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Science and Society

Grow Your Own Fuel?
ave you heard of biodiesel? Biodie- Why would we want to use vegetable oil is used. People behind such a biodiesel-
Hsel is a vegetable-based oil that can to run diesel engines? First, it is a sustain- powered school bus complained that it
be used for fuel in diesel engines. It can be able (or renewable) resource. It also reduces smelled like fried potatoes, making them
made from soy oils, canola oil, or even recy- dependency on foreign oil as well as cuts hungry.
cled deep-fryer oil from a fast-food restau- the trade deficit. It runs smoother, produces There is a website maintained by some
rant. Biodiesel can be blended with regular less exhaust smoke, and reduces the health biodiesel users where you can learn how to
diesel oil in any amount. Or it can be used risks associated with petroleum diesel. The produce your own biodiesel from algae. See
100 percent pure in diesel cars, trucks, and only negative aspect seems to occur when www.biodieselnow.com and search for the
buses, or as home heating oil. recycled oil from fast-food restaurants term algae.

needs. Next petroleum began making increased contributions permits the accumulation of sediments that are exceptionally rich
to the energy supply. Now increased economic and environ- in organic material. This could occur under special conditions in
mental constraints and a decreasing supply of petroleum are a freshwater lake, or it could occur on shallow ocean basins. In
producing another supply shift. The present petroleum-based either case, most of the organic material is from plankton—tiny
energy era is about to shift to a new energy era. free-floating animals and plants such as algae. It is from such ac-
About 97 percent of the total energy consumed today is cumulations of buried organic material that petroleum and natu-
provided by four sources: (1) petroleum (including natural gas), ral gas are formed. The exact process by which these materials
(2) coal, (3) hydropower, and (4) nuclear. The following is a become petroleum and gas is not understood. It is believed that
brief introduction to these four sources. bacteria, pressure, appropriate temperatures, and time are all im-
portant. Natural gas is formed at higher temper atures than is pe-
PETROLEUM troleum. Varying temperatures over time may produce a mixture
The word petroleum is derived from the Greek word petra, mean- of petroleum and gas or natural gas alone.
ing rock, and the Latin word oleum, meaning oil. Petroleum is Petroleum forms a thin film around the grains of the rock
oil that comes from oil-bearing rock. Natural gas is universally where it formed. Pressure from the overlying rock and water
associated with petroleum and has similar origins. Both petro- move the petroleum and gas through the rock until it reaches
leum and natural gas form from organic sediments, materials that a rock type or structure that stops it. If natural gas is present, it
have settled out of bodies of water. Sometimes a local condition occupies space above the accumulating petroleum. Such accu-
mulations of petroleum and natural gas are the sources of sup-
ply for these energy sources.
Discussions about the petroleum supply and the cost of
petroleum usually refer to a “barrel of oil.” The barrel is an
Other (geothermal and accounting device of 42 U.S. gallons. Such a 42 gallon barrel
solar) (1%) Hydro (3%) does not exist. When or if oil is shipped in barrels, each drum
Biomass (3%)
holds 55 U.S. gallons. The various uses of petroleum products
Nuclear (8%)
are discussed in chapter 12.
The supply of petroleum and natural gas is limited. Most of
Petroleum the continental drilling prospects appear to be exhausted, and the
(40%)
search for new petroleum supplies is now offshore. In general,
Natural gas over 25 percent of our nation’s petroleum is estimated to come
(23%)
from offshore wells. Imported petroleum accounts for more than
one-half of the oil consumed, with most imported oil coming
from Mexico, Canada, Venezuela, Nigeria, and Saudi Arabia.
Petroleum is used for gasoline (about 45 percent), diesel
(about 40 percent), and heating oil (about 15 percent). Petroleum
is also used in making medicine, clothing fabrics, plastics, and ink.

Coal (23%) COAL
Petroleum and natural gas formed from the remains of tiny
FIGURE 3.19 Primary energy consumed in the United States
organisms that lived millions of years ago. Coal, on the other
by source, 2005. Source: Energy Information Administration (www.eia.doe.gov/
emeu/aer/pdf/pages/sec1.pdf). hand, formed from an accumulation of plant materials that
3-15 CHAPTER 3 Energy 75