Handbook of Emergy Calculation

The calculation of the socio-environmental impact of projects is an extension of traditional economic accountancy. The basic tool of socio-environmental accountancy is a register of inputs ant outputs flows of the studied systems, and not only of the monetary flows, all are taken into account: goods, contributions (of nature or economics), all products and the products residues.

In practice, parameters are added to the registers of the traditional economy, to take into account:

(a)      contributions of nature,

(b)      losses or the benefits in internal stocks of the system,

(c)      expenditure caused by the system to other systems.

The first parameter are included in order to take into account the contributions of nature.

The second allows to measure the system effectiveness.

The last correspond to the work provided out of the system, they are evaluated by considering the working time which the companies exterieures needed to carry out work.

All the flows, they can be materials, services or moneys, are converted into Emergy flow, which is a physical concept that considers all energy incorporated in the resources to be used in the system (Odum, 1996). It is necessary to make use of data of other researchers that had studied the necessary processes of transformation for the production of each resource and had calculated the effectiveness of this process.

Its calculations of emergy flow use a conversion factor, called Transformity, which is the inverse value of the system effectiveness. You will find a table of Transformity has the following address :

http://www.unicamp.br/fea/ortega/curso/transformid.htm

Application: comparison of production systems

This handbook is still in construction and will be probably transformed during next months. The purpose is to show how calculate the emergy of various inputs and outputs flows in an emergy assessment of an agricultural system. Emergy calculations of inputs and economic resources are relatively easy, at least sufficiently easy to find the appropriated Transformity, and sometimes to carry out some conversions of unit. In the case of the natural resources (as much renewable resources that non-renewable ones), it requires a bigger effort to obtain the value of flows and the conversion of flows into emergy; to facilitate the understanding of the calculation, we will present procedures examples that measure the contribution of the various sources of energy that allow the system functioning. The calculation procedures will be described in the following order:

(A)    Natural contributions of the external system

(A.1) direct Solar energy (solar radiation, wind, rain);

(A.2) Energy of gravity (action of the lunar mass);

(A.3) Energy of Earth internal heat (soerguimento terrestrial);

(A.4) accumulated Solar energy (biodiversity);

(A.5) accumulated Solar energy (supply material);

(A.6) Energy of the human imigration.

(B)    Changes of the internal supplies

(B.1) Energy of the ground;

(B.2) Energy of local biodiversity;

(B.3) Energy of  local water tablecloths;

(B.4) Energy of local infrastructure;

(B.5) Energy of \people (local culture).

(C)    material Contributions

(C.1) Seeds or changes;

(C.2) Inoculating;

(C.3) Ground conditioning;

(C.4) Inoculating;

(C.5) manures;

(C.6) Pesticides;

(C.7) Weedkillers;

(C.8) Other chemical contributions;

(C.9) productive infrastructure;

(C.10) Agricultural machinery;

(C.11) Fuel and lubricants;

(C.12) Inputs needed for recycling;

(D)    economic Work

(D.1) Hard worker manpower;

(D.2) Manpower (operator);

(D.4) Technical asssistance;

(D.5) Trips costs;

(D.6) Insurance cost;

(D.7) maintenance;

(D.8) Agricultural insurance ;

(D.9) Transport to storage cost;

(D.10) Drying and storage cost;

(D.11) Governmental taxes;

(D.12) carried out work for recycling.

(E)     Products and by-products

(E.1) Principal product;

(E.2) By-products;

(E.3) Residues.

(F)     inputs losses

(F.1) Manures;

(F.2) Pesticides;

(F.3) Weedkillers

(G)    external Services (paid by the company)

(G.1) medical Treatments for the workers and their family

(G.2) Effluent treatment

For the calculation of materials and services used in the production, data can easily be gotten in yearbooks and contacts with producers, professors of extension courses and researchers. The main information, consumption and unitary price of inputs, can be gotten in the Agrianual publication, edited by the company of consultoria FNP of São Paulo. They can also be gotten in the data of researchers of Company of Agrarian and Bovine Research Brazilian (EMBRAPA), of public institutes of research (IAPAR of the Paraná, IAC of Campinas, SP), of public companies of agricultural extension (CATI-SP, EMATER-RS) and of Agronomists Engineers. Some informations can be found by means of research in the pages of the InterNet. The Farming National Census provides also interesting data.

A.  ENVIRONMENTAL CONTRIBUTIONS OF EXTERNAL SYSTEMS

RAIN:

We consider that annual rain fall received by a soybean culture of the producing region of Paraná is 0,8 m3 per m2. The annual water balance (700 mm) could be used to plant maize or wheat. If rain is abundant and well distributed, it can allow two harvests per year. In São Paulo we could have 1000 mm of water column during the rain season (season of soybean harvest ) and 500 mm during the dry season (season of maize harvest).

The RAIN (continuation) :

Process of units conversion :

Units of area (m3/ha/ano): hectare: 1 ha = 10 000 m2;

Units of mass (kg/ha/ano): density of water: 1 m3 corresponds to 1,0 E+ 03 kg;

And thus, units of energy (Joule/ha/ano): Gibbs free energy of water: 1 kg corresponds to 5,0 E + 03 J.

The water energy in agriculture depends on its capacity to dissolve solids of the agricultural ground, those solides dissolved can also be absorbed by plants; the Free Energy of Gibbs measures the work potential of the ecosystem.

10000 m2 * 1000 kg * 5000 J * = 5.0 E10 J m2 .
1 ha              m3                  kg                ha . m3

We can now multiply the value of the precipitation by the conversion factor of units obtained above.

