The Trashy Secret of Plastic Bag Bans

by Brian Dunning
January 21, 2020

All around the world, bans on plastic carryout bags are being passed faster than you can keep track, especially in western countries like the United States where environmental sentiment is most prolific. The idea behind the bans is simple and self-evident: a reduction in waste and litter, and a corresponding reduction in associated environmental impacts like greenhouse gases. At first glance, it seems like a perfectly rational step. Shoppers will turn to lower-impact options like reusable bags or easily-recyclable paper bags. The environment will benefit. Or will it? For it turns out that, from end-to-end, virtually every single belief that informs these bans is based on misinformation; and as a result, bans on plastic carryout bags do more harm than good. Most people have heard this claim, and many have dismissed it as pro-industry propaganda. Today we're going to look at the underlying data and uncover the real facts.

It's always difficult to do an episode like this, because we're pitting data-driven policy against the honest impulses of well-intentioned environmentalists; the fact is that some policy that sounds good turns out to be driven more by emotion or ideology than by science. High-profile public issues like ocean trash and global warming are emotionally charged (rightfully so), and many of us support policies which appear to be obvious remedies. But the fact is that banning plastic carryout bags hurts the causes it intends to help.

Let me start by addressing the default feedback I'm going to get from this episode, which is that I'm shilling for the disposable plastic industry. The data I'm going to present today shows that manufacturers of disposable plastic benefit from bans on carryout bags, counterintuitive though that may sound. Carryout bags are their least profitable products — often given away for free at checkout — and as the flimsiest things they make, have the smallest environmental impact. Banning such bags shifts the manufacturers' sales to more profitable products with worse environmental impact. So by presenting arguments against plastic bag bans, I'd be about the worst shill the manufacturers could ask for.

I've assembled what I think are the three most pervasive myths about plastic carryout bags that prompt virtuous people to advocate for bans. Let's have a look each of these three.

Myth #1: Plastic carryout bags contribute to ocean plastics

I'm tackling this one first because it's the most easily dismissed. We covered this in excruciating detail in Skeptoid #665, Ocean Plastics: Facts and Falsehoods. The short version of the answer is that although plastic bags do indeed represent their expected proportion of plastic trash in the oceans, that plastic comes from China and several other East Asian and other developing nations where up to 76% of trash is mismanaged, i.e., ends up as litter. In the United States, only 2% is mismanaged, representing about one half of 1% of what's in the ocean. Our plastic bags represent about 1% of that. Thus, any changes to consumer behavior in the United States have no discernible impact on the amount of plastic in the ocean; the basic reason being that the United States is already among the world's leaders in responsible waste management. For all the gritty details and data, I don't need to repeat myself here, go listen to that episode.

Myth #2: Bans decrease the amount of disposable plastic leaving the supermarket

This is the biggest surprise for many people: banning carryout bags doesn't reduce the number of plastic bags people bring home like you'd think. Here's why.

Somewhere between a fifth and a third of carryout bags end up getting reused, either for picking up dog poop or lining small waste baskets around the house. And why not, they're free and most people have plenty of them in the kitchen cabinet. But in places where they've been banned, people still have a need for small plastic trash bags. So they suddenly find themselves having to buy them when they didn't before. Research published in 2019 in the Journal of Environmental Economics and Management analyzed what's happened in municipalities where carryout bag bans have been put in place, and the results are surprising. Sales of plastic trash bags skyrocketed alarmingly. Sales of the big sizes remained even, but sales of 8-gallon bags shot up by 64%, and sales of small 4-gallon bags more than doubled, rising by 120%! For those of you of a more liberal bent who might hope that your plastic bag ban will strike a blow to the faceless, soulless corporations who manufacturer plastic bags, think again. Bans have multiplied their sales and their profits.

But it's not just the number of bags. The free carryout bags that were banned were extremely flimsy, and the plastic trash bags people bought to replace them are substantially heavier, containing much more plastic material. In all, in the municipalities studied, 40 million pounds of plastic was saved, and 12 million new pounds of plastic was sold to replace it.

Now it's important to note that this "myth" is actually true — bans do succeed in reducing the total amount of plastic leaving the stores. But don't be fooled. The ultimate goal is to minimize environmental impact, not to reduce the number of pounds of plastic sold — and those are two different targets. We want to know the net environmental impact. And it's this next myth that puts us way, way over the top.

Myth #3: Plastic bags are worse for the environment than other options

I'm going to go with carbon footprint here to measure the net environmental impact — though we'll talk about landfills and eyesores soon. Carbon footprint is the ultimate driver of environmental impact today.

