Environmental Engineering Reference
In-Depth Information
NEXT TIME YOU FIND YOURSELF IN TRAFFIC, TRY THIS NIFTY
thought exercise. Ignore the cars
within your field of vision and imagine instead the contents of their fuel tanks. Visualize gas-
oline flowing up and down the highway.
Let's assume the typical American car carries seven gallons of refined petroleum product in its
tank at any given moment (a fifteen-gallon tank half-full). That's a lot of liquid to be carting around.
In fact, gasoline is the second-most-consumed fluid in the United States, after water. Each Amer-
ican household consumes an average of 350 gallons of water per day and 2.5 gallons of gasoline;
milk, coffee, and beer clock in at 0.15 gallons, 0.12 gallons, and 0.1 gallons, respectively.
If you do this visualization exercise, you might find yourself seeing rivulets, streams, and—in
the case of big freeways—
rivers
of gasoline coursing across the land. For the United States as a
whole, four hundred million gallons of gasoline enter and leave the flow every day. But, since we
routinely carry more gasoline with us than we intend to use immediately, the total amount in car gas
tanks at any given moment is roughly seven times larger, so that America's gasoline rivers slosh
with 2.8 billion gallons on any given day.
A real river or stream is the spine of a watershed and the heart of a riparian ecosystem. Trees,
shrubs, insects and their larvae, fish, birds, amphibians, and mammals all derive their livelihoods
from flowing water.
A river of gasoline is sterile by comparison, even though petroleum itself is primarily composed
of the same two elements as living things: carbon and hydrogen. Oil is a
fossil
fuel, after all, made
of heaps and heaps of dead plankton and algae compressed and heated over millions of years so that
carbohydrates became hydrocarbons. Gasoline rivers are no place for nonhuman life forms: only
the most daring of weeds and foolhardy of animals venture there, with the latter often ending up as
road kill. Indeed, highways could be thought of as rivers of death.
Water makes itself seen and felt as it falls from the sky and collects in puddles, ponds, lakes,
and oceans. The tiny fraction of Earth's water that enters municipal delivery systems temporarily
disappears into a maze of pipes but soon reemerges at the ends of faucets and showerheads.
Gasoline is covert and furtive by comparison. Oil emerges from wells and, via pipelines, enters
refineries; from these, gasoline gushes through more pipes that carry it to regional distribution cen-
ters, whence it is delivered by tanker truck to filling stations. We travel to those stations to dispense
gas by hose into the tanks of our cars; from those tanks it is delivered to its final moment of com-
