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OCR for page 74
Technological Trajectories and the Human Environment. 1997.
Pp. 74-88. Washington, DC: National Academy Press.
Freeing Energy from Carbon
NEBOl3A NA~(ENOVIt
The doing of more with less attests to the practical advancement of societies.
In fact, labor, capital, and inputs of other factors to the economy have demonstra-
bly decreased per unit of output and value added since the beginnings of the
industrial revolution some two hundred years ago. These increases in the produc-
tivity of resources owe to numerous technical and organizational innovations and
to an enormous accumulation of knowledge and experience.
A portion of the increases in productivity is attributable simply to the in-
creasing scale of activities, also made possible by technical and organizational
innovations. Often with greater size, cost decreases and efficiency increases
within specific frames. For example, in building electricity-generating plants a
long-standing rule of thumb was that the cost of the plant would grow with two-
thirds the power of its size. We are uncertain now where we stand with respect to
optimal scale of many facilities and systems, but it seems likely that considerable
opportunities to lift efficiency remain.
Perhaps more important than simply size and more certain to continue yield-
ing productivity gains is the accumulation of knowledge and experience. Growth
in output in an economic system with suitable incentives tends to bring positive
returns of its own. This process is sometimes referred to as "learning by doing."
Analysis of learning curves in a range of industries, beginning with the manufac-
ture of aircraft, has provided ample evidence that the costs per unit of output
decrease rapidly at a rate proportional to the doubling of the output (Argote and
Epple, 1990; Christianson, 1995~.
Energy industries and energy systems are not exceptional. This essay will
demonstrate that large secular decreases in energy requirements per unit of eco
74
OCR for page 75
FREEING ENERGY FROM CARBON
75
nomic output have been achieved throughout the world, as we have learned better
how to make, operate, and use energy systems. Furthermore, the emissions of
carbon dioxide from energy systems, coming from the combustion of the carbon
molecules that wood, coal, oil, and gas all contain, have also decreased per unit of
energy consumed. This decarbonization of the energy system proves to be em-
blematic of its entire evolution.
At the same time, because of population and general economic growth,
absolute world consumption of energy (and many other resources) has increased,
especially in the more industrialized countries. This absolute growth often domi-
nates environmental news and views. Rising carbon dioxide emissions are the
main contributor to fears of global climatic change. This and other environmental
concerns associated with carbon makes energy free from carbon a highly desir-
able goal for the energy system. The fact that energy and most of the other factor
inputs have decreased per unit of output over long periods of time provides a
fresh basis on which to project the range of possible future resource use and
emissions.
A glance at the changes in labor and materials requirements helps to estab-
lish the context and the pervasiveness of the phenomenon that we will observe
most closely in energy. Since 1860, the number of hours that workers in the
industrialized countries are engaged in paid work each year has generally de-
creased by half (Figure 1~. Though the Japanese bucked the trend for several
decades around mid-century and continue to work more than their European and
American counterparts, they too are working less. Taking into account the dra-
matic increase in individual income and consumption over the period, we know
that the labor requirements per unit of income and output decreased much faster
than the number of hours worked. Furthermore, because life expec-tancy in-
creased by several decades during this period, the years of paid work required to
sustain lifelong consumption for a worker at prevailing levels decreased from
about three-quarters of a lifetime to less than one-half (Ausubel and Grubler,
1995~.
Decreases in requirements for many materials are similarly dramatic (see
Wernick et al., this volume). For example, in the United States, which is quite
representative of industrialized countries in this regard, steel use declined from
about 70 kilograms per $1,000 of GNP (in 1983 dollars) in 1920 to about one-
third that level in recent years; cement per GNP in the United States has dropped
by about half since 1960 (Williams et al., 1987~. However, this dematerializatio~z
of the economy is varied. In some cases, a lighter steel beam does the work of an
earlier, heavier one. In other cases, new materials replace the steel. In contrast,
demand per GNP has grown steeply since mid-century for certain petrochemicals
(such as ethylene) and for advanced composite materials. Requirements for paper
per GNP have been rather flat since about 1930.
