Plastic, Paper or Cotton: Which Bag is Better for the Environment?

The answer to the question is simple if you believe in science. The bag that is best for the environment would have the least negative impact upon the environment. A scientific assessment was completed by Environment Agency called a Life Cycle Assessment (LCA). LCA is a standard method for comparing the environmental impacts of providing, using and disposing of a product or providing a service throughout its life cycle (ISO 2006). In other words, LCA identifies the material and energy usage, emissions and waste flows of a product, process or service over its entire life cycle to determine its environmental performance. The conventional HDPE bag had the lowest environmental impacts of the lightweight bags in eight of the nine impact categories. The bag performed well because it was the lightest bag considered. The lifecycle impact of the bag was dictated by raw material extraction and bag production, with the use of Chinese grid electricity significantly affecting the acidification and eco-toxicity of the bag. That’s right! The conventional High-Density Polyethylene (HDPE) “plastic" bag had the least impact on the environment of all the bags considered in the study. But that's only considering using each type of bag only. For many eco-friendly people, the whole point is to reuse other types of bags to avoid the perceived environmental hazards posed by the conventional plastic bag. Fortunately, the study revealed how many times the alternatives to the conventional plastic bag would have to be reused to overcome their own negative impacts to the environment:

Here, we find that if a consumer only uses a conventional HDPE plastic bag once (example… to carry their groceries home before throwing the bag away), a paper bag would have to be reused 3 times, a heavy-duty plastic bag made from Low-Density Polyethylene (LDPE) would have to be used 4 times, a plastic "bag-for-life" made of non-woven Polypropylene (PP) would have to be used 11 times, and a cotton (or canvas) bag would need to be re-used 131 times!!! The study reports that a canvas bag is expected to last for 52 trips. With that as a reference, a cotton/cloth canvas bag user does over twice the damage to the environment that a plastic bag using grocery shopper who throws away every plastic bag they get immediately after each shopping trip, as they will likely have to replace their more environmentally-destructive bag at least once long before they reach 131 uses! However, if a consumer reuses 100% of their conventional HDPE plastic bags (say as trash bags), the number of uses needed for the other bags to have a lesser environmental impact than the conventional HDPE plastic bag rises even more, which we see in the table above. For example, that re-usable canvas bag would need to be used at least 327 times to be less damaging to the environment! Wow! Uneducated or stubborn eco-friendly canvas bag users are over six times as destructive to the environment as the conventional consumers who simply re-use all of the plastic bags they get receive from the grocery store just one time. In Closing… Oxo-biodegradable bags have no significant difference (any differences were well under 1%) in environmental impact; due to similarity in functionality, weight, material content and production energy. However, in the case of litter, a comparison between a conventional HDPE bag and an oxo-biodegradable bag, the oxo-biodegradable bag is 75% better for the environment. If only those anti-plastic bag advocates cared more about the environment, perhaps they would do more research instead of making comments and claims based on emotion.... Reference Edwards, Chris and Fry, Jonna Meyhoff. Life Cycle Assessment of Supermarket Carrier Bags. Report SC030148.Environment Agency. A Life Cycle Assessment of Oxo-biodegradable, Compostable and Conventional Bags By Chris Edwards and Gary Parker. May 2012