World energy resources and consumption
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Rate of world energy usage in terawatts (TW), 1965-2005[1]
Global energy usage in successively increasing detail[2][3]
Energy intensity of different economies The graph shows the ratio between energy usage
and GNP for selected countries. GNP is based on 2004 purchasing power parity and 2000
dollars adjusted for inflation.[4]
Energy consumption per capita versus the GNP per capita The graph plots the per capita
energy versus the per capita income for all countries with more than 20 million inhabitants,
the data more than 90% of the world's population. The image shows the broad relation
between wealth and energy consumption.[5]
GDP and energy consumption in Japan from 1958 - 2000 The data shows the correlation
between GDP and energy use; however, it also shows that this link can be broken. After the
oil shocks of 1973 and 1979 the energy use stagnated while Japan's GDP continued to grow,
after 1985, under the influence of the then much cheaper oil, energy use resumed its historical
relation to GDP.[6]
Worldwide energy sources (TW)(2004)[4]
Remaining Oil Breakdown of the remaining 57 ZJ oil on the planet. The annual oil
consumption was 0.18 ZJ in 2005. There is significant uncertainty surrounding these numbers.
The 11 ZJ of future additions to the recoverable reserves could be optimistic.[7][8]
Renewable energy sources worldwide at the end of 2008 Source: REN21[9]
Available renewable energy The volume of the cubes represent the amount of available
geothermal, hydropower, wind and solar energy in TW, although only a small portion is
recoverable. The small red cube shows the proportional global energy consumption.[10]
Solar energy as it is dispersed on the planet and radiated back to space. Values are in PW
=1015 watt.[11]
In 2008, total worldwide energy consumption was 474 exajoules (5×1020 J) with 80 to 90
percent derived from the combustion of fossil fuels.[1] This is equivalent to an average power
consumption rate of 15 terawatts (1.504×1013 W). Not all of the world's economies track their
energy consumption with the same rigor, and the exact energy content of a barrel of oil or a
ton of coal will vary with quality.
Most of the world's energy resources are from the sun's rays hitting earth. Some of that energy
has been preserved as fossil energy, some is directly or indirectly usable; for example, via
wind, hydro- or wave power. The term solar constant is the amount of incoming solar
electromagnetic radiation per unit area, measured on the outer surface of Earth's atmosphere,
in a plane perpendicular to the rays. The solar constant includes all types of solar radiation,
not just visible light. It is measured by satellite to be roughly 1366 watts per square meter,
though it fluctuates by about 6.9% during a year—from 1412 W m−2 in early January to 1321
W m−2 in early July, due to the Earth's varying distance from the sun, and by a few parts per
thousand[clarification needed] from day to day. For the whole Earth, with a cross section of
127,400,000 km2, the total energy rate is 174 petawatts (1.740×1017 W), plus or minus 3.5%.
This value is the total rate of solar energy received by the planet; about half, 89 PW, reaches
the Earth's surface.[citation needed]
The estimates of remaining non-renewable worldwide energy resources vary, with the
remaining fossil fuels totaling an estimated 0.4 YJ (1 YJ = 1024J) and the available nuclear
fuel such as uranium exceeding 2.5 YJ. Fossil fuels range from 0.6-3 YJ if estimates of
reserves of methane clathrates are accurate and become technically extractable. Mostly thanks
to the Sun, the world also has a renewable usable energy flux that exceeds 120 PW (8,000
times 2004 total usage), or 3.8 YJ/yr, dwarfing all non-renewable resources.
