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The second law of thermodynamics and the economic process
Ecological Economics, 7 (1993) 69-71 Elsevier Science Publishers B.V., Amsterdam
69
Letter to the Editor
The second law of thermodynamics and the economic process A.G. Williamson Department of Chemical and Process Engineering, Unicersity of Canterbury, Christchurch, New Zealand (Accepted
22 May 1992)
In 1975 Nicholas Georgescu-Roegen published a paper “Energy and in which he challenged some of the current “axioms” Economic Myths” ’ of economic thinking. In particular he was concerned with what he called the “mechanistic” approach based on what he saw as a conservation principle and a maximisation principle. He asserted that economics could be discussed in terms of principles like the laws of thermodynamics, and that economic processes must, like the physical world, be subject to a law of degradation similar to the second law of thermodynamics. GeorgescuRoegen leaned heavily on the concept of the increase in entropy of isolated systems (he called them “closed systems”) in which any natural process takes place, and argued that economic activity was dependent on the conversion of low entropy material into higher entropy material and that there was therefore a theoretical (and real) limit to economic activity in a finite, isolated system. Although Georgescu-Roegen’s paper contained many statements that a thermodynamicist might argue with, and some that are quite misleading (e.g., “the entropy of water is higher than that of the hydrogen and oxygen after decomposition”), the main thrust of his argument is acceptable. Moreover he recognises in the later stages of his paper that the earth is not an isolated system because it intercepts a flux of solar energy. One way of stating the second law of thermodynamics is to say that any natural process can be made to yield usable work (free energy) and the maximum possible work is obtained as a limiting case as the conditionS under which the process takes place approach reversibility. These observations can be summarised in diagrams of the type shown below:
70 natural
process
initial state - - - - - - - - - - - + final state \ / mechanism
usable work Fig. 1.
This maximum disposable work is described for thermal energy (heat) transfer from an initial state at a high temperature T, to a final state at a lower temperature T, by the (Carnot) expression which incorporates both the first and the second laws of thermodynamics: w(max) = e(T,
- T,)/T,
where Q is the heat drawn from the high temperature source. Moreover the direction of the arrows in Figure 1 can be reversed. In other words, otherwise natural processes can be reversed if the appropriate mechanism can be found and the appropriate energy input can be supplied. It is in this feature that the possibility of using solar energy to recover from our present parlous state resides. Our current problems are being generated by our past and present insistence on treating the earth as an isolated system using the stock of fossil fuel and dumping the products in garbage dumps or even thinly dispersed in the atmosphere around the earth. It is the failure to incorporate the “costs” associated with waste and pollution that has led to the false values that are applied by current economics to growth and development, and it is the myth that “waste is irrelevant” that is the most important one that Georgescu-Roegen pointed out. Recently Khalil has published a paper * purporting to refute GeorgescuRoegen’s arguments and putting forth the view that the second law of thermodynamics does not imply any limits to economic growth. Khalil asserts that there is a previously unrecognised difference between the “entropy law per se and the Carnot cycle” which lies in the fact that the Kelvin statement and the Carnot cycle are derivative of the second law and refer to the production of work by what he calls “purposeful agency”. Khalil argues that the economic process is not governed by the second law but should be conceived after the Carnot cycle as being about the production of goods by purposeful activity. He infers from this that resources are not absolute (as for the entropy law) but relative according to the technological potency of the purposeful agency of production. It is in this extrapolation that I believe the fault of Khalil’s argument lies. The Carnot
71
cycle does indeed purposeful agency natural) process so its thermodynamic
describe (and quantitatively so> the way in which a may be interposed in an otherwise spontaneous (or as to produce useful work. However the Carnot cycle in application describes the upper limit to the potency which any purposeful agency can achieve. To adduce from an analogy with the Carnot cycle that the corresponding purposeful agency in economic activity may be of unlimited potency is surely fallacious. No amount of comment on thermodynamics in general or juggling of algebra analogous to the equations of thermodynamics can get one away from that fallacy or from the fact that any process that involves materials or energy is necessarily subject to the laws of physics. REFERENCES 1 Georgescu-Roegen, N., 1975. Energy and economic myths. South. Econ. J., 41 (3): 347-381. 2 Khalil, E.L., 1990. Entropy law and exhaustion of natural resources: Is Nicholas Georgescu-Roegen’s paradigm defensible? Ecol. Econ., 2: 163-178.
