Environmental Science - 12e - Chapter 13.pdf - po ang - Januszek66

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Energy

How Long Will Supplies

of Conventional Oil Last?

CORE CASE STUDY

To keep using conventional oil at the projected rate of in-

crease, we must discover global oil reserves equivalent to two

new Saudi Arabian supplies every 10 years. Most oil geologists

say this is highly unlikely.

The exciting and urgent challenge for this century is to

sharply reduce our waste of oil and other energy resources and

to find an array of substitutes for oil and other fossil fuels. This

would help to slow emissions of carbon dioxide that contribute

to global warming and climate change. There are no easy solu-

tions because all energy options have advantages and disadvan-

tages, as discussed in this chapter.

Oil, which supplies about one-third of the world’s energy, is the

lifeblood of most of the world’s economies and modern lifestyles.

We use oil to grow most of our food, transport people and

goods, and make most of the things we use every day—from

plastics to asphalt on roads.

Stretched end to end, the number of barrels of oil the world

used in 2007 would circle the equator 650 times! And projected

oil use in 2020 would raise that number to 870. To meet this

rapidly growing demand, oil companies have drilled wells on the

land and at sea (Figure 13-1).

Geologists report that known and projected global reserves

of conventional oil are expected to be 80% depleted sometime

between 2050 and 2100, depending on consumption rates. If

that is correct, conventional oil should be reaching its sunset

years sometime during this century. (See Supplement 15 on

p. S61 for a brief history of the Age of Oil.)

We have three options: look for more oil, use or waste less

oil, or use something else. Many analysts think we should vigor-

ously pursue all three options. Some contend that higher prices

will stimulate the search for new oil to meet global oil needs.

Some doubt that we can increase oil reserves enough to meet

the rapidly growing future demand for oil. For example, between

2000 and 2007, the world consumed nine times more oil than

the oil industry discovered. Yet, because oil companies and many

governments are secretive about oil reserves, no one really knows

how much oil might be available.

Others argue that even if we find much more conventional

oil or if rising prices make it profitable to develop unconventional

sources of oil, we are ignoring the consequences of the high

exponential growth in global oil consumption. Suppose we con-

tinue to use oil reserves at the current exponential rate of about

2.8% per year with the unlikely assumption that the rate won’t

increase. Here are some projections based on this scenario:

•

Saudi Arabia, with the world’s largest known crude oil re-

serves, could supply the world’s entire oil needs for about

10 years.

•

The estimated reserves under Alaska’s North Slope—the

largest ever found in North America—would meet current

world demand for only 6 months or U.S. demand for 3 years.

•

The estimated reserves in Alaska’s Arctic National Wildlife

Refuge (ANWR) would meet current world oil demand for

only 1–5 months and U.S. demand for 7–24 months.

Figure 13-1 Thunder Horse offshore floating oil production platform,

located in the Gulf of Mexico.

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Key Questions and Concepts

13-1 What major sources of energy do we use?

CONCEPT 13-1A About three-quarters of the world’s com-

mercial energy comes from nonrenewable fossil fuels, and the rest

comes from nonrenewable nuclear fuel and renewable sources.

CONCEPT 13-1B Net energy is the amount of high-quality

usable energy available from a resource after the amount of energy

needed to make it available is subtracted.

13-4 Why is energy efficiency an important energy

source?

CONCEPT 13-4 We could save more than 40% of all the energy

we use by improving energy efficiency.

13-5 What are the advantages and disadvantages

of renewable energy resources?

CONCEPT 13-5 Using a mix of renewable energy sources—

especially wind, solar energy, hydropower, biofuels, geothermal

energy, and hydrogen—can drastically reduce pollution, green-

house gas emissions, and biodiversity losses.

13-2 What are the advantages and disadvantages

of fossil fuels?

CONCEPT 13-2 Oil, natural gas, and coal are currently abundant

and relatively inexpensive, but using them causes air and water

pollution and releases greenhouse gases to the atmosphere.

