Energy As a Metric of Sustainability

Under what conditions will a technology be able to survive the energy contraction associated with the depletion of fossil fuels? Which types of technologies are sustainable in a world that can only make use of resources that it is producing on its own rather than relying on resources that it inherited from the past? This article, co-authored by Dr. Rodrigo Castro of the University of Buenos Aires, proposes emergy as a physically sound metric of sustainability. Without taking emergy into account, long-term energy analysis may lead to erroneous conclusions with potentially catastrophic consequences.

At The Oil Drum, many contributions have addressed the ERoEI, energy returned on energy invested, as a measure of energy efficiency. It is evident that a technology that consumes more energy than it produces (ERoEI < 1) is not sustainable in the long run. It is also quite obvious that energy resources with a low ERoEI value must be more expensive to produce than resources with a high ERoEI value. However in the short run, it may sometimes be profitable to even produce energy with an ERoEI < 1, if the production of this resource is being subsidized by a local government using tax revenue.

Some readers of The Oil Drum have interpreted the ERoEI as a measure of sustainability. They expect energy resources with an ERoEI of 1.03 to be sustainable, whereas resources with an ERoEI of 0.98 are predicted to be unsustainable. Unfortunately, this interpretation is incorrect. The reason is that the ERoEI only accounts for the energy used in the production of energy itself, but not for the energy that had been previously used up to create the infrastructure and equipment needed to make said production of energy possible. It takes a whole lot of energy to produce an oil platform, for example. New oil platforms can and will only be produced as long as there is enough surplus energy available to do so.

The crux is thus the hidden energy that is "contained in" (has been used up in the production of) equipment used for the production of energy. Every good sold or service provided on this planet contains hidden energy. This type of energy has been coined emergy [4]. We frequently read about gray energy. Gray energy is emergy traded across (national) borders.

Charles Hall, the prime promoter of the ERoEI (sometimes also abbreviated as EROI) as a metric for energy efficiency, knows about the problem. For this reason, he suggested to consider a technology with an ERoEI < 5 to be unsustainable. Where does this factor of 5 come from? No one really knows, including Charlie. It is simply a safety margin introduced to account for all of the hidden energy cost not included in the computation of the ERoEI. Yet the hidden energy cost may vary from one technology to another. One technology may be perfectly sustainable with an ERoEI value of 2, whereas another may not be sustainable at any ERoEI value (e.g. if it relies on the extraction of a non-renewable raw material). It is thus important to be able to quantify the hidden energy cost of different energy producing technologies.

These same concepts apply not only to the production of energy, but in fact to the production of all goods, including e.g. food. In the Middle Ages in Britain, soils were only being used for agriculture if the so-called harvest factor (the amount of grain produced divided by the amount of seed grain planted) surpassed a value of 1.6 [3]. Otherwise the soil was not used for agriculture. The safety margin of 1.6 accounted for the loss of harvested grain to different types of pests and the need to appropriate some of the grain for consumption.

Many of our readers may consider gray energy irrelevant to the discussion at hand. In the context of the peak oil debate, we are looking at the world as a whole, and in a global context, gray energy does not exist; it is a zero-sum game. All gray energy imported into one country is true energy used up elsewhere.

It is said that China has meanwhile surpassed the United States in terms of energy consumption. China is claimed to now consume more energy (in absolute terms, not per capita) than the United States. This is however incorrect. China has become the largest energy user, but not the largest energy consumer, because China produces lots of goods for export. Much of the energy used up in China is being exported to Europe and the United States in the form of gray energy. China has become the largest net exporter of gray energy on the planet.

Why is gray energy (emergy) important even in a global context?

Japan, a nation with a high population density and few resources of its own, is currently producing a large percentage of the automobiles driven all over the planet. Will Japan still be able to export (e.g. plug-in hybrid) vehicles after the energy contraction? Will Japan not rather use its limited energy resources to satisfy the needs of its own populace than producing goods for export?

The issue here is that the export land model, another favorite topic at The Oil Drum, does not only apply to energy trade, but to trade of all goods, because of their hidden energy (emergy) cost.

Unfortunately, all of these factors influence the sustainability of any energy production technology negatively, as it is not sufficient that the ERoEI of a technology is high enough. For a technology to survive the contraction, enough energy and all other material necessary for the production of said technology need to be available locally where and when the production is supposed to take place. In a post-contraction scenario, the lifecycle of all engineered equipment should be considered in terms of the energy required for its maintenance, clean disposal, substitution, and potential recycling.

In developing countries, energy is the main means through which industrialization can take place, hopefully leading to the abatement of poverty. Here the concept of "needs" changes noticeably. Which energy technologies should be considered as locally beneficial to lift average welfare to a level that can be sustained? It seems to be clear, within an energy contraction scenario, that mimicking the path of industrialization followed in the past by developed countries can only lead to failure in the long run. Therefore, possible balances between development and sustainability should be carefully studied in order to maximize development without neglecting physical constraints. In so doing, ignoring the concept of emergy may lead to unpleasant surprises in the future that could turn out to be irreversible in a post-carbon era.

How can the emergy of a technology be quantitatively assessed at regional or global scales attaining the required levels of comprehensiveness? Which modeling tools may support such an endeavor? These issues are being discussed in two forthcoming articles [1,2].


[1] Castro, R., F.E. Cellier, and A. Fischlin (2013), "Eco-bond Graphs: An Energy-based Modeling Framework for Complex Dynamic Systems with a Focus on Sustainability and Embodied Energy Flows," Proc. SESDE 2013, Intl. Workshop on Simulation for Energy, Sustainability, and Environment, Athens, Greece, September 25-27, 2013.

