Cassandra has moved. Ugo Bardi publishes now on a new site called "The Seneca Effect."

Thursday, June 5, 2014

Deep Future: the ultimate destiny of humankind

In the 1950s, we knew what the future would be: an age of prosperity and unprecedented wonders. Energy too cheap to meter, flying cars, vacations on the moon, and the conquest of space. Then, space heroes would return to Earth to relax on the edge of their swimming pool while the robot-butler would bring them their margaritas. To be sure, the future had a dark side: that of the nuclear holocaust. But it was still a future where human ingenuity would trump everything else. 

The future today is completely different. The way we see the destiny of humankind is inextricably linked to the great "pulse" of carbon burning that has been ongoing for a couple of centuries and which is now reaching its peak. Fossil carbon has taken us to where we are now, creating the prosperity of our industrial civilization. But fossil fuels are rapidly running out and that creates a number of consequences; one is the impossibility of running an industrial society without abundant and cheap energy, the other is global warming which is transforming the earth into a completely new planet. These effects will shape the future of humankind in ways that can't be exactly predicted, but that we can imagine in the form of "scenarios" - futures that could happen. So, here are some possible futures of humankind, arranged from the least exciting one (near term extinction) to highly exciting ones, involving expansion over the whole galaxy.

1. Extinction.

Extinction is a simple scenario to describe: humankind goes extinct and that's it. The time scale of extinction may be millennia, centuries or, perhaps, just decades (in the last case, it may go under the name of "Near Term Extinction," a term popularized by Guy McPherson). In any case, extinction would be very rapid in comparison to the time span of existence of homo sapiens, at least two hundred thousand years.

Extinction is a perfectly possible scenario if we assume the playing out of some of the most dire effects of the human impact on the ecosphere, in particular the emissions of greenhouse gases. The great "methane burp" that could result from the thawing of the Earth's permafrost could raise temperatures up to 6-8 degrees C and even more in times of the order of a few centuries or even much faster. In its extreme version, global warming could evolve into the "Venus catastrophe", where the whole biosphere could be sterilized by extremely high temperatures. To be sure, this scenario seems to be ruled out by the results of the current climate models, but we don't need the Venus catastrophe to unbalance the ecosystem to such a degree that the resources humans need in order to survive would be destroyed. At that point, the outcome could be only one: extinction. 

This is a scenario that leaves little to discuss about the destiny of humankind. But, assuming that the biosphere is not completely destroyed, could the planet recover afterward? Perhaps it could, but not necessarily. Nowadays, the Earth is perilously close to the inner edge of the habitable zone in the Solar system and it is being pushed out of it by the gradual increase of solar radiation. It is a very slow process by human standards, but it is estimated that vertebrates have no more than some 100-150 million years to go before the Earth becomes too hot for them to survive. A major disaster such as the one we are contemplating in this scenario could kick the Earth out of the vertebrate habitable zone. In this case, the Earth's biosphere might revert to a world of unicellular creatures such as it was during the Archean or the Proterozoic eons. In such case, it is possible, and perhaps likely, that vertebrates would never re-evolve and that the planet would remain dominated by unicellular life forms until it gets sterilized by further increases in solar radiation, about one billion years from now.

But let's assume that the ecosystem can recover without major losses of phyla. In times of the order of hundreds of thousands of years, the excess CO2 in the atmosphere would be removed and transformed into solid carbonates. That would slowly cool down the planet and the ecosystem would gradually recover its former productivity. At that point, vertebrates could become again abundant and the Earth would look very much like it looked millions of years ago, when the ancestors of human beings didn't seem to be destined to the great explosion of numbers that was to take place with the Anthropocene.

Is there a chance that the Earth would evolve again a species of sentient beings? It is not impossible. If some species of primates could survive the great carbon pulse, they might re-develop tool making abilities and, in time, human-like intelligence. That would take time, considering that it took some 50 million years to arrive to homo sapiens from the earliest primates, but it would still be possible within the remaining lifetime of the biosphere for vertebrates. If all primates go extinct, then the task becomes more difficult considering that it took more than 400 million years for primates to appear after the evolution of vertebrates. But, again, it would not be impossible and, anyway, perhaps sentient beings don't need to be primates. So, there might be a second (and probably last) chance for intelligent creatures to do better than we did. Good luck to them!

2. The Olduvai Scenario. 

The "Return to Olduvai" was proposed by Richard Duncan in 1996 to describe the effect of the gradual depletion of fossil fuels; taking the name "Olduvai" from the name of a region in Tanzania, Africa, where our remote ancestors lived. The idea is that, without fossil fuels, humans would lose their principal source of energy and would be forced to return to their oldest survival lifestyle: hunting and gathering.

The Olduvai scenario could play out as the result of a combination of factors. First of all, fossil fuels would gradually become so expensive to make an industrial economy impossible. In parallel, global warming would raise temperatures so much that tropical and temperate latitudes would become impossible to inhabit year round for human beings. At this point, humans would be forced to retreat to extreme northern and southern regions, where it is not obvious that agriculture is possible. As we move away from the equator, a strong limiting factor is the low level of solar irradiation. Crops can grow nicely at high latitudes, but the problem is the slow rate of the reforming of fertile soil and the consequent erosion. It is a problem already evident today in regions such as in Iceland and Greenland and which might make agriculture impossible to maintain for long times.

