Monday, August 14, 2017

Which EROI do we need to collect berries?



My wife, Grazia, collecting berries in the woods of Tuscany in a hot day of August. Maybe her ancestors were doing exactly the same, more or less in the same place, hundreds or thousands of years ago. Here, I present some reflections and some calculations showing that the EROI of this simple way of collecting food may be over 100, better than almost anything we have nowadays. Of course, no empire in history was based on hunting and gathering, but was that a bad thing?


The question of EROI - the energy return on energy invested - is raging nowadays, with some people insisting that a civilization cannot exist without an EROI of at least variously estimated values, at least 10 and higher (image on the right by Charles Hall). And that is said to mean we absolutely need sophisticated technologies, such as nuclear, in order to survive.

Yet, this morning I had been collecting berries in the wood with my wife and wondering: 'what is the EROI of what we are doing?' A reasonably good EROI, I am sure, enough for what our ancestors needed when they survived on hunting and gathering. All you have to do is to walk in the woods, find the berries and pick them up (and watch your step, you don't want to fall into a thorn bush).  If our hunter-gatherer ancestors used this method, and if we are here today - their descendants - it means it was an effective strategy for survival. Collecting what you can find is an ancient and tested strategy that goes under the name of "gleaning" and it has accompanied humankind for millennia. It is a good strategy just because it is so simple: no tools, no written laws, no overlords, no police, no fences. And it works.

As I was collecting berries, I started thinking things. How to program a drone to collect berries, for instance. Sure: a perfect way to bring down the EROI of the whole thing to nearly zero. And to destroy the bushes forever. Humans are like this, with their attempt of "improving" things they always pull the levers in the wrong direction. And that means making things more complicated, needing more and more energy to keep them running, and then complaining that we don't have enough.

Of course, with more than seven billion humans on this planet, it is hard to think that we can go back to gleaning to feed them all. But for how long we can trust the expensive, complex, delicate, and terribly inefficient enterprise we call "industrial agriculture"? I can't say. What I can say is that collecting berries is a big satisfaction, as you see below.





And now some approximate calculations: Today we collected 2 kg of berries. According to the available data, berries contain 125 kJ/100g. So, the total collection was about 2500 kJ, about 700 Wh.

Now, it was about one hour of low-intensity work for two people, so let's say it involved a total of 50x2x1h = 100 Wh of human work. Then, I found values of 20-25% for the human metabolic efficiency of converting food to mechanical energy, it means we consumed some 400-500 Wh of food energy in order to collect 700 Wh.

Very approximate, or course, but the final result is an EROI = 1.4-1.7. Not comparable to crude oil, but probably more than enough for our ancestors to enjoy berries as a seasonal treat.

But, of course, no one ever lived on berries alone, not even in paleolithic times. The energy content of several kinds of foods that you can find in a natural environment may be more than an order of magnitude larger than that of blackberries. Walnuts are reported to have more than 10,000 kJ/100 g. If you can collect one kg/hour, as we did for berries, it means an EROI of more than 100 (!!). Larger than the mythical EROI of crude oil of a hundred years ago. Wheat and cereals, in general, have also high energy content, wheat is reported to have 15,000 kJ/kg, showing how gleaning could be an extremely efficient food gathering strategy.

So, life was simple and easy, once, until we decided to make it complicated and difficult.






Thursday, August 10, 2017

Our Photovoltaic Future: the Next Five Billion Years

As part of a series of posts on photovoltaic energy as a metabolic revolution of the earth's ecosystem, I am reproposing a post that I published last year on "Cassandra's Legacy" with the title "Five Billion Years of Energy Supply". 



