Figure 5-3. Less than 100 years ago, animals were the energy source for
most farmwork in the United States. In many countries, animal power is still
widely used. This photo shows mules being used for plowing in the 1920s on
a farm in the American Midwest. (U.S. Department of Agriculture)
A B
Figure 5-2. Basic renewable energy resources. A—Animals. (U.S. Department of Agriculture)
B—Food. (U.S. Department of Agriculture) C—Wood. (U.S. Department of Agriculture) D—Alcohol.
(DaimlerChrysler)
Renewable and Inexhaustible Energy Sources
C D
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