Kyoto University has identified that enzymes can be used to breakdown poly(ethylene terephthalate) (PET), a common form of plastics used in bottles and clothing. These enzymes might be introduced to a plastic filled landfill and allowed to work their magic. But the product from this enzyme breakdown is Ethylene-glycol and terephthalic acid. I am uncertain of the ultimate results of this enzyme action.
Recently, National Geographic published an article detailing a discovery that a different species of waxworms work much in the same way that was reported in the 2014 study mentioned above. The article details the accidental discovery that a beekeeper had discovered. It just happened that the beekeeper was also a developmental biologist. She found waxworms in her beehives and removed them, placing them in a plastic bag for disposal later. An hour later, she found the bag was empty and had holes in it. She guessed what had happened. Since they eat wax ( a large chain polymer molecule), it was possible that they had developed a way to eat the long chain polymer of the plastic. She started working on the concept and experimented a little. Her team identified in a controlled study, that the waxworms consumed 92 milligrams of a plastic shopping bag overnight. At this rate, 100 worms would consume a 5.5-gram plastic bag in a month.
Plastic Waste is a Global Problem
It is recognized that plastic wastes are a global problem and only growing. The idea of adding worms or enzymes to a landfill to consume the plastic sounds well and good. However, keep in mind that any time humans try to meddle with nature, unseen problems pop up. Adding waxworms or any other worm to a food source will cause an explosion in the population. And the worms eventually pupate and become a different kind of pest. If you add an enzyme to a landfill, will it migrate or stay in place?
Finally, we are aware of the production of Biodegradable Plastics (BDPs). BDPs can be manufactured from strict plant-based (bio-based) as well as petrochemical-based or a mix of the two. This increases the confusion of how to treat the wastes and what the resulting products might be. Bioplastics may not be as ideal as one might think.
Reports suggest that bioplastic polymers are much higher in cost than traditional plastic products with bio-plastics being generally being 2 to 4 times as expensive to produce. Ultimately, we need to initially focus on reduction and recycling. Reduction when possible is preferred. Take cloth bags to the grocery when buying your goods and encourage your compatriots to do the same. When you cannot avoid using plastic, recycle it. These options are much more cost effective to all the choices listed above.
Photo Source: Free Great Pictures