Scientists from the National Autonomous University of Mexico (UNAM) discovered a new method based on the use of two species of beetle larvae, from the Tenebrionidae family, to identify biodegradable and compostable plastics, in less time than conventional techniques. The patent was requested by the Environmental Engineering Coordination of the Institute of Engineering, where the study was carried out.
The goal is for the manufacturers of bags made of these materials to have quick results, a maximum of three months, instead of a year and a half. “There is no test that confirms biodegradability one hundred percent, and those that exist cannot be considered fast, since they take more than a year,” explained María Neftalí Rojas Valencia, in charge of the project.
It is necessary to develop renewed methods that consider the criteria already established by the regulations, but that add more evidence and reduce the time to determine if a bioplastic is compostable or biodegradable, he added.
The specialist pointed out that these larvae, known as weevils, had already been studied, but the tests focused on Styrofoam. After two years of research it was found that they give excellent results in plastics.
He added that the Pestalotiopsis sp fungus was used, bought abroad, which had also been used for Styrofoam and with which it was possible to degrade plastic bags. In the investigation, a fungus of a particular strain was discovered, which also feeds on this biodegradable material; This organism, which develops easily in the temperature and climate conditions of our country, still has no name, said Alberto López Juárez, a master’s student.
When a bag is not biodegradable, but hydrocarbon, the fungus has no effect, but “breaks” those that are in a matter of days. “The problem is that after 11 days the life of the fungus begins to decline. I am working to make it last longer and complete the biodegradation process,” said the young man.
Rojas Valencia highlighted that there are 500 billion plastic bags circulating; within a minute of use, a million of them are thrown in the trash and only about one percent is sent for recycling.
Today we also face the problem of microplastics. There are studies that not only demonstrate its presence in places as far away as Antarctica, but also in the human placenta and blood, the expert warned.
Plastics, he clarified, are biodegradable due to their composition of carbon and hydrogen, which makes them organic compounds; the problem is that they decompose very slowly, some in more than 150 years. “What has been done to prevent them from lasting so long is to add an additive; this component ‘helps’ the bag to break down, but also to break into fractions; that has caused the increase in microplastics.”
The Mexican norm says that the bags must be “biodegradable or compostable”, but it is not so easy to prove that they are. The main difference between the two is that the first has an additive and the second, a resin. “To certify them, the former must demonstrate their ability to decompose in the natural environment, speed of disintegration, ecotoxicity and content of heavy metals.”
To determine which ones meet the characteristics of each category and help manufacturers obtain their certification seals, the Institute of Engineering tests plastics based on four national and international biotoxicity standards, among others.
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