Renewable energy sources include energy from the sun, wind, water, and plant- and waste-based materials that reproduce themselves constantly. Non-renewable sources like coal and oil are being used faster than they can replenish and will eventually run out. While non-renewables like oil currently supply over 40% of the US's energy, renewable alternatives like hydropower, bioenergy, wind, solar and geothermal are growing in popularity and importance as cleaner, sustainable options.

1. RENEWABLE AND NON-RENEWABLE ENERGY.
Energy resources can be described as renewable and non-renewable. Renewable energy
sources are those which are continually being replaced such as energy from the sun (solar)
and wind. If an energy resource is being used faster than it can be replaced (for example, coal
takes millions of years to form) then it will eventually run out. This is called a non-renewable
energy source.
These days most people are familiar with the concept of sustainable development,
which on broad terms refers to the type of development that takes into the account the impacts
that human enterprise has on the Earth, trying to mitigate it as much as possible. It means that
the planet’s vulnerability to human activity is factored in. Another equally important concept
is the one that differentiates between renewable and non-renewable energy. Since the early
days of the Industrial Revolution, renewable and non-renewable energy have been powering
the world’s economies. In the developed countries in the northern hemisphere, non-renewable
energy has played a more significant role since modern machines were designed to be
powered by coal and fossil fuels. These non-renewable sources of power have been the main
sources of heat-trapping greenhouse gases that cause climate change.
In America, oil (fossil fuel) remains the biggest source of energy, supplying more than
40% of the total. Besides, more than 99% of cars and trucks in the country run on oil. Apart
from pollution, oil resources are finite (hence, non-renewable), therefore finding cleaner,
renewable alternatives is not only environmentally correct, but also necessary. Since the
1980s we have grown more acutely aware of the need to shift the economy to renewable
energy, that is, energy that relies on sources that reproduce themselves in self-perpetuating
cycles, such as water, sun power, wind and plant- and waste-based energy.
Hydropower is the largest source of renewable energy currently in place. In Norway,
for instance, it accounts for 99% of the country’s energy matrix. In the United States it
produces enough power for 28 million households. Bioenergy is also very popular. This
generic term refers to any type of renewable energy that is made out of raw materials such as
agricultural crops, crop wastes or residues, wood wastes, municipal wastes etc. It’s more
commonly available as part of a fuel blend (for instance, ethanol and gas). Wind and solar are
also much-talked about sources of renewable energy, although they still account for a
relatively small portion of the electricity being produced worldwide. But it’s growing. In
Denmark, for instance, wind accounted for 18.9% of electricity production in 2008.

2. Geothermal is also growing in popularity. Geothermal refers to the energy tapped from
the heat of the Earth. It is extracted from shallow ground, hot water or hot rock that exists a
few miles beneath the Earth’s surface. It can be explored anywhere. Hydrogen is also a much
coveted source of renewable energy. It can be made from other renewable sources such as
wind, solar, geothermal as well as more traditional sources such as nuclear power and fossil
fuels. There is considerable research into the use of hydrogen to power passenger vehicles,
but storage remains a technical challenge to be overcome. At present renewable and non-
renewable energy co-exist in unequal proportions, with the latter still ruling the world. But as
technology develops and renewable energy becomes more scalable and sustainable, the
balance will start to tip in its favor.