At a time when plastic pollution is reaching such alarming proportions that it is creating floating continents, how can we be sure that our efforts are not in vain? And for example, the thin plastic bags in which we package our vegetables at the supermarket, supposedly biodegradable, really are? Researchers suggest you check it out for yourself. By digging, not very deep, in your lawn or in the planter on your balcony.
The PlastiZen participatory science experiment was launched in May 2021 by Camille Larue and Arthur Compin, two scientists from the Functional Ecology and Environment Laboratory* (Lefe) in Toulouse. The principle is simple: bury two pieces of plastic – one “conventional”, the other supposed to be biodegradable – in the same soil and visually check their condition once a month for three months. But “The speed of degradation depends on many parameters, such as the temperature or the nature of the soil,” explains Camille Larue. And to obtain solid results, it would have been necessary either to deploy throughout France, or to transform the lab into a gigantic molehill by varying the weather. We might as well empty the ocean, and the microplastics that wander around in it, with a teaspoon…
42% of samples intact after three months
The idea is therefore to recruit enthusiastic “research assistants” everywhere. And to provide them with a rather simple kit: the two pieces of plastic in their little nylon pocket, a strip to measure the pH of the soil, two tea bags, which we leave buried throughout the experiment to measure the microbial activity of the place, a tube to send a sample of its soil to the laboratory, and even a pre-stamped envelope for returning the sample.
Since the start, more than 300 PlastiZen kits have been ordered. “Around a hundred participants completed the experience,” explains Arthur Compin. For the moment, roughly speaking, the results show that a third of biodegradable plastics have actually disappeared after three months. But 42% of the samples also remained intact or almost intact. Furthermore, there is a “bias”, as scientists say. The operation spread through “word of mouth” among those around the team. Suffice to say that the returns come more from Marseille to Strasbourg. On the map, 47 departments – Gers, Var or Pas-de-Calais to name a few – are still in the “white zone”.
Obtain robust scientific results
This is why PlastiZen goes into overdrive. A YouTube channel went online on Monday. And now, although the participants interviewed find the handling easy and not very time-consuming, an app makes it “easier to manage” the sending of information to the lab. “We also plan to distribute humidity or temperature sensors in classes,” adds Camille Larue. Because one of the unexpected lessons from the first phase is that PlastiZen is a good educational support, particularly for middle school programs. Teachers, simply curious people, green people at heart… new experimenters are welcome! “. The more there are, the more likely the project will be to transform into “a scientific publication supported by robust results”. And, who knows, to make industrialists who are fans of “greenwashing” tremble.
*CNRS/UT3/INPT