Renewable energy sources

C O V E R
S T O R Y
Because humans can only harvest or extract so much
of these energy sources from the planet, they are
referred to be nonrenewable. The buried remnants
of ancient marine plants and animals, which lived
millions of years ago, created coal, natural gas, and
petroleum over thousands of years. For this reason,
these types of energy sources are often known as
fossil fuels. Natural gas and coal may also be used to
produce petroleum liquids, although crude oil is the
most common source.
An important component of nuclear power comes
from the nonrenewable source uranium, whose atoms
are divided (via nuclear fission) to generate heat
and electricity. Uranium is thought to have originated
billions of years ago during the formation of stars,
according to scientists. There is a lot of uranium in the
Earth’s crust, but much of it is difficult or prohibitively
costly to extract and turn into nuclear fuel.
Human history has relied heavily on biomass from
plants, which was used primarily for heating, transport,
and plowing, as well as to feed livestock. In the early
1800s, nonrenewable sources started to displace
renewable energy in the United States, and by the
early 1900s, fossil fuels became the primary energy
source.
Although biomass was still used for heating houses,
it was mostly in rural regions and as a supplement in
metropolitan areas. A substantial part of the increase
in biomass and other renewable energy use in the
1980s was due to incentives for their use, particularly
in the production of electric power. In an effort to
limit and prevent carbon dioxide emissions, several
nations are increasing the usage of renewable energy.
Five key sources of clean, renewable
energy
The following are the most important
categories of renewable energy:
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