That every time, although little by little, there are more citizens committed to the environment in one way or another, seems something undeniable. But it is even more undeniable that, with each passing day, they make it more difficult for them. You only have to look at the mirage that has become, for some time, the world of bags (there are all kinds) that we can find in shops: single-use plastic, paper, bioplastic compostable (not all are made with the same compounds), reusable (from raffia or other materials, such as cloth)… How can we know which is the least damaging to the environment? There is no single answer, and therein lies the problem.
Experts explain that it is indeed possible to calculate the impact that the production of a certain type of bag can have on the environment. But that is not enough. This data, they say, cannot be separated from the use that the citizen may make of it later.
That is why the researchers in the field, when they do studies, what they compare are functions, and not so much the materials they are made of. “Yes, we look at its life cycle, but starting from a use, a function”, Jordi Oliver, executive director of Inèdit, a strategic eco-innovation study born from the Autonomous University of Barcelona, ​​explains to La Vanguardia.
For example – he continues -, a calculation can be made on the purchase for a month. “In single-use plastic bags, about 30 would be needed, but if I have a reusable one and I’m reusing it, I’ll only use one.” He explains that it is necessary to generate a scenario and compare the different bags according to their function. “You can’t compare a single-use plastic bag with a reusable one that you use only once, because the reusable one will do worse. It is necessary to look at its cycle of uses”. That’s why he says that “we can’t tell the consumer which bag is better”. “It depends”, he says.
What we can explain to him, he says, “is that it is good to promote reusable, more durable options”. “In principle, they are favorable strategies. But of course, they must be applied”, he says.
If you have a reusable bag – he points out – but you don’t reuse it for whatever reason, it’s disastrous, because there are more materials in its composition and it’s the one that has the most harmful environmental impact when it comes to producing it. But if you reuse it a lot and avoid using single-use bags, “here you are winning environmentally”.
We know, therefore, that to compare different bags it is not only necessary to look at their environmental impact, but also the use that the consumer will make of them. The question is: are there studies that analyze these variables? Yes, but their conclusions do not help the user much when deciding on one bag or another. Because? Because there are infinite conditions.
Take as a reference, for example, a meta-analysis (dissection of many published studies) that the UN did in 2020 on the life cycle analysis of single-use plastic bags and their alternatives. The research determines that the most suitable option from an environmental point of view is a reusable PE (polyethylene) or PP (polypropylene) bag, but always – and here we have one of the first conditions, and the most important – that use enough times to offset the environmental impact of their production.
The study explains that reusable PE bags have less environmental impact than single-use bags, but always taking into account usage rates. The degree of use that makes the reusable plastic bag a better choice varies from 4 to 20 times for reusable bags made from virgin material and 8 times for those made from recycled PE.
The research looks at more types of bags. For example, he argues that a reusable LDPE bag (low-density polyethylene) has less environmental impact than a conventional single-use plastic bag – the LDPE one that is not designed for multiple uses and weighs less than the reusable one – as long as it is used 5 to 10 times more than the latter. However, there are studies that ensure that the average rate of reuse of this type of bag in the US is only 3.1. “It’s only a better option if it’s actually reused,” emphasizes Jordi Oliver.
The conditions do not end here, and the fact is that the UN compares more types of bags (there are a lot) in its meta-analysis. He explains that durable PPs are heavier than reusable LDPE bags, but, as the name suggests, they last longer. Consequently, to be more competitive from an environmental point of view, they must be used more often.
In this regard, the data suggests that they are used an average of 14.6 times in the US, which is about what it takes to make PP bags more competitive than conventional single-use plastic bags.
Then there are fabric bags made, for example, of cotton (they can be made of other materials). The meta-analysis says that they even have to be used more often to be truly competitive. There are studies, included in the UN analysis, which state that a bag of this type, reused 50 to 150 times, is probably less harmful to the climate if (and here we have the umpteenth condition) “the system of waste management is dominated by incineration or the efficient recovery of wasteâ€.
“Cotton bags have a high impact due to the environmental footprint of growing this textile plant,” argues Oliver. “They can be a good alternative (durable, repairable, profitable…), but hundreds of uses must be guaranteed”, he adds.
We also have the comparison between disposable bags. Here the analysis explains that rigid plastic bags “rank better than paper bags and single-use biodegradable bags in almost all environmental categories”. Those of LDPE or HDPE (high density polyethylene) have a lower rating in their potential as waste.
