Study: Plastic shopping bags less harmful to environment than cotton bags

Little-known data have resurfaced suggesting that plastic bags are generally less harmful to the environment than cloth or cotton bags, which are often used to “fight climate change” due to their reusable quality. 

Figures presented by Our World in Data show the “number of times a given grocery bag type would have to be reused to have as low an environmental impact as a standard single-use plastic bag.” According to the data, an organic cotton shopping bag would have to be reused 20,000 times to match a plastic bag in environmental impact. A conventional cotton bag would have to be reused 7,100 times and a composite bag 870 times.  

The site lists seven more categories which require less uses, but none as harmless as a plastic bag, including recycled PET (84 reuses), polypropylene, non-woven, recycled (52 reuses), polypropylene, woven, recycled (45 reuses), bleached paper (43 reuses), unbleached paper (43 reuses), biopolymer (42 reuses), and polyester PET, recycled (35 reuses). 

The situation is similar when it comes to greenhouse gas emissions, based on an analysis of the “number of times a given grocery bag type would have to be reused to have as low greenhouse gas emissions as a standard single-use plastic bag.” 

Again, an organic cotton bag was found to have the most emissions, requiring 149 uses to match a plastic bag, followed by a conventional cotton bag at 52 reuses, a composite by 23 reuses and eventually reaching bleached paper, unbleached paper and biopolymer, which require no reuses and appear to be on par with plastic bags in having low greenhouse gas emissions. 

The data are based on a 2018 study commissioned by the Danish Environmental Agency, which analyzed 14 types of bags in Denmark. The study compared 'all environmental indicators' which was a combined value for climate change, greenhouse gas emissions, ozone depletion, human toxicity (cancer effects), human toxicity (non-cancer effects), photochemical ozone formation, ionizing radiation, particulate matter, terrestrial acidification, terrestrial eutrophication, marine eutrophication, ecosystem toxicity, resource depletion (fossil), resource depletion (abiotic), and water resource depletion. 

For most categories, the study found that low-density polyethylene (LDPE) bags, which are the usual plastic shopping bags in supermarkets, “are the carriers providing the overall lowest environmental impacts for most environmental indicators.”