Analysis of energy materials and decarbonization may in practice shed light
on the question of dematerialization. Because energy is one of the most important
OCR for page 76
76
NEBO]SA NAKICENOVIC
Hours
3000
2700
2400
2100
1800
.
~_`
1
N "' ' " .
; .~` Japan
Japan
,_ \N 'at, "a ". 1
France\~many
_
1500- 1 1 1 ~ 1 1 1 1
1850 1900 Year 1950 2000
FIGURE 1 Annual working hours in five industrialized countries from 1860 to 1990,
expressed in total working hours per year. NOTE: Hours spent on sick leave, stnkes, and
holidays are subtracted from the formal working time. SOURCE: Ausubel and Grubler
(1995) and Maddison (1991~.
factor inputs and is embedded in most materials, products, and services, de-
creases in specific energy requirements can also decrease the intensity of materi-
als use. The carbon content of energy and the subsequent carbon dioxide emis-
sions form the largest single mass flow associated with human activities,
excepting water. Current annual global carbon emissions are about 6 billion tons,
or more than 1,000 kilograms per person on the planet. In comparison, the global
steel industry annually produces about 700 million tons, or about 120 kilograms
per person. Therefore, decarbonization can contribute in a large way to demateri-
alization.
Let us now turn to energy and examine the savings of carbon that have been
obtained, why they may have occurred, and whether future savings may be suffi-
cient to spare the environment some unwanted heat.
THE GLOBAL HISTORY OF ENERGY AND CARBON SAVINGS
To form a picture of carbon use, we need to be able to sum and compare its
appearances. One way is to index carbon by the ratio of carbon atoms to hydro-
gen atoms in the energy sources that contain both of these fuels. Fuelwood has
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FREEING ENERGY FROM CARBON
77
the highest effective carbon content, with about ten carbon atoms per hydrogen
atom. If consumed without a compensating growth of biomass, which occurred in
the past and still occurs in most developing countries, fuelwood thus produces
higher carbon emissions than any of the fossil energy forms. Among fossil energy
sources, coal has the highest carbon-to-hydrogen ratio, roughly one to one. Oil
has on average one carbon for every two hydrogen atoms, and natural gas, or
methane, has a ratio of one to four. Using these types of elemental analyses, we
can estimate the total amount of carbon contained in a given supply of an indi-
vidual fuel or a mix of fuels and compare this amount to energy consumed or
associated economic output.
Decarbonization can then be expressed as a product of two factors: 1J car-
bon emissions per unit of energy consumption; and 2) energy requirements per
unit of value added, which is often called energy intensity. Available data allow
us to assess with reasonable confidence the trend for each of these factors since
the nineteenth century for major energy-consuming regions and countries, such
as the United States and the United Kingdom, and thus for the world as a whole
as well. As Figure 2 shows, the ratio of carbon emissions per unit of primary
energy consumed globally has fallen by about 0.3 percent per year since 1860.
The ratio has decreased because high-carbon fuels, such as wood and coal, have
been continuously replaced by those with lower carbon content, such as gas, and
also in recent decades by nuclear energy from uranium and hydropower, which
contain no carbon.
1.2
1.1
an
·= 0.8
o
Q
c; 0.7
0.6
0.5 L860 1880 1900 1920 1940 1960 1980 2000
FIGURE 2 Carbon intensity of global energy consumption, expressed in tons of carbon
per ton of oil equivalent energy (tC/toe).