So, humans living in high latitude regions could find that the best survival strategy for them is to adopt a lifestyle similar to that of modern Inuit, even though at much higher temperatures. They would live mainly by fishing and hunting marine mammals in the warm season - retreating in their shelters during the long polar night. In the Northern Hemisphere, this lifestyle would be possible in the ring of land around the North Pole, part of Eurasia and of the American Continent. In the Southern Hemisphere, it would mean the tip of the South American continent, Tierra Del Fuego, and perhaps an ice-free Antarctica, where humans could live for the first time in their history.

Modern humans have been hunters and gatherers for at least two hundred thousand years. Their hominid ancestors have been using this strategy for a couple of million years, at least. So, hunting and gathering is a stable and successful way of living that humans could adopt for a long time, at least as long as the planetary ecosystem would be able to maintain a sufficient biological productivity. In time, the ecosystem could stabilize and return the planet to the conditions of the past ten million years or so. In this case, the high latitude regions would probably freeze again and become covered by ice. Humans could then move back to lower latitudes. At this point, they would probably rediscover agriculture and restart with agricultural civilizations, as they had done tens or hundreds of thousands of years before. And so, we move to the next scenario; the return to agriculture. 

3. The return to agriculture.

Suppose that we run out of cheap fossil fuels, that is, fuels as cheap enough to sustain an industrial society. And suppose that we haven't used the energy we had - while we had it - to build up an alternative. Then, we will be forced to return to the world as it was before we started burning fossil fuels: an economy wholly based on biological resources; that is on agriculture.

This is a straightforward scenario that doesn't imply special events other than assuming that the effects of climate change would not be so drastic and ruinous as some scenarios describe them. Not that the transition won't be traumatic for humans. The world without fossil fuels and without alternatives to them won't be able to support, not even remotely, the same population that the fossil-powered agriculture had supported. And it is not just the lack of fossil fuels that will reduce agricultural productivity, it is the fact that centuries of intensive agriculture have destroyed a large fraction of the fertile soil that had created the human civilization. That would necessarily bring a drastic reduction in human population. In such a scenario, "traumatic" is surely an understatement. But humankind would survive.
In this farming future, there would hardly be a chance for a new industrial revolution. The fossil fuels that created the present one will be gone and will need millions of years to reform, if they ever will. Metal ores would also be scarce, although our farming descendants would do well by scavenging the ruins of our cities for metals. They would have plenty of iron and copper and they could even use aluminum for their cooking pans by melting down the zillions of beverage cans that we left behind. But their technological level would be severely limited by the lack of fuels: they would have only wood charcoal for their metallurgy. So, our descendants could still work iron and they could still kill each other with swords and spears (and, maybe, even with occasional muskets and cannons). But we know of no society in the past that could develop an industrial revolution without a cheap and abundant source of energy.

Curiously, however, there is a possibility for a new burst of industrialization in this remote future. It would be the result of mining Antarctica and, in minor measure, Greenland and other high latitude northern regions. Because of the ice cover, so far these regions have been scarcely exploited for minerals (or not at all, in the case of Antarctica). But the great carbon pulse could heat the planet enough that the world's glaciers would melt completely and open up these lands to mining. In this case, our ancestors could have a second (and likely last) chance to develop a new coal based industrial revolution. That would bring back everything to square one: with the new industrial society threatened by the deadly combination of depletion and climate change. Would our descendants be able to do better than us? Considering that they are - indeed - our descendants, probably not. Hence, this second cycle of industrialization might truly be the last one on the planet.

Apart from Antarctic coal, our descendants could remain farmers for a long, long time. It is said that agricultural societies of the past could be described as "peasants ruled by brigands", but this is an over-simplification for an integrated social structure where different layers perform highly specialized tasks: peasants, warriors, priests, artisans, and more. In time, agricultural societies could evolve converging to the social structure typical of other species which practice agriculture: mainly ants and termites. These species are "eusocial" (or "ultrasocial", according to some definitions) and practice extreme specialization, for instance with "queens" taking care of reproduction, while the other members of society are sterile female workers and warriors. Could future human agricultural society become something similar? Why not? At least one other species of mammals has developed full eusociality (the naked mole rat).

Eusocial species are highly resilient and tend to dominate the ecosystem, as ants and termites do and have been successfully doing for at least 50 million years. In principle, eusocial humans could also maintain their dominance of the ecosystem and continue in this role for tens or hundreds of millions of years, until they gradually disappear in a remote future as the earth becomes too hot for vertebrates to survive. If that happens, they would have been the most successful vertebrate species of earth's history; a species that even briefly dreamed of conquering space.

4. The great metabolic revolution

In more than four billion years of existence, the Earth never stood still. Powerful forces have shaped it in a continuous series of revolutions which have seen the development of more and more complex life forms, increasingly able to exploit the thermodynamic gradient created by sunlight. During this long time span, we have seen several metabolic revolutions; of which two have been the most important ones. The first was photosynthesis, some 4 billion years ago. The second is the aerobic metabolism, about 2.5 billion years ago. It is the latter revolution which, eventually, generated vertebrates and us.

