The sunflower
It bows down to the Sun
The image of resilience.

Wednesday, May 31, 2023

Is the Energy Return of Renewables Really Higher than that of Fossil Fuels? A Rebuttal to Art Berman's Criticism


The "net energy cliff," a popular graphic often used to demonstrate that renewables will never be able to support an industrial society. It is mostly wrong or at least obsolete. The EROI of crude oil never was so high as shown here, and the idea that there is a "minimum EROI needed" to support modern society is debatable, to say the least.

It is a very good thing that Art Berman, a well-known expert in oil and fossil fuel matters, has intervened in the EROI debate on renewables with a recent post. It means that the EROI is becoming the focus of the debate, as it should be. The most recent data indicate that the EROI of renewables significantly surpasses that of oil when examined at the "point of use" rather than at the "well mouth." And, of course, as users of energy, the point of use it is what we are interested in.

First of all, a note: nowadays, the debate on the energy transition is almost purely political. As such, it is based on slogans, and we know that slogans are not based on data or facts. So, it is a pleasure to see that Art Berman, a well-known expert in matters related to oil and fossil fuels, engages in a fact-based debate. That allows me to respond with a different interpretation, still remaining within the boundaries of what a debate should be; with the discussants respecting each other. 

This said, let me go to Berman's criticism which is specifically directed to a recent paper by Murphy et al., where the authors make the point that the EROI of renewables is now significantly larger than that of fossil fuels when a correct comparison is made. 

The problem, here, is that social media are flashing with messages that say that Murphy's paper is "wrong" or that it contains "mathematical errors." It is not true, but when everybody keeps repeating the same thing, it becomes true. It has already happened with the 1972 study, "The Limits to Growth," which was said so often to contain "wrong predictions" that it became common knowledge that it did. Except that it didn't. But that's the way the memesphere works. 

I think that the element that has generated the idea of "errors" in Murphy's paper is described here by Berman.

This statement from that paper was a huge red flag for me.

“Even if crude oil were measured to have an EROI of 1000 or more at the point of extraction, the corresponding EROI at the point of use, using global average data for the energy “cost” of the process chain, would still only be a maximum of 8.7.”

This means that the supply-chain energy costs for refining and product distribution create a permanent penalty that prevents oil from reaching an EROI of more than 8.7. It furthermore implies that refining must be a marginally profitable business at best which it is not.

At first sight, the statement by Murphy et al., looks strange, even unreasonable. But it is not so. It is a correct interpretation of how the concept of EROI works. 

The EROI is the ratio of the energy produced to the energy spent to make a certain energy production system work. It is something deeply embedded in the concept of "biophysical economics." It derives from the idea that the human economy works in the same way as an ecosystem. Not just because they have the same term "eco" (from the Greek oikos) in the name, but because they are both "dissipation structures," in the sense described by Prigogine long ago. A dissipation structure turns energy into waste or, if you prefer, does its job of increasing the entropy of the universe. (see some references at the bottom of this post).

So, the EROI is analogous to the economic return on investments. In mathematical terms, it is the same as the "effective reproduction rate" in biology, and also to the "reproduction number" (Rt) that was so fashionable during the pandemic, when people struggled to "flatten the curve." In EROI terms, they were striving to reduce the EROI of virus replication. The opposite of what we are trying to do with energy sources!

Unfortunately, as they say, "the devil is in the details," and the discussion on EROI is affected by misunderstandings and by the unavoidable uncertainty involved in evaluating complicated systems such as the oil industry. The paper by Murphy et al. that Berman discusses is aimed at clarifying a fundamental problem: "energy" is a well-defined physical quantity, but we are not interested in energy as such, but in energy potentials. A concept that defines how much useful work can be obtained from energy. The energy potential is a mix of the two fundamental concepts of energy and entropy. We are interested in, basically, how much entropy we can create using what we call an "energy source" (sun, oil, wind, whatever). 

And here is the point of the discussion: you can measure the energy embedded in a barrel of oil and compare it to the energy embedded in a lithium battery. But the battery will dissipate that energy in the form of electric power at more than 90% efficiency. To obtain the same amount of work from the oil contained in the barrel, you have to go through a series of steps, including transporting, processing, refining, more transporting, and finally burning it inside a thermal engine that, typically, has an efficiency of about 30%. Not all energies are created equal!