[2] Cellier, F.E. (2013), "Emergy Tracking - Safe Transition from a World of Exponential Growth to one of Sustainability," Proc. SESDE 2013, Intl. Workshop on Simulation for Energy, Sustainability, and Environment, Athens, Greece, September 25-27, 2013.

[3] Müller-Herold, U. (2013), personal communication.

[4] Scienceman, D. (1987), "Energy and Emergy," in: Pillet, G. and T. Murota, eds. Environmental Economics - The Analysis of a Major Interface, Geneva, Switzerland: Roland, Leimgruber, pp. 257-276.

Francois, understanding emergy and emergy flows is obviously an important field. Equally important I believe is understanding the ERoEI of the energy source of emergy. As you point out China is a major exporter of emergy using high ERoEI coal as the main source and high "ERoEI" workers in the conversion process (i.e. workers that consume little energy at home).

This introduces the concept of chained ERoEI. I used to be one of those who believed that low ERoEI approaching 1 was unsustainable but I have changed my mind. I now recognise that low ERoEI energy "sources" are not energy sources at all but energy conversions, more like electricity from coal or gas. Bio fuel converts nat gas (fertilizer) to liquid fuel which is a more highly prized energy store. At the end of the day we get all of the energy that was in the nat gas back again but in liquid form. So it is important to consider the ERoEI of the input natgas. If the fertilizer is coming from Qatar, it will be very, very high.

The same applies to tar sands with ERoEI of about 5, most the inputs are nat gas. It becomes interesting then to consider tar sands production using shale gas. I don't know what the answer is, but I'm pretty sure that distortions to the energy system brought about by the finance system may result in some pretty unsustainable activities going on, that have a deleterious effect that may be hidden from view.

The magic ERoEI number of 7 comes for the net energy cliff concept and net energy. If all our energy sources average out below 7 then this means that a huge number of folks are engaged in energy production leaving not enough to man schools, hospitals, factories and retirement homes.

I agree with your comment, Euan. As long as there is enough high ERoEI energy in the mix, it is possible to use it for generating lower ERoEI energy ... even with an ERoEI value of below 1. Whether this makes economic sense or not is a political question. It is always possible to subsidize energy production until it becomes economically interesting for the producer.

However, such an enterprise will certainly not be sustainable in the long run as it necessarily drives the local economy into bankruptcy. One exception (currently) may be the US due to its reserve currency status. Here it is the entire world that financially supports local US political decisions. Thereby energetically irresponsible decisions may be perpetuated for a while longer ... but it does not make them sustainable in the long run nevertheless.

It becomes interesting then to consider tar sands production using shale gas.

So we have cheap Chinese steel to subsidize US shale gas, shale gas to subsidize tar sands.... when does it end? If steel was more expensive would a massive increase in the number of wells be possible? Can anyone see steel prices as low as today powered by wind or solar PV? If natural gas was at Asia LNG prices, what would the cost of tar sands oil be?

Cheap (high EROeI) energy allows the extraction of resources that would otherwise never be produced. I think we are going to actually see reserves converted back to resources as average world energy EROeI falls.

What might the end shape of world oil production look like?

More likely, Canadian shale gas (which is close to the oil sands) will supply Canadian oil sands production (which will in future go to China), and Canadian Arctic Island iron ore will supply Chinese steel mills, fueled by Western Canadian coal.

Where does the US fit into this picture? Not at all.

"Where does the US fit into this picture?"

LOL, I think they will manage to find a way to squeeze their war machine in somehow... Do you honestly believe that when the US dollar hyperinflates and the US oil trade deficit can no longer be maintained (and US oil consumption goes down by 1/3), and when US tight oil production tanks because the Wall Street ponzi schemes funding it collapse when the dollar hyperinflates (probably bringing consumption down another third), that the US war machine is going to just sit idly by and worry about wars in the Middle East? You honestly believe that the US is going to let Canadian oil sands production go to China, the enemy of the US? What the hell are we going to say to them when they point the guns at us and politely ask for our oil? Harper's dreaming if he thinks Canada is going to be able to exercise sovereignty over its oil resources in the future.

Isn't that why all you commonwealth folk keep the British monarch on your's a voodoo charm to ward off those upstart colonials that pasted that traitor Washington's picture on their dollar bill ?-)

It worked for the last hundred fifty years or so for you guys hasn't it? War machines do fail, sometimes limping off with a barely a wimper...think USSR. But yeah I think you've a bit of insight into your friendly southern neighbor. Canada is much too easy a plumb to pick especially if transocean transport gets to be a real dicey endevour.

Since you are a young guy you best hope Obamacare morphs into something that actually works or when the takeover happens you will be in the same boat most of us are, out of health care coverage whenever out of work with a little pile of hard won assets ready to evaporate in an instant if you have the misfortune to need even a moderate amount of health care.

Or maybe better yet you can hope the US somehow doesn't go broke and that things like growing food actually start to pay its way. Remember just little old Iowa (it does rank third among states for agricultural receipts) grows as much grain as all of Canada while at the same time growing near as much soybean as all of China.

Your countryman who loves to play the gadfly here when it comes to the US and who you contradicted has gone from being a global warming denier to a warming enthusiast (though he may be talking tongue in cheek) as it will turn what is now the frozen north of Canada into an economic powerhouse. Likely things will not pan that smoothly for any concerned if things change that much very quickly.