69
Letter to the Editor
The second law of thermodynamics and the economic process A.G. Williamson Department of Chemical and Process Engineering, Unicersity of Canterbury, Christchurch, New Zealand (Accepted
22 May 1992)
In 1975 Nicholas Georgescu-Roegen published a paper “Energy and in which he challenged some of the current “axioms” Economic Myths” ’ of economic thinking. In particular he was concerned with what he called the “mechanistic” approach based on what he saw as a conservation principle and a maximisation principle. He asserted that economics could be discussed in terms of principles like the laws of thermodynamics, and that economic processes must, like the physical world, be subject to a law of degradation similar to the second law of thermodynamics. GeorgescuRoegen leaned heavily on the concept of the increase in entropy of isolated systems (he called them “closed systems”) in which any natural process takes place, and argued that economic activity was dependent on the conversion of low entropy material into higher entropy material and that there was therefore a theoretical (and real) limit to economic activity in a finite, isolated system. Although Georgescu-Roegen’s paper contained many statements that a thermodynamicist might argue with, and some that are quite misleading (e.g., “the entropy of water is higher than that of the hydrogen and oxygen after decomposition”), the main thrust of his argument is acceptable. Moreover he recognises in the later stages of his paper that the earth is not an isolated system because it intercepts a flux of solar energy. One way of stating the second law of thermodynamics is to say that any natural process can be made to yield usable work (free energy) and the maximum possible work is obtained as a limiting case as the conditionS under which the process takes place approach reversibility. These observations can be summarised in diagrams of the type shown below:
70 natural
process
initial state - - - - - - - - - - - + final state \ / mechanism
usable work Fig. 1.
This maximum disposable work is described for thermal energy (heat) transfer from an initial state at a high temperature T, to a final state at a lower temperature T, by the (Carnot) expression which incorporates both the first and the second laws of thermodynamics: w(max) = e(T,
- T,)/T,
where Q is the heat drawn from the high temperature source. Moreover the direction of the arrows in Figure 1 can be reversed. In other words, otherwise natural processes can be reversed if the appropriate mechanism can be found and the appropriate energy input can be supplied. It is in this feature that the possibility of using solar energy to recover from our present parlous state resides. Our current problems are being generated by our past and present insistence on treating the earth as an isolated system using the stock of fossil fuel and dumping the products in garbage dumps or even thinly dispersed in the atmosphere around the earth. It is the failure to incorporate the “costs” associated with waste and pollution that has led to the false values that are applied by current economics to growth and development, and it is the myth that “waste is irrelevant” that is the most important one that Georgescu-Roegen pointed out. Recently Khalil has published a paper * purporting to refute GeorgescuRoegen’s arguments and putting forth the view that the second law of thermodynamics does not imply any limits to economic growth. Khalil asserts that there is a previously unrecognised difference between the “entropy law per se and the Carnot cycle” which lies in the fact that the Kelvin statement and the Carnot cycle are derivative of the second law and refer to the production of work by what he calls “purposeful agency”. Khalil argues that the economic process is not governed by the second law but should be conceived after the Carnot cycle as being about the production of goods by purposeful activity. He infers from this that resources are not absolute (as for the entropy law) but relative according to the technological potency of the purposeful agency of production. It is in this extrapolation that I believe the fault of Khalil’s argument lies. The Carnot
71
cycle does indeed purposeful agency natural) process so its thermodynamic
describe (and quantitatively so> the way in which a may be interposed in an otherwise spontaneous (or as to produce useful work. However the Carnot cycle in application describes the upper limit to the potency which any purposeful agency can achieve. To adduce from an analogy with the Carnot cycle that the corresponding purposeful agency in economic activity may be of unlimited potency is surely fallacious. No amount of comment on thermodynamics in general or juggling of algebra analogous to the equations of thermodynamics can get one away from that fallacy or from the fact that any process that involves materials or energy is necessarily subject to the laws of physics. REFERENCES 1 Georgescu-Roegen, N., 1975. Energy and economic myths. South. Econ. J., 41 (3): 347-381. 2 Khalil, E.L., 1990. Entropy law and exhaustion of natural resources: Is Nicholas Georgescu-Roegen’s paradigm defensible? Ecol. Econ., 2: 163-178.