Today, we seem to have reached an impasse in this ever increasing growth of biological complexity. Actually, we may be heading for an inversion of tendency created by long term changes of the ecosphere. The planetary thermostat which stabilizes the Earth's temperature works by regulating the concentration of CO2 in the atmosphere. But with the gradually increasing solar radiation, these concentrations are already near the lower limits necessary for photosynthesis. So, the present ecosystem is in a no-win situation: in the long run, either it will be destroyed by the lack of CO2 or by high temperatures. So, in order for a complex ecosystem to survive, we need a truly drastic metabolic revolution. Organic photosynthesis has reached its limits: we need to move to a completely different kind of substrates.

What is in photosynthesis, after all? It is a way to transform solar energy into excited electrons and use them to create chemical compounds which can give back this energy on demand. The efficiency of photosynthesis in this process is reported to arrive to about 13% in ideal conditions - in practice it is of the order of 8%. Note also that plants can't function as photosynthetic machines outside a narrow range of temperatures and without of nutrients and chemicals which are not always available.

So, if we want another metabolic revolution, we need something that can be both more efficient and less demanding in terms of environmental conditions. A possibility is the photovoltaic (PV) cell. The efficiency of a modern silicon PV cell can be higher than 20% in creating excited electrons. By themselves, the cells do not store energy, but can be coupled to energy storage devices and used to power a variety of processes and reactions for an overall efficiency that is comparable (and arguably higher) to that of photosynthesis. Silicon PV cells function using abundant elements: mainly silicon and aluminum, plus traces of nitrogen, boron, an phosphorous. The present generation uses also silver, but that's not a crucial. But the great advantage of "silicon photosynthesis" is that solid state PV cells do not need water or gaseous oxygen, and can operate in freezing temperatures or at high temperatures, up to a few hundred degrees centigrade. The "habitable zone" for PV cells is not a narrow shell around the sun: it spans a huge volume that includes all the major planets and probably extends even closer and farther from the sun. The quantity of solar energy that can be gathered in this volume is incredibly larger than the tiny amount intercepted by the Earth.

Of course, solid state PV devices are not normally considered the photosynthetic part of an ecosystem. They enjoy the name of "cells"; but unlike biological cells they don't reproduce themselves. But PV cells delegate their reproduction to specialized entities; cell factories, just like worker ants delegate their reproduction to specialized entities: queen ants. So, it is all part of a new ecosystem that is emerging; one which starts from the beginning as eusocial.

We know that complex systems become more complex the more energy flows through them. If the solid state ecosystem turns out to be more effective than the biological one, then the perspectives are mind boggling even if we limit our horizon to the surface of the Earth. Of course, it is hard for us to imagine the consequences of such a revolution (think of how difficult it would be for a protist of the Proterozoic age to imagine the advent of vertebrates). What we can see is that such a system is born connected at the planetary scale. The rapid development of the internet is giving us a taste of this new situation of extended interconnectedness. From our viewpoint of human beings, it is an unpleasant loss of privacy. On the other hand, ants in an anthill don't enjoy much privacy. It is, again, one of the characteristics of eusociality: you pay the advantages of efficiency with a loss of individuality. But we can hardly say more than that: if the new system is to be born, it will. What it will do, it is impossible to say, but it can - theoretically - expand to the whole solar system and survive for the whole remaining lifespan of the Sun, about 5 billion years - and even more.

In a way, it would be the ultimate triumph for human beings who would have engineered the birth of a new ecosystem encompassing the whole solar system and perhaps over the whole Galaxy. Would they still exist in this new ecosystem? If so, which role could they play? And, if not, will they be remembered with gratitude? (Note, however, that we don't feel particularly indebted to our one-celled ancestors).

5. Where are we going, anyway?

All civilizations of the past have declined and collapsed. But collapse is nothing more than rapid change and, as long as the sun shines, the ecosystem has at least a chance to move to higher levels of complexity. The future that we can dimly see today is rich in possibilities. Billions of years ago, Mars - and possibly also Venus - had a chance to develop an organic ecosphere. But in both cases the time available was too short and soon both planets left the habitable zone and were sterilized. The Earth has had a much longer time, billions of years more to develop the ecosystem we know today. But the Earth never stood still and it is not standing still: change is accelerating to speeds never seen before in history. We may go down to a sterile planet or move on to a new system of unbelievable complexity. It is the ultimate challenge for humankind; one that we cannot avoid to face.


  1. Excellent article. Just one remark: the probability of the two possible outcomemes: "go down to a sterile planet or move on to a new system of unbelievable complexity" are not just the same. Isn't it?

    1. Surely they are not the same, but which one is the most probable?

    2. It isn't either/or although I hope it isn't the sterile planet or without humans. Living is beautiful.

  2. Ugo Bardi, you are such a brilliant systems thinker it perplexes me that you do not see the total energy, nonfuel minerals, and environmental destruction connected to the devices that collect the energy from the sun and wind - wind machines and photovoltaics coupled with their high tech controllers, inverters and all that goes with the system.
    I have said this to you before but not as directly. ERoEI is low for photovoltaics according to Hall and Prieto’s work. And my research into the components of the devices and their auxiliary parts essentially makes them extensions of the fossil fuel supply system and not clean, green or sustainable. So as not to be seen as spam I refrain from giving the URL’s for this information but would willingly if asked.

    I believe if we don’t blow ourselves up, that we will wind down to a world like the middle ages. But without wisdom we will overshoot again only regionally instead of globally as now.

    1. I read Hall and Prieto's work. It is a series of wrong answer to the wrong questions. Photovoltaics is not the solution to the energy problem, not any more than Humans are the solution for the monkey problem. Photovoltaics is a new metabolic system in itself - eons away from the primitive form of energy which we wrongly call "fossil fuels".