Contents
[hide]



1 Consumption
o 1.1 Primary energy
 1.1.1 Fossil fuels
 1.1.2 Nuclear power
 1.1.3 Renewable energy
 1.1.3.1 Hydropower
 1.1.3.2 Biomass and biofuels
 1.1.3.3 Wind power
 1.1.3.4 Solar power
 1.1.3.5 Geothermal
o 1.2 By country
o 1.3 By sector
2 Resources
o 2.1 Fossil fuel
 2.1.1 Coal
 2.1.2 Oil
 2.1.3 Sustainability
o 2.2 Nuclear power
 2.2.1 Nuclear fission
 2.2.2 Nuclear fusion
o 2.3 Renewable resources
 2.3.1 Solar energy
 2.3.2 Wind power
 2.3.3 Wave and tidal power
 2.3.4 Geothermal
 2.3.5 Biomass
 2.3.6 Hydropower
3 Alternative energy paths




4 See also
5 References
6 Further reading
7 External links
[edit] Consumption
[edit] Primary energy
The United States Energy Information Administration regularly publishes a report on world
consumption for most types of primary energy resources.
Average power in TW[12]
Fuel type
1980
2004
2006
Oil
4.38
5.58
5.74
Gas
1.80
3.45
3.61
Coal
2.34
3.87
4.27
Hydroelectric
0.599
0.933
0.995
Nuclear power
0.253
0.914
0.929
Geothermal , wind,
0.016
solar energy, wood
0.133
0.158
Total
15.0
15.8
9.48
[edit] Fossil fuels
Main article: Fossil fuel
The twentieth century saw a rapid twentyfold increase in the use of fossil fuels. Between 1980
and 2006, the worldwide annual growth rate was 2%. [1] According to the US Energy
Information Administration's 2006 estimate, the estimated 471.8 EJ total consumption in 2004
was divided as follows, with fossil fuels supplying 86% of the world's energy:
Coal fueled the industrial revolution in the 18th and 19th century. With the advent of the
automobile, airplanes and the spreading use of electricity, oil became the dominant fuel
during the twentieth century. The growth of oil as the largest fossil fuel was further enabled
by steadily dropping prices from 1920 until 1973. After the oil shocks of 1973 and 1979,
during which the price of oil increased from 5 to 45 US dollars per barrel, there was a shift
away from oil.[13] Coal, natural gas, and nuclear became the fuels of choice for electricity
generation and conservation measures increased energy efficiency. In the U.S. the average car
more than doubled the number of miles per gallon. Japan, which bore the brunt of the oil
shocks, made spectacular improvements and now has the highest energy efficiency in the
world.[5] From 1965 to 2008, the use of fossil fuels has continued to grow and their share of
the energy supply has increased. From 2003 to 2008, coal, which is one of the dirtiest sources
of energy,[14] was the fastest growing fossil fuel.[15].
[edit] Nuclear power
In 2005 nuclear power accounted for 6.3% of world's total primary energy supply.[16] The
nuclear power production in 2006 accounted 2,658 TWh (23.3 EJ), which was 16% of world's
total electricity production.[17][18] In November 2007, there were 439 operational nuclear
reactors worldwide, with total capacity of 372,002 MWe. A further 33 reactors were under
construction, 94 reactors were planned and 222 reactors were proposed.[17] The People in the
US have been and are being led to believe that the development of nuclear power in the world
essentially ended with Chernobyl, but several CANDU reactors have been reactivated in
Canada and two new ones put into service in China. One CANDU, at least, is being finished
in Romania. Another CANDU is being refurbished in Canada. A new reactor is being built in
France and another ordered. A new design one is being built in Finland, but is far behind
schedule. Italy has formed a consortium with French companies to build new reactors in Italy.
China has built other reactors and ordered two new ones from Russia. Japan has continued
operating and building nuclear power plants, and both Canada and Australia are expanding
their uranium mines and exports. After new elections, the German government is revising its
intent to continue using nuclear power and has bought a lot of it from France. The US has
enrichment facilities being planned as well as new nuclear reactors. A Canadian company has
selected a site for a nuclear reactor to generate heat for bitumen extraction from tar sands. The
US has an approved operational repository in a deep salt bed for nuclear radiative materials of
all forms that has received materials of many kinds, but is only authortized for governmental
military materials, but contains materials from reactor prototypes of commercial reactors. If
coal, gas or oil electric generators are replaced by nuclear power plants, they must be
considered CO2 negative when a pound of recycled military plutonium or uranium can
replace 3,000,000 pounds of coal energy, and the fossil energy used in construction and fuel
mining and preparation is replaced by CO2 free generation in a few months. The IAEA has
news of all these reactors and more. Former anti nuclear activist, Gwyneth Cravens, revisited
her anti nuclear thoughts in her book "Power to Save the World" in 2007 because of chance
meeting with a nuclear scientist and subsequent discussions about energy and concerns of
global warming and heath effects from using fossil fuels.