That's the key point of the reasoning in Murphy's paper. They note, correctly, that the EROI of crude oil is often measured at the "mine mouth" or "well mouth." That is, it does not include the energy lost in the various steps needed to turn the oil into useful energy. They use the term EROI(POU) (point of use) to indicate the correct way of estimating the EROI of crude oil when it is a question of comparing it with that of solar or wind energy, which directly produce useful electric energy. 

In this procedure, it is perfectly reasonable that the EROI of oil at the "mine mouth" or "well mouth" has no importance in determining the EROI at the point of use (POU). It is because a multi-stage EROI chain works like a metal chain: it is as strong as its weakest link. In the ratio of "Energy Out" to "Energy In," the first term is the energy produced by the last step of the chain, instead, the "Energy in" is the energy lost (and hence in need to be replaced) at each step. We could write that:

EROI = Eout/(Ein(1) + Ein(2) + Ein(3) +.....).

And you see that if, say, Ein(2) (refining) is much larger than Ein(1) (extraction), then reducing Ein(1) (increasing the EROI of extraction) will have no significant effect on the overall EROI. Note that in this view, all energy inputs are treated as the same. They may not be in terms of monetary costs, but it is another matter. 

Having established that Murphy et al.'s proposal that oil's EROI is no more than 8.7 is not a mistake but a correct interpretation of the definition of EROI, we need to examine whether it is a likely interpretation of the current situation. Berman criticizes it on the basis of several observations; for instance, that it would mean that refining would be at best an unprofitable business, which is not. 

I trust Art completely if he says that refining is profitable. But we don't have a precise correspondence between profitability and EROI. Besides, if we think of an EROI of 8.7 in financial terms, you would be very happy the return on your investment is more than 8 times the capital invested! The problem, here, is that the EROI is a ratio of two energy flows, but it says nothing about how large these flows are. If they are very small, of course, it matters little how large the EROI is. Here, Berman makes a correct point when he notes that, 

"Society does not function and survive on the per-unit net energy to society but on the full-system net energy delivered to society. This is like saying that I can solve my personal financial problems by delivering newspapers because the per-unit returns are so high. The net income from the paper route is so small, however, that it wouldn’t even help with the monthly escrow payment on my mortgage."

Equivalently, we could say that engaging in a career as a beggar requires a very small initial investment, and hence it has a high ROI, but it is not a good way to make a living. Nevertheless, while this is true in financial terms, in terms of energy production it is a restatement of what I called the "Godzilla Egg" fallacy: a small egg does not mean that the adult creature will be small. Obviously, renewables will not solve any problem as long as the energy they provide to society is small -- no matter how low the cost. But, of course, renewables can grow

Their potential of renewables in terms of solar energy available is enormous, even though we may run into other kinds of limitations in terms of mineral resources. But, at present, these limits are not preventing renewables from growing fast, and their good EROI indicates that the materials used can be effectively recycled using the energy that renewables themselves produce. Some European economies already produce half or more of their electric power from renewable sources, for instance, Germany. So, it is possible to move onward and create a sustainable energy infrastructure that will last for a long time and that will sustain a resilient human civilization, not anymore depending on the vagaries of the depletion of mineral energy resources.   

There are many more points that could be discussed in relation to Berman's post, mainly about the idea that the low EROI of fossil fuels cannot be so low as some studies indicate because it would be insufficient to sustain a complex industrial civilization such as ours. That would require a long discussion. Let me just say, here, that the "minimum EROI needed" for civilization is, at best, a debatable concept and that the value of "5-7" should be understood as highly uncertain, to say the least. 

