On the same data basis as for the Benchmark Calculation [EN/DE] we also did the Waterfootprint calculation and rating [EN/DE] for all supplied products of the 150 businesses over 2019, 2020, and 2021. Overall we looked at more than 3.5M purchases, the file is bigger than Excel can handle it.
The average scarce water value of all supplies turn out to be 91.56 liters per Daily Food Unit - DFU [EN/DE]. Also, the distribution is a lot more exponential than with the CO₂ values (meaning: some few products like almonds, cashews, olives, etc. coming from specific regions where water is scarce have a really high > 5000 liters / DFU value, while most other products are well below the average.)
As the goal is to come up with a diet, that reduces our dependency on scarce water by 50%, it turns out that we only would need to avoid those really high valued outliers. Indeed, by only eating those products that have a lower value than 1059.85 liters / DFU the cumulative fraction of all products water footprint and DFU value is exactly half the average (45.78 liters - see table below).
So it is fair to label products that have an actually higher water footprint than average as still being “ok”.
| Daily Food Unit | Water Scarcity Footprint [liter] | Month | Water / DFU | Cumulative DFU | Cumulative Water | Cumulative DFU / Water | # |
|---|---|---|---|---|---|---|---|
| … | … | … | … | … | … | … | … |
| 73.4114 | 77804.363 | 2021-10-01 | 1’059.8403381491 | 6’404’681.99279550 | 293210216.3717717 | 45.7806049858 | 1866597 |
| 73.4114 | 77804.363 | 2021-09-01 | 1’059.8403381491 | 6’404’755.404195502 | 293288020.73477167 | 45.7922281533 | 1866598 |
| … | … | … | … | … | … | … | … |
To stay on line with a A,B,C,D,E rating that easy to comprehend we defined it as follows.
| Threshold | Water / DFU value | Comment | Illustration |
|---|---|---|---|
| A vs B | 91.56 | This is the average value of all products purchased. | Any product guarantees to reduce our dependency on scarce water. Optimal consumption of scarce water |
| B vs C | 183.12 | This is the average value times two of all products purchased (2x). | Still a very low consumption of scarce water. |
| C vs D | 366.24 | This is the average value times four of all products purchased (4x). | Substantially higher consumption of scarce water (at least four times the average). |
| D vs E | 1’059.85 | This is the threshold for the cumulative distribution. | If we would eat the same distribution of the foods below this value, we would reduce our dependency on scarce water by 50%. Everything above this value can only be bad. |
You find all rating summarized here: