http://www.ck12.org Chapter 2. Numbers, Not Adjectives
I’ve again taken the physiological liberty of assuming “animals are like humans;” a more accurate estimate of the
energy to make chicken is in this chapter’s endnotes. No matter, I only want a ballpark estimate, and here it is. The
power required to make the food for a typical consumer of vegetables, dairy, eggs, and meat is 1. 5 + 1. 5 + 1 + 8 =
12 kW hper day. (The daily calorific balance of this rough diet is 1.5 kWh from vegetables; 0.7 kWh from dairy; 0.2
kWh from eggs; and 0.5 kWh from meat – a total of 2.9 kWh per day.) 0.7 kWh from dairy; 0.2 kWh from eggs;
and 0.5 kWh from meat – a total of 2.9 kWh per day.)
This number does not include any of the power costs associated with farming, fertilizing, processing, refrigerating,
and transporting the food. We’ll estimate some of those costs below, and some in Chapter Stuff.
Do these calculations give an argument in favour of vegetarianism, on the grounds of lower energy consumption? It
depends on where the animals feed. Take the steep hills and mountains of Wales, for example. Could the land be
used for anything other than grazing? Either these rocky pasturelands are used to sustain sheep, or they are not used
to help feed humans. You can think of these natural green slopes as maintenance-free biofuel plantations, and the
sheep as automated self-replicating biofuel-harvesting machines. The energy losses between sunlight and mutton
are substantial, but there is probably no better way of capturing solar power in such places. (I’m not sure whether
this argument for sheep-farming in Wales actually adds up: during the worst weather, Welsh sheep are moved to
lower fields where their diet is supplemented with soya feed and other food grown with the help of energy-intensive
fertilizers; what’s the true energy cost? I don’t know.) Similar arguments can be made in favour of carnivory for
places such as the scrublands of Africa and the grasslands of Australia; and in favour of dairy consumption in India,
where millions of cows are fed on by-products of rice and maize farming.
Figure 13.6:Will harvest energy crops for food.
On the other hand, where animals are reared in cages and fed grain that humans could have eaten, there’s no question
that it would be more energy-efficient to cut out the middlehen or middlesow, and feed the grain directly to humans.
Fertilizer and other energy costs in farming
The embodied energy in Europe’s fertilizers is about 2 kWh per day per person. According to a report to DEFRA
by the University of Warwick, farming in the UK in 2005 used an energy of 0.9 kWh per day per person for farm
vehicles, machinery, heating (especially greenhouses), lighting, ventilation, and refrigeration.
The energy cost of Tiddles, Fido, and Shadowfax
Animal companions! Are you the servant of a dog, a cat, or a horse?
There are perhaps 8 million cats in Britain. Let’s assume you look after one of them. The energy cost of Tiddles?
If she eats 50 g of meat per day (chicken, pork, and beef), then the last section’s calculation says that the power