The Grocery Bag Conundrum

The Grocery Bag Conundrum
StableDiffusion Prompt: "The grocery bag conundrum. Ethereal. Dreamscape."

An Issue:

I saw this comparison from 'Our World in Data' on the number of times a given grocery bag type would need to be reused to have comparable greenhouse gas emissions as a standard single-use plastic bag -

So if you want to use a nice organic cotton bag for your grocery shopping, you would need to use it 149 times before you break even with respect to 'greenhouse gas emissions' when compared to using one of those ugly single-use plastic bags...once.

Fine, you could argue that your organic cotton bag is built to last, you will use it every time you go shopping and that this is not a deal breaker...

But then when you compare the number of times a given grocery bag type would have to be reused to have the same environmental impact as a standard single-use plastic bag across 'all indicators' we see -

To forgo the ugly single-use plastic bag at the shops, you would need to use your nice organic cotton bag 2,375 times to break even from an environmental impact standpoint.

(It turns out that cotton farming has a disproportionate effect on ozone depletion due to electricity use for irrigation - the electricity is generated from gas; and two ozone-depleting gases are used in gas transport.)

Would anyone object if I suggested that this is practically impossible to achieve?

The Source:

This all comes from a 2018 report from the Danish Environmental Protection Agency titled 'Life Cycle Assessment of grocery carrier bags'.

A life-cycle analysis (LCA) "...measures the total environmental impacts (such as greenhouse gas emissions) of a product across their full value chain (including inputs needed for their production)."

The 'all environmental indicators' assessment included "...greenhouse gas emissions, ozone depletion, human toxicity (cancer), human toxicity (non-cancer), 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."

Practical Maths:

In my cupboard right now I have piles of old 'reusable' shoping bags, including:

  • The 'Coles Better Bag (Since 2018)' - a 'plastic' bag made from 80% recycled material - made in Malaysia = unclear how many reuses required x Quantity = 1
  • The 'Woolworths Reuse and Recycle Bag' - another 'plastic' bag made from at least 80% post-consumer plastic by weight - also made in Malaysia = unclear how many reuses required x Quantity = 1
  • The 'Woolworths 70% Recycled Paper Bag - made in Vietnam = about 10 reuses required x Quantity = 1
  • Permutations of insulated reusable bags - PET (polyethylene terephthalate - polyester) = 8-25 reuses required x Quantity = 8
  • Permutations of Polopropylene bags = 10 reuses required x Quantity = 14

So, charitably, I think I am about 250 Bag-Uses in debt.

If we map this against a weekly 'grocery shop' in which I usually need three bags, I have at least 12 months ahead of me until I pay off this debt to the environment, assuming that:

  • None of my bags break before their reuse requirement (resulting in unrecoverable debt)
  • I always remember my bags (purchasing new bags at point of sale simply adds to my environment debt)
  • No one buys me a nice organic cotton bag for Christmas (I would be buggered then...)

I think I am ready to call this as implausible.

An Answer:

So, what should we do?

Well, those gross, single-use, plastic bags are actually not that bad.

Assuming you don't go feeding them to turtles (you know who you are...), then we shouldn't lose sleep.

There are probably bigger fish to fry, like organic cotton shopping bag snobs...


Conveniently, Australia was pretty much all on board for banning single use plastic bags by 2018 (yeah, different states at dfferent times) such that Coles and Woolies only offer their 'reusable' plastic bags at checkout - $0.15 each.

A more interesting discussion would be if this has had any net impact across 'all environmental indicators' since then.

A more-more intersting discussion would be on the financial effects of this decision - I assume Coles and Woolies are making a profit on that $0.15 line item. And they can safely assume that I will forget my reusable shopping bags every time...