In fact, since the beginning of food waste collection, the purple bags (once emptied of their contents at the sorting center) have been sent to incineration. They are non-biodegradable and currently cannot be recycled. During the opening ceremony last year.. the sun The City is working to find ways to properly clean the bags to allow them to be recycled, and we’d hoped to find a solution by mid-2023, but that apparently hasn’t happened yet.
“We are currently conducting trials to recycle plastic bags. I cannot say more at the moment because the tests and analysis of the results are not complete,” a Quebec City spokesperson told me Thursday morning.
So the purple bags, the contents of which are sent to the Quebec biomethanization center, are always incinerated after use.
Now there are reasons behind all this. “They have no choice but to separate the bags from their contents, because we cannot put these bags in biomethanization,” explains Pierre Sarazin, an expert in chemical engineering who has already worked with municipalities on this type of bag. In Europe, they tried, but it was blocked by mechanical shredding equipment. »
Because to resist transportation in a garbage truck, it is necessary to choose a plastic resin that is very resistant, but has the disadvantage of not shredding well (by definition). The alternative would have been a brown bin, but with thousands of truck trips and millions of extra dollars in separate collection that comes with it.
We also can’t use biodegradable plastics, Mr Sarazin continues, because these bags are made to degrade in compost piles or out in the open. In a biomethanization reactor, there is no oxygen, the bacteria present are not the same, and they have difficulty breaking down compostable plastics.
So the last option remains recycling, but to achieve this, the plastic bags have to be very clean, suggests Mr Sarazin. “To recycle polyethylene [dont sont faits les sacs mauves, ndlr], we heat them to dissolve them and the solid contaminants will degrade. In the case of food residue, it burns, it releases gases and there is a risk of occasionally introducing defects into the recycled product,” he explained.
However, it is currently not possible to sufficiently clean “used” purple bags to obtain good recycled plastic. “In a few years, it will be possible to recycle them much better,” predicts Mr. Sarazin.
In the meantime, burning them is not ideal, but not a disaster either. “As long as the plastic is not dispersed in the environment, the impact is minimal. Whatever the end of its life, it will be minimal, if not environmentally best,” assured Mr. Sarazin.
true Initially, the purple bags were supposed to start being recycled this year, but that’s not the case and it’s unclear when they will be. We can’t even make them from compostable plastic because it’s a material that doesn’t lend itself well to biomethanization.