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The Earth’s the Limit (2): Peak Oil—Peak Energy?

[First part]

During the last years, humanity has consumed about 500 exajoules of energy per year (an exajoule is a million million megajoules, or 1018 joules). As usual, levels of energy consumption vary strongly from country to country. While the average consumption per person is about 70 GJ (gigajoules), the inhabitants of Bangladesh, Eritrea, and Senegal use less than 10 GJ on average.

At the other extreme, the inhabitants of the United Arab Emirates and Iceland use 450–500 GJ per year, while per-capita usage in the small emirate of Qatar is a whopping 900 GJ. Germany uses about 180 GJ per person—more than twice the global average. Other Middle European countries are similar, while the United States and Canada use twice as much (330–350 GJ).

Is it realistic that in the future, everybody will reach the consumption level of Germany or the USA, or even more? There are reasons for doubt, especially due to the source of the energy we use. More than 80 percent of the consumed energy result from burning fossil fuels: oil (~36%), coal (~27%), and natural gas (~23%). This is problematic for two reasons: (1) fossil fuels are non-renewable sources of energy that will be exhausted sooner or later. (2) The burning of fossil fuels is the main source of global warming, the human-made climate change that threatens humanity and other species with dramatic and often fatal consequences.

Peak Oil, Peak Gas, Peak Coal

If consumptions of oil continues at the current level, we will run out of oil in approximately 43 years. Estimates for the remaining gas and coal reserves are more varied. According to the estimates of the US Department of Energy (cited in the same source), gas will last for 61 years and coal for 148 years. Other estimates are somewhat more optimistic, but in any case it is clear that none of the fossil fuels will last forever.

In reality, of course, future consumption levels won’t remain constant until reserves suddenly “run out”. On the one hand, consumption is likely to increase due to economic growth and due to the growth of human population (if world population increases from 6.7 billion to 9 billion in 2050, that alone would mean an 35% increase in the usage of fossil fuels, even if the average usage per person remains constant). On the other hand, easily accessible reserves are usually exploited first. At some point worldwide extraction of petroleum will start to decline, after accessible reserves have been exhausted and can only slowly be replaced by reserves that are more expensive and energy-consumptive to exploit. This point is known as peak oil.

In the US, the peak of oil extraction was reached in the the early 1970s; since then, oil extraction has gradually declined. It seems quite certain that the global peak of oil extraction is not very far away. Most analysts seem to suppose that peak oil will occur sometime before 2020; some believe that it already occurred in about 2007, before the start of the current economic crisis (oil extraction declined since then due to shrinking demand).

When the oil supply starts to decline while demand is still stable or (more likely) growing, it will not only mean higher oil prices and possibly violent struggles for the distribution of the remaining resources. It will also mean that the resulting supply gap will be partially filled by a faster exhaustion of gas and coal. Most estimates therefore conclude that peak gas and peak coal will occur at most a few decades after peak oil, probably between 2020–40 for peak gas and before 2050 for peak coal. Since the energy gained from fossil fuels will thus start to shrink in the near future, humanity will have to learn to survive with less energy or to rely much more strongly on renewable energy—or more realistically, both. (Nuclear power is sometimes advertised as another option, but it can’t fill the gap since it’s not really renewable and suffers its own peak; also nuclear power would clearly be unsuitable for a decentralized peer economy for various reasons.)

This will be quite a challenge, since only about 1.6% of the current energy comes from the renewable energy sources that have a large untapped potential—mainly solar energy (1.3%) and wind power (0.3%). There are other sources of renewable energy that currently play a more important rule, namely biomass and biofuels (13.5%) and water power (3.3%), but these have already reached a high share of their maximum capacity—they lack the theoretical potential to yield enough energy to replace today’s non-renewable energy sources. Solar power currently mainly comes in the form of solar thermal energy used for heating; the contributions of solar photovoltaics are negligible. (These and the following figures are from the Renewables 2007 Global Status Report, p. 9, 12, 38, unless another source is specified.)

If humanity wants to continue (or even increase) its current levels of energy consumption, it will have to increase the energy produced from solar and wind power by factor 50 or more before fossil fuels run out.

Limited Renewable Sources

There are some other renewable sources of energy, but their potential is limited. About 3.3% of the current energy mix comes from hydropower, but the International Hydropower Association estimates (PDF) that one third of the realistic global potential of water power has already been developed. If this estimate is true, it means that water power will never be able to contribute more than about 10% to the global energy mix.

Biomass plays an important role as energy source, mainly in the form of so-called traditional biomass: wood, charcoal (made from wood), and agricultural waste used for heating and cooking, especially in Africa and Asia. These “traditional” uses comprise about 13% of the global energy mix, while nontraditional uses (biofuels and electricity made from biomass) comprise about 0.5%.

