The existing reserves of conventional fossil fuels are estimated at:[6]​.

There is significant uncertainty to these data. Estimating the remaining fossil fuel on the planet depends on a detailed understanding of the Earth's crust. This understanding is still imperfect. While modern drilling technology makes it possible to drill wells into up to 3 km of water to verify the exact composition of the geology, half of the ocean is deeper than 3 km, leaving a third of the planet beyond the scope of detailed analysis. Reports from the Energy Monitoring Group show that oil demands cannot be met[40]​ and that the uranium resource will be exhausted in 70 years.[41]​.

Coal is the most abundant fossil fuel. According to the International Energy Agency, the confirmed reserves of coal are around 909 billion tons, which could maintain the current rate of energy production for 155 years.[42] It was the fuel that fueled the industrial revolution and its use continues to be very important. China, which has one of the most polluted cities in the world,[43]​ built about two coal-fired power plants a week during 2007.[44]​[45]​ However, coal production in China peaked in 2013 and has declined since then.[46]​ Recently, China has canceled the planned construction of more than 100 coal plants, favoring the installation of renewable energy in its place.[46][47][48]​.

Coal nevertheless remains one of the main fossil fuels and its large reserves would make it a favorite candidate to meet the energy demand of the global community, if it were not for concerns about global warming and other pollutants.[49]​ With the Fischer-Tropsch process, liquid fuels such as diesel or aviation fuel can be obtained from coal. The Stop Coal campaign calls for a moratorium on the construction of new coal plants and the abandonment of existing ones, based on concerns about global warming.[50]​ In the United States, 49% of electricity generation comes from burning coal.[51]​.

It is estimated that there may be 57 ZJ of oil reserves on Earth (although estimates vary from the low 8 ZJ,[10] consisting of currently proven and recoverable reserves, to the high of 110 ZJ) consisting of available but not necessarily recoverable reserves, and including optimistic estimates for unconventional sources such as tar sands and oil shales. The current consensus around the 18 recognized estimates of supply profiles is that peak extraction will occur in 2020 at a rate of 93 million barrels per day. Current oil consumption is at a rate of 0.18 ZJ per year (31.1 billion barrels), or 85 million barrels per day.

There is a growing consensus that peak oil production could be reached in the near future, leading to higher oil prices. Oil decreased from 84.63 million barrels per day in 2005 to 84.60 million barrels per day, but grew in 2007 to 84.66 million barrels per day, and is expected to grow to 87.7 million barrels per day in 2009.

Political considerations over security of supplies, and environmental implications related to climate warming and sustainability will eventually shift global energy consumption away from fossil fuels. The peak oil concept shows us that we have used approximately half of the available oil resources, and predicts a decline in production.

A government leading the phase-out of fossil fuels should create economic pressure through carbon emissions trading and eco-taxes. Some countries are developing actions based on the Kyoto Protocol, and there are proposals to go further in this direction. For example, the European Commission has proposed that the European Union's Energy Policy should establish binding targets to raise levels of renewable energy use from the current less than 7% to 20% in 2020.[54]​.

The Easter Island Effect is cited as an example of a culture that was incapable of developing sustainably, destroying practically 100% of its natural resources.[55]​.

According to estimates by the International Atomic Energy Agency, the equivalent of 2,500 ZJ of uranium remains.[56] This assumes the use of the fast breeder reactor, which is capable of generating more fissile material than it consumes. The IPCC estimates that currently proven economically recoverable uranium deposits for direct fuel cycle reactors reach only up to 2 ZJ. The ultimately recoverable uranium is estimated at 17 ZJ for direct cycle reactors and 1000 ZJ for fast breeder reactors that perform reprocessing.[57]​.

Neither resources nor technology limit nuclear energy's ability to help meet energy demand throughout the century. Even so, political and environmental implications regarding nuclear safety and radioactive waste began to limit the growth of this energy supply at the end of the last century, especially due to certain nuclear accidents. Concerns about nuclear proliferation (especially regarding Plutonium produced by breeder reactors) suggest that the development of nuclear energy by countries such as Iran or Syria is being actively discouraged by the international community.[58]​.

