Food-Related Energy Requirements

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Science  12 Apr 1974:
Vol. 184, Issue 4133, pp. 134-138
DOI: 10.1126/science.184.4133.134


I have used data from input-output studies to determine the quantities of primary and electric energy consumed in the agricultural, processing, transportation, wholesale and retail trade, and household sectors for personal consumption of food.

Before one draws conclusions from these results, it is important to note the assumptions and approximations used in this analysis. First, the economic input-output data published by the Department of Commerce are subject to a number of inaccuracies, including lack of complete coverage for an industry, restriction of data for proprietary reasons, and use of different time periods for different data.

Second, aggregation can combine within the same sector industries whose energy intensities differ widely. For example, eating and drinking establishments probably consume more energy per dollar of sales (because of refrigerators, stoves, and freezers) than do department stores. However, both types of establishment are included in retail trade. Thus energy use for food-related retail trade may be underestimated because of aggregation.

Third, the energy coefficients are subject to error. In particular, the coefficients for the agricultural and trade sectors are vulnerable because energy use within these sectors is not well documented.

Finally, the scaling factor used to estimate food-related energy use for the 1960's is approximate, in that it neglects the possibility that these energy coefficients changed differently with time. Because of these limitations, which are described more fully by Herendeen (6), a number of important issues were not addressed here. such as relative energy requirements for fresh, frozen, and canned vegetables; and for soybeans as compared to beef.

This analysis shows that the U.S. food cycle consumes a considerable amount of energy, about 12 percent of the total national energy budget. The residential sector, which accounts for 30 percent of the total, is the most energy-intensive sector in terms of energy consumed per dollar of food-related expenditure. This is because food-related expenditures in homes are primarily for fuel to operate kitchen appliances and automobiles.

The electricity consumed in these activities constitutes 22 percent of the total amount used in the United States. More than half of the electricity is used in homes, and more than two-thirds in the trade and household sectors. Thus agriculture and processing consume little electricity relative to the total amount used.

From past trends, it appears that the amount of energy used in food-related activities will continue to increase at a rate faster than the population, principally because of growing affluence, that is, the use of processed foods, purchase of meals away from home, and the use of kitchen appliances equipped with energy-intensive devices, such as refrigerators with automatic icemakers. However, fuel shortages, rapidly increasing fuel prices, the growing need to import oil, and a host of other problems related to our use of energy suggest that these past trends will not continue. Fortunately, there are many ways to reduce the amounts of energy used for food-related activities.

In the home, for example, smaller refrigerators with thicker insulation would use less electricity than do present units. If closer attention were given to the use of ranges and ovens (for example, if oven doors were not opened so often) energy would be saved. Changes in eating habits could also result in energy savings. Greater reliance on vegetable and grain products, rather than meats, for protein would reduce fuel use. Similarly, a reduction in the amounts of heavily processcd foods consumed—TV dinners and frozen desserts—would save energy.

Retailers could save energy by using closed freezers to store food and by reducing the amount of lighting they use. Processors could use heat recovery methods, more efficient processes, and less packaging. Shipping more food by train rather than by truck would also cut energy use.

Farmers could reduce their fuel use by combining operations (for example, by harrowing, planting, and fertilizing in the same operation), by reducing tillage practices, by increasing thc use of diesel rather than gasoline engines, and by increasing labor inputs. A partial return to organic farming (that is, greater use of animal manure and crop rotation) would save energy because chemical fertilizers require large energy inputs for their production.

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