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…]

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