Energy is one of the most important Pre-requisites of life. Currently the sources of energy in global use are:
(1) Fossil fuels (coal, oil and natural gas) – 88%
(2) Nuclear energy (Fission and fusion of atoms) – 05%
(3) Other sources (hydel, tidal, wind, geothermal, solar, fuel wood, solid waste and biomass conversion energy) – 07%
Concerns about the adverse environmental and social consequences of fossil fuel use, such as air pollution or mining accidents, and about the finite nature of supplies, have been voiced intermittently for several countries. But it was not until the 1970s,with the steep price rises of the “oil crisis “and the advent of the environmental movement, that humanity began to take seriously the possibility of fossil fuels “running out” and that their continued use could be destabilizing the planet’s natural ecosystem and the global climate. Continuing concerns about the “sustainability “of both fossil and nuclear fuels use have been a major catalyst of renewed interest in the renewable energy sources in recent decades.
Sustainable Energy
Sustainable energy refers to energy that can be used without running out in the future. These energy sources also are called renewable energy. Mostly these sustainable resources use what is already out in our environment or our waste to generate energy. Sustainable energy source is that which can be provided without change to the earth’s biosphere. That is not substantially depleted by continued use, does not entail significant pollutant emissions or other environmental problems, and does not involve the perpetuation of substantial health hazards or social injustices.
Solar Power
One of the most popular sources of renewable energy, solar power is used throughout the world already. However, solar panels that are used are not necessarily super efficient... yet. People are researching not only how to make solar panels more efficient, but also how to print solar panels easily and cheaply (even on sheets of paper!) and how to use solar on homes and in work places. Currently, there are devices on the market to allow people to power laptops, cell phones, and more via mobile solar panels. Some even suction to windows; others include solar panels embedded in clothing or backpacks. Solar energy is an attractive renewable energy source for the future.
Wind Power
Wind power is another very popular source of renewable energy. Most people know about solar or wind power as renewable energy sources. Wind power doesn't necessarily only come from tall windmills either. New devices are making wind energy as easy to capture as placing fan-like windmills on the side of a house or apartment.
Tidal Power
They generate power by rapidly-moving water. This energy source isn't widely used yet, but is thought to be more consistent than either wind or solar power.
Geothermal Power
A person gets power from geothermal energy by taking it out of the earth in a natural way. It can be done to give heat to a home or produce energy on a wider scale in a geothermal power plant. It used to be limited to areas that were near edges of tectonic plates. The only downside to geothermal energy is that drilling for it can be expensive. However, the profits from geothermal can outweigh the risks and costs because a large geothermal power plant can power whole cities.
Energy from biomass
Biomass is plant matter produced as a result of photosynthesis. Some of it can be burnt to provide heat, for example wood, agricultural waste. Biomass can also be used for power generation or converted into alcohol (liquid or methane gas) to be used as fuel. Since these are obtained from plant material, they are called bio-fuels. Biomass is renewable energy and shall be available as long as plants grow on earth. Thus for supplying fuel wood, fast growing trees like oil palm, species such as Euphorbia,Jatropha etc. are planted. Another use of biomass as fuel is to collect agricultural waste and crop residues and animal manure.

Organic wastes, sewage and any other solid biomass can be converted by bacteria into bio-fuels such as biogas. Biogas digesters are large vessels in which organic wastes (plants and animals waste) are made to undergo bacterial fermentation and produce biogas which can be used for heating and cooking. Biogas is a mixture of methane and Carbon-di-oxide. Methane can be obtained by anaerobic (in absence of air) digestion of manure and sludge of sewage treatment units by means of anaerobic bacteria. Recently, the idea of using ethanol as car fuel is doing the rounds. It is made from sugar cane, sorghum, corn or beet root by fermentation and distillation.

Source of




Nuclear energy

Nuclear fission
(splitting of atom) and
Nuclear fusion

No air pollution
Fuel efficient

•High cost of construction of nuclear plant.
• Fear of security and nuclear accidents.
•Problem of safe disposal of nuclear waste.

Hydel power or

Dams built on river for
electricity generation

World’s hydro
electricity capacity

• Ecosystems behind dams disturbed.
• Human settlements up rooted for building dam.
• Habitat loss and consequent biodiversity loss.
• Developmental cost high.
• Fertile farm  land lost and amount of nutrient rich silt on down river agricultural fields reduced.

Solar energy

From natural sunlight

Environment friendly
Ample or unlimited availability.

 • Limited capacity for storage of sunlight.
• Cloud cover may man usefulness.
•Collecting equipment expensive.

Wind energy

Fans for directing
winds in use from long
for irrigation crops

• No pollution
• Available for free

• Not available everywhere or intermittently available.
• Fans of wind mills visual hazards for flying birds and aero planes (visual pollution).

Tidal energy

Harnessing tidal
power by suitable

Free and clean

• Structures (plant) used for harnessing energy expensive.
• Plant disrupts natural flow of estuary and concentrate pollutants in the area.


Wells drilled to trap steam which powers electrical generators.
Steam naturally
produced from
underground water
which gets heated due
to very high
temperature that region.

Environment friendly

• Steam contains Hydrogen Sulphide (H2S) having odor of rotten eggs.
• Minerals in the steam corrosive to pipe lines and equipment causing maintenance problems.
• Minerals in the water toxic to fish.

(1) Fuel wood

Cutting trees for fuel
wood and burning
them straight away

Cheap so popular in
under developed and
developing countries

• Comparatively low level of energy.
• Bulky so difficult to transport.
• Burning wood causes air pollution.
• Destruction of forests to obtain fuel wood and so desertification.
• Release lot of fly ash.

(2) Biomass

Obtaining energy from chemical energy.
Stored in biomass (or live material). Burned
directly for cooking or
to produce electricity
converted to ethanol or
methane (biogas)

Renewable energy

• May lead to food shortage because nutrients not returned to soil from biomass.
• Growing maize for ethanol requires more energy expenditure than the amount of energy in the form of alcohol retrieved.
• Land for growing food used for growing
Biomass for conversion into fuel.


Waste sorted and
burnable material

Decreases cost of
fresh disposal
• Reduces need for
land fill sites

• Causes air pollution for burning releases CO2 and other gases.
• Waste such as bleached paper and plastics have chlorine containing compounds which form dioxins which are highly toxic and suspected to be carcinogenic.

It is the energy from sources which are not expected to be depleted in a timeframe relevant to the human race, and which therefore contribute to the sustainability of all species. These sources generally include all renewable sources such as solar power, wind power, wave power, geothermal power, tidal power and others. Although the energy from nuclear fission and fusion processes meet the requirement of sustainability, these are not generally seen regarded as sustainable energy sources due to the controversy over the process as these could potentially involve the nuclear risks.
Future of Alternative Energy: Report
“Residential energy use in the United States will increase 25 percent by the year 2025, according to U.S. Department of Energy (DOE) forecasts. A small but increasing share of that extra power will trickle in from renewable sources like wind, sunlight, water, and heat in the ground.” National Geographic News
Sustainable Energy from Various sources
An overview of various sustainable energy sources such as hydroelectric, solar, wind and other sources,