Environmental Studies Factsheet: 56. Energy Ratios in Agriculture
Environmental Studies Factsheet: 56. Energy Ratios in Agriculture
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 Code: ESAFSPI056

If we get exactly the same amount of energy out as we put in the ratio would be 1/1 so the ratio would be 1. If we get out 10 units of energy but put 20 in, we would have a ratio of ½ =0.5. It is impossible to get an energy ratio of >1 or even of 1. Energy is lost at every stage of a food chain and every mechanical operation loses energy as heat and sound –we can never get out what we put
in. So our energy ratio will be less than 1. The key questions are:
1. How far below 1 are our systems?
2. Is there anything we can do to improve them?
Finding useful ie quantitative data on energy ratios is very difficult. One problem is that many studies only look at the energy inputs on the actual farm –they ignore inputs such as the transport of fertilisers etc from the warehouse to the farm and even the energy to transport the food from the farm to the shop/supermarket to process the food. Some studies ignore the input of direct sunlight! If you miss this huge input out, the ratio of output/input looks very good –and in US studies that do this, we often find energy ratios >2!