Environmental Engineering Reference
In-Depth Information
the world's TPES and roughly the same as for produc-
tion of all inorganic fertilizers.
The most innovative industrial sector of the last quar-
ter of the twentieth century was the production of semi-
conductors. That sector has been following Moore's law,
doubling the number of transistors per microchip about
every 12 months until 1972 and every 18 months since
that time (Intel 2003; Moore 1965). In 1972, Intel's
8008 chip had 2,500 transistors; a decade later, a single
memory chip had more than 100,000 components; by
1989 the total surpassed 1 million; and by 2000, the
Pentium 4 processor had 42 million transistors. Given
this phenomenal growth, it is surprising that the first
fairly complete energy analysis of microchip production
became available only in 2002 (Williams, Ayres, and
Heller 2002).
The analysis focused on the 32 MB DRAM chip and
calculated that 1.6 kg of fossil fuels (all of it to generate
electricity) and 72 g of chemicals (as well as 32 kg of
water and 700 g N
2
) were needed to produce a single
2-g device. The analysts traced energy costs for principal
stages of the production chain for silicon wafers (silicon
from quartz and carbon; trichlorosilane; polysilicon; sin-
gle crystal ingot; wafers) and then for the subsequent
fabrication and assembly of a microchip. The energy
needed for the silicon wafer chain and final assembly
amounted to about 41 MJ/chip, and 9.4 kg of raw Si
was needed to produce 1 kg of final wafer. During its
typical four-year lifetime the chip uses about 1.4 kWh
of electricity, or about 15 MJ, assuming an average of
10.7 MJ/kWh. This means that unlike cars or houses, a
microchip embodies nearly 75% of its lifetime energy
costs, substantially higher than its operating cost. This
highlights the need for increasing the longevity of
computers. Using the average of 41 MJ/chip implies
10.7 What goes into a Volkswagen Golf A4: the most im-
portant materials, according to a detailed energy cost account-
ing prepared by Schweimer and Levin (2000).
substitute steel parts. In 1996, Volkswagen began an
LCA of its Golf automobile. A detailed account for the
year 2000, based on 40 production input categories (fig.
10.7) shows specific energy costs very similar to the ear-
lier U.S. data (Schweimer and Levin 2000). Production
of an Otto cycle version of the Golf A4 (mass 1.059 t,
fuel consumption 6.55 L/100 km) needed 85.6 GJ,
or 80 GJ/t. Production of a slightly heavier but much
more efficient diesel version (mass 1.181 t, fuel con-
sumption 4.95 L/100 km) required 88.4 GJ, or 75
GJ/t. The LCA, assuming ten years of useful life or
150,000 km, showed overall costs of 445 GJ and 407
GJ, respectively, with production accounting for 19%
and nearly 22%. With an annual output of about 40 mil-
lion units, the global energy cost of passenger car pro-
duction in 2000 was about 4-4.5 EJ, less than 1.5% of