I don't know what all this hoopla is about regarding peak oil being dead. As far as I'm concerned, all of the alleged "nails in the coffin" of peak oil have been repeatedly beaten to death and then urinated on, year after year, right on this site. The reality of the situation is that the end of unconventional oil is going to be rather ugly, regardless of how last it longs, seeing as how atrocious the depletion rates are. This is simply a one-off, just like the opening up of new agricultural lands and fossil fuels easing the pressures of diminishing returns are simply one-offs which are just delaying the IMO inevitable return to Malthusian equilibrium, which has historically reigned throughout all of human history up until the New World and Old World came together and fossil fuels began being exploited and put towards the uses which we know them today for.

As for alternatives, I don't believe that any convincing case has been made for the position that they will replace even a substantial fraction of the energy supplied by fossil fuels (oil in particular).

Yeah, sure, hand-waving about how solar is on the rise as installed capacity explodes and costs are plummeting is rather convincing at face value, however, this must be viewed in the context of the obvious to just about anyone subsidized solar bubble: The whole thing was built on politically & economically unsustainable subsidies from beginning to end. On the demand-side, feed-in tariffs in Germany and other European countries as well as the United States, along with tax breaks or in some cases other subsidies to homeowners who purchased solar PV installations, artificially inflated the demand for solar panels, which resulted in higher utility bills for rate payers and money channeled from taxpayers indirectly to manufacturers — many of them in China. On the supply-side, China, using its tried-and-true mercantilist industrial policies for boosting targeted industries, rapidly ramped up its production of solar panels, driving many German and American manufacturers out of business.

Unfortunately for the solar miracle, Chinese supply-side subsidies outraced disproportionately German demand-side subsidies, leading to global overcapacity and plummeting prices. China is now the victim of its own success in trying to corner the global solar panel market via government-subsidized dumping. These improvements in solar, IMO don't exist, as they're transient.

Wind I guess I can be slightly more sympathetic towards but not by much. Wind energy promoters usually quote the maximum attainable output as the capacity of the wind farm. This is the maximum power that could be produced if ideal winds blew all the time at all turbines. However this needs to be multiplied by the capacity factor to get the actual power likely to be generated. Because of the variable winds and the energy unable to be captured by the generator, the capacity factor lies in the range 25% - 35%. However it can be much lower. UK offshore wind rarely exceeds 20%.

The Danish "success story" with wind doesn't exist. The unreliable Danish wind farms only survive because they call on hydro power from Norway and Sweden to step in at short notice when wind fails. Then they sell excess wind power produced at times of low demand back into the Scandinavian grid. Danish electricity consumers pay higher prices than any other Europeans. And well before they could repay the initial capital, the wind towers are reaching the end of their life and will need to be replaced. Not one coal power plant has been replaced by wind power.

The fact remains, despite all the hand-waving and sensationalism, renewables still only meet a miniscule fraction of the world's energy & electricity demand, and are extensions of edifice that oil & natural gas have built up.

Wind & solar simply are too high entropy (too far down the energy gradient, too dispersed) for me to consider viable alternatives for keeping BAU running anywhere near even 25% capacity.

Nuclear doesn't fare much better. Nuclear's close to the upper limit of how efficient and how allegedly great it can get. The only new developments in nuclear are going to be increasing the size of plants in order to economize on nuclear's strength: relatively low marginal costs. Economies of scale. Thorium's alleged EROEI of 50:1 really makes very little difference in efficiency compared to the EROEI of around 20:1 for your good old thermal light water reactors (it's only 3%). In fact, I know a number of nuclear engineers, and they all invariably say that thorium is a bit of a joke with people who actually do nuclear engineering. Fusion is just a series of laboratory curiosities which will never amount to anything. I know it's frowned upon to say it like this, but IMO that's the way it is.

We are not entering into an age of renewables. We are entering into a age (which will probably only last perhaps 5-10 years) of unconventional oil and the more extensive use of natural gas and coal (even though all it's really doing is temporarily smoothing out the decline, not really replacing it). This will probably make the situation in 5-10 years much worse, as the peaks in oil, natural gas, & coal will be closer together.

Diminishing returns and limits to how much technology can do are now exerting their pressure on us full-force again. Productivity gains simply aren't being made at the extraordinary rate they once were. We're now being forced to search the ends of the earth to find important mineral resource and fossil fuels & being forced to accept increasingly marginal ones. The only reason agriculture is keeping up is because we're exploiting more and more marginal land each and every year. Grain yields is most everything have stagnated or slowed considerably. The amount of arable land per capita has already peaked. In fact, what's even more scary is that per capita grain production may have already peaked as well.

All in all, there's no reason to be optimistic simply because you got bored of reporting on rather mundane things instead of what you were expecting: something closer to a crash and burn scenario.

I'm disappointed with what the TOD staff decided to do.

For my part, I continue to be disappointed by the absolutist arguments that come forth, claiming that since renewables 'will not be able to perpetuate BAU', that they are a lost cause. It's on a parallel course to the constant uproar about EV's not being able to replace our whole Auto fleet.

What if that's not the only path forward that might help us keep some societies going? The BAU claims make it a bit too easy to knock down all these hopeful upstarts, when I think it's actually Hope that is being targeted.

Well, with that said, Capoeirista said 'Wind & solar simply are too high entropy (too far down the energy gradient, too dispersed) for me to consider viable alternatives for keeping BAU running anywhere near even 25% capacity.'

I'll leave the end of that one alone, as I feel it is not really the question that Wind and Solar are going to have to answer, and just say that there are countless forms of 'Wind and Solar', many of which can be built by individuals and created using cast-off materials from the great surpluses that the last century has left, and will continue to leave behind for a while yet. Just left over glass and mirrors and 'stuffing' (insulation of various forms) could provide enormous amounts of energy for heating, hot water, cooking and process heat and lighting at a technology level that any village could muster a few able people to employ.. People have been building windmills from old bikes and auto bearings.. Now, if you're going to sniff at the level of renewables so far, you'll no doubt have little time for these sources, and yet, since there are so many millions who could be quickly taught how to take advantage of these approaches, the effect such equipment could have on Hundreds of Millions of people would be profound.