People have four common choices of carryout bags. First, the single-use cheap plastic bags that are the subject of the bans. Second, paper bags. Third, durable reusable plastic bags (either polyethylene or polypropylene); and fourth, reusable cotton bags. For each of these products, we look at the carbon footprint over the entire product life cycle: from the sourcing of its material, to its manufacture, through transportation and logistics, through its use phase (taking into consideration how many times it's used, how many groceries it transports), and finally through its end of life which may end up in recycling, in landfill, or even in incineration. This is a lot of data, but it is all tracked by various industry stakeholders. If you want all the details, see the references at the bottom of this page. For the purposes of this podcast, I'm just going to give you the final numbers, and these numbers already take into account that a minority of disposable carryout bags are reused at home as trash bags. These numbers come from a 2011 study by the UK Environment Agency.

It should come as no surprise that the humble single-use plastic carryout bag has by far the lowest carbon footprint, the basic reason being that there's simply so little material there. Plus, it's plastic, which has a low melting temperature; it requires less energy to manufacture and recycle than most other materials. So, right off the bat, the target of the bag bans is actually the product that best meets the objectives of true environmentalists.

The second best alternative is paper bags, with 4 times the carbon footprint of the single-use plastics. A lot of this has to do with the amount of water used to make and recycle paper, and it takes a lot of carbon-emitting energy to purify and reclaim fresh water. However, if you reuse your paper grocery bag 4 times before recycling it, its net environmental impact is comparable to that of the single-use plastic. (You are all taking your paper grocery bag back to the supermarket and reusing it 4 times, aren't you? No? Then if you're environmentally minded, you should be asking for plastic at checkout.)

The next is the durable reusable plastic bag, the type increasingly being offered by supermarkets as an alternative, often for some low price like 10 cents. These are quite a bit heavier, and have 14 times the carbon footprint; meaning you need to use it 14 times to match the efficiency of the single-use. This surprising difference is mainly because there's a lot more plastic in the durable reusable bag; it weighs 108-136 grams, compared to only 3.5 grams for the single-use bag.

Worse still are cotton bags; growing cotton involves tractors and seeds and irrigation and a whole other level of impact. You'd need to reuse a cotton grocery bag 173 times to match the carbon footprint of bringing home a single-use plastic instead on each of those trips. It's noteworthy that a 2018 study by the Danish government, which compared organic cotton bags to single-use plastics, found the environmental impact 20,000 times worse. The irony is that if you ask many environmentally-focused consumers what type of bag they'd most like to use instead of single-use plastics, many of them might well answer organic cotton. This is the difference between data-driven policy, and emotion or ideology-driven policy.

So what's so bad about single-use plastics?

Universally acknowledged as the biggest downside of unmanaged plastic waste is the fact that it does not biodegrade. Plastic trash is definitely an eyesore, and that's bad for everyone. But let's also consider it from an ecological perspective, not just an aesthetic one. If we have to shovel plastic bags into landfills, that's actually not the world's most terrible thing to do with plastic. Of course the preference is always to recycle it, but the market doesn't always support that: there has to be a buyer for the recovered material, or else it's not worth the cost (both monetary and carbon) to recycle. So it goes into landfills. Plastic in landfills does not release greenhouse gases. The carbon in it remains sequestered; and if we have petrochemical materials like plastic already in our environment, having its carbon sequestered is far from a terrible thing. Obviously it would be best if that plastic had never been manufactured in the first place; but the reality is that it has, so we're better off deciding what to do with it than wishing we didn't have to.

What should we do, if banning them is so much worse?

Economists have a pretty good answer for this. Keep the single-use bags available as always. Charge a small fee for them, as this drives people to start using the durable plastic alternatives. People who want to keep a few of the single-use bags around for household use will have as many as they want, and they won't need to buy so many more of the heavier, higher-impact trash bags. Stop offering the cotton reusable alternatives. And, of course, continue working toward plastics based on lower-impact petrochemical alternatives.

Let this following piece of irony not be lost on a single listener: It is rabid insanity to allow plastic bag manufacturers to sell plastic trash bags in supermarkets — and even to allow the markets themselves to sell their own store brands — but not allow bags to be sold individually at checkout!

And so the final conclusion on the subject of plastic bag bans is that the best solution — supported by climate science, ecology, economic theory, and proven by experimentation — is to continue to allow lightweight single-use bags to be provided for a fee by retail merchants, and to encourage shoppers to reuse durable reusable plastic bags.

By Brian Dunning
Follow @BrianDunning