OCR for page 78
78
NEBOJ:A NAKICENOVIC
2.2
2.0
1.8
1.6
so
~1.4
o
ye
-
~1.0
.m
0.8
0.6
0.4
0.2
o
Former
Soviet
Union
\
MESA
Germ
France
NEW
Pa
Japan~SA
France
~,,~Pacific Asia
1 1 1 1 1 1 1 1
1860 1880 1900 1920 1940
Year
1960 1980 2000
FIGURE 3 Primary energy intensity, including biomass, per unit of value added from
1855 to 1990, expressed in kilograms of oil equivalent energy per GDP in constant 1990
US dollars (kgoe/US$1990~.
The historical rate of decrease in energy intensity per unit of value appears to
have averaged about 1 percent per year since the mid-nineteenth century and
about 2 percent per year in some countries since the 1970s. The overall tendency
is toward lower energy intensities, although paths of energy development in
different countries have varied enormously and rather consistently over long
periods (Figure 3~. For example, France and Japan have always used energy more
sparingly than the United States, the United Kingdom, or Germany. In some of
the rapidly industrializing countries, such as China or Nigeria, commercial en-
ergy intensity is still increasing. Because commercial energy replaces traditional
energy forms not sold in the markets whose transactions find their way into
national statistical data, total energy intensity may diminish while commercial
energy intensity increases. The present energy intensity of Thailand resembles
the situation in the United States in the late 1940s. The energy intensity of India
and its present improvement rates are similar to those of the United States about
a century ago.
Combining the two factors of carbon intensity and energy intensity (Figure
OCR for page 79
FREEING ENERGY FROM CARBON
2.0
U.
oo
-
_
o1.5 _
cn ~
O It
cn1.0
-
._
~~0.5
~0
x 1870
O 1913
· 1950
1970
1988
~ _
, _, ~
0.5 0.6 0.7 0.8 9.9 1.0 1.1 1.2 1.3 1.4
Carbon Intensity (kgC/kgoe)
·~
France
l
-~ ~ _ >uaDan
ChinaJ ~ U.S. 1820
1988 - 2.77~0.932.47~1.27
l j India /
_ . .
U.S.
/ 1 850
S. K; or
Carbon Spanng
1 1 1 1 1 1 1 1 1 1
FIGURE 4 Global decarbonization by carbon and energy sparing from 1870 to
1988, expressed in kilograms of carbon per kilogram of oil equivalent energy (kgC/
kgoe) and in kilograms of oil equivalent energy per $1,000 of GDP in constant 1985
dollars (kgoe/US$1,000 1985J. SOURCE: Grubler (1991~.
79
4) reveals the large differences in the policies and structures of energy systems
among countries. For example, though Japan and France have both achieved high
degrees of decarbonization, they have followed disparate routes. At the global
level, the long-term overall reduction in carbon intensity per unit of value from
both factors totals about 1.3 percent per year since the mid-1800s.
The major determinants of energy-related carbon emissions can be repre-
sented as multiplicative factors in a simple equation. Placing carbon emissions on
one side, on the other we have population growth, per capita value added, energy
consumption per unit of value added, and carbon emissions per unit of energy
consumed (Yamaji et al., 1991~. As we have seen, the last two terms in this
equation are decreasing globally. However, their decline is counteracted by rising
values for the preceding terms, population and economic activity, resulting in an
overall global increase in energy consumption and carbon emissions.
The world's global population is currently increasing at a rate of about 1.6
percent per year. The longer-term population growth rate since 1800 has been
about 1 percent per year. Most population experts predict at least another dou-
bling during the next century (see United Nations, 1992, and Vu, 1985; see also
Kates, this volume). Economic activity has been increasing in excess of global
OCR for page 80
80
NEBOl:A NAKIC-ENOVIC
population growth since the beginning of industrialization, made possible by the
productivity increases referred to at the outset of this essay. In recent decades
global economic growth, stirred by both population and productivity gains, has
proceeded at about 3 percent per year. Subtracting 1.3 percent for decarbonization,
the result is that global carbon emissions have been increasing at about 1.7
percent per year. A continuation would imply a doubling of emissions in about
forty years. Fearing such an increase, we must examine in detail the differing
paths to decarbonization to see what the limits of the process might be.