I think these are the main elements of the story. If you want to know more about the concept of EROI as an essential element of biophysical economics, I suggest two recent papers that I published together with my coworkers Perissi and Lavacchi

The Role of Energy Return on Energy Invested (EROEI) in Complex Adaptive Systems, by Ilaria Perissi, Alessandro Lavacchi, and Ugo Bardi), Energies, 2021

Peaking Dynamics of the Production Cycle of a Nonrenewable Resource, by Ilaria Perissi, Alessandro Lavacchi, and Ugo Bardi, Sustainability 2023


  1. Hi Ugo - I assume you watched last weeks video overview of EROI and boundaries. The issue w Murphy paper is 'chaining' and where to include the energy (from oil/gas) that is put back into refining the oil. Its akin to using in situ heat to process tar sands, or burning the bagasse to make sugar cane ethanol. In any case, EROI too complex to be useful now - it's gotten worse in 15 years since I wrote my PhD on EROI boundaries, not better:

    1. Honestly, Nate, I don't think any serious scientific matter can be treated on youtube. I watch clips of funny dogs and cats, there, not science. But I made an exception for your video :-). But I already knew the story. I think we should stick to what we can measure and, more than that, compare what's comparable. In this sense, the point that Murphy et al. make is correct. If we stick to the basic definition of EROI, nowadays renewables do better than fossil fuels. Then, you may reason that some inputs are less expensive than others in monetary terms, and then there are matters related to variability, storage, availability of mineral resources, etcetera. In the end, the great beast that you call the superorganism and I call the holobiont, will adapt to the available food. I think it will thrive nicely on renewables, but it will have to lose a lot of weight.

    2. Hi, Ugo, if the EROI of renewables is so high, why the holobiont will have to lose a lot of weight?

    3. It is explained here: But, in short, it will be because of the energy return from the new infrastructure will have to be used in part to make the infrastructure grow. This fraction won't be available to fatten the holobiont.

    4. Ugo - I strongly disagree with your first point and strongly agree with your last. Peer review is ossified and people get their friends to review their papers. I have seen many papers make it through that sucked, and novel, great ones get dinged. The 'science' of EROI isn't advancing in productive way imo -but the *understanding* of our energy reality is becoming widely understood -and that is because of youtube and other places. As to your last point - I agree that future societies will thrive nicely on renewables - it was only 150 years ago that global human culture was almost 100% renewable energy devices and lifestyles. The questions are 1) how much 'weight' will need to be lost 2) how do we get from here to there w/o 'breaking'. Ulimately I don't think 'pro-renewable' or 'anti-renewable' arguments matter much any more - it's too late in game (Cue Russia, BRICS, financial overshoot, political dysfunction etc. Renewables -for time being - are good for jobs and GDP and they stabilize the system (temporarily) buying time to prepare for 'weight loss'. Hope you and family are well.

    5. Nate, I personally know Murphy and the others (except for Dr. Rubio-Estrada). They are among the best scientists I know in the world. Their paper is definitely NOT hack-and-slash written just to publish one more paper. It is a fundamental paper that redresses a basic misunderstanding in many EROI analyses. That is the need to compare what's comparable, making sure that the boundaries are the same. Then, you are right that a lot of papers published in scientific journals are not so good (not to use the term you used :-)). But, honestly, youtube stuff is way, way worse!!! (excluding your work, of course). The problem is that young researchers (Murphy et. al are all relatively young) are stuck in the academic "point" system; aka the "academic rat race." This is one of the tragedies of our times that valuable work is forced into a straightjacket that doesn't allow people to express themselves in ways that people can understand. I keep telling young researchers not to confine themselves inside their academic bunkers, but very few of them can afford to do so. And onward we go. Maybe it is too late, as you say, but I won't discount the possibility that we can still build a resilient renewable infrastructure that will avoid the worst when the worst comes. As long as there is a chance, it would be morally unacceptable not to try.

    6. I think it's morally unacceptable to try to do something (a full transition to electricity with renewables) that is highly unlikely to work. Consider all of the energy work done in all aspects of our industrialised technological civilisation. If we are wasting resources on trying to attain a sustainable civilisation with unsustainable energy then that is morally unacceptable. Accepting reality and working from there is the correct approach. Ultimately, our way of life will need to drastically change so let's start working on a new one instead of trying to keep an unsustainable one going a little longer.

    7. Ugo - agreed. I didn't mean that youtube is a substitute for real science - I meant the world is moving very fast and to unpack the systems synthesis in real time in peer review is an impossibility. In Berlin now - Im waving at you to the west.

  2. My colleague Ugo Bardi wrote a rebuttal to my recent post in which I explained why the EROI of renewable energy remains lower than that for fossil fuels.

