That every time, although little by little, there are more citizens committed to the environment to a greater or lesser extent, seems undeniable. But it is even more undeniable that, day by day, they make it more difficult for them. You just have to see the gibberish that the world of bags has become, for a long time (there are all kinds) that one can find when going to different shops: single-use plastic, paper, bioplastic compostable (not all are made with the same compounds), reusable (raffia or other materials, such as cloth)... How can we know which is the least harmful to the environment? Well, there is no single answer, and therein lies the problem.
The experts explain that it is indeed possible to calculate the impact that the production of a certain type of bag may have on the environment. But that is not enough. This data, they say, cannot be separated from the use that the citizen may make later.
That is why researchers in the field, when they do studies, what they compare are functions, and not so much the materials with which they are made. "Yes, we look at its life cycle, but based on a use, a function," explains Jordi Oliver, executive director of Inèdit, a strategic eco-innovation studio born from the Universitat Autònoma de Barcelona 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 reuse it, I will use one." Explain that it is necessary to generate a scenario and compare the different bags based on the function they are satisfying. “You cannot compare a single-use plastic bag with a reusable one that you use only once, because the reusable one will be worse for you. You have to look at its cycle of uses”. Hence, he asserts that "you cannot tell the consumer which bag is better." "It depends," she says.
What can be explained to him, he asserts, "is that it is good to promote reusable, more durable options." “In principle, they are favorable strategies. But of course, you have to apply it ”, she maintains. If you have a reusable bag, he points out, but for whatever reason you don't reuse it, "it's disastrous because there are more materials in its composition and it's the one with the worst environmental impact in its production." Now, if you reuse it a lot and thus avoid the use of single-use bags, "here you are winning environmentally".
We know, therefore, that in order to compare different bags, it is not only necessary to look at their environmental impact, but also the use that the consumer will make. The question is: are there studies that analyze these variables? Yes, but its conclusions are not going to help the user too much when deciding on one or the other bag. Because? Because there are infinite conditions.
We take as a reference, for example, a meta-analysis (dissection of many published studies) that the UN did in 2020 on the analysis of the life cycle of single-use plastic bags and their alternatives. The research concludes that the best option from an environmental point of view is a reusable bag made of PE (polyethylene) or PP (polypropylene), but always -and here goes one of the first conditions, and the most important- that a number of enough times to offset the environmental impact of its production.
The study explains that reusable PE bags have a lower environmental impact than single-use bags, but always taking utilization rates into account. The degree of use that makes the reusable plastic bag a better option ranges 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, it defends that a reusable LDPE (low-density polyethylene) bag has less environmental impact than a conventional single-use plastic bag - the LDPE, which is not designed to have several uses and with a lower grammage than the reusable one - always that 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 is only a better option if it is really reused”, emphasizes Jordi Oliver.
The conditions do not end here, and it is that the UN compares more types of bags (there are an infinity) in its meta-analysis. He explains that durable PP bags are heavier than reusable LDPE bags, but on the contrary, as the name suggests, they last longer. Consequently, to be more competitive from the environmental point of view, they have to be used more times.
In this regard, the data suggests that they are used an average of 14.6 times in the US, which is roughly what is needed to make PP bags more competitive than conventional single-use plastic bags.
Then there are cloth bags made, for example, of cotton (they can be made of other materials). Regarding these, the meta-analysis affirms that they must be used even more times to become competitive. There are studies, collected in the UN analysis, which affirm that a bag of this type reused 50 to 150 times is probably better for the climate if (and here goes the umpteenth condition) "the waste management system is dominated by the incineration or the efficient recovery of the same”.
"Cotton bags have a high impact due to the environmental footprint of growing this textile plant," Oliver argues. "They can be a good alternative (durable, repairable, profitable...), but it is necessary to guarantee hundreds of uses," adds.
There is also the comparison between single-use bags. Here the meta-analysis explains that rigid plastic bags "rank better than paper bags and single-use biodegradable bags in almost all environmental categories." Where those made of LDPE or HDPE (high-density polyethylene) have a worse rating is in their potential as waste.
The study points out that the order of classification of the bags in relation to their potential as waste "is more or less the opposite of the order of classification with respect to other environmental indicators." And the weight of the bags contributes to this difference: a heavier bag is harder for the wind to blow away, thus reducing the likelihood that it will become debris. On the other hand, a greater weight increases all the other environmental impacts of the bag.
Oliver defends that this type of bag, the single-use one, is the one that “should be eliminated and bet on those that have a greater environmental impact (in terms of their production) but are reusable”. He says that certain regulations force companies to use more resistant bags, "and also more expensive", and that they complain that the user uses them as if they were single use. "If this change in the supply of bags is not accompanied by a change in consumer habits, what happens in the end is that the environmental impact increases," he says.
The UN study also points out that paper ones are not an ideal option either - "they have a significant impact on the degradation of aquatic ecosystems and, often, on the climate - and that biodegradable ones present "significant uncertainty in their impacts environmental”. For Oliver, the latter represent "a whitening of single-use bags" because some of their compounds do not degrade.
In theory - "it is the cycle that corresponds to them", says Oliver - they would have to be thrown into the organic container, but organizations like Rezero are committed to throwing them into yellow because some of their materials are not compostable.
It is because of this myriad of conditions that, surely, experts like Oliver focus on "the appearance of the habits" and not only on the material from which the bags are made. Anna Peña, environmentalist and communication director of Rezero, sees it in the same way. “We must think about future scenarios prioritizing the usability and durability of the product. The product must be looked at not only as something made of a specific material”.
He understands that if the debate is only about whether the wheat starch bag is more ecological than the plastic one and does not talk about its durability, it is "perpetuating the culture of using and throwing away and, therefore, making inefficient use again of the resources".
He defends that "the main victim" of increasing the complexity and diversity of products "are the town councils and the public", because they are the ones who "must manage waste and suffer its consequences". “We must eradicate disposable products from containers and bins, whatever the material they are. We will all win."
And he proposes to conclude: "Let's start by ensuring that the bags or containers are reused a minimum of 10 times and that the complexity of their composition is reduced to the maximum. This will help to drastically reduce the exploitation of resources that we currently live with”.