DECONSTRUCTING DECARBONIZATION
An examination of five countries China, France, India, Japan, and the
United States furthers our understanding of the decarbonization process
(Nakicenovic, 1996. These countries represent diverse economic and energy
systems and life-styles as well as a significant share of the world's energy use.
The United States has one of the highest energy intensities of all the industrial-
ized countries, and the highest per capita energy consumption in the world.
France and Japan have among the lowest energy intensities in the world, but for
different reasons, as we shall discuss. China and India are rapidly developing and
still replacing traditional energy sources with commercial ones, and thus they
exhibit very high energy and carbon intensities. Together, the five countries
account for about 45 percent of global primary energy consumption and more
than 40 percent of energy-related carbon emissions.
To determine more precisely the various causes and determinants of the
decreasing carbon intensity of energy, we disaggregate the energy system into its
three major constituents: primary energy consumption, energy conversion, and
final energy consumption. Primary energy consumption embraces the require-
ment for original resources such as coal, crude oil, and uranium. Final energy
refers to the gasoline pumped into a car's fuel tank, the electricity for powering a
room air conditioner, or firewood if used directly for cooking or heating. Primary
energy, such as coal, is rarely consumed in its original form in a household or
office but rather is converted into electricity, fuel, and heat. Thus, final energy,
which is consumed directly, in some sense represents best the actual energy
requirements of the economy and individual consumers.
In fact, neither primary energy consumption nor conversion is transparent to
consumers. For example, the production process for electricity is invisible to
most consumers. Because electricity itself is carbon-free, it does not emit carbon
(or soot, sulfur dioxide, and other pollutants) at the point of consumption. How-
ever, carbon can be emitted in converting primary energy forms into electricity.
To a lesser degree this is also true of other forms of final energy, such as oil
products. Although the carbon emissions per liter of diesel or gasoline finally
used in a truck are basically the same throughout the world, the carbon emissions
OCR for page 81
FREEING ENERGY FROM CARBON
81
produced in converting different grades of crude oil into the two products can
vary substantially.
To Reconstruct the constituent decarbonization rates of the energy system,
we make three assumptions. First, the carbon intensity of primary energy is
defined as the ratio of the total carbon content of primary fuels to total primary
energy consumption for a given country. Second, the carbon intensity of final
energy is defined as the carbon content of all forms of final energy divided by the
total final energy consumption. The third assumption is that the carbon intensity
of energy conversion is the difference between the two intensities just described.
So, for example, the carbon intensity of primary energy runs high when wood and
coal supply most of the fuel. The carbon intensity of conversion runs high when
coal burns to make most of the electricity and when the conversion (or transmis-
sion and distribution) system itself is wasteful. Efficiency improvements in the
energy system mean that less primary energy is consumed per unit of final en-
ergy; lower conversion losses therefore result in lower carbon emissions. The
carbon intensity of consumption runs high when the final consumer cooks with
coal or travels by gasoline and when end-use devices are inefficient.
Let us now compare the carbon intensities of final, primary, and conversion
energy for the United States, Japan, France, China, and India in recent decades
(Figures 5 through 7~. Steady reductions in the carbon intensity of final energy in
all five countries stand out above all. On average, the three industrialized coun-
tries have spared about 20 percent since 1960, while the pair of developing
countries have cut back about 15 percent since the early 1970s. The reductions
converge tightly in the three industrialized countries. The gap between the devel-
oped and the developing countries is also slowly narrowing because of the slightly
more rapid declines in intensity in the latter.
The major reason for the decarbonization of final energy is the increasing
share of electricity in final energy throughout the world. The percentage of global
primary energy used to create electricity has climbed during this century from 5
in the year 1910 to 20 in 1950 to about 35 in 1990. A second reason is that the
average mix of other fuels consumed for final energy has a decreasing carbon
content, that is, greater shares of oil products and natural gas. Accordingly, these
products also have a higher hydrogen content, a point that will be discussed in the
final section of this essay.
