Monday, August 7, 2017

Our Photovoltaic Future: The Metabolic Revolutions of the Earth's History.

Illustration from the recent paper by Olivia Judson on "Nature Ecology & Evolution (2017) "The Energy Expansions of Evolution". 

Olivia Judson published a very interesting paper this March on "Nature Ecology & Evolution". It is a wonderful cavalcade along 4 billion years of the history of the Earth, seeing it in terms of five "metabolic revolutions." It is an approach that goes in parallel with a paper that I wrote last year on BERQ; even though I focussed on the future rather than on the past. But my paper was very much along the same lines, noting how some of some of the major discontinuities in the Earth's geological record are caused by metabolic changes. That is, the Earth's changes as the life inhabiting it "learns" how to exploit the potential gradients offered by the environment: geochemical energy at the very beginning and, later on, solar energy.

Seen in these terms, the Earth system is a gigantic autocatalytic reaction that was ignited some four billion years ago, when the planet became cool enough to have liquid water on its surface. Since then, it has been flaring in a slow-motion explosion that has been going faster and faster for billions of years, until it is literally engulfing the whole planet, sending offshoots to other planets of the solar system and even outside it.

Judson correctly identifies the ability to control fire as the latest feature of this ongoing explosion. Fire is a characteristic ability of human beings and can be argued that it is the defining feature of the latest time subdivision of the planet's history: the Anthropocene.

Judson stops with fire, calling it "a source of energy" and proposing that "The technology of fire may also, perhaps, mark an inflection point for the Solar System and beyond. Spacecraft from Earth may, intentionally or not, take Earthly life to other celestial objects." Here, I think the paper goes somewhat astray. Calling fire a "source" of energy is not wrong, but we need to distinguish whether we intend fire as the combustion of wood, that humans have been using for more than a million years, and the combustion of fossil hydrocarbons, used only during the past few centuries. There is a big difference: wood fires could never take humans to contemplate the idea of expanding beyond their planetary boundaries. But fossil energy could fuel this expansion at most for a few centuries and this big fire is already on its way to exhaustion. If the Anthropocene is to be based on fossil fuels, it is destined to fade away rather rapidly.

Does this mean that we have reached the peak of the great metabolic cycle of planet Earth? Not necessarily so. Judson seems to miss in her paper that the next metabolic revolution has already started: it is called photovoltaic conversion and it is a way to transform solar energy into an electric potential, coupled with the capability of controlling the motion of electrons in solid state conductors. It is a big step beyond fire and thermal machinery (*). It is, by all means, a new form of metabolism (**) and it is generating a new ecology of silicon-based life-forms, as I discussed in a previous post that I titled "Five Billion Years of Photovoltaic Energy". 

So, we are living in interesting times, something that we could take as a curse. But it is not a choice that we are facing: we are entering a new era, not necessarily a good thing for humans, but most likely an unavoidable change; whether we like it or not may be of little importance. It is a new discontinuity in the billion years long history of planet Earth that will lead to an increased capability of capturing and dissipating the energy coming from the sun.

The great chemical reaction is still flaring up and its expansion is going to take us somewhere far away, even though, at present, we can't say where. 

A new lifeform, just appeared in the Earth's ecosystem:

(*) The Jews have been arguing for about a century whether electricity has to be considered a form of fire and therefore prohibited during the Sabbath. It is surely an interesting theological discussion, but for what we are considering here there is no doubt that fire (a hot plasma ignited in air) is not the same as electricity (controlled movement of electrons in solids)

(**) The supporters of nuclear energy may argue that the next metabolic revolution should be seen as the production of energy from nuclear fission or fusion. The problem is that the resources of fissionable material in the whole solar system are too small that they could hardly fuel a truly new geological epoch. As for fusion, we haven't found a technology able to control it in such a way to make it an earth-based source of energy and it may very well be that such a technology doesn't exist. But, on the sun, fusion works very well, so why bother?


  1. Ugo
    Interesting paper by Judson.
    Given that Life (!) is essentially signalling, I wonder if we should consider information density and its continuity over evolutionary time? Sure, living signalling needs energy to run, but the need is surprisingly little given the colossal information stream and embedded memory. My understanding is that the ratio of in silico information density to energy requirement limits any possible parallel with living systems. I maybe unnecessarily comparing apples with doughnuts, but we are talking hypothetically, of course.