13-6 How can we make a transition to a more

sustainable energy future?

CONCEPT 13-6 We can make a transition to a more sustainable

energy future by greatly improving energy efficiency, using of a mix

of renewable energy resources, and including environmental costs

in the market prices of all energy resources.

13-3 What are the advantages and disadvantages

of nuclear energy?

CONCEPT 13-3 The nuclear power fuel cycle has a low

environmental impact and a low accident risk, but high costs,

radioactive wastes, vulnerability to sabotage, and the potential for

spreading nuclear weapons technology have limited its use.

Note: Supplements 7, 8, 15, and 16 can be used with this chapter.

Typical citizens of advanced industrialized nations

each consume as much energy in six months

as typical citizens in developing countries consume

during their entire life.

MAURICE STRONG

13-1 What Major Sources of Energy Do We Use?

CONCEPT 13-1A About three-quarters of the world’s commercial energy comes from

nonrenewable fossil fuels, and the rest comes from nonrenewable nuclear fuel and renew-

able sources.

CONCEPT 13-1B Net energy is the amount of high-quality usable energy available from a

resource after the amount of energy needed to make it available is subtracted.

Most of Our Energy Comes

from the Sun and Fossil Fuels

Almost all of the energy that heats the earth and our

buildings comes from the sun at no cost to

us—one of the four scientific principles of sus-

tainability (see back cover). Without this

essentially inexhaustible solar energy (solar

capital, Concept 1-1A , p. 6), the earth’s aver-

age temperature would be

The commercial energy, sold in the marketplace,

makes up the 1% of the energy we use that is not sup-

plied directly by the sun. Currently, most commercial

energy comes from extracting and burning nonrenew-

able energy resources obtained from the earth’s crust, pri-

marily carbon-containing fossil fuels—oil, natural gas,

and coal (Figure 13-2—formed from the decay of

plants and animals over millions of years.

About 82% of the commercial energy consumed in

the world comes from nonrenewable energy resources—

76% from fossil fuels (oil, natural gas, and coal) and 6%

from nuclear power (Figure 13-3, left). The remaining

18% of the commercial energy we use comes from

renewable energy resources—biomass, hydropower,

geothermal, wind, and solar energy ( Concept 13-1A ).

F),

and life as we know it would not exist. This direct in-

put of solar energy produces several indirect forms of

renewable solar energy: wind, hydropower (falling and

flowing water), and biomass (solar energy converted to

chemical energy and stored in trees and other plants).

240

C (

400

280

Links:

refers to the Core Case Study.

refers to the book’s sustainability theme.

indicates links to key concepts in earlier chapters.

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Oil and natural gas

Oil storage

Coal

Contour

strip mining

Geothermal energy

Oil drilling

platform

Hot water storage

Oil well

Geothermal

power plant

Pipeline

Gas well

Mined coal

Area strip

mining

Pump

Drilling

tower

Pipeline

Coal seam

Water penetrates

down through

the rock

Figure 13-2 Natural capital: important nonrenewable energy resources that can be removed from the earth’s

crust are coal, oil, natural gas, and some forms of geothermal energy. Nonrenewable uranium ore is also extracted

from the earth’s crust and processed to increase its concentration of uranium-235, which can serve as a fuel in

nuclear reactors to produce electricity. Question: Can you think of a time during a typical day when you are not

directly or indirectly using one of these resources?

Nuclear power

Geothermal,

solar, wind

2.5%

Nuclear power

Geothermal,

solar, wind

Hydropower

4.5%

Hydropower,

Natural

gas

23%

Natural gas

21%

Biomass

11%

Coal

23%

Biomass 3%

Coal

22%

Oil

39%

Oil

33%

World

United States

Figure 13-3 Commercial energy use by source for the world (left) and the United States (right) in 2004. Commer-

cial energy amounts to only 1% of the energy used in the world; the other 99% is direct solar energy received

from the sun and, of course, not sold in the marketplace. Question: Why do you think the world as a whole relies

more on renewable energy than the United States does? (Data from U.S. Department of Energy, British Petroleum,

Worldwatch Institute, and International Energy Agency)

281

CONCEPTS 13-1A AND 13-1B

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SCIENCE FOCUS

Net Energy Is the Only Energy That Really Counts

tios for various types of space heating, high-

temperature heat for industrial processes, and

transportation.