[edit] Renewable energy
Main article: Renewable energy
In 2004, renewable energy supplied around 7% of the world's energy consumption.[19] The
renewables sector has been growing significantly since the last years of the 20th century, and
in 2005 the total new investment was estimated to have been 38 billion US dollars. Germany
and China lead with investments of about 7 billion US dollars each, followed by the United
States, Spain, Japan, and India. This resulted in an additional 35 GW of capacity during the
year.[3]
[edit] Hydropower
Main article: hydropower
Worldwide hydroelectricity consumption reached 816 GW in 2005, consisting of 750 GW of
large plants, and 66 GW of small hydro installations. Large hydro capacity totaling 10.9 GW
was added by China, Brazil and India during the year, but there was a much faster growth
(8%) in small hydro, with 5 GW added, mostly in China where some 58% of the world's small
hydro plants are now located.[3]
In the Western world, although Canada is the largest producer of hydroelectricity in the
world, the construction of large hydro plants has stagnated due to environmental concerns.[20]
The trend in both Canada and the United States has been to micro hydro because it has
negligible environmental impacts and opens up many more locations for power generation. In
British Columbia alone the estimates are that micro hydro will be able to more than double
electricity production in the province.
[edit] Biomass and biofuels
Main articles: biomass and biofuel
Until the end of the nineteenth century biomass was the predominant fuel, today it has only a
small share of the overall energy supply. Electricity produced from biomass sources was
estimated at 44 GW for 2005. Biomass electricity generation increased by over 100% in
Germany, Hungary, the Netherlands, Poland and Spain. A further 220 GW was used for
heating (in 2004), bringing the total energy consumed from biomass to around 264 GW. The
use of biomass fires for cooking is excluded.[3]
World production of bioethanol increased by 8% in 2005 to reach 33 billion litres (8.72
billion US gallons), with most of the increase in the United States, bringing it level to the
levels of consumption in Brazil.[3] Biodiesel increased by 85% to 3.9 billion litres (1.03 billion
US gallons), making it the fastest growing renewable energy source in 2005. Over 50% is
produced in Germany.[3]
[edit] Wind power
Main article: Wind power
According to the World Wind Energy Association, the installed capacity of wind power
increased by 29 % from the end of 2007 to the end of 2008 to total 121 GW, with over half
the increase in the United States, Spain and China.[21] Doubling of capacity took about three
years. The total installed capacity is approximately three to eight times that of the actual
average power produced as the nominal capacity represents peak output; actual capacity is
generally from 13[22]-40% of the nominal capacity.[23]
[edit] Solar power
Main article: Solar energy
The available solar energy resources are 3.8 YJ/yr (120,000 TW). Less than 0.02% of
available resources are sufficient to entirely replace fossil fuels and nuclear power as an
energy source. Assuming that our rate of usage in 2005 remains constant, we will run out of
conventional oil in 40 years (2045), coal in 154 yrs (2159). In practice neither will actually
run out, as natural constraints will force production to decline as the remaining reserves
dwindle.[24][25][26]
In 2007 grid-connected photovoltaic electricity was the fastest growing energy source, with
installations of all photovoltaics increasing by 83% in 2009 to bring the total installed
capacity to 15 GW. Nearly half of the increase was in Germany, now the world's largest
consumer of photovoltaic electricity (followed by Japan). Solar cell production increased by
50% in 2007, to 3,800 megawatts, and has been doubling every two years.[27]
The world's most powerful photovoltaic solar power plant is the 20 megawatt Beneixama
photovoltaic power plant in Spain, although a 116 megawatt plant is under construction in
southern Portugal, one of the sunniest places in Europe.[28] The largest photovoltaic
installation in North America is the 18 megawatt Nellis Solar Power Plant.