    1. Write on, Phil! Ugo had not yet approved comments when I wrote my comment below about information, communication (signalling), and cooperation.

      Under simple physical forces and laws (e.g., gravity and second-law entropy), the system runs downhill and dies a heat death. Life, accumulating information (complexity), acts to slow down the clock by counteracting gravity, for example.

      Salmon hatch in the headwaters of mountain streams in the Pacific Northwest and grow for a year or so. Then the jack salmon head out to circulate for a few years in the Pacific Ocean, collecting and concentrating nutrients that physics had washed down from the mountains and diffused in the ocean water. Finally, the mature salmon expend accumulated free energy swimming against gravity back up to the birthing headwaters in the mountains, where they spawn and die. Both living (pre-spawning) and dead (post-spawning) salmon are eaten by mammals and birds, who then deposit the nutrients collected from the Pacific waters on the floors of the Northwest Pacific rain forest, restoring what had been lost by the action of simple physical force and maintaining the hydrologic cycle. Life sets the hands of the clock back.

    2. Thanks Bill. It was good to read your thoughts and the Russian papers. The salmon example above is a good one. The signalling system finds its way home – one might say a little poetically perhaps - the instinct moves ‘uphill’ against time as well as gravity. I guess we need to widen our view of ‘intelligence’. I am interested in the properties we call ‘instinct’ and ‘personality’, ‘point of view’ and ‘recognition’ (and ‘intelligence’). Not in the same league as the Russian papers but this essay (link below) kicks around some fun-ideas based on the comparative ratios of energy efficiency mostly as they relate to cognition. I am again staggered by the gap between the animate and inanimate.

    3. This comment has been removed by the author.

  2. Thank you, Ugo, for this interesting perspective on our planetary eras. In the far long-term, solar panels of the photovoltaic variety have a tremendous downside: the manufacture of these panels creates a toxic by-product that is terribly polluting and is having devastating impact on Chinese agriculture. Our planet's anthropocene needs to be based on cyclical technologies that are completely non-toxic. It is an incomplete idea that humans can manufacture items that produce toxins and then throw those toxins "away." There is no such place as "away." It's all here, on one planet. By a cyclical technology I mean a technology that closes the circle. For example the nutrient cycle: man grows food, man eats food, man excretes manure, man composts manure, man uses compost to fertilize the growing of food. Another cycle uses hemp to produce energy: man grows hemp, hemp produces fiber, cellulose pulp by-product of hemp is processed into fuel, fuel burning releases CO2 into atmosphere, next crop of hemp breathes in CO2 to build cell structure.

    1. Lindi, hi. Panel manufacturing is not a dirty process. It is already clean, it can be made cleaner. And the circle can be closed. (and bacioni, of course!)

  3. Thank you for the reference to the very interesting paper by Judson. I printed it on paper for reading and discussion with my children at meals.

    I like the explicit standpoint throughout the paper that the proper view is of an evolving total system of organisms and environment (in contrast to the limited view an organism evolving in a given environment).

    The important role of information, communication, and cooperation as the primary driving force of life evolution is implicit (constantly appearing "between the lines"). I defend my judgment that it is implicit by first listing the explicit appearances of the terms in context.

    Information: appears twice on page 9: "Additional information
    Reprints and permissions information is available at"

    Communication: does not appear

    Cooperation: appears once in the title of reference 28 on page 6: "Schink, B. Energetics of syntrophic cooperation in methanogenic degradation."

    It is implicit probably because we (so far as I know) do not have fully adequate definitions of the terms and consequently use the concepts only in a vague, handwaving sense. Information is an emergent, i.e., it exists only in a configuration (pattern) of matter and/or energy. In the evolving system under consideration, matter is conserved, roughly speaking. Free energy is degraded (second law of thermodynamics). Information increases through communication and cooperation. I give a simple example.

    A gene, a sequence of DNA-triplet codons, contains a certain amount of information, which we can quantify using Shannon entropy, for example. But I note that this information measured in bits is useless without an "understanding and cooperating reader in an appropriate environment." Without going into the details, I assume the gene is useful and used. Then amino acids are assembled into a protein (degrading free energy replaced acid configuration) has an increased information content because of the communication of information from the gene. But the gene had no decrease of information content. Hence, the total information has here increased.