    2. "But without wisdom we will..."

      In the past. humans have occasionally shown a remarkable capacity for developing what is needed to overcome a present barrier or obstacle.

      Perhaps now humans will develop some wisdom?

  3. Personally, I think the key aspect is the size of the human population which "we" wish to maintain (meaning what we actually CAN maintain rather than what we may WANT to maintain) (or THINK we may wish to maintain) going forward and how fast and sudden or gradual the collapse will be when it comes.

    If the collapse is not sudden and total but is instead slow and gradual, I think we easily could ADJUST and redeploy ourselves around the surface of the earth (or even deep under it, if needed) as might be required to support a population of 10 million humans on geothermal energy, solar energy and whatever fossil fuels are still left over and also FEED IT, (one way or another from whatever biomass we could scrounge up) even if the earth got quite hot and we all had to reside in Antarctica.

    There would be PLENTY of left over artifacts (both material artifacts and intellectual artifacts of all types as well as resources albeit a bit harder to get) that the future population could SCAVANGE and live off of for centuries if not hundreds or even thousands of millennia. And a population of 10 million could probably still manage to build and operate the main half-way worthwhile technologies that we have managed to invent and develop up until now.

    The Wikipedia article on human population says: "Until the development of agriculture around the 11th millennium BC, it is estimated that the world population stabilized at about three million people,[23] who subsisted through hunting and foraging – a lifestyle that by its nature ensured a low population density. The total world population probably never exceeded 15 million inhabitants before the invention of agriculture.[24] By contrast, it is estimated that around 50–60 million people lived in the combined eastern and western Roman Empire in the 4th century AD.[25]"

    So with the benefit of all the know-how and the technologies that we have managed to invent or develop over the past 1000 years or so in particular, and with geothermal and solar energy now available, we should be able to maintain a population of about 5 to 50 million earthlings SOMEWHERE, SOMEHOW. (and WITHOUT having to only hunt and forage, or live in caves wearing loincloths and rubbing sticks together to make a fire)

    The additional 7 billions (though probably 9 or 10 by the time the collapse happens in earnest) were NOT missed during the Roman Empire nor will they be missed by the much smaller and more sensible generations of the future.

    Naturally we also could FAIL at our own gradual managed shrinkage and redeployment and adjustment DOWNWARD in which case we may just have to re-evolve again later (with lots of luck) or simply go extinct.

    In any case the COSMOS will NOT notice the difference one way or the other.

    But although I may be totally wrong I find it hard to believe that a few million humans could NOT somehow manage to redeploy, adjust and survive through whatever will come. Unless of course the Venus scenario happens in which case everything will be nicely fried.

    And let me see, who might get to be the LUCKY 70 million or so who would be left over and could go on for another million years or so? Very AUSPICIOUSLY 70 million happens to be 1% of 7000 millions or the current SEVEN BILLIONS. So maybe the head of Goldman Sachs and all his other buddies in THE ONE PERCENT would all be able to make it through INTO THE BRIGHT NEW FUTURE? Naturally it would be very helpful if a bit of last minute innovative financial engineering might be able to raise the capital required for the BIG ADJUSTMENT. So perhaps what I am saying is that basically all of the pieces of the puzzle are BOUND to come together at the last minute.

  4. Max - interesting. I agree with the numbers (unfortunately) and at my age I don't need to worry about being one of them. I agree with mining the remains of civilization. We can even rig up passive solar. But it takes an industrial infrastructure to make photovoltaics, controllers, inverters, and so much more. We will do this next phase with little or no electricity. I believe we will have the per captia energy consumption akin to the middle ages with human, animal and some mechanical wind and mechanical water as sources.
    I invite you to view these essays.
    This essay has diagrams and pictures of how we get copper, aluminum, glass, black chrome – the chemicals, heavy machinery, and industrial processes that are necessary to make the devices to capture the energy of the sun and wind.

    And even if you could get around the environmental degradation, the low ERoEI and could amass enough extra energy to reproduce the capturing devices and their equipment, then how about the rest of the STUFF of high tech, high energy society?

    1. Many thanks John, I am happy that you seemed to enjoy reading my bright ideas. Naturally it is PRETTY DIFFICULT to know in advance exactly (or even totally inexactly) how the BIG ADJUSTMENT, the BIG REDEPLOYMENT and the BIG REDUCTION all might take place. And we wouldn’t want to know -even if we could- just so that some happy element of surprise could be left over.

      I think roughly 10,000 megawatts of geothermal energy is being produced worldwide right now and that might be enough to support roughly two million people or only one million if a good bit of it would have to be used to decompose seawater to get oxygen to breathe, or desalinated so that humans (or animals) could drink it. Assuming of course that all fresh water sources would be TOTALLY polluted by then by a huge range of toxic wastes from fracking and etc. to a completely “beyond purification” point.

      And geothermal is probably much easier (or so I think) to produce than either solar or wind energy. Regrettably it is not ALL nearby Antarctica so that could complicate things a bit. However, given that the earth’s environment and biosphere would be totally wrecked already anyway there probably would be enough petroleum or coal left over to burn for a few hundred thousand years to support a population of just one million people. Only a few additional gigatons of CO2 in the atmosphere or in what is left of the earth’s dead garbage-dump oceans -covered with lots of useful plastics that also could be “mined” - will not make that much of a difference at that point.