Since 1991 the largest solar power plant has been the 354 megawatt Solar Energy Generating
Systems, in the Mojave Desert in California, using parabolic trough collectors. Stirling
Energy Systems is currently building a 500MW solar power plant using solar concentrators
and Stirling engines with a 750MW plant also planned.
The consumption of solar hot water and solar space heating was estimated at 88 GWt
(gigawatts of thermal power) in 2004. The heating of water for unglazed swimming pools is
excluded.[3]
[edit] Geothermal
Main article: Geothermal power
Geothermal energy is used commercially in over 70 countries.[29] In the year 2004, 200 PJ (57
TWh) of electricity was generated from geothermal resources, and an additional 270 PJ of
geothermal energy was used directly, mostly for space heating. In 2007, the world had a
global capacity for 10 GW of electricity generation and an additional 28 GW of direct
heating, including extraction by geothermal heat pumps.[3][30] Heat pumps are small and
widely distributed, so estimates of their total capacity are uncertain and range up to
100 GW.[29] Heat pump capacity factors are low since demand is seasonal.
[edit] By country
See also: Energy by country and List of countries by energy consumption per capita
Energy consumption is loosely correlated with gross national product, but there is a large
difference even between the most highly developed countries, such as Japan and Germany
with 6 kW per person and United States with 11.4 kW per person. In developing countries
such as India the per person energy use is closer to 0.7 kW. Bangladesh has the lowest
consumption with 0.2 kW per person.
The US consumes 25% of the world's energy with a share of global GDP at 22% and a share
of the world population at 5%. The most significant growth of energy consumption is
currently taking place in China, which has been growing at 5.5% per year over the last 25
years. Its population of 1.3 billion people (20% of the world population) is consuming energy
at a rate of 1.6 kW per person.
Over the past four years, electricity consumption per capita in the U.S. has decreased about
1% per year between 2004 and 2008. Power consumption is projected to hit 4,333,631 million
kilowatt hours by 2013, an annual growth rate of 1.93% for the next five years. Consumption
increased from 3,715,949 in 2004 to an expected 3,937,879 million kilowatt hours per year in
2008, an increase of about 1.5% per year. The rate of increase has been steadily decreasing - it
was 2.5% in the 1990s.[31] U.S. population has been increasing about 1.3% per year, a total
increase of about 6.7% over five years.[32] The decrease has been mostly due to efficiency
increases. Compact fluorescent bulbs, for example use about one third as much electricity as
incandescents. LED bulbs, however, use about one tenth as much, and over their 50,000 to
100,000 hour lifetime are cheaper than compact fluorescents.
One metric of efficiency is energy intensity. This is a measure of the amount of energy it
takes a country to produce a dollar of gross domestic product.
[edit] By sector
Industrial users (agriculture, mining, manufacturing, and construction) consume about 37% of
the total 15 TW. Personal and commercial transportation consumes 20%; residential heating,
lighting, and appliances use 11%; and commercial uses (lighting, heating and cooling of
commercial buildings, and provision of water and sewer services) amount to 5% of the total.
[33]
The other 27% of the world's energy is lost in energy transmission and generation. In 2005,
global electricity consumption averaged 2 TW. The energy rate used to generate 2 TW of
electricity is approximately 5 TW, as the efficiency of a typical existing power plant is around
38%.[34] The new generation of gas-fired plants reaches a substantially higher efficiency of
55%. Coal is the most common fuel for the world's electricity plants.[35]
[edit] Resources
[edit] Fossil fuel
Main article: Fossil fuel
Remaining reserves of fossil fuel are estimated as: Assessment Team |url=
http://pubs.usgs.gov/dds/dds-060/ESpt4.html#Table | accessdate=2007-01-18}}</ref>
Fuel
Coal
Energy reserves in
ZJ
290.0
Oil
18.4
Gas
15.7
Significant uncertainty exists for these numbers. The estimation of the remaining fossil fuels
on the planet depends on a detailed understanding of the Earth crust. This understanding is
still less than perfect. While modern drilling technology makes it possible to drill wells in up
to 3 km of water to verify the exact composition of the geology, one half of the ocean is
deeper than 3 km, leaving about a third of the planet beyond the reach of detailed analysis.