The carbon intensity of primary energy has also fallen in all five countries,
though only very slightly in the United States, where coal has retained its strong
role. The carbon intensities of conversion give a completely different picture,
however. The diversity in the development and structure of the energy systems of
the five countries becomes apparent. In the developing countries, the carbon
intensity of conversion has increased, while in France it dropped sharply; in the
United States and Japan the conversion intensity initially rose before declining
during the latter part of the period analyzed.
Should China and India continue to rely heavily on coal as their primary
OCR for page 82
82
NEBOlSiA NAKICENOVIC
1.1
a' 1.0
-
V
<1, 0-9
-~
~ 0.8
o
cat
0.7
0.6
1 1
Final
~ France
tape
India
1960 1965 1970 1975
Year
1980 1985 1990
FIGURE 5 Carbon intensities of final energy, expressed in tons of carbon per ton of
oil equivalent energy (tC/toe).
1.1
a_
O 1.0
-
~ 0.9
a'
._
. -
(n
~ 0.8
-
o
<~5 0.7
0.6
0.5
Primary
China
India
U SA
Japan
-
~ France
1 1 1 1 1 1 1
1960 1965 1970
1980 1985 1990
FIGURE 6 Carbon intensities of primary energy, expressed in tons of carbon per ton
of oil equivalent energy (tC/toe).
OCR for page 83
FREEING ENERGY FROM CARBON
1.3
_ -
~ 1 . 1
to
.,& 0.9
._
In
~ 0.7
o
Q
0.5
0.3
Conversion
C~
India
Japan
\France
1
1960 1965 1970 1975
Year
1980 1985 1990
FIGURE 7 Carbon intensities of energy conversion, expressed in tons of carbon per
ton of oil equivalent energy (tC/toe).
83
source of energy, continuing to lessen the carbon intensity of primary energy in
these countries will prove difficult. In fact, sometime in the next century the
downward trend in the carbon intensity of primary energy could reverse itself,
caused by an even higher share of electricity in end use but generated with coal.
Alternatively, China and India could restructure their energy systems to make
increasing use of natural gas or nuclear energy and other zero-carbon options.
Such shifts would align their energy systems with those of the more industrial-
ized countries.
Focusing on the United States and Japan, we see that the carbon intensity of
primary energy exceeds that of final energy, with conversion intensity the highest
of the three. While final carbon intensity decreases somewhat faster in Japan
(about 0.8 percent per year) than the United States (about 0.5 percent per year),
the difference in the conversion intensities is much more dramatic. In both coun-
tries the changes in the carbon intensity of energy conversion are erratic, espe-
cially compared to the steady improvements in final intensities. The overall re-
duction of carbon intensity in Japan stems primarily from improvements in energy
efficiency and, to a lesser degree, from the replacement of carbon-intensive en-
ergy forms.
France provides a contrast. Here, the rapid introduction of nuclear energy
since the mid-1970s has led to higher rates of decarbonization of primary energy
OCR for page 84
84
NEBOJSA NAKICENOVIC
and of conversion (because an increasing share of electricity is produced without
carbon emissions) than of final energy. This strategy to achieve low carbon
emissions is completely internal to the energy system and fundamentally
decoupled from the consumer. Nevertheless, the relatively smooth improvement
in final carbon intensity is similar to that observed in Japan and the United States.
China and India present a different picture, though they resemble one an-
other. The three energy ratios and their evolution are similar in these countries
despite their many social and cultural differences, as well as those differences
that may be attributed to the varying development paths of planned and market
economies. In both countries, the carbon intensity of primary energy is diminish-
ing slightly. The carbon intensity of final energy, on the other hand, decreases at
rates comparable to those observed in industrialized countries. In India, the faster
decarbonization of final energy is due to the replacement of traditional fuels by
commercial energy forms. For example, the use of biomass (mainly wood that is
not replaced by a new forest) is more carbon intensive than using either kerosene
or bottled gas. The difference in carbon intensity between electric lighting (espe-
cially if efficient light bulbs are used) and traditional illumination is even more-
pronounced. In any case, the developing economies are undergoing basically the
same process of decarbonizing final energy use as the most developed countries.
