Partial report of collaborative work on emergy analysis of olive oil production in Crete, Greece, carried out by Khalaf, D., Tsatsarelis, C. A., Silva, R., Ortega, E.



Ecological Engineering

Traditionally, Ecology refers to study of natural systems without human interference, however, it occurs that this kind of space is being reduced to a minimum and a new science (Ecological Engineering) was developed with the basic objective of understanding ecosystems dominated by humans (Ortega, 1998). It was born of a junction of Engineering and Ecology. The key to obtain this collaboration between science branches is the use of General Systems Theory (Odum, 1993). Ecological Engineering is defined by Mitsch (1989, 1995) as the science that takes care of design of integrated system between nature and human organization for the benefit of both.

Ecological Engineering is able to measure the proportion of inputs of nature (renewable) and economy (mainly non-renewable) in the production of raw materials and products, using:

The aim of all its efforts is to supply criteria for guidance of those involved in resource management to move toward Sustainable Development (Ortega, 1997)

Sustainable Development

Sustainable Development is a commitment assumed by governments of all the nations of the world at UNO’S conferences on Environment and Economic Development, held in Rio de Janeiro 1992 (Ortega, 1998)

Energy, Sequestered Energy, and now, Emergy Balance

Energy is essential for the maintenance of life and, as part of it, of economic system. The energy we use comes from renewable sources (solar, moon gravity, internal deep heat, geological, biodiversity) and from sources that can be considered as non renewable, due to high rate of consumption, much bigger than reposition: fossil fuels, biodiversity products (soil, subsoil water, species).

Fossil fuel energy has acquired a strategic character in modern society, as it is the basic factor for mainstream economy. Its use has direct and indirect impact on the environment.

In order to maximize the return; the cost of cultivation must be minimized. Economic analysis must be carried out to identify where cost saving may be made without impairing yield or profitability (Antonio, 1998).

The environmental decay caused by modern development, based on intensive use of energy, has became a worldwide concern. A balanced environment is a basic condition for the maintenance of human society, which also happened to be the main agent responsible for it is relation (Russel, 1987)

According with Pimentel (1989), there is a strong relation between agriculture and energy and sequestered energy analysis can be used as a powerful tool for planning agriculture strategies for the future.

In addition a "sequestered energy" analysis can indicate ways in which energy inputs may be minimized and energy efficiency increased (Fluck and Baird, 1982; Tsatsarelis, 1994)

According to Odum (1996), energy flows analysis is a methodology that allows to understand how a system works, showing by means of energy symbolic language the elements of the system and their interactions and also allows to quantify all the economic and ecological flows,.

The Ecological, Economic, Social and Energy problems of the World

Ortega (1997) resumes present crisis in the following form:

The main reasons of our problems

The same above-mentioned author tries to explain the reasons of world problems

Limitations in energy analysis

The caloric energy gives us a partial image of energy, only combustion energy. Emergy gives us a more complete idea of the real value of a product, considering the energetic value of a natural resources and all of the work added by nature, a true energetic value, which constitutes energy memory (Ortega, 1997)

Nature Extraction Manufacture

(Free) Economy Economy

(energy and mass flows) (money flows) (money flows)

Even "sequestered energy" method, besides its powerful results in diagnosis of agricultural projects, is not a properly a complete scientific tool. It considers partial energy flows not taking into account environmental energy sources and services.

A new scientific method relating thermodynamics, energetics of biological systems and economy of ecosystems is now under construction. Several schools of scientific taught are carrying out this effort and some progress has being obtained, at least a place of convergence and times for discussion were defined recently (Ulgiati, 1998).

Emergy methodology, a tool of Ecological Engineering, is a leading method of ecosystems analysis, developed by H. T. Odum of University of Florida and a group of collaborators in USA, Italy, Taiwan, Switzerland, Suede and Brazil (Ortega, 1999). This research of olive oil production is the first effort being carried out in Greece of use of emergy analysis for agricultural projects.

Limitations in emergy analysis of Agroecology projects

The emergy analysis of agricultural systems reported in scientific literature refer, almost completely, to farms of "developed economies". These systems have over-simplified schemes, really economic and not ecological systems, this kind of agriculture is based on chemical fertilizers, insecticides, herbicides and other high energy inputs. The farms in "underdeveloped countries" could be similar to those, but, on the other hand, a lot of farms work based on traditional ecological methods or even new Agroecology proposals, in these cases the examples of emergy analysis of "chemical agriculture" do not represent in adequate form what is happening in biological farms and new procedures of emergy analysis are needed, Ortega (1998) makes some interesting suggestions for energy diagrams and emergy spreadsheets



Odum (1999) resumes its concepts on Emergy Analysis the following way:

Energy Analysis of ecosystems show how the work of nature and society can be evaluated on a common basis (equivalent solar energy Joules) so as to select alternatives which succeed in the long range.

