The study takes into account a variety of factors including, but not limited to, resource and water depletion, ecosystem toxicity, and climate change (full list of factors in the report; link at the end of this article).
Included in the study were 14 kinds of bag - including LDPE (low-density polyethlene) plastic, standard and recycled PET, paper (bleached and unbleached), cotton (organic and conventional), and composite (jute, pp, cotton) ones.
Surprisingly, they found that LDPE plastic bags had both the lower overall environmental impact, and the lowest impact on climate change specifically. The worst offenders? Organic cotton.
It’s worth noting that the study took into account the entire life-cycle of a bag, from production to disposal. For LDPE, the assumption is that a bag will be used once for its primary purpose (e.g. grocery shopping), and then be used for household waste collection and subsequently incinerated.
As part of the study the researchers outlined how many times a bag would have to be reused in order to have the same impact as the best performer, i.e. LDPE plastic. They found that recycled LDPE came second, followed by unbleached paper ones.
Specifically, this is how many times some common bags would have to be reused in order to have the same overall impact:
That means that an organic cotton bag would need to be used 5 days a week for nearly 77 years in order to have the same environmental impact as a standard LDPE plastic bag. Looking at climate change specifically, this is brought down to 149 times, while for instance an unbleached paper bag would not need to be reused a single time to have the same climate change impact.