The Energy Watch Group reports suggest that supplying the demand for oil may be
insufficient,[36] and that uranium resources would be exhausted within 70 years.[37] However,
these views are greatly at variance with those of most industry observers.
[edit] Coal
Main article: World coal reserves
Coal is the most abundant fossil fuel. This was the fuel that launched the industrial revolution
and has continued to grow in use; China, which already has many of the world's most polluted
cities,[38] was in 2007 building about two coal fired power plants every week.[39][40] Coal is the
fastest growing fossil fuel and its large reserves would make it a popular candidate to meet the
energy demand of the global community, short of global warming concerns and other
pollutants.[41] According to the International Energy Agency the proven reserves of coal are
around 909 billion tonnes, which could sustain the current production rate for 155 years,[42]
although at a 5% growth per annum this would be reduced to 45 years, or until 2051. With the
Fischer-Tropsch process it is possible to make liquid fuels such as diesel and jet fuel from
coal. Citing concern for global warming, the Stop Coal campaign calls for a moratorium on
the construction of any new coal plants and on the phase out of all existing plants.[43] In the
United States, 49% of electricity generation comes from burning coal.[44]
[edit] Oil
See also: Oil reserves and Peak oil
It is estimated that there may be 57 ZJ of oil reserves on Earth (although estimates vary from
a low of 8 ZJ,[1] consisting of currently proven and recoverable reserves, to a maximum of
110 ZJ[citation needed]) consisting of available, but not necessarily recoverable reserves, and
including optimistic estimates for unconventional sources such as tar sands and oil shale.
Current consensus among the 18 recognized estimates of supply profiles is that the peak of
extraction will occur in 2020 at the rate of 93-million barrels per day (mbd). Current oil
consumption is at the rate of 0.18 ZJ per year (31.1 billion barrels) or 85-mbd.
There is growing concern that peak oil production may be reached in the near future, resulting
in severe oil price increases.[45] A 2005 French Economics, Industry and Finance Ministry
report suggested a worst-case scenario that could occur as early as 2013.[46] There are also
theories that peak of the global oil production may occur in as little as 2–3 years. The ASPO
predicts peak year to be in 2010. Some other theories present the view that it has already
taken place in 2005. World crude oil production (including lease condensates) according to
US EIA data decreased from a peak of 73.720 mbd in 2005 to 73.437 in 2006, 72.981 in 2007,
73.697 in 2008.[47] According to peak oil theory, increasing production will lead to a more
rapid collapse of production in the future, while decreasing production will lead to a slower
decrease, as the bell-shaped curve will be spread out over more years.
In a stated goal of increasing oil prices to $75/barrel, which had fallen from a high of $147 to
a low of $40, OPEC announced decreasing production by 2.2 mbd beginning January 1,
2009.[48]
[edit] Sustainability
Political considerations over the security of supplies, environmental concerns related to global
warming and sustainability will move the world's energy consumption away from fossil fuels.
The concept of peak oil shows that we have used about half of the available petroleum
resources, and predicts a decrease of production.