But the Earth’s surface area that could be used for biomass production is limited. According to the FAO (UN Food and Agriculture Organization), energy gained from wood accounts for 7–9% of the energy consumed worldwide (up to 80% in some developing countries), but wood fuels already account for 60% of the global consumption of forest products. Forests cover about four billion hectares—30% of total land area of the Earth. 34% of these forests are primarily used for the production of wood and other forestry products; more than half of all forests are used for productive purposes either primarily or in combination with other functions such as recreation or biodiversity conservation. A large part of the rest (36% of all forest area) are primary forests largely untouched by human activity—which should better remain so, since wilderness areas are important for biodiversity and for keeping Earth a planet that is not totally subjected to utility concerns (Global Forest Resources Assessment 2005, p. 4, 6).

So the area available for biomass production is already largely used for this purpose, since the 70% of land surface that aren’t covered by forests are usually needed for human habitation or agriculture (except where they are deserts or natural reserves). Even if the energy extracted from biomass was doubled, it wouldn’t account for more than one quarter of humanity’s current energy needs, and it is hard to see how more than that could be achieved. Modern biofuels don’t seem to do better than traditional fuel wood regarding their space requirements—ethanol and other biofuels already consume 17% of the world’s grain harvest (Richard Heinberg, Searching for a Miracle, p. 48), but contribute only 0.3% of the energy produced. And biofuels have rightly come under criticism for absorbing grain that could otherwise be used for human consumption and contributing to raising food prices during the last years.

Geothermal power is another source of energy that is marginal as of today but might play a more important role in the future. It utilizes heat stored below the surface of the Earth for heating or for generating electricity. Geothermal energy comes in two flavors: there are geothermal heat pumps, which can be an efficient and decentralized approach to heating (or cooling) buildings. And there are geothermal plants that generate electricity. This latter flavor is a large-scale technology that interferes much more heavily with the Earth; construction of geothermal plants has triggered earthquakes (e.g. in Basel, Switzerland) and caused slow deformation of the land surrounding the plant (e.g. in the German Black Forest).

This makes geothermal plants problematic, especially for a peer production–based society that favors decentralized and unobtrusive technologies. In any case, the electricity generation potential of geothermics is limited—estimates vary wildly, ranging from 35 to 2000 GW. Even the highest estimate—2000 GW—, which is almost certainly strongly exaggerated, would correspond to only 13% of the current worldwide energy demand; space heating (which could partially be satisfied though geothermal heat pumps) makes up another less than 16% of the total energy demand. Thus the contributions of geothermal energy are necessarily limited as well.

So, while water power, biomass, and geothermal heat will be able to contribute to a global renewable energy mix, they hardly will be able to make up for the energy currently extracted from fossil fuels. The biggest part will have to come from solar and wind energy.

[To be continued…]

Kategorien: Commons, English, Reichtum & Knappheit, Theorie

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31. März 2010, 18:11 Uhr   12 Kommentare

1 The Earth’s the Limit (1) — (31.03.2010, 18:14 Uhr)

[…] [Second part] […]

2 Martin (01.04.2010, 22:02 Uhr)

Fusion power would be a real post-scarcity technology – if it can be made to work! The technology seems to be the only one without inherent limits. Even many of the currently discussed „sustainable energies“ are not really sustainable if one counts consumption of nature, of beautiful places, of earth space etc. Even now, many big rivers are irrevocably changed by dams, wind mills are littering landscapes, and many old villages (i.e. in the German black forest) looked much better without those solar panels on the roofs. On the other hand, all energies releasing substantial amounts of greenhouse gases (this includes biomass power) or dangerous waste (i.e. nuclear fission power) will certainly not be able to lead us into post-scarcity (though they can be continued for some time, at high cost for future generations).

Fusion power is futuristic by any standards, but its high development costs might well be worth the effort. However, for a peer economy, it has one major drawback – it is inherenty centralized. Therefore it would have to be supplemented by a decentralized technology (like photovoltaic systems). It could be highly useful, however, for metropolitan areas, where decentralized systems are ineffective and take to much space, for certain production technologies (like steel), etc.

3 benni (02.04.2010, 13:41 Uhr)

@martin: Radioaactive pollution is the inherit limit of fusion power, simmilar to nuclear fission.

4 Christian Siefkes (02.04.2010, 19:42 Uhr)

Fusion power has been in the research stage for a very long time (more than 50 years) and still hasn’t passed beyond the experimental stage. There seems to be no breakthrough in sight, so I frankly doubt that the next 50 years will be much more successful than the last. As the English Wikipedia states:

Research, while making steady progress, has also continually thrown up new difficulties. Therefore it remains unclear whether an economically viable fusion plant is possible. A 2006 editorial in New Scientist magazine opined that „if commercial fusion is viable, it may well be a century away.“

While the German Wikipedia jests:

Als Fusionskonstante wird mit scherzhaftem Unterton … die Erscheinung bezeichnet, dass seit Jahrzehnten die technische Beherrschung der Kernfusion und entsprechende Energiegewinnung von der Gegenwart aus gerechnet für jeweils 30–40 Jahre in der Zukunft als möglich vorausgesagt wird.

Fusion power may thus fall into the same category as „artificial intelligence“: forever a promise, never a reality.

Regarding biomass: biomass power doesn’t release greenhouse gases, at least in theory. The burning of biomass does release CO2, but only the CO2 that has been captured by the tree (or whatever plant it is) before. When you regrow the plants, the same amount of CO2 will be captured by the successors. So you can use biomass permanently without ever increasing the CO2 in the atmosphere—only if you don’t regrow the plants, the CO2 level will increase.

