Cubic mile of oil

The cubic mile of oil (CMO) is a unit of energy. It was created by Hew Crane of SRI International to aid in public understanding of global-scale energy consumption and resources.^[1]

Significant sources of energy include oil, coal, natural gas, nuclear, hydroelectric, and biomass (primarily the burning of wood). Other energy sources include geothermal, wind, photovoltaic, and solar thermal. The various energy units commonly used to measure these sources (e.g., joules, BTUs, kilowatt hours, therms) are only somewhat familiar to the general public,^[2] and their relationships can be confusing.^[3] These common energy units are sized for everyday activities (a joule is the energy required to lift a small apple one metre vertically). For regional, national, and global scales, larger energy units, such as the exajoule, the billion barrels of oil equivalent (BBOE) and the quad are used. Derived by multiplying the small common units by large powers of ten these larger units pose additional conceptual difficulties for many citizens.^[4]

Crane intended the cubic mile of oil to provide a visualizable scale for comparing the contributions of these diverse energy components as a percentage of total worldwide, energy use.

The global economy consumes approximately 30 billion barrels of oil (1.26 trillion U.S. gallons or 4.75 trillion litres) each year.^[5] Numbers of this magnitude are difficult to conceive by most people.^[4][6] The volume occupied by one trillion U.S. gallons is about one cubic mile. Crane felt that a cubic mile would be an easier concept for the general public than a trillion gallons.

Definition and energy equivalents

The CMO is the energy released by burning a cubic mile of oil. Conversions to other units may be calculated based on the barrel of oil equivalent (BOE), an approximation of the energy released by burning one 42-US-gallon barrel of crude oil. Since one BOE is about 7009611932394519600♠5.8×10⁶ BTU^[7] and one cubic mile is about 7010262000000000000♠2.62×10¹⁰ barrels:^[8]

1 CMO	≈ 7020160000000000000♠1.6×1020 joules
		= 160 exajoules
	≈ 7013445400000000000♠4.454×1013 kilowatt-hours
		= 44.54 petawatt-hours
	≈ 7020160368489598240♠1.52×1017 BTU
		= 152 quads
		≈ 150  trillion (1012) cubic feet of natural gas
	≈ 7020160288015840000♠2.62×1010 BOE

Annual energy consumption by source

2008 worldwide renewable-energy sources. Source: REN21^[9]

The world consumes approximately 3 CMO annually from all sources. The table ^[10] shows the small contribution from alternative energies in 2006.

A CMO/yr is about 5.084 TW continuous, making current world energy use around 15 TW.

Global energy reserves

Proved oil reserves are those that can be extracted with reasonable certainty under existing conditions using existing technology. Global proved oil reserves are estimated at approximately 1,300 billion barrels (210×10^⁹ m³).^[11] This corresponds to roughly 43 cubic miles, or 43 CMO. At the current rate of use, this would last about 40 years. Technological advances, new discoveries, and political changes will likely lead to additional proved oil reserves in the future. Concurrently, the International Energy Agency predicted in its 2005 World Energy Outlook that the annual consumption will increase by 50% by 2030.^[12] Coal and natural gas currently provide 1.42 CMO of energy per year. Global reserves of these fossil resources are as follows:

• Natural gas reserves total 42 CMOs (69 years at current consumption)
• Coal reserves total 121 CMOs (150 years at current consumption)
• Additionally, there are large, albeit uncertain, amounts of tar sands, shale gas, and other unconventional fossil sources

Replacement of oil by alternative sources

While oil has many other important uses (lubrication, plastics, roadways, roofing) this section considers only its use as an energy source.

The CMO is a powerful means of understanding the difficulty of replacing oil energy by other sources. SRI International chemist Ripudaman Malhotra, working with Crane and colleague Ed Kinderman, used it to describe the looming energy crisis in sobering terms.^[13] Malhotra illustrates the problem of producing one CMO energy that we currently derive from oil each year from five different alternative sources. Installing capacity to produce 1 CMO per year requires long and significant development.

Allowing fifty years to develop the requisite capacity, 1 CMO of energy per year could be produced by any one of these developments:

• 4 Three Gorges Dams,^[14] developed each year for 50 years, or
• 52 nuclear power plants,^[15] developed each year for 50 years, or
• 104 coal-fired power plants,^[16] developed each year for 50 years, or
• 32,850 wind turbines,^[17][18] developed each year for 50 years, or
• 91,250,000 rooftop solar photovoltaic panels^[19] developed each year for 50 years

The energy produced is the power rating of the source multiplied by the duration it is operational. These comparisons take into account the variability of available power (solar panels work only during the day, turbines work only when the wind blows). Also, whereas 1 kWh is equivalent to 3412 BTU of primary energy, in practice it takes closer to 10,000 BTU to produce 1 kWh of electricity from coal and other fossil sources. Thus, when considering sources such as wind and solar which directly produce electricity, the required installed capacity was calculated by using 1 kWh as equivalent to 10,000 BTU.

The environmental, social, and financial costs of such development projects are immense:

• The Three Gorges Dam is the world's largest, flooding 632 km², displacing 1.25 million people, and costing roughly US$30 billion.
• A conventional nuclear power plant produces hazardous radioactive waste, raises fears of radiation or nuclear proliferation, requires 10 years to construct for a 40-year lifetime, occupies about 4 km², and may cost upwards of US$5 billion.
• A 500 MW coal-fired power plant may contribute to acid rain, global warming, and air pollution, occupies about 2 km², may obtain its fuel via controversial methods such as mountaintop removal, and costs about US$650 million.
• A large wind turbine requires a location with an abundance of steady wind, may be visually obtrusive, can interfere with aviation, needs about 0.16 km² to avoid interfering with adjacent turbines, and costs about US$2 million.^[20]
• A 2.1 kW rooftop solar array requires technical skills for installation, needs a sunny location, presents few aesthetic or environmental problems, covers about 14 m², but costs around US$15,000.

For comparison, US$3.2 trillion is the approximate gross domestic product of Germany, China, or the United Kingdom. The total land area of New Zealand is approximately 270,000 square kilometres (100,000 sq mi).^[21]

At a 2008 market price of US$120 per barrel (US$750/m³), the cost of one CMO was about US$3 trillion. So for the cost of about one year's global oil consumption at 2008 market prices, enough wind turbines could be built to generate the same energy for 40 years, assuming sites are available.

Replacement of oil by speculative alternative sources

Space-based solar power offers one way StratoSolar offers another. At ~5 TW per CMO/yr, it would take about 1000 five GW power satellites to replace a CMO. To compete with coal, the maximum cost for space based solar power plants would be $2.4 B/GW. At that, the cost would be ~$2.4 T for one CMO or ~$7.2 T to replace the entire fossil fuel use of humans. There is room in GEO for more than ten times the current energy use. ^[22] At a peak production of 315 new power satellites per year, it would take less than a decade to get off fossil fuels.

StratoSolar has the advantage that solar can be tapped at 20 km regardless of the local weather.

In both cases, a huge energy flow to carbon neutral synthetic fuel plants would be required to replace the oil used for transportation. The technology for making synthetic transport fuels is well understood. See Oryx GTL

References

External links

• 'Doug Englebart's colloquium' Hewitt Crane discusses the state of the world's energy supply
• Ripudaman Malhotra talks about A Cubic Mile of Oil at the University of Toledo.
• [cmo-ripu.blogspot.com] Blog for posting updates to A Cubic Mile of Oil.