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So you’ve followed this link because you have an interest in what bag use actually means to the environment. First, let’s talk about what carbon footprint actually means:
Footprint (in this context) is a measure of the total impact something has; whereas Carbon is shorthand for all the different kinds of greenhouse gases. Therefore Carbon Footprint is considered the best estimate for the impact something has on the environment through the process of its creation.
The calculation of an item’s carbon footprint is not always as simple as it seems. When assessing the true impact of a product you must consider all the processes that went in to making it; that’s all electricity, gas, food, emissions from transport of parts, and the creation of all the ingredients that are used to make that product (once again including all the electricity, gas, food etc.).
Now let’s break down some misconceptions about bags and carbon footprint:
A paper bag has a worse carbon footprint than a plastic one
As surprising as it may seem, the paper industry’s use of electricity is very intensive. Printed virgin paper typically produces between 2.5 and 3kg CO2e per kilo of paper that is manufactured. Compare this to the approximate 60g of carbon emissions required to make 1kg of plastic polypropylene bags. What’s more is that paper bags actually have to be much heavier than a plastic one driving up the carbon footprint up to anything from 12g (a recycled lightweight paper bag) to 80g! (fancy bag like you get from clothing retailers).
Recycled paper does produce a lower carbon footprint than virgin paper does (around 1.5kg per kilo) but it still produces more carbon emissions than a plastic bag.
Another issue is the durability of the paper bag. Their reuse life span is shorter than plastic bags (evident from rainy shopping trips and contents bursting on to pavements).
Disposal:
If you ever use a paper bag recycle it. Bags that end up on landfills will rot and release CO2 and methane into the atmosphere (further increasing their overall carbon footprint). Even if the landfill site burns the paper (for instance waste to energy plants) there will still be around 500g of greenhouse emissions produced per kilo of paper burned.
The honest truth about plastic bags
Recent legislation now requires all UK companies and institutions over a certain size to charge for plastic bags. This is overall a very positive step to reducing the amount of plastic bags we use and encourage the re-use of sturdier bags such as cotton and canvas bags to do our shopping.
While it’s true that plastic bags produce a lower carbon footprint than paper bags (around 10g carbon footprint per standard supermarket bag), the issue comes in their disposal. They have a habit of surviving the elements a bit too well and hanging around for potentially hundreds of years before they fully waste away. What’s more they can potentially end up injuring animals through ingestion etc.
Disposal:
The best way to get rid of plastic bags may surprisingly be landfill. Burning the bags through waste to energy, or recycling releases carbon (and toxins) into the atmosphere (although technology is improving to try to combat this). If the bag is in landfill and stored appropriately the hydro-carbons that make it up will eventually return to the ground from which they came… over hundreds of years mind you…
Probably the best thing you can do is just not to use them at all, as who wants to live amongst thousands of landfills whilst we patiently wait for them to break down.
Which brings us to:
Fabric bags
Cotton/canvas totes, rucksacks and wheelie baskets are all good sturdy choices. However although natural materials like cotton sound ‘greener’ they actually carry a much higher carbon footprint than one may initially think. The average weight of the cotton tote sold in Art Shop is 85g (black is slightly heavier than plain due to the dye), and cotton has a carbon footprint of 7kg per kilo. This will mean a single cotton tote has a carbon footprint of approximately 6kg. Compare that to 12g for a paper bag, and 10g for a plastic bag and the difference is quite staggering.
The trick in making the fabric bag sustainable is the amount of use you will get out of it. A quick calculation shows that you would need to use your cotton bag at least 60 times before you outweigh using a new plastic supermarket bag for each trip.
Tips on making your bag perform to its best ability:
The more you use your fabric bag the more you will reduce its carbon footprint. Let the bag wear itself out and when you wash it let it dry without tumble drying it (this would push its carbon footprint back up again…actually best to avoid using tumble driers where you can for all your clothing).
So make sure when you buy a fabric bag that is made to last, easy to clean and dry, repair it where possible, and you can even buy it second hand.
Further reading and sources
Information for this post was gathered from various verified studies and sources through M. Berners-Lee book ‘How Bad are Bananas – A Carbon Footprint of Everything’ (2010). It is available in UAL libraries for further reading.