Emergy –

The concept of energy memory

By Sergio Ulgiati and Eric Poettschacher

Visuals by Christoffer Relander

August 22, 2016

Here is a thought experiment.

Imagine the computer you are using right now to read this essay has – in addition to its ordinary working memory – a device that recorded all the energy and materials it took to produce this piece of technology. Not just the human labor, machinery, intellectual property and transportation logistics it required, but also the invisible work that took place in nature over millions of years to generate deep heat and sunlight from gravitational collapse, fossil fuels from sunlight, Rare Earths and other minerals from deep heat, to finally become plastic, high-tech components and eventually a valuable good in your hands. Of course the energy required for all those transformations and matter convergences to take place in nature is no longer available in your computer; it was used up in the making. Emergy is a measure for this depleted energy now embodied in your computer. It would be an intriguing figure in the computer’s energy memory, if there was one.

In real life there is no energy memory that gives you an idea how much energy nature invested in a final product or service. As a matter of fact there is not a single place in nature where Emergy can be actually measured or observed; it exists merely in the calculations of environmental accounting, as developed by American ecologist Howard T. Odum (1924 – 2002).

For most people Emergy is a completely unknown idea, but it has the power to change our overall perception of energy and matter. Looking at products and services through the lens of Emergy provides a bigger picture of energy that goes way beyond the normal range of human perception. If you allow yourself to delve further into the world of Emergy you might start to realize that the economic value of any product does not necessarily have anything to do with its energetic value in nature. Within the donor-side Emergy perspective, the value of a resource is determined by the effort that is displayed for its generation by nature and processing by society over an evolutionary trial and error process that ensures the optimization of a resource cycle. Mainstream economic theories address the concept of value in monetary terms (i.e. willingness to pay, a user-side value). Emergy-based value is related to the amount of primary resources (solar energy, geothermal heat, etc.) invested by nature.

Emergy is not energy. It is instead
the memory of past work done by nature.
So what is to be gained by applying an Emergy
perspective on economics and society?

Emergy was suggested by Howard Odum
as a scientific measure of the biosphere’s
work in support of life processes on earth.

He identified natural capital and ecosystem services as the real source of wealth, as an alternative and complement to the common belief that only labor and economic capital can be such a source. Traditional energy or economic analyses usually don’t take into account inputs they cannot evaluate on a monetary or energy basis. Only monetary values are recognized by the market, but economies rely upon very large inputs from the environment; if these inputs are not considered and given an appropriate value, misuse of resources can follow, and future prospects for the system cannot be inferred. While it is impossible to measure most of these human-dominated flows in a way that captures their complex value to the final users, it is much easier to generate a hierarchy of values in the biosphere processes by means of the Emergy concept. Emergy advocates a different concept of value, rooted in the cost of production of resources by nature, revealing the effort displayed by nature to generate resources in favor of a much larger set of users: all species on Earth, not only humans in the marketplace. Maximizing market value in the eyes of humans may (and often actually does) jeopardize survival patterns for other species. Emergy demands optimization – not maximization – and policy choices that give consideration to all species and the quality of resources in terms of what it takes (energy, time, materials) to create them, even if this is not recognized by market value assessments.

Odum was convinced we cannot understand
a system if we only perceive its state in the
here and now within a constrained scope. 

We need to see its connections with larger scales in order to understand where the current systems dynamic comes from and where it is heading. So far we are used – and primed – to perceive only that part of the entire energy spectrum that provides the energy qualities we can utilize immediately for our work, well-being and progress: food, fuel, and electricity are refined and concentrated forms of energy we use and value. But a myriad of energy transformations take place in nature and perform the necessary work to create and sustain the energy forms we eventually utilize. We fail to perceive all those energy transformations because they are too small (think of all the photosynthetic processes that allow you to have your lunch every day) or too slow (such as the million of years to transform fossils into fossil fuel) or too large (like the huge energy metabolism of a whole city or nation). But not paying attention doesn’t mean they’re not there. Emergy is a way to understand the entire chain of energy transformations, the manifold invisible stages it takes to get from sunlight to other forms of energy that allow us to manufacture computers, launch space ships and cook soup.  Emergy reveals general energy principles that connect everything in an ecological order. Odum sought to illustrate that the same metabolic energy processes underpin every type of system, whether a forest, a household, a city or even a culture.

Emergy and Energy Politics

The concept of Emergy also has political power and can create cognitive dissonances, as the following episode illustrates. In 1975 the USA was on the brink of an energy revolution quite unique in nature. It was a question of acknowledging the big picture, of taking the metabolism of a nation into account and facing an energy reality, which we usually fail to notice even in the present era. The oil crisis of 1973 had just painfully illustrated the extent of fossil fuel dependency. President Nixon took action and demanded that the American Congress pursue a fundamental reorganization of American energy policy. He dubbed his vision “Project Independence.” Its goal: the United States of America was to become energy self-sufficient by 1980 (!).

Nixon did not have enough time to see his project take shape. The Watergate Affair saw President Nixon step down and thus it was left to his successor, Gerald Ford, to implement a forward-looking energy policy. On October 11, 1974 Ford signed the “Energy Reorganization Act” and in doing so laid the foundations for a National Energy Agency of formerly unseen proportions. With the establishment of “The Energy Research and Development Administration,” or ERDA for short, research on all available or imaginable sources of energy in the US – from fossil fuels to nuclear and solar energy, geothermal sources and what were known as Advanced Energy Systems – were brought under one roof. All possible scenarios were to be evaluated on the basis of informed research. The ultimate aim was to provide a secure and future-proof energy supply.