Currently, oil has a high net energy ratio

because much of it comes from large, acces-

sible, and cheap-to-extract deposits such as

those in the Middle East. As these sources are

depleted, the net energy ratio of oil will de-

cline and its price is expected to rise sharply.

Electricity produced by nuclear power has

a low net energy ratio because large amounts

of energy are needed to extract and process

uranium ore, convert it into nuclear fuel,

build and operate nuclear power plants, dis-

mantle the highly radioactive plants after

their 15–60 years of useful life, and store the

resulting highly radioactive wastes safely for

10,000–240,000 years. Each of these steps

in the nuclear fuel cycle uses energy and

costs money. Some analysts estimate that

ultimately the conventional nuclear fuel cycle

will lead to a net energy loss because we will

have to put more energy into it than we will

ever get out of it.

t takes energy to get energy. For ex-

ample, before oil becomes useful to us,

it must be found, pumped up from beneath

the ground or ocean floor, transferred to a

refinery and converted to useful fuels, trans-

ported to users, and burned in furnaces and

cars. Each of these steps uses high-quality

energy. The second law of thermodynamics

tells us that some of the high-quality energy

used in each step is automatically wasted

and degraded to lower-quality en-

ergy ( Concept 2-4B , p. 33).

The usable amount of high-quality energy

available from a given quantity of an energy

resource is its net energy . It is the total

amount of energy available from an energy

resource minus the energy needed to find,

extract, process, and get that energy to con-

sumers ( Concept 13-1B ). It is calculated by

estimating the total energy available from the

resource over its lifetime and then subtracting

the amount of energy used, automatically

wasted because of the second law of ther-

modynamics, and unnecessarily wasted in

finding, processing, concentrating, and trans-

porting the useful energy to users.

Net energy is like the net profit in a busi-

ness after expenses. For example, the net

profit in a business with $1 million in sales

and $800,000 in expenses is $200,000, and

that is the only number that really matters.

For example, suppose that it takes 8 units

of energy to produce 10 units of energy from

a particular energy resource. Then the net

energy yield is only 2 units of energy. We can

express net energy as the ratio of energy pro-

duced to the energy used to produce it. In

this example, the net energy ratio would be

10/8, or approximately 1.25. The higher the

ratio, the greater the net energy. When the

ratio is less than 1, there is a net energy loss.

Figure 13-A shows estimated net energy ra-

Space Heating

5.8

Passive solar

Critical Thinking

Should governments require that all energy

resources be evaluated in terms of their net

energy? Why do you think this is not being

done?

4.9

4.5

Natural gas

Oil

Active solar

Coal gasification

Electric heating (coal-fired plant)

Electric heating (natural-gas-fired plant)

Electric heating (nuclear plant)

1.9

1.5

0.4

0.3

High-Temperature Industrial Heat

28.2

Surface-mined coal

Underground-mined coal

Natural gas

Oil

Coal gasification

Direct solar (concentrated)

25.8

4.9

4.7

1.5

0.9

Figure 13-A Net energy ratios for various energy systems over their

estimated lifetimes: the higher the net energy ratio, the greater the

net energy available ( Concept 13-1B ). Question: Based on these

data which two resources in each category should we be using?