Nuclear fusion is the physical process by which energy is produced in stars, including the Sun. It generates large amounts of heat by fusing the nuclei of hydrogen isotopes. The heat can theoretically be used to generate electricity. The temperatures and pressures necessary to accommodate fusion make it a very difficult process to control and therefore an unsolved technological challenge. The tantalizing potential of fusion is represented by its theoretical ability to deliver large amounts of energy, with relatively little associated pollution.[59] Both the United States of America and the European Union support the research (such as investing in ITER), as well as other countries. According to one report, limited investment has delayed progress in fusion research for the past 20 years, putting it 50 years away from commercial availability.[60]​

renewable resources

Renewable resources are available over time, unlike non-renewable resources. A simple comparison can be that of a coal mine and a forest. While the forest can be depleted, if managed properly it represents a continuous supply of energy, compared to the coal mine which once depleted is gone. Most of the energy resources available on Earth are renewable resources.

Renewable energy sources are even greater than traditional fossil fuels and in theory can easily supply the energy the world needs. 89 PW[61]​ of solar energy reaches the surface of the planet. Although it is not possible to capture all of it, or even most of it, even capturing less than 0.02% of this energy would be enough to meet current energy needs. Obstacles to the development of solar production include dependence on weather factors and lack of space for solar panels in high-demand areas such as cities. Furthermore, solar generation does not produce electricity at night, which is a notable problem for countries located in high boreal and northern latitudes; Energy demand is higher in winter, while the availability of solar energy is lower. Globally, solar generation is the fastest growing energy source, showing an average annual growth of 35% over the past few years. Japan, Europe, China, the United States of America and India are the fastest growing investor countries in solar energy. Advances in technology and economies of scale, as well as the demand for solutions to global warming, have led photovoltaics to become the best candidate to replace nuclear energy and fossil fuels.[62]​.

The available wind energy is estimated to range from 300 TW to 870 TW.[61]​[63]​ Taking into account the lowest estimate, only 5% of the available wind energy could supply the current global energy needs. Most of this wind energy is available over the open ocean. The ocean covers 71% of the planet and the wind tends to blow more intensely over closed waters because it encounters fewer obstacles.

At the end of 2005, 0.3 GW of electricity was produced by tidal energy. Due to the gravitational forces created by the Moon (68%) and the Sun (32%), and the relative rotation of the Earth with respect to the Sun and the Moon, tidal variations occur. These give rise to an average dissipation rate of about 3.7 TW.[64]​ As a result, the Earth's rotation speed decreases, and the distance from the Moon to Earth increases, on geological time scales. In several billion years, the Earth will rotate at the same speed as the Moon rotates around it. Because of this, many TW of tidal energy can be produced without significantly affecting celestial mechanics.

Another physical limitation is the energy available in the tidal fluctuations of the oceans, which is about 0.6 EJ (exajoules).[65] Note that this represents only a small 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 semidiurnal tidal periods. In this way, 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% dissipation rate) in order not to alter the tidal dynamics too much.

Denmark and Germany have begun investing in solar energy, despite their unfavorable geographic locations. Germany is currently the largest consumer of photovoltaic cells in the world. Denmark and Germany have installed 3 GW and 17 GW of wind energy respectively. In 2005, wind generated 18.5% of all electricity in Denmark.[73] Brazil invests in the production of ethanol "Ethanol (fuel)") from cane sugar, and this has become a significant part of the transport fuel used in the country. Starting in 1965, France invested heavily in nuclear energy and to date three-quarters of its electricity comes from nuclear reactors.[11] Switzerland plans to cut its energy consumption by more than half to become a "2000 Watt Society" by 2050 and the United Kingdom is working on achieving specifications for the construction of new homes according to the "Zero Energy Building" principle by 2016. China for its part part, will adhere to a sustainable energy strategy and make active contributions to sustainable energy development and energy security in the world, has outlined a plan to reduce energy consumption in gross domestic product per unit by about 20 percent by 2010, compared with the level of 2005.

In the 20th century, many of these different energy strategies could become more relevant and displace the ubiquitous fossil fuels.

It should be noted that when the Green Revolution transformed agriculture across the planet, between 1950 and 1984, grain production increased by 250%. The energy for this Green Revolution was supplied by fossil fuels in the form of fertilizers (natural gas), pesticides (petroleum), and energy-forced irrigation.[74]​ Peak global hydrocarbon production (Hubbert's Peak Theory) may test Malthus's criticisms.[75]​.

• - Annex: Countries by energy consumption.

• - International Energy Agency. (2006) World Energy Outlook 2006. ISBN 92-64-10989-7.

• - Smile, Vaclav. (2003) Energy at the crossroads MIT Press. ISBN 0-262-19492-9.

