1 The distinction between renewable and non-renewable resources is not always straightforward. For instance, many of the processes which give rise to deposits of non-renewable resources continue to occur naturally, even if the speed at which resources are deposited is very slow by comparison with the speed at which resources are extracted. Equally, the so-called renewable resources may often be harvested by society at a rate faster than they are replenished through natural processes, sometimes leading to deforestation and the loss of diversity in the natural environment.
2 This sector is also sometimes called the commercial sector or the service sector. In a later chapter of this book, the implications of these different names for the tertiary sector will become clearer. In fact, they form the basis for a reconsideration of the historical division between economic sectors.
3 1 megajoule (MJ) is equal to 1 million joules. A joule is a unit of energy measurement.
4 These figures are taken from I.Bousted and G.Hancock, Handbook of Industrial Energy Analysis, Ellis Horwood, Chichester, 1979.
5 In fact this law is only approximately true. Because of the equivalence of mass and energy (as expressed by Einstein's famous equation E=mc2) there are situations in which mass is transformed into energy and vice versa. In these circumstances the conservation law applies to the total balance of energy/mass equivalents.
6 During nuclear transformations, some individual elements change from one type to another, so that this kind of conservation law does not hold. Instead it is replaced by different conservation laws. But the complexity of these nuclear processes is beyond the scope of this book. In global terms, these kinds of processes still represent a relatively minor contribution to the material activities of the industrial economy.
7 The interested reader will find a full discussion of the implications of the second law in P.Coveney and R.Highfield's (1991) book, The Arrow of Time, Flamingo, London. A more detailed discussion of the importance of the second law for the interaction between economy and environment is given in T.Jackson (ed.), Clean Production Strategies: developing preventive environmental management in the industrial economy, Lewis Publishers, Boca Raton, FL, 1993.
8 A.Eddington, 1953, The Nature of the Physical World, Cambridge University Press, New York.
9 Georgescu-Roegen was really the first to highlight the importance of the second law of thermodynamics for economic processes. His book (The Entropy Law and the Economic Process, Harvard University Press, Cambridge, MA, 1971) is fascinating, if complex, reading.
10 This interpretation is due to the physicist Boltzmann, who devoted much of his life to the formulation of statistical thermodynamics. The Boltzmann equation which expresses it was engraved on his tombstone in Vienna.
11 A system is closed—but not isolated—when it can interchange energy with its environment but cannot interchange materials.
12 This view has been developed within thermodynamics by the Nobel laureate Ilya Prigogine and his co-workers (see I.Prigogine and I. Stengers, Order out of Chaos, Heinemann, London, 1984) and also within ecology—most notably by E.Schrodinger (What is Life? The physical aspects of the living cell, Cambridge University Press, Cambridge, 1945), A.Lotka (Elements of Physical Biology, Williams & Wilkins, Baltimore, 1925, reprinted as Elements of Mathematical Biology, Dover, New York, 1956) and more recently by H.T.Odum (Systems Ecology, John Wiley, New York, 1982).
13 A system is open when it can interchange both energy and matter with its environment.
14 The word 'organic' has two important—and unfortunately entirely unrelated—uses in environmental literature. The sense in which it is used here derives from the discipline of organic chemistry which is chemistry based on the element carbon. The second use of the term 'organic' refers to practices and procedures which are holistic in nature, and attempt to utilise natural ecological processes as much as possible.
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