In the industrialized countries, the decarbonization of final energy consump-
tion has been accompanied by additional structural changes in the energy system.
These led to improvements in decarbonization in the energy system itself, as
demonstrated by the downward trends in the carbon intensity of conversion. In
contrast, China and India have not undergone this transition. Their energy sys-
tems depend heavily on coal, whereas most industrialized countries have in large
measure replaced coal with less carbon-intensive sources, even in electricity
production. As a consequence of their dependence on coal, both China and India
show rapid increases in the carbon intensity of conversion. Should a transition to
a lower carbon intensity in developing countries not occur in the coming decades,
the likely reductions in carbon emissions in the industrialized countries will be
offset, hampering efforts to halt the global increase in carbon emissions.
In sum, determining decarbonization only as the ratio of total carbon emis-
sions per unit of primary energy consumption may veil the interaction between
the energy system and the economy. As the structure of an energy system changes,
so does the carbon intensity of its three constituent parts. The actual forms of
final energy demanded and consumed matter greatly in the logic of
decarbonization. Because electricity and heat contain no carbon, the carbon in-
tensity of final energy is generally lower than the carbon intensity of primary
energy. In addition, its rate of decrease exceeds that of primary energy because of
the increasing share of electricity and other fuels with lower carbon content; such
as natural gas, in the final energy mix. At the level of final energy, decarbonization
is a durable, pervasive phenomenon. The likely explanation is a congruence in
OCR for page 85
FREEING ENERGY FROM CARBON
85
consumer behavior and preferences as expressed in the structure of final energy
over a wide range of income and developmental levels.
THE ELEMENTAL EVOLUTION
We have seen the increasing needs for electricity and hydrogen-rich forms of
final energy. Can these be reconciled with the relatively slow and often opposing
changes in the structure of energy systems and the primary energy supply? The
historical replacement of coal by oil, and later by natural gas, at the global level
shows the way. The well-documented evolutionary substitution of sources of
primary energy suggests that natural gas and later carbon-free energy forms will
become the leading sources of primary energy globally during the next century
(Ausubel et al., 1988; Grubler and Nakicenovic, 1988; Marchetti and
Nakicenovic, 1979; Nakicenovic, 19904.
The competitive struggle between the five main sources of primary energy-
wood, coal, oil, gas, and nuclear has proven to be a dynamic and regular pro-
cess that can be described by relatively simple rules. A glance reveals the domi-
nance of coal as the major energy source between the 1880s and the 1960s after
a long period during which fuelwood and other traditional energy sources led
(Figure 8~. The mature coal economy meshed with the massive expansion of
railroads and steamship lines, the growth of steelmaking, and the electrification
of factories. During the 1960s, oil assumed a dominant role in conjunction with
the development of automotive transport, the petrochemical industry, and mar-
kets for home heating oil.
The model of energy substitution projects natural gas (methane) to be the
dominant source of energy during the first decades of the next century, although
oil should maintain the second largest share until the 2020s. Such an exploratory
look requires additional assumptions to describe the later competition of potential
new energy sources such as nuclear, solar, and other renewables that have not yet
captured sufficient market shares to allow reliable estimation of their penetration
rates. In Figure 8 it is assumed that nuclear energy will diffuse at rates compa-
rable to those at which oil and natural gas diffused half a century earlier. Such a
scenario would require a new generation of nuclear installations; today such
prospects are at best questionable. This leaves natural gas with the largest share
of primary energy for at least the next fifty years. In the past, new sources of
energy have emerged from time to time, coinciding with the saturation and subse-
quent decline of the dominant competitor. In Figure 8, "Solfus" represents a
major carbon-free energy technology, such as solar or fusion, that could emerge
during the 2020s at the time when natural gas is expected to reach the limits of its
market niche.
