Energy yield of liquid fuels is declining, not just volume
March 16th, 2009 by Jim JustThe latest edition of Oilwatch Monthly contains this chart showing the gross energy content of liquid fuels 2004-2009:
The energy content of liquid fuels has been dropping more, and for a longer time, than the volume of liquid fuels. As an ever-growing portion of the world’s liquid fuels comes from natural gas liquids and biofuels, that trend can only grow.
Here’s what a quick search reveals about the energy content of the fuels shown in the chart above. Remember, these figures are for gross energy. For biofuels especially, the net energy is a small fraction of the gross energy and may be negative. Also, the range of gross energy estimates varies pretty widely among different sources.
Crude oil 5.8 million Btu/barrel
Natural gas liquids 4.2 million Btu/barrel
Biofuels (ethanol, biodiesel) 3.5 – 5.4 million Btu/barrel
And as Oilwatch Monthly emphasizes, it’s net energy, not gross energy, that really matters:
The actual energy available for society to consume is lower than shown in chart 13, however, because an incremental amount is needed to bring the oil out of the ground. The oil industry has to drill deeper at more extreme locations which costs more energy. Additional energy is thus needed to reach the oil. Also more energy is needed to process it to a useful product due to a decline in quality from conventional to increasingly unconventional oil. Studies by Professor Charles Hall and his science group at State University New York show that the energy necessary to draw a barrel of 159 liters of oil out of the ground from conventional oil, has increased from approximately 3 liters of oil equivalent in the beginning of the 1990s to 6 liters of oil equivalent now. It is unknown how much of this energy input comes from oil, gas or coal, the main energy inputs to the oil and gas industry.
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