Glass and Aluminum production both currently use great volumes of 24/7 energy, but why couldn't those producers be positioned near Niagara, and below the Alps, where access to Hydro matches this need? We're not in any danger of running out of Aluminum or Silica, and there's plenty in the waste stream too.

I'm just afraid I find the hand-waves in this argument to gloss over the areas with real potential to help ourselves deal with this.. NOT "continue BAU", just take on whatever parts of the problems we can.

“We're here to get each other through this thing, whatever it is. ― Mark Vonnegut.

Oh, no, no, no. Don't get me wrong. I'm not envying against alternative energies or renewable energy. I'm just differentiating between the normative and the positive.

I fully agree that renewables should be implemented. If I was in charge, that's what would happen.

However, I don't believe that they will be implemented on a significant scale, or that if they will, it will make too much of a difference in the long-run. I do believe that they will be implemented, just on a much more modest, much smaller scale (the household, local, municipal levels).

As for the recycling, sure. But in the end that really doesn't matter, does it (also the materials used to build the mills and cells is really irrelevant to my point about entropy)? Just like there's no such thing as true recycling, only downcycling (the quality of the "recycled" material goes down each time it is "recycled"). Just like there's no such thing as reversing entropy in a closed system. Solar and wind are simply already too far down the energy gradient.

I don't believe so. I think it's more than possible to recycle materials into uses where they can serve a far longer lifetime than was ever in store for them before. Glass, in particular has the potential for a very long life and can be working at harvesting solar heat for all of that time.. then is of course fully recycleable again.

Many of our plastics are bound for what is called 'downcycling', but even there, we must be careful not to insist that every use is going to be a short step on an unstoppably speedy descent. Given uses that don't degrade the polymers from excessive heat, wear or exposure to UV, they can serve 'unnaturally long life cycles' too. Find the book 'Green Plastics' for some thoughts on a more perennial view of polymer science.

So much of this all is about appropriate design and use of materials.

Solar Silicon PV is pretty specialized, and has a high embedded energy.. but it has been shown to have terrific longevity in many cases, so PV's energy loading should be considered apart from roads, ditches and concrete (part of another discussion) that might go into some types of PV installations, and be considered by its own merits. This has repeatedly given it an eroei well past the fingers of one hand, while the overall 'SOLAR' category gets another firm leg-up beyond that when you look at the far higher EROEI potential of simple solar heat applications made with materials like Glass and Stainless Steel, Copper or Aluminum, which could easily be serving for many decades, giving a net energy benefit that really deserves our attention.

It's easy to sniffle at Recycled and 'used' materials.. but they are no older than the 'new' materials that are in current, on-the-shelf products. The potential of these materials must be weighed by the 'content of their character', as it were. (Today, 50 yrs ago was Dr. King's 'Dream' speech.) Stainless steel doesn't care if it used to be the shell of a 'fancy' fridge or microwave. Copper Pipe will do what it does, depending only on how it's treated.


"Glass, in particular has the potential for a very long life and can be working at harvesting solar heat for all of that time."

Right on, Bob. For years now I've been listening to the air conditioners and heat pumps down our valley, sucking coal-fired electrons, allthewhile living quite comfortably with windows that allow in seasonal solar energy for heat, and actually open to passively cool our home, using thermal mass to moderate things. In our climate, it's fairly rare we need more inputs. I wonder what the emergy is there.

I'm building a small 'scullery' in the space behind our kitchen and will install a heavy stainless sink that I salvaged from my mother's house a few years ago when the new owners remodeled; manufacturing date still on the bottom - 1971. With a little polishing, it may look better now than it did when new, with that glow that old stainless acquires, and will last for more decades of use, if not centuries. I wonder what the emergy is there.

The 42 years old plastic pipe we buried to bring spring water to my parents' home looked like it was buried last month when they dug it up to build a new road. It provided gravity flow spring water from high on the mountain (70 psi). Never went dry. Wonder what the emergy is there. It was replaced with a deep well and electric pump. Wonder what the emergy is there. The new owners didn't want to occasionally check and clean the spring.

Our 40 years old woodstove, soapstone and cast iron, still in great shape, and upgraded to be more efficient, well maintained, provides backup to our passive solar and solar hot water during the coldest, cloudiest spells, and heats much of our domestic hot water in winter, using only deadfall from the forest around our house. I expect it to outlive me, by far. Wonder what the emergy is there.

I could go on, but it became clear to me that highly centralized, complex "solutions" have problems with emergy that I don't worry about much. One wonders what the emergy/population ratio does, as population density, complexity, and expectations increase. It may be counter-intuitive.

And *I* don't understand where the hoopla is coming from that there's no more to be said about Peak Oil, or a dearth of quality articles to post on the Oil Drum! Just look at the wealth of knowledgeable, interesting articles on a variety of topics we've been treated to this past month!! If there were even half, or a third as many such articles available, it would make the Oil Drum a terrific continuing site.

If they hadn't made the decision to restrict the topics of the articles to only technical and geological topics, and instead opened it up to the other half of the contributing factors to Peak Oil (financial and economic topics), then they could have the opportunity for just as many articles over again. This is a huge topic of which TOD barely scratched the surface. But they won't do that, because they don't understand how financial and economic factors are part of PO, which in itself isn't a problem, but they won't bring in articles by those who do understand it.

The thing is, TOD created something and filled a role as the central go-to location for good technical analysis of PO related issues. I don't know if I can accept that they wan to shut it down because they want to move on to other pursuits in life, because the importance of a site like this is now critical ... to the future of the world, literally.

