2023-11-11 10:15:00
Facts
The Quebec City website actually asks to put only food residues in the purple bag, the contents of which are intended for the Center for biomethanization of the agglomeration of Quebec (CBAQ). There, our organic waste is placed in “anaerobic digesters” where bacteria, in the absence of oxygen, transform it into methane, essentially natural gas but without being a fossil fuel. The solid part that comes out is used as compost or fertilizer.
“To know what goes in the purple bag,” says the City, “you just have to ask yourself the question: is it edible or is it part of something that can be eaten?” According to this criterion, therefore, it is clear that “Kleenex”, napkins and paper towels should not be included.
But now, the same website also mentions that in addition to 86,600 tonnes of food waste per year, the CBAQ can also treat 96,000 tonnes of “biosolids (…) coming from the water treatment plant”. Essentially, this is the solid portion of sewage, following the water itself has been removed and purified. However, toilet paper constitutes a significant part of these “solids” — between 30 et 40 %it varies from one study to another.
This is not a problem in itself: most of the studies show that the bacteria that populate anaerobic digesters transform very well toilet paper, which is not very surprising since the main chemical components of paper — cellulose and lignin which, in wood, roughly act as “bricks” and “mortar,” so to speak — are natural molecules that bacteria have been degrading since the dawn of time. It seems like lignin resists more to degradation in the absence of oxygen (as in digesters), but not enough to say that toilet paper does not “biomethanize” well.
So why should it be any different for facial tissues, napkins and paper towels? Well, there is no reason: they are made essentially of the same molecules as toilet paper and are just as well transformed in digesters. This also applies to composting — the city of Calgary, for example, which composts instead of making biogas, accept all these papers. (It should be noted here, however, that unlike large industrial compost piles, small domestic composters do not reach the temperatures needed to kill pathogens. In these cases, it is probably better not to put them in. his handkerchiefs soiled with bodily fluids.)
The spokesperson for the City of Quebec Jean-Pascal Lavoie confirmed to me that the CBAQ is perfectly capable of processing tissues, napkins, etc. It is to simplify the message that the City has chosen to stick to “what is eaten or is part of something that is eaten”.
“The problem,” he said, “is that it caused confusion among users and opened the door to questions from citizens who wondered if they might use waxed, parchment or aluminum paper. (…) We preferred to avoid the risks of contaminating the input with waxed, sulfurized and aluminum paper by allowing other types of paper such as tissue paper and kitchen towels.”
This “confusion” was noted during the pilot project which took place in 2020, but Mr. Lavoie was not able to provide data (for example, on the contents of the purple bags) which would have demonstrated it .
Verdict
The host was right: the biomethanization plant is perfectly capable of processing handkerchiefs and napkins. It is for reasons of communication that Quebec has decided to ask its citizens to stick to “what is eaten or is part of”.
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#tissues #purple #bag