It seems to be popular nowadays to maintain that photovoltaic energy is just an "extension" of fossil energy and that it will fade away soon after we run out of fossils fuels. But photovoltaics is much more than just a spinoff of fossil energy, it is a major metabolic revolution in the ecosystem, potentially able to create a "stereosphere" analogous to the "biosphere" that could last as long as the remaining lifetime of the earth's ecosystem and possibly much more. Here are some reflections of mine, not meant to be the last word on the subject, but part of an ongoing study that I am performing. You can find more on a similar subject in a paper of mine on Biophysical Economics and Resource Quality, (BERQ)






"Life is nothing but an electron looking for a place to rest," is a sentence attributed to Albert Szent-Györgyi. It is true: the basis of organic life as we know it is the result of the energy flow generated by photosynthesis. Sunlight promotes an electron to a high energy state in the molecule of chlorophyll. Then, the excited electron comes to rest when a CO2 molecule reacts with hydrogen stripped away from an H2O molecule in order to form the organic molecules that are the basis of biological organisms. That includes replacing degraded chlorophyll molecules and the chloroplasts that contain them with new ones. The cycle is called "metabolism" and it has been going on for billions of years on the earth's surface. It will keep going as long as there is sunlight to power it and there are nutrients that can be extracted from the environment. 

But, if life means using light to excite an electron to a higher energy state, there follows that chlorophyll is not the only entity that can do that. In the figure at the beginning of this post, you see the solid state equivalent of a chlorophyll molecule: a silicon-based photovoltaic cell. It promotes an electron to a higher energy state; then this electron finds rest after having dissipated its potential by means of chemical reactions or physical processes. That includes using the potentials generated to manufacturing new photovoltaic cells and the related structures to replace the degraded ones. In analogy with the biological metabolism, we could call this process "solid state metabolism". Then, the similarities between the carbon-based metabolic chain and the silicon-based one are many. So much that we could coin the term "stereosphere" (from the Greek term meaning "solid.") as the solid-state equivalent of the well known "biosphere". Both the biosphere and the stereosphere use solar light as the energy potential necessary to keep the metabolic cycle going and they build-up metabolic structures using nutrients taken from the earth's surface environment.

The main nutrient for the biosphere is CO2, taken from the atmosphere, while the stereosphere consumes SiO2, taking it from the geosphere. Both metabolic chains use a variety of other nutrients: the stereosphere can reduce the oxides of metals such as aluminum, iron, and titanium, and use them as structural or functional elements in their metallic form; whereas the biosphere can only use carbon polymers. The biosphere stores information mostly in specialized carbon-based molecules called deoxyribonucleic acids (DNA). The stereosphere stores it mostly in silicon-based components called "transistors". Mechanical enactors are called "muscles" in the biosphere and are based on protein filaments that contract as a consequence of changing chemical potentials. The equivalent mechanical elements in the stereosphere are called "motors" and are based on the effects of magnetic fields on metallic elements. For each element of one of these systems, it is possible to find a functional equivalent of the other, even though their composition and mechanisms of operation are normally completely different.

A major difference in the two systems is that the biosphere is based on microscopic self-reproducing cells. The stereosphere, instead, has no recognizable cells and the smallest self-reproducing unit is something that could be defined as the "self-reproducing solar plant factory." A factory that can build not only solar plants but also new solar plant factories. Obviously, such an entity includes a variety of subsystems for mining, refining, transporting, processing, assembling, etc. and it has to be very large. Today, all these elements are embedded in the system called the "industrial system." (also definable as the "technosphere"). This system is powered, at present, mainly by fossil fuels but, in the future, it would be transformed into something fully powered by the dissipation of solar energy potentials. This is possible as long as the flow of energy generated by the system is as large or larger than the energy necessary to power the metabolic cycle. This requirement appears to be amply fulfilled by current photovoltaic technologies (and other renewable ones).

A crucial question for all metabolic processes is whether the supply of nutrients (i.e. minerals) can be maintained for a long time. About the biosphere, evidently, that's the case: the geological cycles that reform the necessary nutrients are part of the concept of "Gaia", the homeostatic system that has kept the biosphere alive for nearly four billion years. About the stereosphere, most of the necessary nutrients are abundant in the earth's crust (silicon and aluminum being the main ones) and easily recoverable and recyclable if sufficient energy is available. Of course, the stereosphere will also need other metals, several of which are rare in the earth's crust, but the same requirement has not prevented the biosphere from persisting for billions of years. The geosphere can recycle chemical elements by natural processes, provided that they are not consumed at an excessively fast rate. This is an obviously complex issue and we cannot exclude that the cost of recovering some rare element will turn out to be a fundamental obstacle to the diffusion of the stereosphere. At the same time, however, there is no evidence that this will be the case.