In this methodology, Systems diagrams are used to clarify the simplifications that humans need in their window of attention. They illustrate the flow and conservation, as a total, of energy (first law), but also its transformation on work and dispersed heat (second law). In side the system energy can be processed and stored. The storage is represented with a tank symbol. The heat sink symbol represents the dispersal of available energy from processes and storages according to the second law. The structures and storages that operate our world (of humanity and environment) are sustained against the depreciation of the second law by productive inputs for replacement and maintenance (external sources mediate by internal storages).

Maximizing the products and services for growth and support appears to be a design principle of self-organization as given by Alfred Lotka as the maximum power principle. Autocatalytic loop is one of the designs that prevail because they reinforce power intake and efficient use. Feedback interacts as a multiplier increasing energy intake.

Energy Hierarchy

Self-organization develops a network of energy transformations in a series. The total quantity of energy decreases, but the quality increases (in the sense of more energy transformations required in the making).

Since energy flows are converging at each step to make fewer flows of energy at the next, it is an energy hierarchy. Energy decreases along energy chain, but the transformed energy increases its ability to reinforce other units of the system.

Since all known processes can be arranged with each other in series network, the energy hierarchy appears to be a universal law. Examples are the energy chains in organisms, ecosystems, economies, earth processes, and the stars.

Work, in the emergy methodology, is defined as the available energy degraded in an energy transformation. Since many Joules of available energy are required to make the successive transformations to form a few Joules of available energy in chain products, it is quite invalid to use Joules of one kind of energy as equivalent to Joules of another for purposes of evaluating contributions (Martínez - Alier, 1987; Odum, 1996). However, we can express each kind of available energy in units of one kind of available energy.

Emergy (spelled with an "m") evaluates the work previously done to make a product or service.

Emergy is a measure of energy used in the past and thus is different from a measure of energy now. The unit of emergy (past available energy use) is the emjoule to distinguish it from Joules used for available energy remaining now.

Scienceman describes emergy as energy memory (Odum, 1986, 1996, 1998; Scienceman, 1987, Scienceman, D., Odum, H. T., Brown, M. T., 1998). A book summary of emergy concepts and accounting is available (Odum, 1996), and elementary introductions and examples are included in our new text on Florida (Odum, H.T., Odum, E. C. & Brown, M. T., 1998) and, in a near future, about Brazil (Ortega, E., Safonov, P., Comar, V., 1998).

There is a different kind of emergy for each kind of available energy. For example: solar emergy is in units of solar emjoules, coal emergy in units of coal emjoules, and electrical emergy in units of electrical emjoules. There is no emergy in degraded energy (energy without availability to do work). Like energy, emergy is measured in relation to a reference level. In most applications we have expressed everything in units of solar emergy.

Empower. The rate of emergy flow is named empower with units: emjoules per time. Flows of entirely different kind may be compared by expressing them all in empower units of the same kind such as solar empower or electrical empower.

Transformity. The transformity is defined as the emergy (in emjoules) of one kind of available energy required directly and indirectly (through all the pathways required) to make one Joule of energy of another type. Transformity is the ratio of emergy to available energy. In Figure 1 the transformity of the output is 10 type A emjoules per Joule. With the units sej/J, transformity is not a dimensionless ratio. Ten ways of calculating transformities were suggested (Odum, 1996, p. 277). The most common way is to evaluate a system in which the item of interest is a product.

Transformity measures the position of any energy flow or storage in the universal energy hierarchy.

A familiar plot in many fields of science is the graph of turnover time versus territory. Items of larger territory have longer turnover times. Transformity also increases with scale. In our systems diagrams, items are placed in their position according to their transformity. Scale of time, space, and transformity increases from left to right.

The expression of storage transformity is the emergy accumulated divided by the energy accumulated.

Revised concepts in few words:

Available Energy = Potential energy capable of doing work and being degraded in the process (units: kilocalories, Joules, BTUs, etc.)

Useful Energy = Available energy used to increase system production and efficiency (units: available Joules, kilocalories, etc.)

Power = Useful energy flow per unit time (units: Joules per time)

Emergy = Available energy of one kind previously required directly and indirectly to make a product or service (units: emjoules, emkilocalories, etc.)

