Carbon and water footprints

The total amount of carbon dioxide gas emitted over a definite time because of a person, a product, an activity or an institution is called its carbon footprint. Because a great deal of data is needed, and because carbon dioxide is also produced naturally, calculating a complete carbon footprint exactly is hard.

Figure 15.41 — the water footprint of some foods.

Why beef costs so much water

The water footprint counts all the water behind a food, not just what is in it. A kilogram of beef includes the water drunk by the animal over years and, far more, the water used to grow all the grass and grain it ate. That is the energy pyramid again: because only about 10% of the energy passes up each level, an animal food needs many times the crops, and so many times the water, of a plant food. The carbon footprint works the same way — fuel for tractors, fertiliser factories and transport all add to it. Choosing more plant food, less waste, and local produce shrinks both footprints.