So, can the stereosphere expand on the earth's surface and become a large and long-lasting metabolic cycle? In principle, yes, but we should take into account a major obstacle that could prevent this evolution to occur. It is the "Allee effect" well known for the biosphere and that, by similarity, should be valid for the stereosphere as well. The idea of the Allee effect is that there exists  a minimum size for a biological population that allows it to be stable and recover from perturbations. Too few individuals may not have sufficient resources and reciprocal interactions to avoid extinction after a collapse. In the case of the stereosphere, the Allee effect means that there is a minimum size for the self-reproducing solar plant factory that will allow it to be self-sustaining and long-lasting. Have we reached the "tipping point" leading to this condition? At present, it is impossible to say, but we cannot exclude that it has been reached or that it will be reached before the depletion of fossil fuels will bring the collapse of the current industrial system.

The next question is whether a self-sustaining stereosphere can coexist with the organic biosphere. According to Gause's law, well known in biology, two different species cannot coexist in the same ecological niche; normally one of the two must go extinct or be marginalized. Solid state and photosynthetic systems are in competition with each other for solar light. There follows that the stereosphere could replace the biosphere if the efficiency of solid state transduction systems were to turn out higher than that of photosynthetic systems. But this is not obvious. PV cells today appear to be more efficient than photosynthetic plants in terms of the fraction of solar energy processed but we need to consider the whole life cycle of the systems and, at present, a reliable assessment is difficult. We should take into account, anyway, that solid state creatures don't need liquid water, don't need oxygen, are not limited to local nutrients, and can exist in a much wider range of temperatures than biological ones. It means that the stereosphere can expand to areas forbidden to the biosphere: dry deserts, mountaintops, polar deserts, and more. Silicon based creatures are also scarcely affected by ionizing radiation, so they can survive in space without problems. These considerations suggest that the stereosphere may occupy areas and volumes where it is not in direct competition with the biosphere.

The characteristics of the stereosphere also allow it the capability of surviving catastrophes that may deeply damage the biosphere and that will eventually cause its extinction. For instance, the stereosphere could survive an abrupt climate change (although not a "Venus Catastrophe" of the kind reported by James Hansen). Over the long run, in any case, the earth's biosphere is destined to be sterilized by the increasing intensity of the solar irradiation over times of the order of a billion years. (and smaller for multicellular organisms). The stereosphere would not be affected by this effect and could continue existing for the five billion of years in which the sun will remain in the main sequence. Possibly, it could persist for much longer, even after the complex transformations that would lead the sun to become a white dwarf. A white dwarf could, actually power PV systems perhaps for a trillion years!

A more detailed set of considerations of mine on a related subject can be found in this article on "Biophysical Economics and Resource Quality, BERQ). 


Notes: 

1. I am not discussing here whether the possible emergence of the stereosphere is a good or a bad thing from the viewpoint of humankind. It could give us billions of years of prosperity or lead us to rapid extinction. It seems unlikely, anyway, that humans will choose whether they want to have it or not on the basis of rational arguments while they still have the power to decide something on the matter. 

2. The concept of a terrestrial metabolic system called the stereosphere is not equivalent, and probably not even similar, to the idea of the "technological singularity" which supposes a very fast increase of artificial intelligence. The "self-reproducing solar plant factory" needs not be more intelligent than a bacterium; it just needs to store a blueprint of itself and instructions about replication. Intelligence is not necessarily useful for survival, as humans may well discover to their chagrin in the near future.

3. About the possibility of a photovoltaic-powered Dyson sphere around a white dwarf, see this article by Ibrahim Semiz and Salim O˘gur.

4. The idea of "silicon-based life" was popularized perhaps for the first time by Stanley Weinbaum who proposed his "Pyramid Monster" in his short story "A Martian Odissey" published in 1933. Weinbaum's clumsy monster could not exist in the real universe, but it was a remarkable insight, nevertheless. 







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?