      The one or two million population -though they might be able to be as many as seven millions i.e. the full complement of the direct descendants of today’s ONE PERCENT - and in fully egalitarian fashion whether they be American, European, Chinese, Russian or from other “neoliberally- emerging” countries (though they probably all would be graduates of at least Harvard, Princeton or Oxford or Cambridge) could all live happily in climate controlled units in a large city or “urban complex”, called POLARIS located at the “dead center” of Antarctica…. but with “feeder spokes” manned by slaves (drawn from those who might have been spared of the 99% who regrettably had to die and that the ONE PERCENT had conscripted to help it to make the move, and build POLARIS) to man the immediately surrounding production centers (industrial, agricultural and/ or services) and to scavange and mine the abandoned ruins of all of industrial civilization’s earlier cities a bit further “afield”. (and of course to also filter all the useful plastics from the oceans and finally burn them or recycle them)

      So all that really remains to be done is for Goldman Sachs et al (with due assistance from the Federal Reserve and the ECB and the IMF) to “financially engineer” how to extract every last bit of accumulated wealth (and whether it is presently in the form of equities, bonds, cash or ANY tangible assets) from the 99% to pay for the three BIGGIES above, and for the Military Industrial Complex and the Internal Security Complex to maintain “peace and order” during the transition and the construction of the new ONE PERCENT ANTARCTICA HUB.

      At just the right moment ALL NATIONALITIES would be suppressed by the Bank-i-Moon of the moment and a single highly coveted ONE PERCENT ANTARCTICA POLARIS citizenship would be awarded to the TRULY MERITORIOUS who clearly and demonstrably will deserve to have it.

      Regrettably very strict border controls may have to be enforced to ensure that no non-citizen “illegal aliens” from any stray survivor groups, can come in to free-load.

      And if you happen to be interested in some of my “background thinking” along similar lines, (but much more current and empirically observable) you can refer to an earlier post of mine here:

    2. Quite good job, John. Thanks for the links, they're useful.

      I guess you don't mind being mentioned in a work I'm doing in Spanish:

      I'm totally in the same lines you post. I found mind boggling such an smart person like Prof. Bardi, that writes about mineral depletion and other issues, and he doesn't explain the main drawbacks on the many rare earth and quite rare materials used for electronics, not only PV.

      Many of those materials are used in the production process, not in the final product, that makes them 'invisible' for many people. It is not only an energy issue.

      I guess you will find interesting this document:

    3. There is no need for rare earths and rare materials for a metabolic PV system. You believe you need them because you are still thinking to the obsolete and wasteful human-made electric grid.

    4. And as much rare earths needed for the geothermal for a happy earthly population of one million -homo very sapiens- denizens

    5. Besides the fact that often PV uses palladium and indium, that maybe can be replaced, the semiconductors required to control anything use them indeed. A chain is as strong as the weakest of the slabs. Control and transfomer electronics used are the weakest in this case. As well as processes and production, since it also uses electronics.

      And the question is not only the materials that are IN the end product. There is also all the vast amount of different materials and technologies required in the PRODUCTION of the final product. Helium, and other noble gases are used, just as starting point. High vacuum. Quite pure materials for different processes. Extremely expensive optics (more than 5M€ each) used with excimer lasers, polished to lambda/10s of the 198nm wavelength, just for some of the photomasking processes.

      The highest peak in human technology, when view from the complexity point of view, is electronics, semiconductor manufacturing. the section about microprocessors gives some insights.

      I'm thinking to write another series about this part, but I wish to prepare it in more depth, and then discuss with Dr. Turiel about it.


    6. You should learn a little more about photovoltaics before stating that "often PV uses palladium and indium"

    7. You imply we don't know what we are talking about but do not supply sources for your position.
      I did above. Are you saying there is no mining, processing, refining, manufacturing, fabricating, transportation, maintenance and parts replacement involved? Are you saying Hall is wrong? How? I expected more from you.

    8. John, Hall and Prieto's work is not "wrong" strictly speaking. It just asks the wrong questions and it is not possible to give the right answer to a wrong question. The point is that Charles Hall said many times before getting involved in this book is that the concept of EROEI is not absolute but depends on the boundaries of the system. By choosing different boundaries, you can arrive to different values of the EROEI. This is how H&P arrive to relatively low values of the EROEI for PV in their book, much lower than those of practically all serious studies on the same subject. If they were to apply the same methods to fossil fuels they would also get much lower numbers. It is, BTW, the same trick used in reverse by proponents of nuclear energy to get values of the EROEI much larger than those of most other studies.

      In any case, the point is not whether the EROEI of PV is larger or smaller than that fossil fuels. A metabolism based on fossil fuels is a detritivore metabolism and it can last only for extremely short times. Fossil fuels are doomed by definition. Instead, the current metabolic process based on organic photosynthesis has been around for a very long time because it recycles everything at 100%. But the photosynthetic mechanism it is also doomed because of the growing solar irradiation and the resulting planetary feedbacks. It is going to die, although probably in rather long times from the human viewpoint.

      The point is whether a new metabolic process can replace (or complement) the organic photosynthesis process, as it has happened a few times over the Earth's history. Among the various possibilities that I have listed in the post, one is that we can develop a new silicon based metabolic system and that this system will be stable and able to recycle the nutrients it uses. Whether this is actually possible on a very long time span it is to be seen. I think, however, that it is highly probable that such a system can be built and I argue that we should make an effort to try to build it. It may not last billions of years, but it may help us to prosper for quite a long time.

