Material Monday Sustainable Stories Eco Excite: Carrier Bag

Material Monday Sustainable Stories Eco Excite: Carrier Bag

Posted 8 July 2019 by Katie Kubrak

‘Sustainability’ tends to be a very fluid term these days, and when something means many things, does it mean anything at all? In recent years, we have witnessed many sides to the story of lightweight carrier bags and their alternatives.

On the regional scale in the UK, consumers use approximately 10 billion lightweight carrier bags annually, which equates to around 10 bags a week per household. Unfortunately, a large number of these do not end up disposed of properly. Many of these find their way into the waterways and oceans. Alarmingly, the most recent report from The Ellen MacArthur Foundation estimates that by 2050 plastics will outweigh fish in the world’s oceans.

As an individual brand or consumer, looking at those harrowing numbers can be overwhelming and therefore it is hard to imagine that small actions could move the needle at all, but we have to start somewhere.

As a result, to reduce plastic carrier bag consumption and encourage ‘reduce, reuse’ practices, in October 2015 UK customers have had to pay at least 5p for each single-use plastic bag, with a high chance of the price increasing to 10p by end of the year. Nevertheless, the debate, due to a combination of public, media and legislative pressure to reduce the environmental and social impacts of carrier bags continues.

With this in mind, at Nirvana we have asked ourselves what is the most sustainable carrier bag alternative out there? What is it made out of and what is its end of life scenario? To define this, we have referenced our previously outlined approach to the material lifecycle. You can read more about it here.

Step 1 – Define available material alternatives to understand and define their lifecycle

There are many materials that a carrier bag can be made out of, including a range of plastics, paper or textile-based materials. Designated substrate is often selected based on single use or multiple use user scenario. To expand, these materials can be listed as follows:

  • a conventional, lightweight carrier made from high-density polyethylene (HDPE);
  • a lightweight HDPE carrier with a pro-degradant additive designed to break the down the plastic into smaller pieces;
  • a biodegradable carrier made from a starch-polyester (biopolymer) blend;
  • a paper carrier;
  • a “bag for life” made from low-density polyethylene (LDPE);
  • a heavier more durable bag, often with stiffening inserts made from non-woven polypropylene (PP);
  • a cotton bag.


Step 2 – Define scenario

This is where sustainable thinking comes into place. By using regenerative design – which promotes materials to be viewed as nutrients circulating in healthy and safe metabolisms, in combination with Ellen MacArthur’s circular economy model, our user scenario needs to be characterized by reduce, reuse and recycle.


Step 3 – Define lifecycles

The best solution can be determined through a study into the lifecycle of all enlisted alternatives.

Such research was carried out by Environment Agency and it concluded that:

  • The environmental impact of all types of carrier bag is dominated by resource use and production stages. Transport, secondary packaging and end-of-life management generally have a minimal influence on their performance.
  • Whatever type of bag is used, the key to reducing the impacts is to reuse it as many times as possible and where reuse for shopping is not practicable, other reuse, e.g. to replace bin liners, is beneficial.
  • The reuse of conventional HDPE and other lightweight carrier bags for shopping and/or as bin-liners is pivotal to their environmental performance and reuse as bin liners produces greater benefits than recycling bags.
  • Starch-polyester blend bags have a higher global warming potential and abiotic depletion than conventional polymer bags, due both to the increased weight of material in a bag and higher material production impacts.
  • The paper, LDPE, non-woven PP and cotton bags should be reused at least 3, 4, 11 and 131 times respectively to ensure that they have lower global warming potential than conventional HDPE carrier bags that are not reused. The number of times each would have to be reused when different proportions of conventional (HDPE) carrier bags are reused are shown in the table below.
  • Recycling or composting generally produce only a small reduction in global warming potential and abiotic depletion.

Tab. 1 The amount of times each carrier bag alternative should be re-used to offer lower environmental impact to conventional 5p carrier bags. (Source: Environment Agency)


Step 4 – Material Alternatives Analysis vs reduce, reuse, recycle

By conducting material analysis based on Tab 1, material lifecycles (Step 3), recycling rates for paper (79%) vs plastic (46.2%) in UK we estimate that if a brand can ensure a paper carrier bag is to be reused more than 9 times, it could be most environmentally responsible alternative to use. The risk here is that the paper carrier bag might not be as durable as plastic or cotton. In result, cotton bags, despite being the most carbon intensive to manufacture, are the most durable and will have a much longer life than any paper or plastic counterpart.

When we find the most sustainable bag alternative, one issue remains – many people forget to bring their reusable bags on their weekly supermarket trip, and end up having to buy more bags when at the checkout. Would positive practice encouragement as implemented by Trader Joe’s and Whole Foods, which give a discount on the purchase when a consumer brings their own bag, be the way the way forward?

Tab. 2 The material lifecycle comparison between: paper carrier bag, plastic carrier bag and cotton carrier bag.


Step 5 – End of life and Disposal

If a brand prefers the use plastic for their carrier bag it should be the brand’s responsibility to ensure that the consumer (on both regional and global scale) understands the disposal route. Should an obvious route not be available (again on both regional and global scale), it’s suggested that an in-store collection in exchange for a deposit needs to be arranged. Notably, small deposits are marked at the most successful ways to encourage positive consumer behaviour.

Do let us know if you found this of interest and please do not hesitate to get in touch should you have any questions! We’re here to try to tailor this information to you and your specific needs, so definitely don’t be a stranger and chat with us.