How many times do you have to use reusable bags to make it sustainable?

Novel process to create fuel with plastic 0:52

(CNN) --

The battle against single-use plastic bags may not be won, but we're certainly on the right track.

Restrictions on its use have been placed in nearly a dozen US states and many other countries around the world.

And, in many cases, these efforts have succeeded in eliminating new sales of thin, flimsy plastic bags that float to trees, clog drains, leach microplastics into soil and water, and harm marine life.

(Of course, these restrictions do not take into account the plastic bags that already exist and will take centuries to decompose.)

But this environmental success hides another problem.

Many of us are drowning in reusable bags—made of cloth or thicker, more durable plastic—that retailers sell on the cheap or give away to customers as a supposedly greener alternative to single-use plastic.

(I have 15 cotton bags and 12 heavy plastic bags stored in a kitchen drawer, only a few of which see the light of day.)

The answer to what is the most ecological substitute for a single-use plastic bag is not easy, but the advice is: reuse the bags you have at home, as many times as you can.

(Credit: Adobe Stock)

Activists claim that this accumulation of bags creates new environmental problems, as reusable bags have a much higher carbon footprint than thin plastic bags.

According to a staggering estimate, a cotton bag would have to be used at least 7,100 times to be a truly eco-friendly alternative to a conventional plastic bag.

The answer to what is the most ecological substitute for a single-use plastic bag is not easy, but the advice is: reuse all the bags you have at home, as many times as you can.

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And here are some things to keep in mind when you go to the mall or supermarket.

unintended consequences

Well-intentioned bans and limitations on single-use plastics are having unintended consequences in some cases.

In New Jersey, a ban this year on single-use plastic and paper bags has caused grocery delivery services to switch to large-capacity bags.

Your customers are now complaining that there is an excess of large-capacity reusable bags that they don't know what to do with.

In the UK, where I live, the average person now buys about three single-use bags a year, up from 140 in 2014, the year before a single-use bag tax was imposed.

However, Greenpeace pointed out that British supermarkets sold 1.58 billion durable plastic bags in 2019 – known here as "lifetime bags" – which is equivalent to 57 per household and more than one bag a week.

And this represented an increase of 4.5% compared to 2018.

This suggests that this model of offering a heavier bag to encourage reuse is simply not working.

"If companies just give us thicker plastic bags, then I would say the policy is a total failure," said Judith Enck, a former regional administrator for the Environmental Protection Agency and now president of Beyond Plastics, a US nonprofit organization. for-profit that works to end pollution caused by single-use plastic products.

• Impressive video shows how they trap huge patch of plastic in the ocean

When evaluating the environmental impact of a bag throughout its useful life, many aspects must be taken into account: the material, its weight, the manufacturing process and how it is disposed of.

A strong plastic bag made from the same material as a classic single-use plastic bag but with twice the weight has twice the environmental impact, unless it is reused more times, which is why a thin plastic bag single use may seem like a benign option based on its climate impact.

The key to heavy-duty plastic bags is to reuse them faithfully and dispose of them carefully so they don't end up as plastic pollution.

According to a 2020 report for the United Nations Environment Program (UNEP), it is estimated that a thick, durable polypropylene (PP) bag (they tend to have a woven feel) should be used between 10-20 times compared to a single-use plastic bag, while a thinner but still reusable polyethylene (PE) bag 5-10 times.

"There will always be cases where we forget our (reusable) bags at home. We should try not to, but when we do, we will have to buy a bag. And if we then already have too many durable bags at home, it would be better from a climate perspective, at least buy a single-use plastic or paper bag," said Tomas Ekvall, one of the authors of the UNEP report and an adjunct professor at Chalmers University of Technology, Sweden.

However, he stresses that the single-use plastic bag epitomizes throwaway culture, and that alone may be a reason to avoid using it.

"If we aspire to a sustainable future with less of a buy-and-throw mentality, the single-use bag isn't very consistent with that way of life. So, in that sense, it might be reasonable to try to avoid it, even if that choice doesn't specifically mean an environmental benefit."

The cotton problem

The cotton bag has become a cheap status symbol for all those —brands and individuals— who want to do without plastic and show an ecological position.

But cotton is a resource-intensive crop, needs a lot of water and uses considerable amounts of pesticides and fertilizers, which introduce nitrates into the soil and waterways and lead to the creation of nitrous oxide, a greenhouse gas.

This means that your environmental footprint is larger than many people appreciate.

According to the UNEP report, a cotton bag needs to be used between 50 and 150 times to have less impact on the climate compared to a single-use plastic bag.

A 2018 report from the Danish Environmental Protection Agency suggested that a cotton bag should be used at least 7,100 times to offset its environmental impact compared to a classic plastic supermarket bag that is reused once as a garbage bag and then it is incinerated.

(If that cotton is organic, the figure rises to 20,000 times, the report assuming a lower yield, but the same input of raw materials).

• Single-use plastic wreaks havoc on the planet.

  What can you do to minimize its impact?

The report looked at 15 different environmental indicators, such as climate change, ozone depletion, air pollution, water consumption and land use.

However, when focused solely on the climate impact of cotton, it suggested that a cotton bag would need to be reused at least 52 times, in line with the UNEP report.

The Danish report is what is known as Life Cycle Assessment (LCA), a set of methods that scientists use to assess the environmental costs associated with a product throughout its entire useful life.

The UNEP report looked at 10 LCAs conducted in different countries since 2010. However, Ekvall said this approach is often based on assumptions and simplifications, and the results often vary widely.

"It's a problem that the LCA results are seemingly easy to understand, but it takes an expert to understand how the results were calculated and why they are different," he said.

According to him, it is better to consider the LCA as "a rule of thumb" rather than a rigid guide.

In addition, they do not take into account factors that are difficult to measure, such as microplastics, whose impact on human and animal health is not yet known, and marine debris.

How to quantify, for example, a dead whale with 40 kilos of plastic bags in its intestine?

• Shocking images showing the damage plastic causes to marine life

What can be done?

It is also important to note that plastic bags are responsible for a significant part of the garbage, but play a very small role in the climate crisis compared to other products and raw materials, according to the UNEP report.

Therefore, perhaps it is much more important to think about what goes into the shopping bag and consume less.

Enck, who has used the same cotton bag for 20 years, agrees.

"I think we should not let the LCA take away our common sense. Single-use plastic has enormous environmental damage."

Enck said he donated leftover reusable bags to a pantry or food bank or, in the case of the cotton bags, used them to wrap gifts.

It may also be more sensible to make a bag out of old clothes, sheets or curtains than to buy a new one, he suggests.

Consumers could encourage businesses to lend out bags for a refundable fee, rather than selling consumers (who have forgotten their reusable bag) bags they don't need, Ekvall said.

Enck insisted that it's better to reuse plastic bags where possible than try to recycle them, as the different chemicals and dyes used in different plastics make recycling them notably difficult.

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