    9. Thank you for more clarity. As for the ERoEI of other reports, all that I have read only deal at the factory door and not all the inputs (energy and material) prior. As for nuclear, I don't believe humanity is mature enough to handle nuclear. And I of course agree that fossil fuels is a short term experience of high quality energy. That we have done some miraculous things with it as well as some horrendous ones highlights the glory and limitations of our humanity.
      Personally I worry about us tinkering more with nature. I think the evolved photosynthesis is adequate for a healthy, joyful although strenuous life. It is us that needs to be "engineered". There are five natural factors that determine and will continue to determine our history and future.
      * All life reproduces to the maximum their environment allows (population density).
      * All life will use all the resources in its environment to promote its present living (population pressure).
      * Much of life manifest an us against them protectionism (even plants release poisons to the soil to protect their territory. This is the convergence of territoriality (which is manifest by all life) and the need to belong for this dependently social animal called human.
      * We are immersed in an environment of our own making and our "brilliance" threatens us with unintended consequences (whether agriculture or nuclear power).
      * Groups larger than the small group of 30 to 200 people, which is the social environment in which we evolved for a million years, creates power-over and inequality.
      These five factors are a natural part of being human. For more detailed exposition:
      Once again thanks for the clarity

    10. Carlos de CastroJune 10, 2014 at 4:53 AM

      Ugo: You are right that the fossil fuel boundaries for an EROEI > 10 are not the same that Hall and Prieto use for PV. Yes, fossil fuels with Hall and Prieto boundaries could down the EROEI to 4 or 5 for oil (my gross estimation). The right question is, how Hall and Prieto PV EROEI of 2,4 will be affected for the new boundaries of fossils: down to 2 or less... Therefore, provided that PV need fossils at present and not the contrary, the problem is bigger. If you want a metabolic PV pathway, please, read again Prieto and Hall work, it approach much better than the rest of "all serious studies" the metabolic question. This is your right question; that paradoxically you forgive in your over optimism on PV technology.

      Again, PV cell efficiency is 20% or even 40%, but to integrate PV in a metabolism, you need much more than a cell. The present park efficiency (even not a metabolism) is lesser than 2,5% respect to the radiation over the park occupation (as we demostrate: Renewable and Sustainable Energy Reviews: 28 (2013): 824-835).
      Biosphere does not use only photosynthesis, but also solar heat, wind and other sources. Taking all this into account the biosphere metabolism efficiency is greater than PV cells in forests for instance (around 30%). Biosphere technology is far away of humans (you say that biosphere recycle with 100%, not so, only 99,5%, is not perfect).


  5. I'm talking from the top of my memory. Years ago, I was in a PV assembly (PV cells were bought to Germany and China) in Valencia, IIRC. I was installing the Nd:YAG used to engrave the channels for the metallizations and to 'cut' (break, in fact) the wafers. The people in charge of the plant told me that the metalization deposition used to increase the conductivity of the Si top side uses palladium, titanium, aluminum, some silver, and that probably it would be replaced by Indium Tin Oxide (a transparent, not quite good conductor, not fully transparent, neither, used in resistive touch panels also).

    The metallizations are tricky, since they might be resistive, ohmic contacts, without electron migration and son on. Not Schottky contacts, so that makes sense to me.

    BTW, palladium, as well as platinum and other platinum group metals, are commonly used in many electronic components, like (schottky) diodes, ceramic capacitors. Rare earths are also used not only for semiconductors or optoelectronics (often as phosphors for the TFT industry), like Cerium, Europium, Yttrium, Arsenicum, Gallium, Indium for LED's, but also for ferrite beads, just to mention a few.

    And, in any case, ¿why electrification? Netherlands had a quite impressive industry based on eolic energy. Direct energy, without electricity can be used for many purposes, with higher efficiency.

    A big part of the energy bill in a house (>50%) is used for heat purposes. Why do we need to heat up water for the shower by photovoltaics if we can do exactly the same with a much more simplier and with much greater efficency (up to 95%) solar hot water? Why not solar cooking? Why not other simple, resilient energies that can be developed, built, mantained and handled in our backyard?

    Why do we have to be electric men? Why this obsession with photovoltaic? Can't we do electricity at home with concentration solar systems, small, that can supply us with two kind of energies: heat and electricity? According with Dr. Hall and Pedro Prieto, concentrating sun thermodynamic energy centrals have higher EROEI, and adapt better to the energy demand along the day. They can be build with some skills without the need for too complex systems, if the control of the mirrors can be solve by some mechanical (clockwork) way.

    A look at can give some ideas that might be as good as PV at this job, but done at our backyards, much more resilient, much more 'green', and much more suitable for our needs. An uneployed person, with little effort, some skills and small investment can improve its energy inputs by reading this web.

    After all, all the PV manufacturing companies I know are pure BAU, large companies installed in a profit basis that are interested in growing like all the system that is about to collapse. So, switching from oil to PV is simply change the name of the companies ruling the world. I guess there is much more like a total change in the social paradigm, not only the energy paradigm.

    My personal thoughts, take them with a grain of salt.