Friday, August 4, 2017

Does Propaganda Still Work? Donald Trump and Russiagate




Image above, from the Washington Post, 17 July 2017. Donald Trump seems to have been basically unaffected by the Russiagate campaign, even with those who disapprove him. Is it a sign that propaganda doesn't work anymore as it used to in the past?



It has been said that the best trick of the devil is to convince you that he doesn't exist. The same holds for propaganda, which draws most of its power from being able to convince people that it doesn't exist. Yet, it exists and its impact on people's lives has been gigantic. The more we try to ignore it, the more it affects us, especially those of us who claim to be immune from it.

Yet, it would seem that propaganda can work only when it can eliminate or marginalize the opposing voices in environments. Maybe the concept of "free press" is a little optimistic today in the Western World. Still, with the availability of the Internet, everyone can verify the media statements and there is no lack of opposing voices in the galaxy of the social media and the various independent media sites. That had led someone to prophesize "The end of Spin".

Can it be that propaganda has been weakened by the Web? Difficult to say, but some examples indicate that something has changed. A good example is the attack on Russia. It was done literally by the book, applying all the recipes that are known to work and have worked beautifully well in the past. In particular, it was based on demonizing the bad guy of the moment, Vladimir ("Vlad") Putin, accused to be a bloodthirsty dictator and compared to, well, you guess whom! The real objective, however, soon became to use the already done demonizing work to bring down the hated Donald Trump, accused over and over of connivance with the evil Russians,

Did it work? In short, no. At least for what it was its main purpose, that of bringing down Donald Trump, it was an abject failure. Despite the daily hammering of all sort of accusations about Trump being Putin's straw man, the idea just didn't stick. Even with those who disapprove Trump as president, the idea that he is somehow connected to, or working for, Russia and Putin ranks very low among the criticism list.

But that doesn't mean that the anti-Russian propaganda didn't work. Here are some recent Gallup poll results:


The barrage of anti-Russian news on the mainstream media has clearly had some effect, bringing 70% of Americans to have an unfavorable opinion of Russia. So, propaganda still works, it seems.

Yes, but only within some limits. If we compare these data with those for Iraq, we find that in 2003, 93% of Americans (!!) declared to have an unfavorable opinion of Iraq. That was a true triumph of modern propaganda that could obtain this result on the basis of a complete fabrication: that of the "weapons of mass destruction" allegedly deployed in Iraq. Such an extreme view of Russia seems unlikely to be attainable today.

So, could it be true that propaganda doesn't work anymore so well and so smoothly as it did in the past? Or is it Trump the maverick who is disrupting everything? The only thing we can say is that propaganda may have weakened a little, but it is still the formidable weapon it has been from the time when it was developed in its modern form by people such as George Creel and Edward Bernays.

Yet, in the long run, even the most wondrous contraptions are subjected to the Seneca Collapse. And one of the reasons why empires collapse is because of the mountains of lies that the elites tell to their subjects. It has happened in the past, it may happen again. It probably will.






Wednesday, August 2, 2017

The stoic viewpoint: make the best of what's in our power and we take the rest as it naturally happens.


 The Stoics are the people on the top of the hill. They are applying Epictetus' maxim that says "What, then, is to be done? To make the best of what is in our power, and take the rest as it naturally happens." (Discourses, 1.1.17). 
(Image courtesy: Nate Hagens.)


There comes a point in which you have to acknowledge reality: Business as usual, BAU, is dead. Not that it would be impossible to avoid, or at least soften, the imminent disruption of our way of life caused either by resource depletion or climate change (or both). But that implies making sacrifices, renouncing something today for a better world tomorrow. And people are just not going to do that. We are not wired to plan for the future. We are wired to exploit what we have at hand.

The recent global events have shown that humans, worldwide, are unable to see priorities. The richest country in the world, the US, has turned its back to what science says about our faltering ecosystem, pursuing the impossible dream to return to an imaginary world of happy coal miners as England was at the time of Charles Dickens. The US is not the only example of a society that desperately tries cling to the old ways, refusing to change. Practically every country in the world is pursuing a dream of economic growth which, at this point, is just as impossible as a return to coal.

