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Rid plastic bags of their ‘dirty-urchin’ image!

Life-cycle analyses show that plastic bags perform better than cotton or paper bags when it comes to environmental impact

Multiple use is decisive

Prejudices and even misjudgements can persist longer if they are repeated enough times. All too often, it is only on closer inspection that they turn out to be misleading. You can experience a similar situation when you meet a person from whom you have only ever heard negative things: when you meet him or her personally for the first time; they sometimes turn out to be a nice person. It also happens in discussions, such as when it becomes clear that the eco-balance of returnable plastic bottles is actually much better than that of the often ‘hyped’ glass bottle. And a similar picture emerges if we compare the environmental impact of plastic bags with alternatives made of other materials. Numerous studies on this issue have made it perfectly clear that the much-maligned plastic bag is not a dirty ecological urchin after all. On the contrary, it is definitely better than bags made of cotton or paper!

For example, the German Nature and Biodiversity Conservation Union (NABU) has found that a cotton bag needs to be used between 50 and 150 times before its carbon footprint is better than that of a plastic bag. This is because the production of cotton causes considerable environmental pollution due to the consumption of large amounts of water and the extensive use of pesticides when this ‘natural product’ is grown. As NABU also admits, it is questionable from an ecological point of view whether banning certain plastic bags is the right instrument for achieving a positive environmental impact.

From an ecological point of view, the cotton bag only offers benefits if it is used lots of times. The same can be said as well for plastic bags made of tear-resistant plastic: the decisive factor for their ecological balance is their multiple use. That is why the German Federal Environment Agency (UBA) believes that plastic bags are not inherently bad.

Studies refute negative image

International studies also refute the plastic bag's widespread negative image. For example, a Canadian study commissioned by the Quebec provincial government concluded that from an environmental as well as an economic point of view the conventional plastic shopping bag is the best alternative when compared with all other comparable methods for transporting shopping that are available on the market. A particularly interesting fact revealed by the systematic analysis of the environmental impact of shopping bags over their entire life cycle (a so-called life-cycle analysis, LCA) is that the reuse rate for the plastic bag is very high: 77 per cent.

The Canadian study compared eight different shopping bags available on the market in Quebec. The authors of the LCA concluded that a ban on plastic bags would not benefit the environment. This is partly because the reusable plastic bag is superior to all other reusable shopping bags from an environmental point of view. Furthermore, in the comparative study the plastic bag was also rated as the most economical solution.

A life cycle analysis carried out by the UK Environmental Agency also found that the conventional plastic carrier bag had the lowest environmental impact in eight out of the nine assessment criteria investigated. For example, when it comes to the global warming impact associated with a paper bag, such bags would need to be used at least four times more often than their plastic counterparts before they outperform them. The authors of the study found that the cotton bag came out worse than the conventional plastic bag in seven of the nine criteria evaluated.

In another LCA, scientists at Clemson University in South Carolina, USA, found that even paper bags containing 100% recycled material have a significantly higher environmental impact than plastic bags, regardless of whether the plastic bags are used several times or even only once.

International consensus

One could extend this short list of life cycle assessments of bags made of plastic or other materials by adding further studies from the USA, Denmark, Australia, Slovenia, South Africa, Portugal, Canada, Austria and other countries. They all come to the same conclusion: when it comes to environmental compatibility, plastic bags are markedly superior to those made from alternative raw materials. This applies to the much-heralded bags made of cotton or paper as well. The authors of the international studies agree on their assessments here.

The scientists also make it clear that life cycle analyses of such products are the only possible way to achieve a comprehensive assessment of the environmental impact that can withstand critical review. This is because such LCAs analyse the environmental impacts of products and materials over their entire life cycle, 'from the cradle to the grave' as it were. According to scientists, this is the only way to achieve valid, unfettered assessments of ecological impacts. Meaningful results are usually obtained at the end of such analyses, but these may often contradict common views, preconceived opinions and political objectives. But at least one can say that an LCA produces reliable evaluations of environmental performance!

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