One of the reasons for doing this calculation is because many people do not realise the energy they use by ‘consuming’ various products and their packaging.
The Calculation
The UK throws away over 3 million tonnes of plastic every year1. Some estimate are 5 million tonnes2. I am not going to worry too much about the exact figure because all we want is a rough figure. So let us take 3million tonnes.
One tonne is 1000Kg so this is 3×106 x 103 = 3×109Kg
The energy needed to produce one kilogram of plastic varies with the type of plastic and the production process. It is known as the embodied energy3 of the plastic. It can vary between about 60 and 100MJ/Kg 1,4. So let us take a figure of 75MJ/Kg.
30% of the plastic in the UK is recycled5. The energy needed to recycle the plastic is still considerable1 Let us say 35MJ/Kg.
We therefore have 3×109 x 0.7 = 2.9 x 109Kg going into landfill
So the energy needed to produce the 3 million tonnes of waste is
3×109 x (1-30%) x 75 = 1.575 x 1011MJ for landfill and
3×109 x 30% x 35 = 0.315 x 1011MJ for recycled.
Total = 1.89 x 1011MJ
This is a very large number but does not mean much to me. So in terms of energy how many nuclear power stations do we need to produce this amount.
If we divide this figure by the number of seconds in a year (31,557,600) we then get the power required in MW
1.89 x 1011/31557600 = 7130MW
Sizewell B produces 1195MWe of electricity so you would need 7130/1195 = 5.97 Sizewell B’s to produce this energy.
However, nuclear power stations do not run all the time – they need refueling and they break down so I think it is fair to say this is 5 reactors.
Even with 100% recycling it is still over 2.75 reactors.
Further Comments
Please note that I am not saying that the output of five nuclear power stations are used to produce/recycle the plastic. It is just showing how much energy it is.
Much of the energy used is not in the form of electricity but from direct heating by burning gas and that much of the plastic we consume is produced outside this country – for example in China.
More information on plastic and climate change can be found in the report Plastic & Climate – The hidden Costs of a Plastic Planet6.
1 Recycling of Plastics, Cambridge University ImpEE Project (http://www-g.eng.cam.ac.uk/impee/topics/RecyclePlastics/files/Recycling%20Plastic%20v3%20PDF.pdf)
2 Plastic waste, House of Commons Library (https://researchbriefings.parliament.uk/ResearchBriefing/Summary/CBP-8515)
3 Embodied Energy, Wikipedia (https://en.wikipedia.org/wiki/Embodied_energy)
4 Embodied Energy, Wikipedia (https://en.wikipedia.org/wiki/Embodied_energy#In_common_materials)
5 Plastic Recycling, British Plastic Federation (https://www.bpf.co.uk/Sustainability/Plastics_Recycling.aspx#2)
6 Plastic & Climate – The hidden Costs of a Plastic Planet, Center for International Environmental Law, May 2019 (https://www.ciel.org/wp-content/uploads/2019/05/Plastic-and-Climate-FINAL-2019.pdf)
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