Several municipalities throughout the United States now shred and burn
waste. See Figure 5-8. The heat energy is then used to produce electricity
or for industrial processes. This type of bioconversion also helps solve a
growing societal problem. As landfills reach capacity, there is a growing
concern of how to get rid of unwanted waste generated by society. These
waste-to-energy plants have gained in popularity in recent years because
they are economically viable.
Inexhaustible Energy Sources
Inexhaustible energy sources are those sources of energy that will
never run out. We are fortunate to have such energy sources, and it is in
the best interest of our nation and the world to learn how to develop them
for long-term use. The roots of most inexhaustible energy sources can be
traced back to solar energy. It is solar energy that produces the changes in
temperature that ultimately create tides and winds. The most frequently
used of the inexhaustible energy sources is hydroelectricity, but others
include geothermal energy, the wind, tides, Ocean Thermal Energy
Conversion (OTEC), and hydrogen. Since forces beyond our control renew
these sources, these sources are considered to be inexhaustible.
Hydroelectric Energy
Years ago, flowing water was used as a source of energy. See Figure 5-9.
Waterwheels have few applications in contemporary America, but they
were a major source of mechanical power for factories of colonial
America. Water tapped from a nearby river is diverted into a sluiceway.
A sluiceway is a channel that carries the water to a waterwheel. The force
Methane digester:
A vessel that
converts shredded
organic materials
into methane gas,
which can be used
for heating, used
for power genera-
tion, or purified
and stored for
distribution.
Anaerobic
digestion: Decay
without the use of
oxygen.
103
Figure 5-7. A methane digester produces usable methane gas from decaying
organic matter.
Digester
liquid
Shredded organic
materials
Methane gas
Gas to purification
or combustion
Anaerobic
decay
Digester effluent
oxidation pond
Pump
Pond effluent to slurry make-up
Sludge recycle
Sludge to
drying bed
Feed
slurry
Pump
Waste-to-energy
plant: A plant that
shreds and burns
waste. The heat
energy is then used
to produce elec-
tricity or for indus-
trial processes.
Renewable and Inexhaustible Energy Sources
G R E E N T E C H
A newer type of
gasohol is called E85
and contains up to
85% ethanol. Flex-
fuel vehicles can run
on E85 the same
way vehicles run on
regular gasoline.