You can't fool Mother Nature and you can't change the laws of physics.

It is clear enough that a sufficiently high EROEI must n be achieved for any energy extraction or capture technology to work long term.

it is clear that the embedded energy used in supporting infrastructure must also be taken into account in estimating the sustainability of any energy extraction (mining, etc) or capture process such as biofuel, wind , and pv.

Nature sets the limits.

We apparently don't know with any certainty just where these limits lie, but I presume the figures given by the authors are "close enough" for discussion purposes.

I know only a little about such things, about as much as any dedicated follower of this site may be expected to know.

But I know a couple of things that are dxxed important.

A sound understanding of the limits is necessary to understanding what is and is not going to be technically possible in the future, and such an understanding is critical to controlling the debate as the future, like rust and depletion, never sleeps.

It is very important that we do all we can to control the debate- we don't need another evolution versus creation struggle, or another climate change versus denialist scenario .

But- and this is a big old BUT- we don't want the "puristas" to gain too much influence either.

I love birds and don't have anything against desert tortoises -I'ver never met one but I'm sure I would like him if i did, lol- but reality dictates that we either accept the collateral losses associated with wind and pv, etc, or accept the orders of magnitude greater losses associated with the continued use of depleting fossil fuels. Political reality is such that we simply do not have the will to do a perfect job.

We will be extremely lucky just to survive , over the long haul, as an industrialized society.Even if we had the will, we don't have the resources, since there are so many previous undeniable claims on our limited capital.

So- as I see it, the real question FOR NOW is not the ultimate EROEI question, because we simply aren't doing any thing to solve the EROEI problem. We aren't even seriously thinking about it, except in a few ivory towers, and a few forums such as this one.

What we need to be doing NOW is whatever we can to further the development of renewable energy technologies , and build them out to the maximum possible extent, without worrying about long term EROEI questions.

We must accept that this strategy, combined with an equally heavy emphasis on efficiency and conservation, is our only real hope of pulling thru the coming bottleneck.

It simply DOES NOT MATTER if we put some energy - any amount of energy - into renewables which are ultimately unsustainable , because we have no way of conserving that energy.

It is use it or lose it, given our real life situation.We can put it into wind and solar and other renewables, or we can just stand by as it is all wasted to no good purpose- fetching beer in three ton trucks, heating uninsulated buildings , keeping the skyline lit in cities shut down for the night.

Hopefully- again hopefully- we will figure out ways to improve the EROEI ratios of renewables to the point that they are truly sustainable- if they aren't, already .

Personally I don't think we yet have a good answer to the this question- Pv and wind seem to be efficient enough, if one ignores the emergy aspect.

Including emergy seems to indicate that we are in a heap o' long term trouble.

What we need to be doing NOW is whatever we can to further the development of renewable energy technologies , and build them out to the maximum possible extent, without worrying about long term EROEI questions.

We need whatever we can get ... and we need it now, because creating a new energy technology consumes additional energy. Thus, replacement technologies for fossil fuels need to be in place before the fossil fuels run out, i.e., while cheap energy is still available. If we wait until energy is expensive, it will be too late -- we won't be able to afford the transition any longer.


What we need to be doing NOW is whatever we can to further the development of renewable energy technologies , and build them out to the maximum possible extent, without worrying about long term EROEI questions.

We need anything that we can get ... and we need it now, because creating a replacement technology for fossil fuels consumes lots of additional energy to get it started. Thus, we need to have new alternative (sustainable) technologies in place, before we run out of fossil fuels, i.e., while there is still plenty of cheap energy available. If we wait until the fossil fuels have been depleted, i.e., until we really need the replacement technology, we won't be able to afford it any longer.


Thank you, this is an important and interesting subject.

Some years ago I was involved in discussions about energy processes with ERoEI < 1, and concluded that the qualities/properties of the energy resources matters. For instance it could be feasible to use hydroelectricity to extract oil with ERoEI < 1 if oil was the desired end product due to its unique properties. (It is [still] hard to make a jet plane fly for some distance on electricity). There is of course a limit to the scalability of such a process.

I consider (net) energy flow (stocks are as well…. if long term considerations are given any attention) to be an important metric. If there was some process with say ERoEI < 1 involving vast resources (stocks) that were scalable (meeting [society’s] need for energy flow of specified qualities) and that resulted in affordable end products, it would happen. Just to make it clear; presently and to my best knowledge I am not aware of such resources and processes.

It could be interesting to integrate energy flows (inclusive ERoEI) into financial models (thus improving the understandings of the dynamics of energy flows (and thus indirectly ERoEI) within the financial framework. This could help illustrate how the financial system (inclusive of subsidies) also may distort energy usage amongst energy sources.

Some of the low ERoEI processes like oil sands are made possible due to financial distortions. Oil sands are primarily about money production (producing financial profits). It could be interesting to see if natural gas prices moved above some threshold, if coal (provided coal became the cheaper substitute) would be introduced to generate steam for the SAGD process also used in oil sand extraction.

I am not fond of Gross Domestic Product (GDP). It is primarily a metric measuring volume of financial transactions. It poorly meters total energy consumption and in recent decades a lot of energy use has been outsourced to countries with lower wages and imported as consumption (embedded energy) in products by countries that previously manufactured the same products.

This has created a distortion that is a favorite amongst economists (thus illustrating how poorly energy flows are understood) pointing out that the developed economies in recent years have become more energy efficient illustrated by the growth in specific GDP expressed as $$$/kJ (or $$$/MTOE or similar).

I am not aware of any studies that have had any in depth looks into this.