    Bardi’s post Is the Energy Return of Renewables Really Higher than that of Fossil Fuels? A Rebuttal to Art Berman’s Criticism presents no data and is, therefore, little more than a philosophic rejection of science. The Catholic Church tried that for several centuries before losing its futile battle.

    Bardi reveals his failure to understand the mechanics of EROI (energy returned on energy invested) in this, the core of his rebuttal.

    “And here is the point of the discussion: you can measure the energy embedded in a barrel of oil and compare it to the energy embedded in a lithium battery. But the battery will dissipate that energy in the form of electric power at more than 90% efficiency. To obtain the same amount of work from the oil contained in the barrel, you have to go through a series of steps, including transporting, processing, refining, more transporting, and finally burning it inside a thermal engine that, typically, has an efficiency of about 30%. Not all energies are created equal!”
    EROI is the ratio of the total energy output divided by the total energy input over the life cycle of an energy source. The efficiency of a lithium battery is not a measure of its EROI because it is not a measure of either its energy output or input but rather its conversion rate. His argument ignores the energy required extract, ship, manufacture and distribute its components.

    In the interest of pedantic generosity, however, I will take Bardi’s statement at face value and show why it is hopelessly wrong even though it is irrelevant to any honest discussion of EROI.

    The output of a standard Tesla lithium ion battery is about 13.5 kWh. A standard barrel of oil contains approximately 1,700 kWh of work. If we use Bardi’s 90% efficiency for a battery and 30% efficiency for a barrel of oil, the battery delivers 12.2 kWh and the barrel of oil, 510 kWh. Oil wins.

    I am not arguing in favor of oil or fossil fuels. Quite the contrary, as I said in my original post,

    “I favor a future society that is based largely on renewable energy. That society will look very different that what we know today. Substituting renewables for fossil fuels is not a solution without greatly curtailing our total energy consumption. That’s what the physics indicates will happen in a renewable future. I suggest that we stop trying to make renewables look like something that are not and cannot be, and just learn to live with them as they are.”
    I am arguing in favor of the truth based on the facts that we have today. Those facts indicate that the EROI of renewable energy is lower than fossil fuels.

    That is not a win for fossil fuels but rather a reflection on of how difficult it will be for humans in a renewable energy-based future. Pretending it is otherwise is simply not helpful.

    1. Why do you limit yourselves to electricity? If I wanted to heat a home, then the loss to convert to electricity just dissapears. If I wanted to build bricks, concrete or melt iron, then I don't need electricity either. Sure, there are applications where we need electricity, but that's not our biggest energy need.

    2. Electricity is not a limit: it is an opportunity. You can use electricity to create heat, the reverse is possible, but much more difficult.

    3. What I mean is that in comparing the embedded energy in a barrel, Arthur employs the inefficiencies of an engine or a electric generator, whereas a non negligeable part of the oil consumption is in processes that just require heat, like heating and melting. Had he compared the efficiency of heating a space or melting metals or making concrete, it would look much more favorable to oil.
      Yes, I know you can get heat from electricity, but it seems such a waste when there are cheaper alternatives for heating.

  3. To Nate's comment about "chaining" and your reply about how this cannot be addressed in a video, I showed a diagram and explained its significance in my post rebutting Murphy's paper.

  4. I want to give a hint to avoid a lot of confusion: use the term “power” because this is a relative term, thus context and process dependent.
    We have the concept of “power” as the quantification of the energy difference involved in one transformation step in a process. If the power is equal to zero, then we quantify that equilibrium has been reached (and that is what is meant by the underlying concepts of “exergy” and “entropy”). So the power is the energy per second (Joule/second), the energy per cubic meter (Joule/m3), the energy per degree of freedom (Joule/n=½ kBT°), the energy per dollar (Joule/$), etc. … depending on the processes we consider (expressing then that we consider the denominators of the fractions relevant).
    A ratio of powers is independent of the chosen parameter (independent of the denominators of the fractions). Everyone is then free to describe a complex process path that corresponds to reality and starts with a freely chosen initial state and ends with a freely chosen final state.

    1. Well, yes, but for renewables we have a problem with the capacity factor, which is never 100%, and often not so well known. So, I think it is normally clearer to use energy; which is what renewables produce for a given power times the capacity factor