Freeing Energy from Carbon
Journal article by Nebojsa Nakicenovic; Daedalus, Vol. 125, 1996
Journal Article Excerpt
Freeing energy from carbon. by Nebojsa Nakicenovic 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 demonstrably decreased per unit of output and value added since the beginnings of the industrial revolution some two hundred years ago. These increases in the productivity 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 increasing 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 yielding 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 manufacture 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.(1) Energy industries and energy systems are not exceptional. This essay will demonstrate that large secular decreases in energy requirements per unit of economic 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 emblematic 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 dominates 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 desirable 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 establish 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 decreased 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 dramatic 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 expectancy increased 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.(2) Decreases in requirements for many materials are similarly dramatic.(3) 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 1960.4 However, this dematerialization 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 petro-chemicals (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 ... |
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