Abstract
We examine technological progress in the US and Canada to answer the question: has the efficiency (e.g., the edible energy efficiency, or EEE) for producing agricultural products in the US and Canada increased in recent decades? Specifically, we determined the energy efficiency of agriculture at the farm gate in recent decades by dividing the outputs (the total annual crop and animal output in energy units minus the feed used for animal production and the grain used for ethanol production) by the energy inputs: all the energy used by the nation to produce food (the energy used to generate and apply the fertilizer, pesticides, seed and to operate machinery) minus the energy inputs to produce grain for ethanol. Our data comes primarily from national and international agricultural censuses. Our study found that the energy efficiency of US agriculture has more than doubled from 0.8:1 in 1970 to 2.2:1 by 2000, then increased more slowly to 2.3:1 by 2009. The energy efficiency of the agricultural sector in Canada has not changed appreciably since 1980, and has varied about a mean of 2:1 from 1981 to 2009. Our study found that EEE improvements in the US could be attributable in part to advancements in crop production per hectare, and lower direct fuel consumption, but also a greater proportion of less energy-intensive corn and changes to the diet of livestock (e.g., increased use of meals and other by-products which have increased the availability of grain). Thus increases due to technological progress alone for the last several decades appear small, less than one percent a year.
Highlights
Both the US and Canada use highly industrialized agriculture and are among the World’s top producers of crops
We determined the energy efficiency of energy used in agricultural production in the US and Canada by dividing the food output, i.e., the caloric energy of the top 15 crops with the highest tonnage output for each ten or five year interval produced in that year, minus the feed used for animal production, by all energy inputs i.e., the energy associated with producing the major inputs of the agricultural system: fertilizer, seed, pesticides, fuel, and machinery
Our results find that agricultural energy efficiency (EEROI) more than doubled in the US from to 1990, from 0.8:1 to 2.0:1, increased more slowly to 2.3:1 by 2009 for a total increase of
Summary
Both the US and Canada use highly industrialized agriculture and are among the World’s top producers of crops. Combined they produce nearly half of the World’s corn and one third of the. World’s wheat exports [1]. Though very productive from a human labor standpoint, are highly dependent on fossil fuels, especially petroleum. In traditional cultures 5 to 50 kcal of food were obtained for each kcal invested; by 1970 one kcal of food was obtained for every 5–10 kcal of total energy (fossil and human labor) invested [2].
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