Thanks, Rune. I fully concur with your statements. There exists a strong linkage between financial markets and energy markets that is being ignored by the economists primarily due to the metrics that they are using. Economists only look at the financial markets, because they believe that they are the primary drivers of our economy ... which they are, but only under the constraint that enough cheap energy is available to support those markets.

The true drivers of our economy are energy flows. Without sufficient (affordable) energy flows, our economy will stall, and the financial markets will be unable to fix the resulting problems (these are the prime issues associated with the time after Peak Oil).

wouldn't we all.

Hi Rune,

I am reading Howard Odum's "Environment, Power, and Society", Columbia, 2007. Chapter 9 is Energy and Economics. He describes some models relating energy and money. Money flows in the opposite direction of energy as a control lever. Later chapters discuss the imbalance in energy vs money flows between countries that is impoverishing the exporters. He also wrote "Modeling for all Scales" which has some implemented models money and energy interactions.

ERoEI is a good idea, but seemingly difficult to apply. Two quotations from this short article:

"Charles Hall ... For this reason, he suggested to consider a technology with an ERoEI < 5 to be unsustainable. "

"In the Middle Ages in Britain, soils were only being used for agriculture if the so-called harvest factor (the amount of grain produced divided by the amount of seed grain planted) surpassed a value of 1.6"

The second quotation disproves the first - if an ERoEI of less than 1.6 (not only seed grain is an input to agriculture) was possible in the Middle Ages, then Hall's estimate of ERoEI minimum of 5 is wrong. Also, this means that an economy based on bioethanol may be possible (but it will not be comfortable for 90% of the population).

Charlie was strongly criticized for his safety margin of 5 ... and rightly so. This is simply too coarse a measure. We need more refined tools to judge sustainability of a given technology. I also believe that there are forms of energy production that are sustainable at EroEI values that are considerably lower than 5.

Bioethanol is a good example, especially if it is generated from waste products. This is insufficient to maintain (drive) our economy, but it can support some facets of it.

Here in Switzerland, our agricultural vehicle park consumes roughly 0.6 percent of the total fuels used up in transportation. It is perfectly feasible to make our agricultural vehicles independent of fuel imports if we use agricultural waste products to generate biodiesel fuels. Our government should create financial incentives to support such ventures.

There is not enough agricultural waste to support Mrs. Meier who currently drives her poodle to its weekly manicure in her SUV ... but at least, we'll eat.

IIRC the EROI of >5 was for our current civilisation? Also the grain harvest of middle ages Britain was not the main energy source, wood was. I have no idea what the EROEI of cutting wood is, but given the energy density, it should be reasonable compared to mining for coal.

EROEI seems to be a useful measure, but I have always suspected that it is too narrow, emergy is useful in that it incorporates the knowledge, and the systems required to produce and maintain that knowledge, though it is a lot harder to accurately quantify.

For an EROEI to be sustainable it must use local, renewable inputs, and be able to sustain the society that consumes it. But we are humans and will always be pushing the Malthusian limits, and will consume resources faster then they can be renewed. Of course it's human nature that is unsustainable.

It's human nature that is unsustainable.

Indeed. (May I steal that quote from you?)

Be my guest.

Excellent, very simple summation of the issue of net energy, Dr. Cellier, merci. Smeagle focuses on the main point of your article, thanks, Smeagle.

Some readers of The Oil Drum have interpreted the ERoEI as a measure of sustainability. They expect energy resources with an ERoEI of 1.03 to be sustainable, whereas resources with an ERoEI of 0.98 are predicted to be unsustainable. Unfortunately, this interpretation is incorrect. The reason is that the ERoEI only accounts for the energy used in the production of energy itself, but not for the energy that had been previously used up to create the infrastructure and equipment needed to make said production of energy possible. It takes a whole lot of energy to produce an oil platform, for example. New oil platforms can and will only be produced as long as there is enough surplus energy available to do so. The crux is thus the hidden energy that is "contained in" (has been used up in the production of) equipment used for the production of energy. Every good sold or service provided on this planet contains hidden energy. This type of energy has been coined emergy [4]. We frequently read about gray energy. Gray energy is emergy traded across (national) borders.

That's why some Oil Drum readers often are way too optimistic about the issue of peak oil. Their interpretations are laced with denial about the basis for our complex society and what it will take. This discussion is an example. Everyone dances in the comment section around the key issue raised in your article, carefully avoiding the issue. Applying fudge factors to inadequate metrics just prolongs the state of denial. I will be sorry to miss your presentation, and will look for the proceedings online.

The higher the EROeI the higher the complexity of society that can be supported. So these concepts are not in conflict. Just the opposite. If you have a society with an energy supply that delivers 1.6 EROeI then you can expect a Middle Ages civilization. And if that technology requires millions of high tech factory workers, then it isn't a plan for a real future, it is a fantasy.

What is the minimum EROeI that can support a civilization able to support a car based society? Hall and Murphy estimated that if you add up the energy needed for the roads, cars, refining the oil, and transporting the oil, then those needs consumed about 66% of the energy of a barrel of oil (assume all energy used to make cars and roads is oil). That means if the EROeI of the fuel falls to 3:1 then getting the fuel out of the ground takes the other 33%. At that point, it does not matter what MPG your vehicle gets, there is no surplus energy to power the vehicle. So to actually move goods and people something like 5:1 (20% consumed) would give you about 14% of the energy to feed into an IC engine (large loss) and move some mass. What is the Minimum EROI a Sustainable Society Must Have?, Hall, Balogh, Murphy, 2009.