A government led move away from fossil fuels would most likely create economic pressure
through carbon emissions trading and green taxation. Some countries are taking action as a
result of the Kyoto Protocol, and further steps in this direction are proposed. For example, the
European Commission has proposed that the energy policy of the European Union should set
a binding target of increasing the level of renewable energy in the EU's overall mix from less
than 7% today to 20% by 2020.[49]
The antithesis of sustainability is a disregard for limits, commonly referred to as the Easter
Island Effect, which is the concept of being unable to develop sustainability, resulting in the
depletion of natural resources.[50]
[edit] Nuclear power
See also: Nuclear power and Nuclear energy policy
[edit] Nuclear fission
See also: Nuclear fuel
The International Atomic Energy Agency estimates the remaining uranium resources to be
equal to 2500 ZJ.[51] This assumes the use of breeder reactors which are able to create more
fissile material than they consume. IPCC estimated currently proved economically
recoverable uranium deposits for once-through fuel cycles reactors to be only 2 ZJ. The
ultimately recoverable uranium is estimated to be 17 ZJ for once-through reactors and 1000
ZJ with reprocessing and fast breeder reactors. [52]
Resources and technology do not constrain the capacity of nuclear power to contribute to
meeting the energy demand for the 21st century. However, political and environmental
concerns about nuclear safety and radioactive waste started to limit the growth of this energy
supply at the end of last century, particularly due to a number of nuclear accidents. Concerns
about nuclear proliferation (especially with plutonium produced by breeder reactors) mean
that the development of nuclear power by countries such as Iran and Syria is being actively
discouraged by the international community.[53]
[edit] Nuclear fusion
Fusion power is the process driving our sun and other stars. It generates large quantities of
heat by fusing the nuclei of hydrogen or helium isotopes, which may be derived from
seawater. The heat can theoretically be harnessed to generate electricity. The temperatures
and pressures needed to sustain fusion make it a very difficult process to control. The
tantalizing potential of fusion is its theoretical ability to supply vast quantities of energy, with
relatively little pollution.[54] Although both the United States and the European Union, along
with other countries, are supporting fusion research (such as investing in the ITER facility),
according to one report, inadequate research has stalled progress in fusion research for the
past 20 years.[55]
[edit] Renewable resources
Main article: Renewable resource
Renewable resources are available each year, unlike non-renewable resources which are
eventually depleted. A simple comparison is a coal mine and a forest. While the forest could
be depleted, if it is managed properly it represents a continuous supply of energy, vs the coal
mine which once it has been exhausted is gone. Most of earth's available energy resources are
renewable resources. Renewable resources account for more than 93 percent of total U.S.
energy reserves. Annual renewable resources were multiplied times thirty years for
comparison with non-renewable resources. In other words, if all non-renewable resources
were uniformly exhausted in 30 years, they would only account for 7 percent of available
resources each year, if all available renewable resources were developed.[56]
[edit] Solar energy
Main article: Solar energy
Renewable energy sources are even larger than the traditional fossil fuels and in theory can
easily supply the world's energy needs. 89 PW[57] of solar power falls on the planet's surface.
While it is not possible to capture all, or even most, of this energy, capturing less than 0.02%
would be enough to meet the current energy needs. Barriers to further solar generation include
the high price of making solar cells and reliance on weather patterns to generate electricity.
Also, solar generation does not produce electricity at night, which is a particular problem in
high northern and southern latitude countries; energy demand is highest in winter, while
availability of solar energy is lowest. This could be overcome by buying power from countries
closer to the equator during winter months. Globally, solar generation is the fastest growing
source of energy, seeing an annual average growth of 35% over the past few years. Japan,
Europe, China, U.S. and India are the major growing investors in solar energy. Advances in
technology and economies of scale, along with demand for solutions to global warming, have
led photovoltaics to become the most likely candidate to replace nuclear and fossil fuels.[58]
[edit] Wind power
Main article: Wind power
The available wind energy estimates range from 300 TW to 870 TW.[57][59] Using the lower
estimate, just 5% of the available wind energy would supply the current worldwide energy
needs. Most of this wind energy is available over the open ocean. The oceans cover 71% of
the planet and wind tends to blow stronger over open water because there are fewer
obstructions.