Does that mean we have to fall into despair? Some people seem to have arrived at this conclusion: there is nothing that can be done, therefore nothing that should be done. After all, what was so bad with the Middle Ages? And, anyway, human extinction would surely solve a lot of problems. Other take the opposite view, desperately hoping for some technological miracle that will lead us to leave the earth, colonize other planets, and mine the inexistent ores on asteroids.

What is to be done, then? Over the years, I found myself closer and closer to that group of ancient philosophers who lived during the times of decline of the Roman Empire who called themselves "Stoics" and who themselves the same question: what's to be done? The answer was given by Epictetus in his "Discourses:" It is "To make the best of what is in our power, and take the rest as it naturally happens". (1.1.17). And, after all, Seneca, to whom I credit the idea of the "Seneca Cliff", was a stoic, too!

So, here is a picture of the vegetable gardens that we planted in the courtyard of a building of the University of Florence (here it is shown with two students who have volunteered to take care of it). We plan to plant many more of these gardens. And, in this way, we make the best of what's in our power and we'll take the rest as it naturally happens.







Sunday, July 30, 2017

What is the worst product ever marketed?



The worst product ever marketed: the disposable butane lighter. Wasteful, expensive, non-recyclable, using non-renewable materials, having benign alternatives (matches). In short, evil. And yet, it was hugely successful. Image from Wikipedia 


Greens often exaggerate in inviting people to save energy and be happier by staying in the dark and eating insects. However, it is also true that sometimes wastefulness goes a few notches higher and becomes truly a scandal. It is the case of the ordinary disposable lighter. Bic alone produces almost a billion lighters per year and has produced some 20 billions of them in the past 30 years. The whole world production is probably of a few billion per year. A good example of a successful product, but is it a good product?

The disposable lighter is surely practical but also, if you think about it, a very bad deal. It contains some 5 cc of butane, that you pay, typically, more than $1. That means around $200 per liter, or $800/gallon. You wouldn't be happy to pay that kind of money when you refill the tank of your car. And, being powered by a fossil fuel, butane, every time you light up one you add some CO2 to the atmosphere, some of which will stay there for tens of thousands of years.

Then, the disposable lighter doesn't contain just non-renewable fuel but plastics manufactured from fossil fuels and also polluting. Then, it contains metals such as cerium, lanthanum, neodymium, praeseodymium and more. These metals are classified as "rare earths;" they are not so rare as the name seems to imply, but they are not so common, either. And the lighter is thrown away after use and it will never be recycled. The rare earths it contains will be lost forever.

Is all that enough to qualify disposable lighters as "the worst product ever marketed"? Well, everything can be questioned, but if you line up the characteristics of a bad product as 1) uses rare and non-renewable resources, 2) is not recycled and not supposed to be recyclable, 3) is manufactured on a large scale, 4) it has non-polluting and less expensive alternatives, there are few examples other than lighters for which you can tick all the four boxes. I can hardly think of anything so wasteful to set something on fire, no matter whether you are a professional arsonist or simply an ordinary smoker.

After all, what was so wrong with using the old matches? Matches contain only recyclable materials: wood, paper, phosphorous, sulfur. I can't see anything that can be done with a lighter that cannot be done with a match, except that a lighter can burn steadily for a longer time. But if your purpose is to light up a cigarette or a kitchen burner, it makes no difference. And, by all means, there is no way that a lighter would cost less than a match, at least if manufactured on a comparable scale.

So, disposable lighters are all an example of how a combination of financial factors and government regulations can push a bad product to dominate the market. It is, after all, what has happened with fossil fuels, still gathering large government subsidies, despite the damage they are doing to all of us.

In the case of lighter vs. matches, the playing field has been made unfavorable to matches from the beginning, because they have been traditionally taxed by governments (also lighters, in some cases, but not always). Add to that the rapid expansion of the cigarette market during the past decades, with some six billion cigarettes sold worldwide every year, and growing, some large companies saw their chance. They engaged in the large scale manufacturing of lighters and they crushed the match manufacturers, mainly small companies that couldn't match (indeed!) the financial power of large corporations. The advertising power, too,  played a big role, with the appeal of colored and fashionable items that could also be collected. And it was world domination for the disposable lighter.

