HUMAN BIOLOGY

hUMaN iMpaCts oN the Biosphere 485

What does our energy future look like?

• Demand is increasing for safe, cost-effective, renewable
  energy alternatives, but all of the technologies now available
  or being developed have drawbacks.


• Energy conservation is the best way to limit negative
  environmental impacts.

taKe-Home messaGe

biofuels Fuel products

made from plants and

organic wastes.

fossil fuels Oil, coal, and

natural gas, all the fossilized

remains of ancient forests.

What about nuclear power?

Today, nuclear power generates electricity at a relatively

low cost. Increasing its use would decrease dependence on

oil from the politically unstable Middle East. Also, nuclear

power does not contribute to global warming, acid rain, or

smog. So why hasn’t there been a “nuclear power revolu­

tion”? Safety concerns are a major reason. For instance,

there is always the potential for a meltdown if the reactor

core becomes overheated. This happened at Chernobyl

in Ukraine in 1986, and in 2011 at the Fukushima Daiichi

power plant in Japan, where three reactors melted down

in the aftermath of a tsunami. In both cases the melt­

downs released potentially deadly

radiation and millions of people

were exposed to dangerous levels of

radioactive fallout.

Radioactive wastes also are

highly dangerous. Some must be

isolated for 10,000 years or longer,

and there is little agreement on the

best way to store them. Debate swirled around the decision

to store nuclear wastes generated in the United States in a

remote area of Nevada.

In the final analysis, all commercially produced energy

has some kind of negative environmental impact. Experts

agree on one thing: The best way to minimize that impact

is for all of us to find ways to use less energy, now and in

the future.

Today solar power, produced by photovoltaic cells in
panels such as those shown in Figure 25.20, is becoming
a viable alternative in places where there is plenty of sun­
light much of the year. Technological advances are bring­
ing down the cost, but a homeowner who wants to install
enough solar panels to supply all of a home’s electricity
often must spend tens of thousands of dollars.
As you know, automakers now sell hybrid vehicles that
run on a combination of gasoline and electric power gener­
ated by batteries. There also has been much research aimed
at developing all­electric vehicles and hydrogen fuel cells
to power cars. So far, though, both are quite expensive and
have other problems as well. Few electric­car “charging sta­
tions” exist, and the process for making hydrogen fuel cells
generates high levels of greenhouse gases.
Another renewable option involves liquid biofuels—
products such as ethanol and biodiesel made from plants
and organic wastes. Unfortunately, growing most biofuel
species (such as corn) and manufacturing and delivering
the liquid fuel to consumers actually costs more in energy
than it produces.
Hydropower from dams is a renewable energy source,
but it too has drawbacks. For example, dams in rivers of
the Pacific Northwest and California generate a great deal
of electricity, but they also prevent endangered salmon
from returning to streams above the dam to breed. As the
salmon populations have suffered, so have endangered
whales that feed on salmon in the ocean.
There are other alternatives, although none has yet
proven itself for widespread use. In windy places, the
mechanical energy of wind generates electricity as wind
turns giant turbines (Figure 25.21). Analysts have estimated
that a “wind power corridor” stretching from Texas north
through South and North Dakota would generate enough
electricity to meet the needs of 80 percent of the continental
United States. Some people object to the turbines as eye­
sores and point out that the turbine blades kill birds.

Figure 25.20 Electricity-producing photovoltaic cells are placed
in panels that collect sunlight, a renewable source of energy.

© zstock/Shutterstock.comFigure 25.21 This array of turbines is harvesting wind energy.

© ssuaphotos/Shutterstock.com

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