The answer is that it may not be as perfect as you think.
Plastic bags get a lot of negative press – they are iconic of our throwaway society, use up limited natural resources, and find their way into the oceans to be eaten by a turtle or albatross.
But there is also an environmental cost to the manufacture and disposal of paper bags.
Did you know that the environmental cost of making a paper bag is way higher than plastic bag. In 2011 it was estimated that it takes about four times as much energy to produce a paper bag than a plastic bag (see note 1). The paper industry is highly energy intensive, and although it takes about the same energy to produce 1 kg of paper as 1kg of plastic, they are a lot heavier – so overall a paper bag has a larger carbon footprint. When they are transported to your shop, it also takes more energy.
Usually plastic bags are made from the waste products of oil refining, but the harvesting of timber has detrimental effects on habitats and wildlife as well. Posh paper bags use virgin paper, toxic chemicals in colourful printing, and even may have a plastic coating. These are definitely worse than a simple plastic bag.
If you dispose of a paper bag in general landfill, it will decompose releasing CO2 and methane into the atmosphere.
And paper bags are not very durable. If you try to use a paper bag for your shopping bag more than a couple of times it is likely to break – and you don’t want your apples and oranges rolling down the street. At least plastic bags tend to be strong and can be re-used lots of times.
So, what is to be done?
Re-use! Whatever bag you have, re-use it. Whether that is a plastic bag, a paper bag, or a cotton bag, use it, re-use it, and re-use it again. (While we are on the subject, you may think a cotton bag is the ideal solution. Not necessarily. You need to re-use a cotton bag 131 times to make it was energy efficient as a plastic bag. (see note 2). This is because of the energy needed to grow and harvest cotton yarn. )
And when you can’t re-use it anymore, recycle!
Note 1: http://www.niassembly.gov.uk/globalassets/documents/raise/publications/2011/environment/3611.pdf