Could we reverse this demonic trend? Maybe there are signs of an inversion of the tendency and, not long ago, I saw again courtesy matchboxes appearing in an Italian Hotel. Maybe it was because finally (in 2015) the Italian government decided to abolish the tax on matches, a good idea that, unfortunately, arrived at least 50 years too late (the French Government did that in 1999). Whatever the case, it is high time that someone realizes that some ideas, such as disposable lighters, are evil to the bone. And that the mythical "free market" cannot turn evil into good.

But maybe you think that the old matches are passé? In this case, we have technologies for getting rid of the obsolete propane lighters without having to get back to the somewhat primitive matches. For instance, we have spark lighters that use only electricity. They are a solid state alternative to propane lighters in the same way as photovoltaic energy is a solid state alternative to fossil energy. In the picture, you see one of these super hi-tech lighters in the hands of my daughter, Donata.


So, eventually, we learn what's the good way to do things. Too bad that it is almost always too late.






Wednesday, July 26, 2017

Stereocene: The Future of The Ecosystem



 During the "golden age" of science fiction, a popular theme was that of silicon-based life. Above, you can see a depiction of a silicon creature described by Stanley Weinbaum in his "A Martian Odissey" of 1934. The creature was endowed with a metabolism in which it would "breathe" metallic silicon, oxidizing it to silicon dioxide, hence it would excrete silica bricks: truly a solid-state creature. It is hard to think of an environment where such a creature could evolve, surely not on Mars. But, here on the Earth, some kind of silicon-based metabolism seems to have evolved during the past decades. We call it "photovoltaics." Some reflections of mine on how this metabolism could evolve in the future are reported below, where I argue that this new metabolic system could usher a new geological era which we might call "Stereocene", the era of solid state devices.
 


Abridged version of a paper published in 2016 in "Biophysical Economics and Resource Quality"

Ugo Bardi
Dipartimento di Chimica - Università di Firenze

The history of the earth system is normally described in terms of a series of time subdivisions defined by discrete (or “punctuated”) stratigraphic changes in the geological record, mainly in terms of biotic composition (Aunger 2007ab). The most recent of these subdivisions is the proposed “Anthropocene,” a term related to the strong perturbation of the ecosystem created by human activity. The starting date of the Anthropocene is not yet officially established, but it is normally identified with the start of the large-scale combustion of fossil carbon compounds stored in the earth’s crust (“fossil fuels”) on the part of the human industrial system. In this case, it could be located at some moment during the eighteenth century CE (Crutzen 2002; Lewis and Maslin 2015). So, we may ask the question of what the evolution of the Anthropocene could be as a function of the decreasing availability of fossil carbon compounds. Will the Anthropocene decline and the earth system return to conditions similar to the previous geologic subdivision, the Holocene?

The earth system is a nonequilibrium system whose behavior is determined by the flows of energy it receives. This kind of system tends to act as energy transducer and to dissipate the available energy potentials at the fastest possible rate (Sharma and Annila 2007. Nonequilibrium systems tend to attain the property called “homeostasis” if the potentials they dissipate remain approximately constant (Kleidon 2004). In the case of the earth system, by far, the largest flow of energy comes from the sun. It is approximately constant (Iqbal 1983), except for very long timescales, since it gradually increases by a factor of about 10 % per billion years (Schroeder and Connon Smith 2008). Therefore, the earth’s ecosystem would be expected to reach and maintain homeostatic conditions over timescales of the order of hundreds of millions of years. However, this does not happen because of geological perturbations that generate the punctuated transitions observed in the stratigraphic record.

The transition that generated the Anthropocene is related to a discontinuity in the energy dissipation rate of the ecosystem. This discontinuity appeared when the ecosystem (more exactly, the “homo sapiens” species) learned how to dissipate the energy potential of the carbon compounds stored in the earth’s crust, mainly in the form of crude oil, natural gas, and coal). These compounds had slowly accumulated as the result of the sedimentation of organic matter mainly over the Phanerozoic era, that is over a timescale of the order of hundreds of millions of years (Raupach and Canadell 2010). The rate of energy dissipation of this fossil potential, at present, can be estimated in terms of the “primary energy” use per unit time at the input of the human economic system. In 2013, this amount corresponded to ca. 18 TW (IEA 2015). Of this power, about 86 % (or ca. 15 TW) were produced by the combustion of fossil carbon compounds.