• - Tester, Jefferson W. et al. (2005) Sustainable Energy: Choosing Among Options. The MIT Press. ISBN 0-262-20153-4.

• - Yergin, Daniel (1993). The Prize. Simon & Schuster: New York. ISBN 0-671-79932-0.

• - World energy outlook (in English) Archived June 15, 2011 at the Wayback Machine.

• - Official energy statistics from the government of the United States of America (in English).

• - 2006 Annual Energy Report, DOE/EIA-0384(2006), by the Energy Information Administration of the US Department of Energy (PDF).

• - World Energy Statistical Report 2007, BP annual report (in English).

• - Toolbar energy consumption.

• - Balance of European electricity consumption for the first half of 2014.

Contenido

Desde el advenimiento de la revolución industrial, el consumo energético mundial ha crecido de forma continuada. En 1890 el consumo de combustibles fósiles alcanzó al de biomasa utilizada en la industria y en los hogares. En 1900, el consumo energético global supuso 0,7 TW (0,7×10 Watts).[11]​.

Fossil fuels

During the twentieth century, a rapid increase in the use of fossil fuels was observed, which multiplied by twenty. Between 1980 and 2004, annual growth rates were 2%.[10] According to 2006 estimates by the US Energy Information Administration, the estimated 15 TW of total energy consumption for 2004 is divided as follows.

Coal supplied the energy for the industrial revolution in the 2nd centuries. With the arrival of the automobile, airplanes, and the widespread use of electricity, oil became the dominant fuel during the century. The growth of oil as the main fossil fuel was reinforced by the continued decline in its price between 1920 and 1973. After the oil crises of 1973 and 1979, in which the price of oil increased from 5 to 45 US dollars per barrel, there was a retreat in oil consumption.[12] Coal and nuclear energy became the fuels of choice for electricity generation and conservation measures increased the consumption. energy efficiency.

In the US, the average car more than doubled its miles per gallon. Japan, which bore the brunt of the oil crises, made dramatic improvements and now has the highest energy efficiency in the world.[13]​ It has become the fastest growing fossil fuel.[14]​. Despite this, solar photovoltaic energy is rapidly being incorporated as a replacement for fossil fuels as the dominant energy source.[15] Note the above comparison on availability: The total resources of all fossil fuels represent 0.4 YJ in total, while the availability of solar energy is 3.8 YJ per year.

Nuclear power

In 2005, nuclear energy represented 6.3% of the total primary energy supply.[16]​ Nuclear energy production in 2006 reached 2,658 TWh, representing 16% of total global electricity production.[17]​[18]​ In November 2007, 439 nuclear reactors were operational worldwide, with a total capacity of 372,002 MW. There were another 33 reactors under construction, 94 planned and 222 in proposed status.[17] Among the nations that do not currently use it, 25 countries are building them or are proposing to do so.[19] Some countries have announced plans to phase out nuclear power, but to date only Italy has implemented this (although it continues to import electricity from nations with active nuclear power plants).[20] In addition to this, although Austria,[21]​ The Philippines[22]​ and North Korea[23]​ have built nuclear power plants, these countries aborted them before they were commissioned.

Renewable energies

In 2004, renewable energy supply accounted for 7% of global energy consumption.[24] The renewable sector has been growing significantly since the latter years of the century, and in 2005 total new investment was estimated at US$38 billion. Germany and China lead investments with around US$7 billion each, followed by the United States, Spain, Japan and India. This has resulted in 35 GW of additional capacity per year.

World hydroelectric consumption reached 816 GW in 2005, consisting of 750 GW of large plants, and 66 GW of micro-hydroelectric installations. The largest increase in total annual capacity with 10.9 GW was contributed by China, Brazil and India, but there was much faster growth in microhydraulics (8%), with the increase of 5 GW, mainly in China where approximately 58% of all microhydro plants in the world are currently located.

In the West, although Canada is the world's largest hydroelectric producer, the construction of large hydroelectric plants has been paralyzed due to its environmental implications.[25] The trend in both Canada and the United States has been towards microhydraulics given its negligible environmental impact and the incorporation of a multitude of locations for energy generation. In British Columbia alone, it is estimated that microhydro will be capable of more than doubling electricity production in the province.