This still leaves out paying for all the schools, trade schools, universities, etc. that are needed to maintain the labor pool capable of doing this work. And the financial services, tax services, etc that concentrate and organize resources. So even 5:1 may be far too low. 5:1 is 20% consumed. 10:1 is 10% consumed. So falling from 10:1 to 5:1 does really cut the energy surplus in half.

At one time in the US oil was cheaper than coal and so it did provide much of the energy for transport. It heated workers homes. It fueled the electric power plants that operated the factories. It paved the roads. It made the plastics. It mined the iron ore. Etc. But as the oil EROeI dropped (and prices rose) then other fuels substituted in. Coal, natural gas, and nukes for the electricity, factories, and heat. This substitution will keep happening as EROeI contracts.

If net energy cannot grow (say natural gas and coal supply peaks), then falling EROeI will cause contraction on the demand side. The road network will decay. The number of cars will start to fall. Schools will close. Fewer students will attend. Homes will go unheated. Etc. The complexity of society will begin to reduce.

Falling ore quality requires more energy to process (more spoil shifting, more crushing, more grinding). This requires that EROeI actually increase to maintain throughput. But that does not happen. Falling fuel quality requires more natural resources (more steel for drilling more wells that produce less and less etc). And we have Limits to Growth.

One last point: Minimum EROeI depends on what a work a person is trying to do. If a person needs light then an oil lamp may be able to support a much lower EROeI as total energy throughput is lower and efficiency is higher. Electric light is nice, but it requires a lot of expensive equipment and engineers to keep it running. Oil Lamps may be the last market of the Albert Tar sands in 2100.

EROEI of 5:1 means 80% of energy is available for driving cars etc.
EROEI of 10:1 means 90% of energy is available.
I think once you get below 5:1 you actually need to start adding some decimal places.

I agree about decimal points! I actually like net energy percent best.

Boundary conditions are really important. Oil EROeI is typically measured at the well head. So refining, transport, the energy to build and support the road system, the energy to build the vehicle, etc are not included. Often the staff to operate the system and the energy they need are not included.

But if you remove the 20% lost to refining, the energy lost in oil and gasoline transport, paving the roads, build the car, etc: You find the net of that whole system might mean 90% is consumed and only 10% net delivered. Then you factor in the losses from the engine (MPG) and you get a tiny fraction of the energy in a barrel of oil actually moving groceries from the store to home.

Once the whole system is analyzed, if you have an energy profit you have a system that can grow. If the whole system just breaks even or is net negative, then you will see contraction (assuming no subsidy from outside, like cheap Chinese steel).

Net energy percent is better because it is linear, people do not understand nonlinearalties, they can't comprehend them. Another classic example is earthquakes, a magnitude 8 is not double a magnitude 4, if it were a linear scale 4 would be 1,000, and 8 would be 10,000,000.

Thanks, Jon, for your excellent comment. You make an important point. Which ERoEI level is sustainable depends on what the energy is being used for. Even an ERoEI of 0 is "sustainable" if no one is around to use that energy.

The emergy calculation helps us (in the context of energy production) to better estimate the true ERoEI, i.e., to more quantitatively take 2nd-order and even 3rd-order effects into account. It also offers tools for better assessing sustainability of a technology (this discussion is in one of the referenced articles), but it does not address the issue of complexity.

Our emergy-based simulation models are dynamic in time, but static in structure. They can tell us whether a given structure is sustainable or not, but they don't tell us anything about what will happen when it isn't.

I am in agreement with your view: If a given structure is no longer sustainable, it will simplify until it becomes sustainable again. If there is surplus energy, this energy can be used to make the structure more complex until there is no longer any surplus energy (limits to growth).

As the ERoEI of most of our energy production schemes contracts, the limits themselves are not fixed but are contracting as well, and thus, the achievable system complexity will reach a maximum, and then our systems will get simplified again in accordance with the contracting ERoEI.

Hi Francois,

I agree. This is one reason I think John Micheal Greer is correct about the Long Descent. As we simplify, we prevent collapse and continue on. A composting toilet instead of a city wide sewer system. An oil lamp instead of a electric light. Bottled gas for cooking instead of a large underground gas network. Long underwear and small room heater instead of central heating. A solar powered head lamp. All of these have much lower capital cost (embodied energy) and yet still provide some fraction of the original service.

You said it really well: dynamic with time, but static with structure. We need a dynamic structure that represents lifestyle change, or simplification. A person in a homeless shelter uses far less energy than a person living in a single family home. I have thought about adding this dynamic structure using "mitigation wedges" similar to carbon reduction wedges. New energy sources and higher efficiency are wedges that typically require increasing complexity (hybrid car) and some of that will happen. But simplification wedges exist: double people in the same household. Cuts energy use in half, but at almost no increase in embodied energy. These kinds of wedges may be possible to estimate.

But how to create a dynamic simulation? Could stocks of population exist at each wealth level? When "priced out" of current stock, a group falls into a lower wealth stock? Moving into a higher efficiency or green energy stock takes investment. Some will afford it and move up in complexity. Some will not be able to afford that investment and will move down a wealth level? I don't have an answer. I am just making this up. It is interesting and worth thinking about.

Policy could be created to help people at each wealth level move to a more sustainable position. So there are fewer who are forced to step down. Capital investments typically prevent people from moving to a more efficient position. But here in the US there are often minimum wealth requirements designed to force the poor to move away. For example, houses in the US often must have minimum room sizes that are very large. This forces houses to be very expensive.

Hi Jon:

Thanks for taking the time to respond. This is very useful.

Actually, houses in the US are comparatively inexpensive, because they are mostly placed on the ground. Houses in Europe usually have an entire story underground, which makes them much more expensive to build. Switzerland is worst of all with its requirement to have a nuclear fallout shelter included in the construction of each newly built home.