    1. I'm sorry, I've typed too fast. I meant I was at a PV panels assembly plant, that bought the semiconductor wafers to Germany and/or China, installing an Nd:YAG lamp pumped laser, TEM00, BTW.


    2. You mention an important point in asking why electric power is so important. In principle, it is possible to transform solar energy directly into heat and mechanical power and in some cases that may be more efficient than going through the PV process. Of course, we can think of a hybrid metabolic process which uses PV only as part of the whole transformation. I stressed PV and electricity in my post in order to simplify things, and also because the electricity is extremely flexible and useful for many things that can't be performed just with mechanical power.

      Then, yes, there are rare elements used in tiny amounts in PV cells. And then, there are the materials used for the manufacturing of the cell - including those for lasers. These elements are part of the "nutrient soup" used by the PV metabolic process. In the evolution of the process, it may turn out to be nutrient limited, just as the biological process is nutrient limited regarding - say - phospates. The maintenance of a metabolic process for millions or even billions of years depends on the ability of reducing to a minimum the reliance on rare and expensive nutrients. That means engineering the whole process in such a way to recycle at 100% all nutrients at a reasonable energy cost. I think it is perfectly possible for PV at the cost of a minor loss of performance: the point is that we never designed PV cells with the goal of optimizing the consumption of rare materials, so this is an open area to explore. In any case, if we have enough energy, we can recycle anything: that's how the ecosystem works and it has been working for about 4 billion years. So, there are good reasons to be optimistic!

    3. Hmm. Interesting idea. I've read your reply to John Weber, and I have to think on it. Unfortunately my 'single neuron processor' is slow and needs some time with the multitasking I'm involved now (hey, I'm a men!! ;oP).

      Anyway, at a first glance, it seems to me that right now it is not only impossible from a technical point of view (but I also thing it is worth to work at it), but as happens with other tecnologies, and as John Weber also mentioned, humankind is not mature to handle it.

      If finally some form of it is viable within, say, a decade, I guess that we will use it to grow even more and do things much worse. While we still have the mantra of infinite growth, any solution would be misused. Hence my proposal of humble energy homemade systems, just to try to handle the descent in a more gentle way.

      And I doubt seriously that we never succeed to manage humankind into maturity.

  6. Thanks for a fascinating flight of imagination and awesome wordsmithery! I love the concept of fossil fuel power as «detritovore metabolism» (perhaps «detritophagy») — that facilitates a flight into alternative energy/metabolism schema…

    Attempting to view possible futures in a «Jetson’s» or Jules Verne manner might be entertaining, but constraining such views to the limits imposed by science, mathematics and economics is more practical — and can be equally entertaining.

    “Trend is not destiny.” (Lewis Mumford, René Dubos, et al.) But it can aid thought processes. Specifically, looking into history can aid thinking about the future. When I was 14 years old, taking Ancient & Medieval History in school, our teacher told us of the steam turbine built by Heron of Alexandria, 1st Century AD. One student asked why it was never put to work. Our teacher (I had a crush on her) replied, “Back in those days, there was so much cheap slave labor that there was no need for labor saving machines.” That made sense to me. At home, I told this to my father, a high school dropout and an artist. Disgusted, he said that people as ignorant as my teacher had no business talking about things they knew nothing about.

    Seeing how irritated I was, my father explained. He said that a steam engine is a power source, not a labor saving machine. Many tools, like a flying shuttlecock, are labor savers but not power sources. No engineer, past or present, could build a practical steam engine if all he had to work with were copper-based alloys of uncertain composition and which cost thousands of dollars a pound. Slave labor was hardly any cheaper than hired labor, and in 19th Century America and Brazil, slaves operated steam engines.

    I was convinced, even tho I thought Dad had dealt to severely with the beautiful Miss Vogelsang, who happened to be ΦBK from the University of Michigan and 19 years old. Education and IQ are necessary but not sufficient for wisdom.

    David F Collins

    1. I forgot to note: Futures are best viewed as being of several different possibilities. Charles Dickens did this also in his «A Christmas Carol».

  7. The notion that vertebrate life couldn't exist after 150 million years seems downright preposterous, to use an old word. According to the linked article, solar insolation would be 1.5% higher, giving a 1.2C rise on the fourth-power radiation law. That might or might not be amplified by 2 or even 5, but there's no reason present-day vertebrate life couldn't occupy most of even a 6C warmer world.

    And present-day vertebrate life exists from near 0C in the oceans all the way to 40C in the tropics. Why wouldn't 150 million years be enough time - many times enough - to extend that slightly by evolving proteins that work fine at 50C or even 60C, given a stress (that doesn't now exist) driving such evolution? Indeed, it seems inconceivable that an energy-rich niche like the moist tropics could possibly ever go unoccupied until such time as the oceans finally go into runaway boil-off.

    1. I wouldn't say "preposterous" - just the less strong term of "uncertain". There are various estimates of the life span of the biosphere (and of vertebrates). Some are even more pessimistic than the one I cited. For instance, Lovelock and Whitefield estimated that the whole biosphere could be sterilized in about 100 Myrs (Lovelock, J. E. and Whitfield, M.: The life span of the biosphere, Nature, 296, 561–563, 1982.)

      The point is, anyway, that it is not heat that kills vertebrates (of course!). But vertebrates are fast metabolic machines and need lots of nutrients. So, it is sufficient a relatively modest reduction in the overall planetary productivity to cause their extinction.

