Environmental Engineering Reference
In-Depth Information
Continuing declines in the energy intensity of steel-
making meant that in 2000 the production of roughly
850 Mt of the world's leading alloy needed about 20
EJ, or just over 6% of the world's TPES (Smil 2003).
Had the energy intensity remained at the 1900 level, fer-
rous metallurgy would now be using almost 20% of the
world's TPES. But despite these impressive efficiency
gains, ferrous metallurgy remains the world's largest
energy-consuming industry, claiming about 15% of all in-
dustrial energy use. In the United States, where steel-
making declined from a peak of 137 Mt in 1973 to 90
Mt in 2001, this share was only about 8% of all energy
used in manufacturing and 2.5% of all primary com-
mercial energy used annually during the early 2000s
(USDOE 2000).
Aluminum is the second most important structural
metal of modern civilization. In 1900 the annual global
output of aluminum from the primary electrolysis of alu-
mina was 8000 t; by 1913, 65,000 t; by the end of WW
II, nearly 700,000 t; and by 2000, more than 20 Mt.
Global aluminum production was about 50% higher
than the worldwide smelting of copper (IAI 2003). The
metal is produced 99.8% pure or alloyed to be used in
construction, transportation (jetliners would be impossi-
ble without it), and countless industrial products from
cooking pots to computers. The Hall-H ´ roult process
of electrolytic aluminum production was invented and
rapidly commercialized during the 1880s. During the
twentieth century the average cell size in Hall-H ´ roult
plants doubled every 18 years, while energy use
decreased by nearly half between 1888 and 1914 and
then dropped by nearly as much by 1980 (fig. 10.5)
(Smil 2005a).
The first commercial aluminum cells consumed nearly
40 kWh/kg of
10.5
Declining specific energy cost of aluminum production,
188-199. From Smil (2005a).
advances lowered this rate to about 15 kWh/kg by
2000. The theoretical minimum requirement for carbide
anode electrolysis is about 6 kWh/kg (Choate and
Green 2003; IAI 2003). Adding the inevitable electricity
losses in generation and transmission, the energy costs of
other fuels, bauxite mining, production of alumina and
carbon electrodes, and casting of the smelted metal raises
the total rate to about 200 GJ/t (U.S. average in 2000
was @196 MJ/t) and well above that for less efficient
producers. Aluminum production thus remains highly
energy-intensive, 1 OM above that of steel from blast
furnace iron. Among structural metals, only titanium
requires more energy (up to 900 GJ/t) to be produced
from its ores. In 2000 about 40% of U.S. aluminum was
recovered for secondary processing, whose theoretical
energy requirement (0.39 kWh/kg for smelting) is less
than 6.5% that of primary production and whose actual
cost is about 50 GJ/t (Stodolsky et al. 1995).
the metal, and continuing technical
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