Cups. A Deep Dive. “Reusables”. Part 2 of 4.
Reusable cups are, by definition, reusable. This typically means that they are made of a more durable material than paper and can be washed and reused.
However, herein lies its biggest environmental concern, it must be reused. The environmental impact (the intensity of ecosystem destruction during resource extraction, the amount and type of material required, and the energy required to produce the product) of production is generally much greater than a paper cup and will also end its life in a landfill.
When comparing reusables to disposables one to one, the disposable product will nearly always have a lower impact at production.
So how many times must a reusable cup be reused to become less impactful than a paper cup?
Well, it depends greatly on material used.
According to an often cited study conducted Martin Hocking in 1994 discussing this very topic, you would have to use a porcelain cup about 50x or a glass cup about 15x to offset this initial deficit.
How the study came to this conclusion is by assigning a per-cup energy use total. At point of first use, Hocking surmised that paper cups embodied 0.55 megajoules (the equivalent of about 153 watt hours) of energy while a porcelain cup embodied 14 mj and glass embodied 5.5mj.
From here, Hocking used the specifications of an average dishwasher to measure whether the porcelain/glass would ever overtake the paper cup accounting for the energy used during the wash cycle.
As previously stated, Hocking concluded that the paper cup was more energy efficient for the first 15-50 uses, at which point the reusables would become superior; though it must be noted that the continuous need to wash the reusable will keep it at a relatively thin beneficial margin.
This study has been referenced by many, including in a video by James Hoffmann on his very popular YouTube channel, to illuminate the issues with the concept of switching to reusables.
However, what Mr. Hoffmann and others have failed to account for is the immense improvement in the efficiency of dishwashers since the study was conducted.
Using this chart from GE, a late 80’s or early 1990’s dishwasher used between 11.4 and 7.5 gallons of water as compared to between 2.8 and 5 gallons with an Energy Star dishwasher of 2022.
This improvement is due, in no small part to the increased ability to recycle water used within a cycle (which retains both water and heat!).
If we assume that we are dealing with two top of the line (in regards to efficiency) washers from the both eras, we can assume a 2.7x improvement in water/energy consumption per wash bringing the total use deficit down to under 20 uses to break even.
This is a nice upgrade and brings an already manageable number into an eminently doable one - even for perennially breakable items like porcelain.