The thermal energy directly produced by combustion is just a trigger for other, more important effects that have created the Anthropocene. Among these, we may list as the dispersion of large amounts of heavy metals and radioactive isotopes in the ecosphere, the extended paving of large surface areas by inorganic compounds (Schneider et al. 2009), the destruction of a large fraction of the continental shelf surface by the practice known as “bottom trawling” (Zalasiewicz et al. 2011), and more. The most important indirect effect on the ecosystem of the combustion of fossil carbon is the emission of greenhouse gases as combustion products, mainly carbon dioxide, CO2, (Stocker et al. 2013). The thermal forcing generated by CO2 alone can be calculated as approximately 900 TW, or about 1 % of the solar radiative effect (Zhang and Caldeira 2015), hence a nonnegligible effect that generates an already detectable greenhouse warming of the atmosphere. This warming, together with other effects such as oceanic acidification, has the potential of deeply changing the ecosystem in the same way as, in ancient times, LIPs have generated mass extinctions (Wignall 2005; Bond and Wignall 2014).

Burning fossil fuels generate the exergy needed to create industrial structures which, in turn, are used to extract more fossil fuels and burn them. In this sense, the human industrial system can be seen as a metabolic system, akin to biological ones (Malhi 2014). The structures of this nonbiological metabolic system can be examined in light of concepts such as “net energy” (Odum 1973) defined as the exergy generated by the transduction of an energy stock into another form of energy stock. A similar concept is the “energy return for energy invested” (EROI or EROEI), first defined in 1986 (Hall et al. 1986) [see also (Hall et al. 2014)]. EROEI is defined as the ratio of the exergy obtained by means of a certain dissipation structure to the amount of exergy necessary to create and maintain the structure. If the EROEI associated with a dissipation process is larger than one, the excess can be used to replicate the process in new structures. On a large scale, this process can create the complex system that we call the “industrial society.” The growth of the human civilization as we know it today, and the whole Anthropocene, can be seen as the effect of the relatively large EROEI, of the order of 20–30 and perhaps more, associated with the combustion of fossil carbon compounds (Lambert et al. 2014).

A peculiarity of the dissipation of potentials associated with fossil hydrocarbons is that the system cannot attain homeostasis. The progressive depletion of the high-EROEI fossil resources leads to a progressive decline of the EROEI associated with fossil potentials. For instance, Hall et al. (2014) show that the EROEI of oil extraction in the USA peaked at around 30 in the 1960s, to decline to values lower than 20 at present. A further factor to be taken into account is called “pollution,” which accelerates the degradation of the accumulated capital stock and hence reduces the EROEI of the system as it requires more exergy for its maintenance (Meadows et al. 1972).

Only a small fraction of the crustal fossil carbon compounds can provide an EROEI >  1, the consequence is that he active phase of the Anthropocene is destined to last only a relatively short time for a geological time subdivision, a few centuries and no more. Assuming that humans will still exist during the post-Anthropocene tail, they would not have access to fossil fuels. As a consequence, their impact on the ecosystem would be mainly related to agricultural activities and, therefore, small in comparison with the present one, although likely not negligible, as it has been in the past (Ruddiman 2013; Mysak 2008).

However, we should also take into account that fossil carbon is not the only energy potential available to the human industrial system. Fissile nuclei (such as uranium and thorium) can also generate potentials that can be dissipated. However, this potential is limited in extent and cannot be reformed by Earth-based processes. Barring radical new developments, depletion of mineral uranium and thorium is expected to prevent this process from playing an important role in the future (Zittel et al. 2013). Nuclear fusion of light nuclei may also be considered but, so far, there is no evidence that the potential associated with the fusion of deuterium nuclei can generate an EROEI sufficient to maintain an industrial civilization, or even to maintain itself. Other potentials exist at the earth’s surface in the form of geothermal energy (Davies and Davies 2010) and tidal energy (Munk and Wunsch 1998); both are, however, limited in extent and unlikely to be able to provide the same flow of exergy generated today by fossil carbon compounds.