The unfolding of primary energy substitution implies a gradual continuation
of energy decarbonization globally. Figure 9 shows how the ratio of hydrogen to
carbon atoms in the world fuel mix has changed as a result of primary energy
OCR for page 86
NEBOJ3A NAKICENOVIC
86
1o2
1o1
lo alp 10°
-
1o-1 _
1 o-2 1 1 ~:
1 850
Wood ~
0.99
0.90
Natural Gas
'-~ ?
I><
Nuclea^<
1 1 1 1 ma/ 1 -by, 1 1
19001950 2000
Year
-
o
0.50 -A,
LL
0.01
2050
FIGURE 8 Global primary energy substitution from 1860 to 1982 and projections
for the future, expressed in fractional market shares (F). NOTE: Smooth lines repre-
sent model calculations and jagged lines are historical data. "Solfus" is a term em-
ployed to describe a major new energy technology, for example, solar or fusion.
SOURCES: Grubler and Nakicenovic (1988) and Nakicenovic (1990~.
substitution. If natural gas becomes the dominant source of energy, this ratio can
be expected to approach the level of four hydrogen atoms to one carbon. Im-
provements beyond this level would have to be achieved by the introduction of
noncarbon energy sources and by the sustainable use of biomass.
A methane economy offers a bridge to the noncarbon energy future consis-
tent with both the dynamics of primary energy substitution and the steadily
decreasing carbon intensity of final energy. As nonfossil energy sources are
introduced into the primary energy mix, new energy conversion systems would
be required to provide zero-carbon carriers of energy in addition to electricity.
The ideal candidate is pure hydrogen, used as a gas or liquid. Hydrogen and
electricity could carry virtually pollution-free and environmentally benign energy
to end users in a carbon-free energy system.
To the extent that both hydrogen and electricity might be produced from
methane, the carbon separated as a by-product could be contained and stored,
probably in underground caverns. As the methane contribution to the global
energy supply reaches its limit and subsequently declines, carbon-free sources of
energy would take over, eliminating the need for carbon handling and storage.
This would conclude the global trend toward decarbonization and the resulting
major transformation of the industrial ecosystem. The emergent system could
accommodate cleanly the foreseeable levels of population and economic activity.
OCR for page 87
FREEING ENERGY FROM CARBON
1o2
o 1o1
Q
o
if_
I
<,, 1 0°
o
I
o
· - 1 0
87
' 1 ' ' ' ' 1 ' ' ' ' 1 ' ' ' ' 1 ' ' ' ' 1 '' ' ' 1 ' ' ' .
- Hydrogen
Economy
~ ~ ~ Nonfossil
Methane: HIC = 4 ~Hydrogen,,
Oil: HJC = 2 / Methane Economy
.. ..... ... ... .... ... .... .. ,, .... ..... .... .... ... ..
Coal: HJC = 1 ~
_ .. _ _ , ,,, _ ,, _ .... _ ,f - ,_V. - - . - · · · - - · · · - - - · · · - - - · ' ' ' - · · ' · · - - · ' ' · - - · · ' ' - - - ' ' ' - - - ' -
1935 (midpoint of process)
° At = 300 years (length of process)
~ Wood: HJC = 0.1
_ ..... .... ... .... .... .... ..... ... ... .... ..... .... .... ... . _
10-2 .,.,I,,,,I,,,,I,,,,I,,,,I,,,,I,,,
1800
1850 1900 1950 2000
Year
2050 2100
0.90
0.80
'_
0.67 O
0.50 I
I
0.09
FIGURE 9 Ratio of hydrogen (H) to carbon (C) for global primary energy consump-
tion since 1860 and projections for the futures expressed as a ratio of hydrogen to carbon
(H/C). SOURCE: Ausubel (1996) and Marchetti (1985).