Compare this with the major resources we are actually using as

shown in Figure 13-3. (Data from U.S. Department of Energy and

Colorado Energy Research Institute, Net Energy Analysis, 1976; and

Howard T. Odum and Elisabeth C. Odum, Energy Basis for Man and

Nature, 3rd ed., New York: McGraw-Hill, 1981)

Transportation

Natural gas

4.9

Gasoline (refined crude oil)

Biofuel (ethanol)

Coal liquefaction

Oil shale

4.1

1.9

1.4

1.2

Nonrenewable fossil fuels are widely used because

they are abundant, easily transportable, and inexpen-

sive compared to most other alternatives. In order, the

three largest users of fossil fuels are the United States,

China, and the European Union, together accounting

for more than half of all fossil fuel consumption. Energy

use per person varies throughout the world (see Fig-

ure 1 on p. S62 in Supplement 16).

Roughly half the world’s people in developing

countries burn potentially renewable wood and char-

282

CHAPTER 13

Energy

83376_14_ch13_p279-322.ctp 8/10/07 2:08 PM Page 283

coal to heat their dwellings and cook their food. Most

of this biomass is collected by users and not sold in

the marketplace. Thus, the actual percentage of re-

newable biomass energy used in the world is higher

than the 11% figure shown in Figure 13-3 (left).

Many of these individuals face a fuelwood shortage that

is expected to worsen because fuelwood is being har-

vested faster than nature replaces it.

All energy resources should be evaluated on the

basis of their supplies, environmental impact, and how

much useful energy they actually provide (Science Fo-

cus, at left).

Examine and compare energy sources used in

developing and developed countries at ThomsonNOW.

13-2 What Are the Advantages and Disadvantages

of Fossil Fuels?

CONCEPT 13-2 Oil, natural gas, and coal are currently abundant and relatively inexpen-

sive, but using them causes air and water pollution and releases greenhouse gases to the

atmosphere.

We Depend Heavily on Oil

Petroleum, or crude oil (oil as it comes out of the

ground), is a thick and gooey liquid consisting of hun-

dreds of combustible hydrocarbons along with small

amounts of sulfur, oxygen, and nitrogen impurities. It

is also known as conventional or light oil. Crude oil and

natural gas are called fossil fuels because they were

formed from the decaying remains (fossils) of organ-

isms living 100–500 million years ago.

Deposits of crude oil and natural gas often are

trapped together under a dome deep within the earth’s

crust on land or under the seafloor (Figure 13-2). The

crude oil is dispersed in pores and cracks in under-

ground rock formations, somewhat like water saturat-

ing a sponge. To extract the oil, a well is drilled into the

deposit. High-tech equipment can drill oil and natural

gas wells on land and at sea (Figure 13-1) to a depth of

8 kilometers (5 miles). Then oil, drawn by gravity out of

the rock pores and into the bottom of the well, is

pumped to the surface.

At first oil almost squirts from the well. But after

years of pumping, pressure disappears and production

starts declining at a point referred to as the peak produc-

tion of a well, usually after a decade or so. For global oil

production to expand, the oil output from newly found

reserves must stay ahead of the declining output from

wells that have passed their peak.

After it is extracted, crude oil is transported to a re-

finery by pipeline, truck, or ship (oil tanker). There it is

heated and distilled to separate it into components

with different boiling points (Figure 13-4)—a techno-

logical marvel based on complex chemistry and engi-

neering. Some of the products of oil distillation, called

petrochemicals, are used as raw materials in indus-

trial organic chemicals, pesticides, plastics, synthetic

fibers, paints, medicines, and many other products.

Producing a desktop computer, for example, consumes

10 times its weight in fossil fuels, mostly oil.

Lowest Boiling Point

Gases

Gasoline

Aviation

fuel

Heating oil

Diesel

oil

Naphtha

Grease

and wax

Heated

crude oil

Furnace

Asp halt

Figure 13-4 Refining crude oil. Based on their boiling points, com-

ponents are removed at various levels in a giant distillation column.

The most volatile components with the lowest boiling points are

removed at the top of the column.

Highest Boiling Point

283

CONCEPT 13-2

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