    There has been some preliminary work in this direction, for example, Gorshkov et al. "Information in the animate and inanimate worlds," Russian Journal of Ecology, Vol. 33, No. 3, 2002, pp. 149–155 ( Other references to papers by Gorshkov and Makarieva can be found at

    NOTE: I have produced the preceding sequence of symbols with the intent (hope?) that it will encounter an "understanding and cooperating reader in an appropriate environment."

    1. Fascinating stuff. Russian science at its best. I don't think anyone in the West arrives to this level of synthesis, at least for the time being.

    2. Also this... Wow!!

    3. And this....

    4. I think the Mongabay article is a bit sensationalistic (typical of popular science press nowadays). By the way, the paper in Atmospheric Chemistry & Physics is open access (, in contrast to the chapter "Governance of Societies" in the book Global Stability through Decentralization? (pp. 75-115).

      I was first introduced to the role of forestation in drawing rain by a Prof. Reed (Reid?) in a conversation at the University of Wisconsin Madison in 1973. Since then I have viewed a forest as an accumulation of slow water (attracting more water).

      I sometimes think that the fascination with photosynthesis and the carbon cycle leads to a false picture. I then remember to consider the dissociation of water (dihydrogen oxide), the combination of the hydrogen with carbon dioxide to produce higher-energy carbohydrates, and the release of the oxygen in photosynthesis followed by the Krebs cycle dissociation of the carbohydrate into carbon dioxide and the recombination of the previously dissociated hydrogen and oxygen back into dihydrogen oxide (water).

      The Krebs cycle of respiration yields energy to maintain life processes during the dark phase of the water cycle. In this sense, the carbon dioxide is the basic element of a chargeable-dischargeable energy storage device with the dissociation and reconstitution of water being basic to the respective charging and discharging of the battery.

  4. looked at in that timeline, the industrial revolution can be seen for what is was/is:

    after billions of years of dark, the ingenuity of humankind brought about our supernova, where the accumulated combustible material contained within the earth is being ignited in one final flash of heat and light

    Who knows, maybe it was all part of a grand plan after all

    1. Sometimes I think the same. Might there be a grand plan? Maybe a plan to purge the earth of the carbon accumulated in 500 million years? And get rid of the icecaps? It is not so common to have icecaps and they show an unstable feedback. A burst of cold, and they expand all the way to the equator, killing all the vertebrates and land plants. It is a safer planet with no icecaps. Surely, the critters who took care of that cleaning had to be sacrificed, but.....

  5. Many materials used in our industrial world require energy from mining to manufacturing for processing and transportation. The energy for some of these products is in the form of high temperatures – 2000° F (nearly 1100°C).

    There are proposals that solar and wind energy collecting devices can provide the energy to maintain the industrial world. To look at this possibility, solar electric panels, wind turbines and concentrated solar installations in the form of parabolic trough collectors (PTC) have been assessed.

    The energy requirements in 2010 for the following essential components of our industrial world are provided: steel, aluminum, chromium, copper, manganese, cement and glass. This energy would be mining, processing and transporting to name some. Other important components of the industrialized world such as nickel and cobalt are not considered because they are part of the high temperature processing of other ore metals.

    The kWh output and area required for installations of solar electric panels, wind turbines and PTC has been researched. This then is divided into the energy (exajoules converted to kWh) required for global production of each material in 2010.
    121,214.45 Square Miles of Solar Electric Collectors
    257,472 square miles and 2,807,276 Wind Turbines
    77183.4 square miles of PTCs

    See maps, images and calculations at:

  6. Reminder: electricity comes at practically infinite temperature. Ask the physicists at CERN
    Hence it can replace, often with higher efficiency, fossil energy sources in most instances.
    What's hard to match is fossil fuels energy density, as needed for long range air travel for example.



Ugo Bardi is a member of the Club of Rome and the author of "Extracted: how the quest for mineral resources is plundering the Planet" (Chelsea Green 2014). His most recent book is "The Seneca Effect" to be published by Springer in mid 2017