Monday, April 4, 2011

It takes more energy to eat than to farm

The increase of energy use in agriculture was in particular very rapid in the period after the second world war and the first oil price chock 1973; while labour force was reduced to half between 1952 and 1972 in England, energy use tripled. In the USA energy use decreased from mid 1970s to mid 1980s as a response to increased oil prices, thereafter it has stabilized. Looking at the whole food chain however, energy use has constantly increased. In pre-industrial and semi-industrial agriculture systems, most of the food is sold, eaten and prepared close to where it is produced, but the modern food chains are highly centralized and globalized. And the energy ratio is just getting worse and worse. In industrial countries between 10 and 15 times more energy is used in the food system than what is contained in the food we end up eating (Uhlin 1997, Hendricksson 1994).

A big part of the energy consumption is caused by the consumers buying, storage and preparation of food. In Sweden 1997, agriculture production represented 15-19 percent, processing 17-20 percent; distribution and retail 20-29 percent and consumption 38-45 percent of the total energy use in the food chain. 7-11 percent of the total energy is consumed by the much discussed transports, and here it is in particular the final stretch that counts. A person driving the car 5 kilometres for shopping uses a lot more energy per food unit than a ship with meat or soy from Argentina. Also, in some developing countries consumption takes the lion's share of energy use; in this case, it is mainly cooking over an open fire that takes energy. 1,500 kWh (corresponding to a bit more than a cubic meter of firewood) is used per capita for cooking, which is somewhere between half and one third of what is used per capita for cooking in Sweden or the USA (Uhlin 1997). Cooking represents more than a fifth of the total energy consumption in Africa and Asia and in some countries, cooking represent up to over 90% of household energy consumption (IEA 2006).  In the absence of new policies, the number of people relying. Another interesting observation is that the use of energy for cooking is more than the total energy in the food. So while farming in developing countries and traditional systems is energy efficient, cooking is not.

Other values of food

Energy ratios in agriculture give a interesting perspective but conclusions can’t be taken into the extreme. Firstly we are, at least not yet, in a situation where we have to equal energy in food with energy in oil, nuclear power or hydro power. At a first glance, one might even consider such comparisons absurd. And they are absurd, if we think that there will be unlimited supplies of energy in the future. Not too many believe that anymore. All staple foods, i.e. the foods that have provided the bulk of the nutrition are foods with a positive energy balance in their traditional way of production. If that was not the case, they could never have been staple foods in the first place. Secondly, it is not only the calories that give value to food. In such a case we could do best keeping to sugar (and sugar cane is one of the most energy efficient crops there are). Vegetables will always be inferior to grain when it comes to energy ratios. They contain a lot of minerals and vitamins, however. Meat is not primarily consumer for its energy content but for its protein (I will discuss meat more another time). Finally, some food is eaten simply because it tastes well or for religious or cultural reasons.

and my all time favourite: 250 million energy slaves
all of them are posts derived from my book Garden Earth.


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  3. I have heard it widely repeated that every Kcalorie of food we eat consumes 10 kcalories of fossil fuel energy (40,000 joules) to plow plant harvest deliver store etc....the insecticides fertilizer fuel refrigeration electricity etc etc.

    This is a scarey stat....particularly since I feel that if you gave me seed, fenced cleared land, tools, and a perfect climate, I don't know how to grow enough food for myself let alone my wife and babies. I am dependant on the Kroger feed lot

  4. It is indeed scary, and unsustainable in the long run. Keep in mind that a lot of it is spent in other places than in production though.