Environmental Engineering Reference
In-Depth Information
8
F
OSSIL
F
UELS
Heat, Light, and Prime Movers
Nature, in providing us with combustibles on all sides, has
given us the power to produce, at all times and in all
places, heat and the impelling power which is the result of
it.
Sadi Carnot, R´flexions sur la puissance motrice du feu
(1824)
ing a solar one. But modern civilization has added two
kinds of energy sources to set itself apart from all
preindustrial societies: fossilized stores of solar energy
extracted in the form of coals and hydrocarbons (crude
oils and natural gases), and electricity generated mostly
by burning these fuels as well as by water and nuclear
fission and, to a much lesser extent, by wind and the
Earth's heat.
Unlike the nearly instantaneous solar flows and their
modestly aged phytomass and animate energy transfor-
mations, fossil fuels were formed through slow heat and
pressure transformation of accumulated biomass, both
terrestrial and marine, which lasted typically 10
7
-10
8
years. Dukes (2003) estimated that typical preservation
factors (fractions of phytomass carbon that remained in
a fossil fuel) for coal are just above 10%, but for crude
oil in marine reservoirs less than 0.5%. Consequently,
during the later 1990s, annual global consumption of
fossil fuels burned organic carbon that required about
All preindustrial societies derived their energy from
sources that were almost immediate transformations of
solar radiation (flowing water and wind) or that took rel-
atively short periods of time to become available in a
convenient form: just a few months of photosynthetic
conversion to produce food and feed crops, a few years
of metabolism before domestic animals and children
reached working age, or a few decades to accumulate
phytomass in mature trees to be harvested for fuel wood
and charcoal. Solar radiation remains as important as ever
because it drives the Earth's climate, energizes its bio-
sphere, powers all photosynthesis, and makes every build-