There remains the possibility of processing the flow of solar energy at the earth surface that, as mentioned earlier on, is large [89,000 TW (Tsao et al. 2006) or 87,000 TW (Szargut 2003)]. Note also that the atmospheric circulation generated by the sun’s irradiation produces some 1000 TW of kinetic energy (Tsao et al. 2006). These flows are orders of magnitude larger than the flow of primary energy associated with the Anthropocene (ca. 17 TW). Of course, as discussed earlier on, the capability of a transduction system to create complex structures depends on the EROEI of the process. This EROEI is difficult to evaluate with certainty, because of the continuous evolution of the technologies. We can say that all the recent studies on photovoltaic systems report EROEIs larger than one for the production of electric power by means of photovoltaic devices (Rydh and Sandén 2005; Richards and Watt 2007; Weißbach et al. 2013; Bekkelund 2013; Carbajales-Dale et al. 2015; Bhandari et al. 2015) even though some studies report smaller values than the average reported ones (Prieto and Hall 2011). In most cases, the EROEI of PV systems seems to be smaller than that of fossil burning systems, but, in some cases, it is reported to be larger (Raugei et al. 2012), with even larger values being reported for CSP (Montgomery 2009; Chu 2011). Overall, values of the EROEI of the order of 5–10 for direct transduction of solar energy can be considered as reasonable estimates (Green and Emery 2010). Even larger values of the EROEI are reported for wind energy plants (Kubiszewski et al. 2010). These values may increase as the result of technological developments, but also decline facing the progressive occupation of the best sites for the plants and to the increasing energy costs related to the depletion of the minerals needed to build the plants.

The current photovoltaic technology may use, but do not necessarily need, rare elements that could face near-term exhaustion problems (García-Olivares et al. 2012). Photovoltaic cells are manufactured using mainly silicon and aluminum, both common elements in the earth’s crust. So there do not appear to exist fundamental barriers to “close the cycle” and to use the exergy generated by human-made solar-powered devices (in particular PV systems) to recycle the systems for a very long time.

Various estimates exist on the ultimate limits of energy generation from photovoltaic systems. The “technical potential” in terms of solar energy production in the USA alone is estimated as more than 150 TW (Lopez et al. 2012). According to the data reported in (Liu et al. 2009), about 1/5 of the area of the Sahara desert (2 million square km) could generate around 50 TW at an overall PV panel area conversion efficiency of 10 %. Summing up similar fractions of the areas of major deserts, PV plants (or CSP ones) could generate around 500–1000 TW, possibly more than that, without significantly impacting on agricultural land. The contribution of wind energy has been estimated to be no more than 1 TW (de Castro et al. 2011) in some assumptions that have been criticized in (Garcia-Olivares 2016) Other calculations indicate that wind could generate as much as about 80 TW, (Jacobson and Archer 2012), or somewhat smaller values (Miller et al. 2011). Overall, these values are much larger than those associated with the combustion of fossil fuels, with the added advantage that renewables such as PV and wind produce higher quality energy in the form of electric power.

From these data, we can conclude that the transduction of the solar energy flow by means of inorganic devices could represent a future new metabolic “revolution” of the kind described by (Szathmáry and Smith 1995). (Lenton and Watson 2011) that could bootstrap the ecosphere to a new and higher level of transduction. It is too early to say if such a transition is possible, but, if it were to take place at its maximum potential, its effects could lead to transformations larger than those associated with the Anthropocene as it is currently understood. These effects are hard to predict at present, but they may involve changes in the planetary albedo, in the weather patterns, and in the general management of the land surface. Overall, the effect might be considered as a new geological transition.

As these effects would be mainly associated with solid-state devices (PV cells), perhaps we need a different term than “Anthropocene” to describe this new phase of the earth’s history. The term “Stereocene” (the age of solid-state devices) could be suitable to describe a new stage of the earth system in which humans could have access to truly gigantic amounts of useful energy, without necessarily perturbing the ecosystem in the highly destructive ways that have been the consequence of the use of fossil fuels during the past few centuries.

References (see original article)

Who

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