Until the end of the century, biomass was the predominant fuel; currently it maintains only a small share of the total energy supply. The electricity produced from biomass was estimated at 44 GW for the year 2005. Biomass electricity generation increased by 100% in Germany, Hungary, the Netherlands, Poland and Spain. An additional 20 GW was used for heating (in 2004), bringing the total energy consumed from biomass to around 64 GW. The use of biomass stoves for cooking has not been considered.

Global production of bioethanol "Ethanol (fuel)") increased by 8% to reach 33 billion liters, with the largest increase in the United States, thus reaching the consumption level of Brazil. Biodiesel increased by 85% to 3.9 billion liters, becoming the fastest growing renewable energy in 2005. Around 50% is produced in Germany.

At the end of 2014, the global installed capacity of wind energy was 318 GW.[26]​ This installed capacity doubles approximately every three years.

Denmark generates more than 25% of its electricity through wind energy, and more than 80 countries around the world increasingly use it to provide electricity in their distribution networks,[27]​ increasing their capacity annually at rates above 20%. In Spain, wind energy produced 21.1% of electricity consumption in 2013, becoming the technology with the greatest contribution to meeting demand, even above nuclear energy.[28]​.

The energy resources available through solar energy are 3.8 YJ/year (120,000 TW). Less than 0.02% of available resources are sufficient to replace fossil and nuclear energy as energy sources. Assuming current usage rates remain constant, oil will be exhausted in 35 years, and coal in 200 years according to Hubbert's peak theory. In practice, exhaustion will not be reached, since as the remaining reserves decline, natural limitations will force production to slow down.[29]​[30]​.

By countries

Energy consumption broadly follows the gross national product, although there is a significant difference between the consumption levels of the United States at 11.4 kW per person and those of Japan and Germany at 6 kW per person. In developing countries like India, energy use per person is close to 0.7 kW. Bangladesh has the lowest consumption with 0.2 kW per person.

The United States consumes 25% of the world's energy (with a productivity share of 22% and 5% of the world's population). The amount of water needed represents almost 50% of water used in the US compared to 35% used in agriculture.[35]​ The most significant growth in energy consumption is occurring in China, which has been growing at 5.5% annually for the last 25 years. Its population of 1.3 billion people currently consumes at a rate of 1.6 kW per person.

Over the past four years, per capita electricity consumption in the US has decreased at 1% annually between 2004 and 2008. Projected energy consumption will reach 4,333,631 million kilowatt hours in 2013, with growth of 1.93% over the next five years. Consumption increased from 3,715,949 in 2004 to the expected 3,937,879 million kilowatt hours per year in 2008, with an increase of around 0.36% annually. The US population has been increasing by 1.3% annually, totaling about 6.7% over the five years.[36]​ The decline is primarily due to increases in efficiency and the use of energy-efficient light bulbs that use about a third of the electricity that incandescent bulbs use or LED bulbs that use a tenth, at most, over its 50,000 years. 100,000 hours of life, this makes them cheaper than fluorescent tubes.

One measure of efficiency is energy intensity. This measures the amount of energy that is necessary for each country to produce one dollar of gross domestic product.

By sectors

Industrial uses (agriculture, mining, manufacturing, construction and fishing) consume around 37% of the total 15 TW. Commercial and personal transportation consumes 20%; heating, lighting and the use of electrical appliances uses 11%; and commercial uses (lighting, heating and air conditioning of commercial buildings, as well as water supply and sanitation) around 5% of the total.[37]​.

The remaining 27% of the world's energy is lost in energy generation and transportation. In 2005, global electricity consumption was equivalent to 2 TW. The energy used to generate 2 TW of electricity is approximately 5 TW, given that the efficiency of a typical power plant is around 38%.[38]​ The new generation of gas thermal plants achieve substantially higher efficiencies of 55%. Coal is the most widespread fuel for global electricity production.[39]​.

The existing reserves of conventional fossil fuels are estimated at:[6]​.

There is significant uncertainty to these data. Estimating the remaining fossil fuel on the planet depends on a detailed understanding of the Earth's crust. This understanding is still imperfect. While modern drilling technology makes it possible to drill wells into up to 3 km of water to verify the exact composition of the geology, half of the ocean is deeper than 3 km, leaving a third of the planet beyond the scope of detailed analysis. Reports from the Energy Monitoring Group show that oil demands cannot be met[40]​ and that the uranium resource will be exhausted in 70 years.[41]​.

