Interesting Questions

What is the best bag for the environment?

What is the best bag for the environment? It is a simple question, but there is more to it than you might think. What do you think now, prior to reading the rest of this? Paper? Cotton, which can be used many times, maybe? It must be one of these two at least, right? I think the answer will surprise you, but first, let us look at how we make decisions.

How we make decisions

Ultimately, I believe most peoples’ actions are motivated by a desire to do the right thing. With this in mind, it is important to appreciate that even people you disagree with are likely seeking the same thing as you: A future that improves upon the present. In the course of writing this piece, I had to return to this fundamental belief often, reminding myself that it is not a lack of good intentions that most often leads to poor decisions, but a lack of relevant knowledge. As the information we have available guides the choices we make, our decisions will change when new, relevant information is made available. At least, that is how it would ideally work.

Allow me to crudely illustrate: 
Dan wants to visit Mary and wants to get there as soon as possible. He has no car. 

Unknown path to Mary's house

There are two routes to Mary’s house. Route A is 10 km; Route B is 12 km. 
Which route should he choose? 
At this point, Route A is the painfully obvious choice but bear with me.

Path A or B based on distance alone

What if Dan has a bicycle, which can only be used on Route B, since Route A is not paved? 
This new piece of information shifts the preference to Route B.

Path A or B based on distance and new information

Though I acknowledge most decisions are far more complex than this, the principle applies in the real world just as well: New information can radically change our decisions if we keep our minds open to it. 

We currently live in a world where ideological polarizations (political, religious, dietary, etc.) cause many of us to oppose any idea presented to us by someone we dislike or disagree with – anyone outside our group. This phenomenon contributes to the stagnation of humanity’s progress, as agreement becomes nearly impossible on larger issues. Many good ideas get lost in the no-man’s-land between the increasingly entrenched opposing forces and only the anomalous few prevail to become widely held among the majority of the population. As time passes, it is hard to believe that ideas we now take for granted – gender and racial equality come to mind – ever had substantial opposition. Yet we are currently debating concepts that will, in time, join the list of basic principles that future generations will take for granted. 

This common source bias does have benefits, don’t get me wrong. Letting our group make decisions for us – particularly macro-level decisions that often do not directly affect our daily lives – frees up our time and mental resources, allowing us to focus on micro-level decisions that only we can make. If we all had to thoroughly understand all the policies that are proposed by the government, no one would have the time to decide what we should have for dinner or what shirt to wear. Group cohesion also ensures that every idea has plentiful opposition, which means it will be properly dissected and its flaws will be exposed; this inclination to skepticism is fundamental to science. However, when skepticality turns to blind opposition, it holds the hold world back from the progress we all seek. We should be wary of new ideas, but when overwhelming evidence suggests we are wrong, we need to change our minds so that we might improve individually and as a society. 

Thus, as we proceed into this potentially contentious subject, please keep an open mind. Let me preface the rest of what you are about to read with this: I think we should take care of the beautiful planet we are living on, lest we make it a worse place for future generations to live. However, this cannot be achieved by blindly following the ideas that are most widely held by the general population. Sometimes efforts to do good lead to the opposite effect of what is desired, and there are few better examples of this than the condemnation of plastic bags.

The best bag for the environment

Following the narrative spun by mainstream media, the conclusion is unambiguous: “Plastic bags are ruining the environment and we should do our best to use alternatives (mainly paper or cotton) that are biodegradable and/or can be used many times.” The evidence, however, tells a different story.

A comprehensive study1 commissioned by the Danish Environmental Protection Agency examined several alternative carrier bags to determine the environmental impact of each – evaluating each bag on their performance across 14 factors. The table below shows the results. To make the comparison of the bags easy to comprehend, a standardized unit of environmental footprint – Bag Environmental Footprint (BEF) – has been used.

