Green Chemistry and the Ten Commandments

6.4. Energy Sources

Two centuries ago, before the steam engine became commonplace, virtually all the
energy used in the world was from biomass sources. Energy for heating came from
burning wood. Other than walking, people and goods moved on land mostly by means
of horses and oxen. Cultivation of soil and other agricultural activities were powered
largely by animals with a significant contribution from people, themselves. The energy
required for people and for beasts of burden was provided by food, a form of biomass.
A significant amount of energy for transportation was from wind, which drove sailing
boats and ships. In any case, most of the energy was from renewable sources.
The use of coal for energy grew spectacularly during the 1800s and by the end of
that century coal had become the predominant source of energy in the United States,
England, Europe, and other countries that had readily accessible coal resources. So there
was a major shift from renewable biomass energy sources to coal, a depletable resource
that had to be dug from the ground. By 1900, petroleum had become a significant
source of energy. By 1950 petroleum had surpassed coal as a source of energy in the
United States. Also by 1950 natural gas had become a significant source of energy
lagging behind petroleum in its rate of development. Hydroelectric power had become
a significant source of energy worldwide by 1900, and retained a significant share of
energy production through the 1900s. By around 1975, nuclear energy had become a
significant source of electricity and has maintained a share of several percent worldwide
until the present. Although just a “blip” in the total energy picture, miscellaneous sources
including geothermal and, more recently, solar and wind energy now make contributions
to total energy supply. Biomass still contributes a little to the total of the sources of
energy used.
Figure 6.5 shows U.S. and world energy sources used annually as of the year 2000.
The predominance of petroleum and natural gas, both in the U.S. and globally, are
obvious. With coal, these fossil fuel sources account for the vast majority of energy

<1%4%

8%

26%

21%

41%

4% 7% 6%

25%22%

37%

Petr

oleum

Natural gas

Coal

Nuclear

Hydr

o

Other

Petr

oleum

Natural gas

Coal

Nuclear

Hydr

o

Other

Figure 6.5. U.S. (left) and world (right) sources of energy. Percentages of total rounded to the nearest
1%

142 Green Chemistry, 2nd ed