Coal is the most abundant fossil fuel. According to the International Energy Agency, the confirmed reserves of coal are around 909 billion tons, which could maintain the current rate of energy production for 155 years.[42] It was the fuel that fueled the industrial revolution and its use continues to be very important. China, which has one of the most polluted cities in the world,[43]​ built about two coal-fired power plants a week during 2007.[44]​[45]​ However, coal production in China peaked in 2013 and has declined since then.[46]​ Recently, China has canceled the planned construction of more than 100 coal plants, favoring the installation of renewable energy in its place.[46][47][48]​.

Coal nevertheless remains one of the main fossil fuels and its large reserves would make it a favorite candidate to meet the energy demand of the global community, if it were not for concerns about global warming and other pollutants.[49]​ With the Fischer-Tropsch process, liquid fuels such as diesel or aviation fuel can be obtained from coal. The Stop Coal campaign calls for a moratorium on the construction of new coal plants and the abandonment of existing ones, based on concerns about global warming.[50]​ In the United States, 49% of electricity generation comes from burning coal.[51]​.

It is estimated that there may be 57 ZJ of oil reserves on Earth (although estimates vary from the low 8 ZJ,[10] consisting of currently proven and recoverable reserves, to the high of 110 ZJ) consisting of available but not necessarily recoverable reserves, and including optimistic estimates for unconventional sources such as tar sands and oil shales. The current consensus around the 18 recognized estimates of supply profiles is that peak extraction will occur in 2020 at a rate of 93 million barrels per day. Current oil consumption is at a rate of 0.18 ZJ per year (31.1 billion barrels), or 85 million barrels per day.

There is a growing consensus that peak oil production could be reached in the near future, leading to higher oil prices. Oil decreased from 84.63 million barrels per day in 2005 to 84.60 million barrels per day, but grew in 2007 to 84.66 million barrels per day, and is expected to grow to 87.7 million barrels per day in 2009.

Political considerations over security of supplies, and environmental implications related to climate warming and sustainability will eventually shift global energy consumption away from fossil fuels. The peak oil concept shows us that we have used approximately half of the available oil resources, and predicts a decline in production.

A government leading the phase-out of fossil fuels should create economic pressure through carbon emissions trading and eco-taxes. Some countries are developing actions based on the Kyoto Protocol, and there are proposals to go further in this direction. For example, the European Commission has proposed that the European Union's Energy Policy should establish binding targets to raise levels of renewable energy use from the current less than 7% to 20% in 2020.[54]​.

The Easter Island Effect is cited as an example of a culture that was incapable of developing sustainably, destroying practically 100% of its natural resources.[55]​.

According to estimates by the International Atomic Energy Agency, the equivalent of 2,500 ZJ of uranium remains.[56] This assumes the use of the fast breeder reactor, which is capable of generating more fissile material than it consumes. The IPCC estimates that currently proven economically recoverable uranium deposits for direct fuel cycle reactors reach only up to 2 ZJ. The ultimately recoverable uranium is estimated at 17 ZJ for direct cycle reactors and 1000 ZJ for fast breeder reactors that perform reprocessing.[57]​.

Neither resources nor technology limit nuclear energy's ability to help meet energy demand throughout the century. Even so, political and environmental implications regarding nuclear safety and radioactive waste began to limit the growth of this energy supply at the end of the last century, especially due to certain nuclear accidents. Concerns about nuclear proliferation (especially regarding Plutonium produced by breeder reactors) suggest that the development of nuclear energy by countries such as Iran or Syria is being actively discouraged by the international community.[58]​.

Nuclear fusion is the physical process by which energy is produced in stars, including the Sun. It generates large amounts of heat by fusing the nuclei of hydrogen isotopes. The heat can theoretically be used to generate electricity. The temperatures and pressures necessary to accommodate fusion make it a very difficult process to control and therefore an unsolved technological challenge. The tantalizing potential of fusion is represented by its theoretical ability to deliver large amounts of energy, with relatively little associated pollution.[59] Both the United States of America and the European Union support the research (such as investing in ITER), as well as other countries. According to one report, limited investment has delayed progress in fusion research for the past 20 years, putting it 50 years away from commercial availability.[60]​

renewable resources

Renewable resources are available over time, unlike non-renewable resources. A simple comparison can be that of a coal mine and a forest. While the forest can be depleted, if managed properly it represents a continuous supply of energy, compared to the coal mine which once depleted is gone. Most of the energy resources available on Earth are renewable resources.