In fact, an energy system of the distant future that relies on electricity and
hydrogen as the complementary energy carriers would also advance dematerial-
ization. Hydrogen has the lowest mass of all atoms, and its use would radically
reduce the total mass flow associated with energy activities and the resulting
emissions. Electricity is free of material emissions, and the only product of ap-
propriate hydrogen combustion is water. Thus, decarbonization not only contrib-
utes to dematerialization but is also consistent with the emergence of new tech-
nologies that hold the promise of high flexibility, productivity, and environmental
compatibility. Weighty carbon is a poor match for the evolving final energy
demands of modern societies. Fortunately, decarbonization has asserted itself
already as a widespread, long-term development driven by deepening, strength-
ening forces.
REFERENCES
Argote, L., and D. Epple. 1990. Learning curves in manufacturing. Science 247:920-924.
Ausubel, J. H. 1996. Can technology spare the Earth? American Scientist 84(2):166-178.
Ausubel, J. H., and A. Grubler. 1995. Working less and living longer: Long-term trends in working
time and time budgets. Technological Forecasting and Social Change 50:113-131.
OCR for page 88
88
NEBOJSA NAKICENOVIC
Ausubel, J. H., A. Grubler, and N. Nakicenovic. 1988. Carbon dioxide emissions in a methane
economy. Climatic Change 12:245-263. Reprinted as International Institute for Applied Sys-
tems Analysis RR-88-7.
Christianson, L. 1995. Diffusion and Learning Curves of Renewable Energy Technologies. WP-95-
126. Laxenburg, Austria: International Institute for Applied Systems Analysis.
Grubler, A. 1991. Energy in the 21st century: From resource to environmental and life constraints.
Entropie 164/165:29-33.
Grubler, A., and N. Nakicenovic. 1988. The dynamic evolution of methane technologies. In The
Methane Age, T. H. Lee, H. R. Linden, D. A. Dreyfus, and T. Vasko, eds. Dordrecht, Nether-
lands, and Laxenburg, Austria: Kluwer Academic Publishers and International Institute for
Applied Systems Analysis.
Maddison, A. 1991. Dynamic Forces in Capitalist Development: A Long-Run Comparative View.
New York: Oxford University Press.
Marchetti, C. 1985. Nuclear plants and nuclear niches. Nuclear Science and Engineering 90:521-
526.
Marchetti, C., and N. Nakicenovic. 1979. The Dynamics of Energy Systems and the Logistic
Substitution Model. RR-79-13. Laxenburg, Austria: International Institute for Applied Sys
tems Analysis.
Nakicenovic, N. 1990. Dynamics of change and long waves. In Life Cycles and Long Waves, T.
Vasko, R. Ayres, and L. Fontvieille, eds. Berlin: Springer-Verlag.
Nakicenovic, N. 1996. Decarbonization: Doing more with less. Technological Forecasting and
Social Change 51:1-17.
United Nations. 1992. Long-Range World Population Projections: Two Centuries of Population
Growth 1950-2150. New York: United Nations.
Vu, M. T. 1985. World Population Projections. Baltimore: Johns Hopkins University Press.
Williams, R. H., E. D. Larson, and M. H. Ross. 1987. Materials, affluence, and industrial energy
use. Annual Review of Energy 12:99-144.
Yamaji, K, R. Matsuhashi, Y. Nagata, and Y. Kaya. 1991. An Integrated System for CO2/Energy/
GNP Analysis: Case Studies on Economic Measures for CO2 Reduction in Japan. Paper
presented at the Workshop on CO2 Reduction and Removal: Measures for the Next Century,
International Institute for Applied Systems Analysis, Laxenburg, Austria, March 19-21, 1991.
Representative terms from entire chapter:
carbon intensity