      Anyway, no sense in getting angry for something that may happen in hundreds or thousands of millions of years. It is just a way to gain some perspective on the future

  8. Another totally unrealistic thought experiment by someone. (in this case, ME)
    ... If someone spent 100 days figuring out the weighted average EROEI from all petroleum sources and every single field being “produced” today it would be SOME number. I would not hazard to guess what the number might be but perhaps someone has computed it already.
    That number would be the average EROEI TODAY needed to "produce" or “extract” or “mine” or “rape the earth of” , the roughly 80 million barrels of oil per day which the roughly 7 billion humans use every day TODAY. Naturally they use it in different proportions and for different purposes both directly and indirectly depending on who they are and where they happen to have been born. Some are more “lucky” than others.
    Now let's magically reduce the number of humans to just 70 millions instead of 7000 millions. (1 %) Never mind how, or where these humans would live or how dispersed or concentrated the new population might be though of course all of that would matter. Someone will say (and should) that a proportional reduction as I am about to make is wrong for 1000 reasons but let me make it anyway and assume that this would reduce the amount of oil that needs to be burned (or otherwise used) each day to just 800 K barrels per day.
    And let us also ASSUME that THOSE 800 K BO/D would be "produced" from whichever fields have the best or the highest EROEI. So NOT from the Orinoco tar sands nor from several miles under the ocean floor.
    Would the AVERAGE EROEI for these 800K barrels be the same as the earlier AVERAGE EROEI calculated for 80 million barrels? "Probably not"? The EROEI would likely be much HIGHER while the amount needed enormously LOWER. And of course depletion rates (and pollution) also would be FAR lower.
    And so at that point would many people be concerned about being at or past "peak oil" ? Or how about at or past "peak uranium" or "peak coal" or "peak copper" or "peak anything else" if the same were done for other non-renewable resources? In fact we might not even think we would be past "peak forests" or "peak fish" or "peak garbage in the oceans" or “peak climate change” (allowing for a joke)
    So QUANTITIES and in particular the quantity (or the number) of humans and hence the quantity of resources “needed” on an ongoing basis on earth DO MATTER.
    So why is it that these QUANTITIES are SO SELDOM explicitly discussed or taken into account?
    Many of the concepts and ideas that we work with routinely are based on an assumption that human population will “inevitably” stay roughly the same or decrease slightly or perhaps increase slightly or significantly.
    Perhaps this is the ONLY assumption which can or SHOULD BE made according to our “values”?
    But is it possible to consider that "different people" might have "different values" or that "values" might CHANGE over time as material, physical and also social, economic and political and ideological and institutional conditions, contexts and situations change through the course of history and evolution?
    Humankind -of the "homo-highly-sapiens" variety- has been around for one or two hundred thousand years. Again, it doesn't really matter if it has been one hundred or two hundred or five hundred thousand . Do we really think that our own "values" (from before we even had a word for them) which shape what we believe is reasonable and what we don't believe is reasonable have NOT changed over both time and space over that period?
    But IF they have indeed changed (and undoubtedly will continue to change) then perhaps more "simple thought experiments" such as the one above might NOT be such a total waste of time?
    I rest my case. Whatever "case" I may or may not have made, at least for "the time being" , though ALSO perhaps for "being in time". (or trying to be)

  9. A brain of sufficient size, and a high encephalisation quotient (large brain compared to body size) is needed for intelligence. Other features for the development of intelligence are forelimbs freed from the demands of locomotion, prehensile hands (able to grasp objects), and opposable thumbs (for fine motor activity).

    The maintenance of the brain requires a system capable of oxygen delivery at a distance (circulating haemoglobin) adequate oxygen carriage (high concentrations of free haemoglobin make blood viscous: the workaround is to contain the haemoglobin in red blood cells), and an efficient gas exchange mechanism (the lungs: much better than gills). Also important is homeothermy and endothermy (maintenance of constant body temperature and generation of one's own heat).

  10. A technology wizardry answer to global warming:

    Return the heat to outer space!

  11. A last vision.

    - The Last Frontier

    After a problematic XXI century, humankind learns to not grow in a limited enviroment. It brings a new age of technology. A civilization moved by renewable energy, mainly solar, abundant elements that learns how to use in new wonderful forms at nanoscale, like superatoms or wonderfull composites that mimic the achievements of nature.
    With open source and new forms of production based on colaboration, plus birth control, and a complete change in economics and social structure, humankind finally succeded bringing abundance (in terms of any real material need, not whim) for all.

    At the finish of the change, humans turns to greater objetives, so looks at the space again.

    With the capability of advanced robotics, becames to create a full army of robots, manufactured directly on space, based on space resources. Then, human begins the colonization of our solar system, but with a new vision and filosophy of full recycling.

    The Earth will have a stabilized population, but not the new colonies in space. Like any other life, a new transformation, exponentially at first, begin, until reach its full potential.
    Then, when life and space colonies fill "every" region of the solar system, the humans will see farther... to the stars.

    Millions of years in the future, when our planet was full of life yet, a lot of life had been spread by the galaxy, and human will have evolved in ways that we could't imagine now. We have became "extint" but not like a closed path but as an open path to new forms.

    A dream that looks impossible for technopessimists, but it has not real limits that avoid to reach it.
    We must face the limits of nature with wisdom, but the space travel and colonization is not beyond our limits. When the times comes.



Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)