Renewable energy sources are even greater than traditional fossil fuels and in theory can easily supply the energy the world needs. 89 PW[61]​ of solar energy reaches the surface of the planet. Although it is not possible to capture all of it, or even most of it, even capturing less than 0.02% of this energy would be enough to meet current energy needs. Obstacles to the development of solar production include dependence on weather factors and lack of space for solar panels in high-demand areas such as cities. Furthermore, solar generation does not produce electricity at night, which is a notable problem for countries located in high boreal and northern latitudes; Energy demand is higher in winter, while the availability of solar energy is lower. Globally, solar generation is the fastest growing energy source, showing an average annual growth of 35% over the past few years. Japan, Europe, China, the United States of America and India are the fastest growing investor countries in solar energy. Advances in technology and economies of scale, as well as the demand for solutions to global warming, have led photovoltaics to become the best candidate to replace nuclear energy and fossil fuels.[62]​.

The available wind energy is estimated to range from 300 TW to 870 TW.[61]​[63]​ Taking into account the lowest estimate, only 5% of the available wind energy could supply the current global energy needs. Most of this wind energy is available over the open ocean. The ocean covers 71% of the planet and the wind tends to blow more intensely over closed waters because it encounters fewer obstacles.

At the end of 2005, 0.3 GW of electricity was produced by tidal energy. Due to the gravitational forces created by the Moon (68%) and the Sun (32%), and the relative rotation of the Earth with respect to the Sun and the Moon, tidal variations occur. These give rise to an average dissipation rate of about 3.7 TW.[64]​ As a result, the Earth's rotation speed decreases, and the distance from the Moon to Earth increases, on geological time scales. In several billion years, the Earth will rotate at the same speed as the Moon rotates around it. Because of this, many TW of tidal energy can be produced without significantly affecting celestial mechanics.

Another physical limitation is the energy available in the tidal fluctuations of the oceans, which is about 0.6 EJ (exajoules).[65] Note that this represents only a small 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 semidiurnal tidal periods. In this way, 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% dissipation rate) in order not to alter the tidal dynamics too much.

Denmark and Germany have begun investing in solar energy, despite their unfavorable geographic locations. Germany is currently the largest consumer of photovoltaic cells in the world. Denmark and Germany have installed 3 GW and 17 GW of wind energy respectively. In 2005, wind generated 18.5% of all electricity in Denmark.[73] Brazil invests in the production of ethanol "Ethanol (fuel)") from cane sugar, and this has become a significant part of the transport fuel used in the country. Starting in 1965, France invested heavily in nuclear energy and to date three-quarters of its electricity comes from nuclear reactors.[11] Switzerland plans to cut its energy consumption by more than half to become a "2000 Watt Society" by 2050 and the United Kingdom is working on achieving specifications for the construction of new homes according to the "Zero Energy Building" principle by 2016. China for its part part, will adhere to a sustainable energy strategy and make active contributions to sustainable energy development and energy security in the world, has outlined a plan to reduce energy consumption in gross domestic product per unit by about 20 percent by 2010, compared with the level of 2005.

In the 20th century, many of these different energy strategies could become more relevant and displace the ubiquitous fossil fuels.

It should be noted that when the Green Revolution transformed agriculture across the planet, between 1950 and 1984, grain production increased by 250%. The energy for this Green Revolution was supplied by fossil fuels in the form of fertilizers (natural gas), pesticides (petroleum), and energy-forced irrigation.[74]​ Peak global hydrocarbon production (Hubbert's Peak Theory) may test Malthus's criticisms.[75]​.

• - Annex: Countries by energy consumption.

• - International Energy Agency. (2006) World Energy Outlook 2006. ISBN 92-64-10989-7.

• - Smile, Vaclav. (2003) Energy at the crossroads MIT Press. ISBN 0-262-19492-9.

• - Tester, Jefferson W. et al. (2005) Sustainable Energy: Choosing Among Options. The MIT Press. ISBN 0-262-20153-4.

• - Yergin, Daniel (1993). The Prize. Simon & Schuster: New York. ISBN 0-671-79932-0.

• - World energy outlook (in English) Archived June 15, 2011 at the Wayback Machine.

• - Official energy statistics from the government of the United States of America (in English).

• - 2006 Annual Energy Report, DOE/EIA-0384(2006), by the Energy Information Administration of the US Department of Energy (PDF).

• - World Energy Statistical Report 2007, BP annual report (in English).

• - Toolbar energy consumption.

• - Balance of European electricity consumption for the first half of 2014.