Empower = Emergy flow per unit time (units: emjoules per unit time)

Work = An energy transformation process which results in a change in concentration or form of energy.

Transformity = Emergy per unit available energy of one kind (units: emjoule per Joule)

Solar Emergy = Solar energy required directly and indirectly to make a product or service (units: solar emjoules)

Solar Empower = Solar emergy flow per unit time (units: solar emjoules per unit time)

Solar Transformity = Solar emergy per unit available energy (units: solar emjoules per Joule


There is a different kind of emergy for each kind of available energy. For example, solar emergy is in units of solar emjoules, coal emergy in units of coal emjoules and etc. there is no emergy in degraded energy (energy without availability to do work). Like energy, emergy is measured in relation to a reference level. In most application we have expressed every thing in units of solar emergy. McGrane (1998) evaluated emergy and transformity for materials and energies of earth cycles. A emergy flow algebra was proposed by Tennenbaum (1988).

Emergy and Money: Emdollar

Real wealth (food, clothes, houses, materials, water, etc.) is measured by its emergy. Money buys real wealth according to market prices. By dividing the total emergy use of a country by its gross economic product. The part of the gross economic product due to an emergy contribution can be estimated as the emergy value divided by the emergy/money ratio. The result is emdollars (abbreviated em$). Rural countries have a higher emergy/dollar ratio because more of their economy involves more direct use of environmental resources without exchange of money.

Emergy evaluation of a system is done by making an evaluation table that includes the inputs to the system, the products, and those items within the system, which may be of special interest. Solar emergy is calculated for each item in the table, and various sums, quotients and indices are calculated giving insight on the role of the system in the environment and the economy. By calculating what is required to make a product in units of the same common sources, a common measure of work and wealth is found that includes both the work of nature and that of human services in the economy.


Emergy Analysis Table

An emergy analysis table is prepared with 6 columns with the following headings














Column number one, is the line item number, which is also the number of the footnote in the table where raw data source is cited and calculation, shown.

Column number two is the name of the item, which is also shown in the aggregated diagram.

Column number three is the raw data in Joules, grams, or dollars derived from various sources.

Column number four is the transformity in solar emjoules per unit (emj/J; emj/g; or emj/$). These are obtained from various studies.

Column number five is the solar emergy. It is the product of columns three and four.

Column number six is the real wealth value in emdollars for a selected year. This obtained by dividing the emergy in column five by the emergy/money ratio for the selected year.

Aggregated diagram

Emergy used includes renewable environmental resources such as rain, non-renewable resources used such as fuel reserves and soil, imported natural resources, economy goods and services.


Aggregated diagram for Agroecology projects

The farm as people living within the farm, biodiversity is promoted inside and outside the system, an effort is carried out to form soil and avoid erosion, so dong soil becomes a renewable resource, water infiltration increases with work done on soil recovering, water from subsoil is used according with renewal rate. Due to use of local biodiversity the system uses less imported natural resources, economy goods and services.




Emergy Indices

The following are emergy indices used to draw inferences from emergy analyses.

The solar transformity of an item or flow is the solar emergy that would be required to generate a unit of that object or resource efficiency and rapidly.

It is defined as the solar emergy required to produce one Joule of another form of energy. It is for main inputs from global climate were obtained from world energy budgets. From many analyses, tables of solar transformity are now available to make future analyses easier.

The emergy yield ratio (EYR) is the emergy of an output divided by the emergy of those inputs to the process that are fed back from the economy. This ratio indicates weather the process contributes more to the economy than is purchased from it for the processing. Ratios for typical agricultural products range from less than 1 to 6.

The emergy investment ratio (EIR) related the emergy fed back from the economy to the emergy inputs from the free environment. These ratios indicate if a process is economical in using the economy’s investments in comparison to alternatives. To be economical, the process should have a similar or lower ratio to its competitors. If the ratio is less, the environment provides more to the process, costs are less and its price tends to be less so that the product can compete in the market.

The emergy exchange ratio (EER) is the ratio of emergy received for emergy delivered in a trade or sales transaction. The exchange ratio for a payment is the emergy of the product divided by the emergy value of the payment. The emergy of the payment is that of the services that it can buy. Raw product such as rural products from agriculture tends to have high emergy exchange ratio when sold at market price.

The emdollar value (em$) refers to the dollar flow generated directly and indirectly in the gross economic product by an emergy input. It is calculated by dividing the emergy inputs by the emergy/money ratio for that year.



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