A specific problem with biofuels, however, is that they are made from corn or other grains, which capture less CO2 than trees. So whenever a forest is cut down in order to produce biofuels, that does indeed permanently release CO2. (Deforestation is the reason for about 25% of global CO2 increase, while fossil fuels are largely responsible for the other 75%.) Another problem with biofuels is that a high amount of energy is required to produce them—the „energy returned on energy invested“ (EROEI) ratio is very bad. This production energy nowadays tends to be largely gained from fossil fuels, hence it does of course release CO2. Biofuels are indeed one of the worst renewable energy sources; they are only popular because of their similarity to conventional fossil fuels.

5 Martin (02.04.2010, 21:10 Uhr)

@benni: Radioactive pollution dangers in fusion power are very different from that in fission power: They would be limited to a small area around the reactor even in case of its complete destruction; and they reach non-dangerous levels after 50 years (not 40.000 years as in fission power). We don’t even know how to communicate the dangers we create today to future civilizations, because the time spans are longer than history, and cultural change is accelerating. The radiation danger of fusion power, on the other hand, is of the same degree as – let’s say – in chemical industry: A risk localized in time and space. If we don’t accept these risks, we have to give up most of technology.

@Christian: I don’t think fusion power is impossible, only very challenging. Computer A.I., on the other hand, was impossible from the start, because computers simply work completely different from human brains and cannot emulate them.

As regards biofuels, there are further disadvantages which make them not viable for a post-scarcity vision: Immense areas would be needed; these would be more or less monocultures, greatly reducing biodiversity even if we took savannae etc. and not forest areas (which, however, are de facto used); they would need giant amounts of fertilizers and pesticides …

For rural areas, a highly decentralized solution might be the best: Some windmills, photovoltaic systems on big roofs, biomass on fields not needed at the moment. But for metropolitan areas, all this doesn’t work (not enough roof space for solar panels, no place for wind mills, etc.). Large offshore wind parks are promising, but only for some coastal areas …

6 (English) The Earth is the Limit : (03.04.2010, 19:35 Uhr)

[…] Part two is about energy consumption: Peak Oil – Peak Energy? See: First part (9 Feb. 2010), second part (March 31, 2010). The author plans to continue the […]

7 Thomas (23.04.2010, 12:03 Uhr)

Ok its time to tell people some truth about energy and limitation.

There is no limitation!

We need no nuclear powerplants no coal-powerplants no solarenergy, no windpower, if we just make a technology popular which has been suppressed for a long time.

What do I mean?

Please watch this documentary:

and do some research about „Free energy“  and „Tesla“ on Youtube and on the Net

8 Christian Siefkes (23.04.2010, 12:32 Uhr)

@Thomas: Making energy out of nothing sounds like fun 😉 But if something sounds to good to be true, it usually is. Wikipedia knows better:

Free energy suppression is a conspiracy theory that claims that advanced technology that would reshape current electrical generation methods is being suppressed by certain special interest groups….

Conspiracy theories won’t help us.

9 Selbstorganisierte Fülle — (17.05.2010, 21:48 Uhr)

[…] die ich in meiner englischsprachigen Serie „The Earth’s the Limit“ (Teil 1, Teil 2) niedergelegt habe, habe ich meine Überlegungen zu einer möglichen künftigen […]

10 Annette (01.06.2010, 09:07 Uhr)


There is another limit, the limit of the dynamic equilibrium of energy in our atmosphere. All use of energy converts it into less valuable Forms of energy (like heat). The use of more energy means more heat and more global warming. This effect is much smaller than the effect of greenhouse gases, but it cant be neglected. This was known since the 70th, but became forgotten because of the more urgend problem of greenhouse gases. There is a (German) paper on our website: (see also Hans-Peter Dürr:

Another topic are the limits of renewable energy.  Some points I analysed in my (also German) paper: „Ist Photovoltaik klima- und umweltverträglich?“ (, see esp.3.2..

More links:

11 Christian Siefkes (24.06.2010, 13:25 Uhr)

@Annette: I understand that the ultimate conversion of all energy into heat poses a theoretical limit, but so far it seems quite irrelevant to me in practice. According to the (German) Energiegleichgewicht text, humanity should not use more than 1% or so of the total solar energy which reaches Earth. According to the article, the total solar energy is 1.78 * 1014 KW, so we could use about 1.78 * 1012 KW, or 1.78 * 1015 W. According to Wikipedia, global energy usage in 2008 was 1.504 * 1013 W, so we’re using only 1% of that theoretical limit.

Hans-Peter Dürr specifies a much lower limit: 9 TW, i.e. 9 * 1012 W. This would mean that we’re already 67% above the “allowed” limit, but I frankly don’t understand how he arrives at that limit. He just quotes another paper (Ziegler) but doesn’t explain or motivate Ziegler’s assumptions, whatever they may be.

12 Selbstorganisierte Fülle | Akademie Integra (13.07.2010, 17:23 Uhr)

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