While out walking today I came across this:

Urban Art

Is this urban art, vandalism or a clever statement on the use of resources?

Just how bad are disposable cups anyway?  Our drinks dispenser at work gives out a plastic cup with each drink.  Most people have around 5 drinks a day (that being the number of free vends we are allowed!), 5 times a week, which is a whopping 1,100 plastic cups per person per year.

Now, if you place a mug in the machine before telling it what you want, it won’t give you a plastic cup.  If we all did that, would our impact on the environment be significant enough to be worth it?  It seems at first glance to be cut and dried – of course using one cup is better than using 1,100!  But, as always, there are complications.

This blog was an invaluable resource in doing this calculation.

Firstly, a list of things to consider:

  • The disposable cups are thin plastic, not polystyrene or paper.
  • The disposable cups are all recycled after use – so no landfill.
  • Mugs need to be washed – although I don’t wash mine after every drink, I know some people would.
  • Ceramic mugs are very energy intensive to make.
  • Transport costs – delivery and collection of disposable cups vs mugs.

A study from the 90’s looked at the energy requirements for different types of cups.  Unfortunately it didn’t compare ceramic with the thin plastic which we use, however it did show that ceramic mugs need to be used 1006 times to break even with polystyrene cups – mainly due to the cost of washing them.

Commercial dishwashers are around 51% more efficient now than they were in the 90s, so I looked at the sensitivity tests done in the Hocking study.  50% less energy in washing led to only 133 uses being needed – much more reasonable.

That study only looked at energy use.  We also have to account for the disposal.  Let’s assume that the breakage of ceramic mugs is negligible and the recycling of disposable cups balances out the extra delivery costs.  Then we can ignore both items in our calculation. (1)

So, with some sweeping generalisations, we come to the conclusion that using a mug instead of disposable plastic cups is well worth it – as long as you use it, say 200 times before you break it.

I’ve been using the same mug for around six years now, so at 1,100 drinks per year I’m feeling pretty good about the results of this calculation.

Which only leaves me with one question – urban art, vandalism or a clever statement on the use of resources?

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(1) For those who get the joke… assume the cow is spherical.

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