1 BEF = the environmental footprint of one Low-density polyethylene (LDPE) bag – the bag you would get in most stores.*

Comparison of bag alternatives

The data boils down to this: If you get a paper bag the next time you are shopping, it has the same environmental impact as 43 plastic bags. Put another way, you need to use the paper bag more than 43 times before you are having a net positive relative impact on the environment, as compared to using plastic bags – and that is if you only use the plastic bags once each. If you typically use a plastic bag twice (e.g. home from the store and more the next time you go shopping), you now have to use that paper bag more than 86 times to save the environment from additional harm.** I have never been able to use a paper bag more than once or twice and though I am certain some people can stretch the usage numbers higher than myself, 43 uses seems incredible. As we need scalable solutions to have a real global impact, the paper-bag solution should be discarded – most people will not come near the number of uses required for a net positive impact.

Next on the docket is cotton. A quick search on Google makes it look as though cotton – organic cotton in particular – is the best solution for the environment. However, looking at the numbers, we find that the cotton bag (non-organic) has the same environmental impact as 7,100 plastic bags. If you use the cotton bag twice daily, 365 days a year, you need to use it for more than 9 years and 8 months before you are having a positive impact, relative to the use of plastic one-time-use bags. That is a long time to use one bag. For organic cotton, you have to use it nearly three times as long.

Matters are made worse for cotton bags when considering that the above number of uses is multiplied by how many times the plastic bag is used. This means that if you are able to use a plastic bag three times (e.g. home from the store, as a lunch bag to work, and once more shopping), the users of cotton bags need to use their bag 21,300 (3 * 7,100) times to break even. Users of organic cotton bags now have to surpass 60,000 (3 * 20,000) uses. With two uses every day, that is more than 82 years of the same bag. Thus, the cotton bags do not seem a good solution either, leaving polypropylene (PP) as the only viable alternative to LDPE. 

The main takeaway from this research is that focusing on using plastic bags (LDPE or PP) as many times as possible would be far better for our environment than changing to other materials at this time – though I am happy to welcome better alternatives as they are developed. 

The importance of following the science

As humans, we tend to be attracted to predictions of imminent doom, always believing that we need to change our collective actions or face the consequences of following a path headed toward a precipice that will be the end of our civilization. Whether the apocalypse will be caused by our religious or scientific sins, it will be caused by our wrongdoing. During the Cold War, we were scared of a nuclear holocaust; now, we are scared that climate change will leave the planet uninhabitable. The general narrative of a path leading to what I call the “Precipice of Doom” is illustrated below. For the current worry of climate change, the start of the path can be considered to be the Industrial Revolution, as that is when humans started to have a large impact on the global environment. 

Perceived path to the precipice of doom

When this is your model of the world, an urge to change our current behavior is understandable, laudable even. We do not want to keep repeating the same mistakes when this is our trajectory. However, if we want positive change we cannot blindly leap to actions that are not grounded in science. We cannot simply follow the “common sense” narrative that plastic is always worse for the planet than paper or organic alternatives. It simply is not true; paradoxically, common sense does not always make sense and actions that are taken to improve our situation might make matter worse. 

The problem with the model above is that it does not account for the power of innovation. The illustration below shows the path I believe we are on – one of technological development that will ultimately cause humanity to steer clear of the precipice. The red path is the one that virtue-signaling actions, blind to science might lead us down. Taking a step away from the path we are on will undoubtedly make some people feel better about themselves. However, before you take that step, I urge you to ensure that you are not engaging on a more expedient path to the very future you seek to avoid.

Technological development avoiding the precipice of doom

* This is contingent on the bag being used as a garbage bag in most cases and therefore not ending up as litter.
** To get the total number of uses necessary, we need to divide the total BEF for paper bags by the BEF per use for LDPE bags when used twice (1 BEF / 2 uses = 0.5 BEFs per use). As such, the number if uses necessary for paper bags 

1 Danish Environmental Protection Agency. (2018). Life Cycle Assessment of grocery carrier bags. Retrieved from:

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