Here's how many times you need to reuse your reusable grocery bags

The answer to what's the greenest replacement for a single-use plastic bag isn't straightforward, but the advice boils down to this: Reuse whatever bags you have at home, as many times as you can.

(CNN)The battle against the single-use plastic bag may not be won but it's definitely under way.

Restrictions on their use are in place in almost a dozen US states and in many other countries around the world. And in many cases, these efforts have been successful at eliminating new sales of thin, wispy plastic bags that float up into trees, clog waterways, leech microplastics into soil and water and harm marine life. (Of course, these restrictions don't address the plastic bags already out there that will take centuries to decompose.)
But this environmental success story of sorts masks another problem.
    Many of us are drowning in reusable bags — cloth totes or thicker, more durable plastic bags — that retailers sell cheaply or give away to customers as an ostensibly greener alternative to single-use plastic. (I have 15 cotton totes and 12 heavy-duty plastic bags stashed in a kitchen drawer, only a few of which see the light of day.)
      Campaigners say these bag hoards are creating fresh environmental problems, with reusable bags having a much higher carbon footprint than thin plastic bags. According to one eye-popping estimate, a cotton bag should be used at least 7,100 times to make it a truly environmentally friendly alternative to a conventional plastic bag.
        The answer to what's the greenest replacement for a single-use plastic bag isn't straightforward, but the advice boils down to this: Reuse whatever bags you have at home, as many times as you can.
        And here are some things to keep in mind as you hit the mall or grocery store.

          Consequences of plastic bags

          Well-intentioned bans and limits on single-use plastics are in some cases having unintended consequences.
          In New Jersey, 2022's ban on single-use plastic and paper bags has meant grocery delivery services have switched to heavy-duty bags. Their customers complain of a glut of reusable, heavy-duty bags that they don't know what do with.
          In the United Kingdom, where I live, the average person now buys around three single-use carrier bags a year, down from 140 in 2014 -- the year before a charge was levied on single-use bags. However, Greenpeace said UK supermarkets in 2019 sold 1.58 billion durable plastic bags — known here as "bags for life" -- equivalent to 57 per household and more than a bag per week. And this was a 4.5% increase compared to 2018.
          This suggests this model, whereby a heavier bag is offered to encourage reuse, is simply not working.
          "If companies are just giving us thicker plastic bags, I would say then the policy is an overall failure," said Judith Enck, a former Environmental Protection Agency regional administrator and now president of Beyond Plastics, a US nonprofit organization working to end pollution caused by single-use plastic products.
          When it comes to assessing the environmental impact of a bag over its life span, there are many different things to take into account: the material, its weight, the manufacturing process and how it's disposed of. A heavy-duty plastic shopping bag made with the same material as classic single-use plastic bag but double the weight has double the environmental impact, unless it is reused more times, which is why a thin single-use plastic bag can appear a benign choice based on its climate impact.
          The key for heavy-duty plastic bags is to faithfully reuse them and dispose of them carefully so they don't end up as plastic pollution.
          A report produced for the United Nations Environmental Programme in 2020 found a thick and durable polypropylene (PP) bag (they often have a woven feel) must be used for an estimated 10 to 20 times compared to one single use plastic bag, while a slimmer but still reusable polyethylene (PE) bag five to 10 times.