The three years following the founding of the ERDA were characterized by an intriguing process in terms of alternative energy scenarios. This exceptional phase was marked by the simultaneous development of the most contradictory plans. The idea of building thousands of nuclear power stations found a foothold despite the simultaneous development of a national solar energy offensive. Biomass strategies were considered while at the same the federal government financed experimental research into electric cars (one of which was driven by Robert C. Seamans Jr., who was the ERDA director at the time, to President Carter´s inauguration ceremony). It was then that Howard T. Odum, ecologist and at that time professor at the University of Florida, introduced Emergy to the debate.

By the year 1975, industrial leaders, scientists and politicians were taking Odum’s model to heart. A certain Senator Mark Hatfield had even sponsored a law requiring an Emergy evaluation of federal energy projects in the US (Public Law 93-577). This resulted in congressional hearings and prominently staffed conferences. According to Howard Odum “instances of confusion” were becoming increasingly frequent. His Emergy language collided with the language of power. In 1976, a blue ribbon commission put an end to the Emergy experiment. Exact reasons for this decision remain unknown. Not long thereafter, the plug was also pulled on the short-lived Energy Research and Development Administration, and the agency later became a subdivision of the Department of Energy (DOE). The concept of Emergy still exists in the scientific debate, and related research is carried on worldwide (see http://www.emergysociety.com/). As a matter of fact, Emergy is receiving enormous interest from Chinese Universities and Research Centers, with a growing number of experts involved in this research.

Financial Accounting vs. Emergy Accounting

Of course there are strong reasons why Emergy has remained only an intellectual pastime. Environmental accounting based on Emergy runs contrary to the financial accounting as we practice it these days, as it turns our usual way of looking at value upside down. It accounts for resource trade in terms of their embodied environmental cost, not in terms of their monetary value (which are embedded in economic terms of trade and market dynamics); even when the economic balance is approximately even, the environmental balance may not be. According to Emergy logic, many developing countries exporting primary raw resources for money lose environmental wealth and work potential that could have been used domestically in support of their economies; such loss is not generally compensated in terms of the Emergy value of the small amounts of manufactured resources purchased in the international market using this money.

As a consequence of environmental support and intermittent resource availability, all kinds of systems go through cycles of growth, climax, descent and restoration. Thus Odum has also written about patterns of descent for the present civilization, pointing out sustainability to be the capacity to adapt to resource oscillations rather than to reach a steady state to be sustained forever. Forest ecosystems have short pulsing cycles with trees blooming and growing in spring, making fruits and seeds (stored information) in summer, losing leaves in autumn (for recycling by soil microorganisms), and recovering in winter, when available resources (solar energy) are fewer. Very similar resource-dependent patterns characterize all other systems and living species on Earth, including humans. The Roman Empire – according to Odum “the greatest world order ever built by solar energy alone” – is over, but through its demise we may be able to recognize its cycle that took more than one thousand years to run and 300 years for descent. It is obvious that it is difficult for us to recognize societal cycles of which we are a part. On top of that, the systems optimization concept – characteristic of the Emergy approach – recognizes patterns of growth and decline on multiple spatial and temporal scales. This is opposite to the growth paradigm focusing on the maximization of individual parameters at all times. Needless to say, Emergy is a controversial concept also because it puts the predominant paradigm of our times in a new perspective.

But as long as our accustomed perception treats the work of nature as non-existent it is hard to imagine how those externalities will ever make it into financial accounting and onto sustainable pathways. Maybe Emergy is even a measure for our willingness to perceive resources in a more systemic way and accept that economy is embedded in natural processes – not the other way around. In that respect understanding Emergy is more relevant than ever.

This essay is partly based on the chapter “Emergy” by Sergio Ulgiati, In: D´Alisa, Giacomo et al. (eds.) (2015). Degrowth. A Vocabulary for a New Era. London/New York: Routledge

Sergio Ulgiati  is Professor of Life Cycle Assessment and General Systems Theory at Parthenope University of Napoli. His research focusses on energy conversion systems, energy and emergy analysis, life cycle assessment and sustainability indicators. He advocates for a new sustainability discourse – a new model of organizing knowledge, ideas, experiences and language around shared values based on qualitative not quantitative growth. 

Eric Poettschacher is co-founder of Energies United – a new type of agency exploring the impact of perception and sensemaking processes on human energy practices.  

Christoffer Relander is  a contemporary photographer based in Finland and especially known for his intentional multiple exposures. His work has been featured in publications and websites such as LA Times,Oprah.com, Huffington Post and China Daily.  Further information about his portfolio can be found at: www.christofferrelander.com


  • Buck, Alice. A History of the Energy Research and Development Administration; U.S. Department of Energy, 1982
  • Odum, H.T. Environment, Power and Society for the Twenty-First Century. The Hierarchy of Energy. Columbia University Press, 2007
  • Odum, H.T. Environmental Accounting. Emergy and Environmental Decision Making. Wiley: New York, NY, 1996.
  • Odum, H.T., Odum, E.C., 2001. A Prosperous Way Down: Principles and Policies. University Press of Colorado.

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