Our simulation models go a long way toward supporting what is needed. Although the model structure is currently static (a fact that cannot be changed quickly and easily -- I'll explain why in due course), they already support the calculation of emergy. If you have a longer path in your model (oil -> electricity -> light) instead of a shorter path (oil -> light), the light will automatically accumulate a higher emergy (ERoEI) value.

Also, if a given structure is not sustainable, the simulation will not only tell you so, but will in addition point to the paths within the model that are the culprits, i.e., that are least sustainable. Thus, we already know where to simplify.

Why can the model structure not be made dynamic? This has to do with the underlying modeling and simulation environment that we are using. We have implemented our tool in Modelica. Unfortunately, none of the current Modelica implementations, including its flagship implementation of Dymola, supports the simulation of variable structure models.

Modelica is by far the most powerful modeling and simulation environment for the modeling of physical systems currently on the market. Thus, the answer cannot be to switch to another tool. The answer must be to enhance the Modelica language in such a way that it will, in the future, support the simulation of variable structure models. One of my former Ph.D. students (Dirk Zimmer) has been working on this problem in his Ph.D. dissertation. He is still pursuing this goal, and he is actively involved in the Modelica consortium. Thus, there is hope that we shall have a suitable tool available for the simulation of variable structure models in the foreseeable future, but currently this is not yet the case.

Isn't emergy just EROI with a wider net to measure the investment?

No, it is not. It is an enhanced version of the ERoEI if applied to energy production, but emergy is considerably more general than that. It can be applied to all production processes. As an introduction to the concept, I strongly recommend the book Systems Ecology: An Introduction by H.T. Odum. The book (published in 1983) is out of print, but you can probably find it in your local library, and if you wish to own it, you may still be able to buy it second hand.

Odum looks at energy flows as the primary drivers of our economy and converts all material flows to (associates all material flows with) equivalent energy flows. He considers the sun as our primary source of energy (which it predominantly is) and converts all energy to (measures all energy in) sej (solar equivalent Joules).

Odum has written a number of books later in his life, e.g. Environmental Accounting: Emergy and Environmental Decision Making. Some of these books are still available in bookstores. Yet, they are (at least in my view) not as good (as clearly written) as his original 1983 book. This book has been pivotal to my understanding of the interrelationship between energy flows and our economy, and I recommend it strongly to your reading.

When I read Howard Odum's books way back in the '70's Environment, Power and Society (1971) and The Energy Basis of Man and Nature (1976), I realized how much trouble humanity was facing. I've tried to pass on this understanding ever since, with almost no success, until the internet made it possible to find an audience. As the TOD shuts down, a great forum for the dissemination of this world view will be lost...

E. Swanson

An excellent, succinct overview of a vital concept. I look forward to the two forthcoming articles. One small quibble. EROEI and emergy are obscure and difficult to understand concepts for the average person - including the typical decision maker. IMO, it's important to maintain the distinction between these ideas of energy 'production' (to use the vernacular) and energy 'consumption', or utilization. The use of the word 'efficiency' blurs this distinction, as most people think of efficiency on the consumption or utilization side - how much use one can get out of a given amount of energy, best expressed as a percent. EROEI, on the other hand is a measure of how much additional energy can one acquire, or make available for use, from a given amount of energy, best expressed as a ratio. This small linguistic point often leads to people mixing up the two concepts, and arguing that EROEI is essentially useless, as clearly the efficiency of energy use is always something less than 1:1, as we consider efficiencies of 80-90% to be excellent, and even 33% to be acceptable, as in thermal electricity generation.

I think perhaps OFM says it most clearly when he uses the words 'energy extraction or capture technolgy' - this is where EROEI applies, whereas efficiency best applies to the end use or consumption of the energy extracted or captured.

I hope I haven't confused things further.

I shall publish the other two articles on my website after the conference is over, but won't do so earlier for reasons of fairness toward the conference organizers. However if you wish to receive those articles already now, you can email me, and I'll gladly send them to you (in PDF format).

I shall publish the other two articles on my website after the conference is over, but I won't do it before then for reasons of fairness toward the conference organizers.

However, if you wish to read the articles already now, you can email me, and I'll gladly send them to you as email attachments.

Thank you Francois for a superb article and thanks to some of the follow up comments which are equally superb. It just breaks my heart to see the dispersal of these great minds as TOD closes its doors. It seems that some of the comments confuse renewable solar energy with renewable solar or wind energy electricity production. Solar/Wind energy has an unlimited future and a brilliant past. Electricity production from both sources will never replace cheap one time carbon sources. Those cheap carbon sources have been at the core of wealth production and wealth production will also plummet as their production plummets. What I didn't see mentioned is the role finance plays in energy production and a financial collapse could render these ivory tower discussions moot. All of this production and distribution of energy and emergy is facilitated by credit and debt creation whether were talking about letters of credit or supply chain issues. Crash that system and discussing the EROEI of the various energy sources is just speculation on how many angels can pass through the eye of a needle.

I've written EROEI. The second post is in the making - probably post it after TOD RIP.

If there is anything more overlooked than the tendency for exporters to show an accelerating rate of decline in net exports, as production declines, it's the CNE (Cumulative Net Exports) depletion rate. Here is a link to a discussion of this topic:

The Six County case history* consists of all major net exporters (100,000 bpd or more of net exports), insofar as I know, that have approached zero net exports, or became net importers, from 1980 to 2010, with the exception of China.

Key 1995-2001 rates of change for the Six Country Case History:

Production: -1.0%/year

Net Exports: -6.0%/year

Post-1995 CNE (Cumulative Net Exports): -23%/year

*Indonesia, UK, Egypt, Vietnam, Argentina, Malaysia