[edit] Wave and tidal power
Main articles: Wave power and Tidal power
At the end of 2005, 0.3 GW of electricity was produced by tidal power. [3] Due to the tidal
forces created by the Moon (68%) and the Sun (32%), and the Earth's relative rotation with
respect to Moon and Sun, there are fluctuating tides. These tidal fluctuations result in
dissipation at an average rate of about 3.7 TW. [60] As a result, the rotational speed of the
Earth decreases, and the distance of the Moon to the Earth increases[citation needed], on geological
time scales. In several billion years, the Earth will rotate at the same speed as the Moon is
revolving around it. So, several TW of tidal energy can be produced without having a
significant effect on celestial mechanics[citation needed].
Another physical limitation is the energy available in the tidal fluctuations of the oceans,
which is about 0.6 EJ (exajoule). [61] Note this is only a tiny fraction of the total rotational
energy of the Earth. Without forcing, this energy would be dissipated (at a dissipation rate of
3.7 TW) in about four semi-diurnal tide periods. So, dissipation plays a significant role in the
tidal dynamics of the oceans. Therefore, this limits the available tidal energy to around 0.8
TW (20% of the dissipation rate) in order not to disturb the tidal dynamics too much.[citation
needed]
Waves are derived from wind, which is in turn derived from solar energy, and at each
conversion there is a drop of about two orders of magnitude in available energy. The total
power of waves that wash against our shores add up to 3 TW. [62]
[edit] Geothermal
Main article: Geothermal power
Estimates of exploitable worldwide geothermal energy resources vary considerably,
depending on assumed investements in technology and exploration and guesses about
geological formations. According to a 1999 study, it was thought that this might amount to
between 65 and 138 GW of electrical generation capacity 'using enhanced technology'.[63]
Other estimates range from 35 to 2000 GW of electrical generation capacity, with a further
potential for 140 EJ/year of direct use.[30]
A 2006 report by MIT that took into account the use of Enhanced Geothermal Systems (EGS)
concluded that it would be affordable to generate 100 GWe (gigawatts of electricity) or more
by 2050, just in the United States, for a maximum investment of 1 billion US dollars in
research and development over 15 years.[29] The MIT report calculated the world's total EGS
resources to be over 13 YJ, of which over 200 ZJ would be extractable, with the potential to
increase this to over 2 YJ with technology improvements - sufficient to provide all the world's
energy needs for several millennia.[29] The total heat content of the Earth is 13,000,000 YJ.[30]
[edit] Biomass
Main articles: biomass and biofuel
Production of biomass and biofuels are growing industries as interest in sustainable fuel
sources is growing. Utilizing waste products avoids a food vs fuel trade-off, and burning
methane gas reduces greenhouse gas emissions, because even though it releases carbon
dioxide, carbon dioxide is 23 times less of a greenhouse gas than is methane. Biofuels
represent a sustainable partial replacement for fossil fuels, but their net impact on greenhouse
gas emissions depends on the agricultural practices used to grow the plants used as feedstock
to create the fuels. While it is widely believed that biofuels can be carbon-neutral, there is
evidence that biofuels produced by current farming methods are substantial net carbon
emitters.[64][65][66] Geothermal and biomass are the only two renewable energy sources which
require careful management to avoid local depletion.[67]
[edit] Hydropower
Main article: hydropower
In 2005, hydroelectric power supplied 16.4% of world electricity.[68]
[edit] Alternative energy paths
Denmark and Germany have started to make investments in solar energy, despite their
unfavorable geographic locations. Germany is now the largest consumer of photovoltaic cells
in the world. Denmark and Germany have installed 3 GW and 17 GW of wind power
respectively. In 2005, wind generated 18.5% of all the electricity in Denmark.[69] Brazil
invests in ethanol production from sugar cane which is now a significant part of the
transportation fuel in that country. Starting in 1965, France made large investments in nuclear
power and to this date three quarters of its electricity comes from nuclear reactors.[70]
Switzerland is planning to cut its energy consumption by more than half to become a 2000watt society by 2050 and the United Kingdom is working towards a zero energy building
standard for all new housing by 2016. In 2005, the Swedish government announced the oil
phase-out in Sweden with the intention to become the first country to break its dependence on
fossil fuel by 2020.