Entropy


book_cover_big.gifIn the economics literature, one can find two opposing points of view: mainstream economists who believe that technological innovation will solve the degradation in quality of both energy and materials and that therefore growth can go on forever; and biophysical economists, who use the thermodynamic laws to argue that mainstream economists do not incorporate long-term sustainability in their models. For instance, the costs to repair the ozone hole or to mitigate increasing pollution are not accounted for in mainstream economic assessments. Industrial and agricultural processes accelerate the entropy production in our world. Entropy production can only go on until we reach the point where all available energy is transformed into non-available energy. The faster we go toward this end, the less freedom we leave for future generations. If entropy production were included in all economic models, the efficiency of standard industrial processes would show quite different results……..

Even if there were no humans on this planet, there would be continuous entropy production. So from that point of view the ecological system is not perfect, either; even the sun has a limited lifespan. The real problem for us is that, in our relentless effort to speed things up, we increase the entropy production process tremendously. In fact, you can see some similarity between economic systems and organisms: both take in low entropy resources and produce high entropy waste. This leaves fewer resources for future generations.

Although recycling will help a lot to slow down the depletion of the earth’s stocks of materials, it will only partly diminish the entropy production process. So whenever we design or develop economic or industrial processes, we should also have a look at the associated rate of entropy production compared to the natural “background” entropy production. We have seen that for reversible processes, the increase in entropy is always less than for irreversible processes. The practical translation of this is that high-speed processes always accelerate the rate of entropy production in the world. Going shopping on your bike is clearly a much better entropy choice than using your car.

Conclusion: the entropy clock is ticking, and can only go forward!

From:  The Second Law of Life

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book_cover_big.gifA few blogs ago,  I wrote about the life cycle analysis (LCA) of Compact Fluorescence Lamps (CFL’s,)[1]. CFL’s do “consume” during their life indeed about 5 times less electricity than incandescent light bulbs (and CFL’s live about 4 times longer). However, the manufacturing of CFL’s is much more complicated and therefore environmentally more demanding than classical bulbs and rightfully the question was raised that when you sum it all up would the environmental advantage still hold? After a careful and detailed LCA, a team of Australian researchers came with the answer: a big yes!

However,  it was pointed out by the researchers at the University of Ghent[2], Belgium, that one needs to look not just at the environmental impact (for  factors such as global warming, ozone depletion, toxics emission, acidification, etc.) of a certain product but also need to take into account  resources such as organic and inorganic, fuel and feedstock, renewable and non-renewable, energy and materials. It is here where thermodynamics kicks in using the concept of entropy[3] (as already suggested by Nicholas Georgescu-Roegen[4] quite a while ago). Entropy, can be used to describe the degradation of resources during the manufacturing and actually usage of products. One can say, very roughly, that the faster and further away from equilibrium a certain production process is done, the more energy is degraded and made not-available anymore to do further work. This is described by an increase in entropy and is non-reversible, i.o.w. high quality energy (such as energy contained in fossil fuels for that matter) is turned into low quality energy (heat).

This sort of analysis is then used to study the environmental impact of bio-foods versus large scale agriculture produced foods. And sure enough you can find situations where bio-foods (because of their poor yields or their transport over large distances) have more negative impact on the environment than have traditional produced foods. It was found[5] that if bio-beans are locally produced they are environmentally better than conventional produced beans. But when the beans needed to get transported from other areas to make it to our stores the balance can easily change and even reverse the situation! Bio-potatoes are always worse than conventional potatoes because they have such a lower yield per surface area land[6].

Therefore, before drawing conclusions on the impact of a given process or product on the environment or resources a careful evaluation (LCA) needs to be done. Such an evaluation is not a trivial matter at all and can only be done by qualified people.

 

© Copyright 2009, John Schmitz

 


[1] https://secondlawoflife.wordpress.com/2008/10/05/compact-fluorescence-lamps/

[2] http://pubs.acs.org/doi/abs/10.1021/es071719a

[3] As a matter of fact a concept of « exergy » is used but it has a very close relationship to entropy

[4] https://secondlawoflife.wordpress.com/2007/04/28/nicholas-georgescu-roegen/

[5] http://www.standaard.be/Artikel/Detail.aspx?artikelId=4I2B40SO

[6] See also: https://secondlawoflife.wordpress.com/2007/07/28/entropy-and-the-food-chain-part-i/ and https://secondlawoflife.wordpress.com/2007/08/22/entropy-and-the-foodchain-part-ii/