0.8  m3    * 5.0 E10 J .m2 = 4.0 E10 J
m2. year          ha . m3                  ha . year

The RAIN (continuation):

The process of conversion into emergy flow uses the Transformity value corresponding to the chemical potential of rainwater (1.82 E+ 04 seJ/J). After performing these operations, we obtained emergy flow : 7.28 AND + 14 sej/ha/year. The equivalent monetary flow of the rain is 196.76 US\$ emergetic/ha/year.

It is noticed that the price of the arable land depends, mainly, of the quantity and the quality of rainwater. The irrigation water will start to be charged in all the catchment areas of the country ; the cost to charge initially the catchment areas is estimated to 0.10 US\$/m3. Is this estimate exact?

B CHANGE OF INTERNAL SUPPLIES (ACCUMULATION OR LOSS)

GROUND LOSS :

Nature produces a much lower rate of  ground than the consumption rate of conventional agriculture. The presence of trees, shrubs and plants in the farming land is important because they prevent the erosion, maintain the grounds, keep moisture and the growths and pump the nutriments with their roots. The nutrients consumption by cultures is less important that the nutrients loss because of erosion caused by rain and wind. The rate of this loss depends on land type, declivity, water regimen, sorts of the cultures, and sort of agricultural process.

Lands submitted to inadequate treatments have a fall of productivity and can become less fertile; they are then given up or if not, it is necessary to carry out a significant agricole work to make it better. The following tables indicate the content of organic substance of various types of ground and the erosion rate of diverse cultures or use of ground.

 organic substance of the grounds type of ground percentage of organic substance very wet ground 5 % fertile ground 3 – 4 % ground of the semi-arid areas 1 – 2 %

 Ground loss cover of the ground annual ground loss (tonne/ha) pasture 0.4 natural forest (0.1) dense natural forest (0.4) plantation forester (eucaliptus or pines) 10 – 15 fruit trees (0.9) market-gardeners 5 – 15 corn, sugar cane 10 – 40 rices, potatoes 25 beans, manioc 35

GROUND LOSS (continuation):

Ground loss of cultures which let the ground discovered is important (20-40 tonne/ha/year). With direct plantation this loss is reduced. In the case of soybean producted in properties that adopts the technology plantation direct - weedkillers, we estimate that this value is low, 1500 kg/ha/year. In the case of organic option, we regard the loss as null and with chemical agriculture, we estimate it at 15 t/ha/year. The value is indicated in mass (kilogramme of ground/ha/year), so, it must be converted into energy (Joule) with the below calculation, that requires knowledge of the content of organic substance of the ground:

1500 kg of ground * 0.04 kg of organic substance * 5400 kcal = 3.24 E+05 kcal

ha. year                        kg of ground                    kg of o.s.       ha. year

The value so obtained is then multiplied by the conversion factor: 4186 Joules / 1 kcal. We obtain an energy in terms of caloric value of dry organic substance of the ground, it is then possible to use it corresponding transformity, that comes from table (7.38 E+04 sej/J), to obtain the emergy flow: 1.00 E+14 Sej/ha/year. The equivalent monetary flow is worth : 27,03 76 emergetic/ha/year US\$.

Comment : as well as in the case of the water, an exaggerated consumption of the ground can be used in the catchment areas to optimize the use of the productive resources.

BIODIVERSITE: Recovery, balance or loss of biodiversity reserves

We can estimate the biomass amount that stops being produced (or is going to be produced) in the sectors incorporated in the soybean farming  (or in the legal, permanent or functional forest reserve). In the case of the mass productivity (kg of biomass/year), we must consider the average moisture of the biomass (60%) and his Transformity in calculation.

Primary productivity of bioma(E.Odum, s/d) in kilojoules per square meter per year:

 Bioma Production kJ/m2/an Bioma Production kJ/m2/an Bioma Production kJ/m2/an 01. Desert 60 02. Desert of shrubs 1320 03.Agriculture (subsistence) 1528 04. Ocean 2420 05. Arctic and Alpine tundra 2650 06. zone semi desert 2650 07. Continental platform 6620 08. moderate meadow 9240 09. lakes, rivers, 9450 10. Shrubs (moderate climate) 11340 11. Commercial agriculture 12290 12. Boreal forest of conifers 13100 13. Tropical savanna 13440 14. moderate forest 22210 15. Tropical marshes 35280 16. Tropical estuaries 35280 17. Algae 35280 18. Tropical forests 36160

ENGAGE OR DISMISSAL:

Integration or exclusion:

By regarding agrochemical agriculture as reference, it is observed that the organic production generates job and the direct plantation - weedkillers option generates unemployment. The productivity of the options direct plantation - weedkillers and agrochemical is the same, the benefit of the option plantation of direct - weedkillers comes from the suppression of manual work in the farming (suspension of manual harvest and weeding). What can be an "advantage" for a big agricultural company, can be a "disadvantage" for a small or average one, which cannot adopt this intensive technology using energetic and economic resources, and which removes manual work (agricultural work). Above everything, it is a disadvantage for the society, that has to assume the burden of agricultural unemployment and the direct and indirect expenses of the exodus towards the cities, and the resulting favelisation and marginalisation. This fact must be considered in the quarrel about the Agriculture Public Policy. Manpower is an energy source of the agricultural  production, therefore, the loss of the workers (direct plantation - weedkillers) can be regarded as an energy loss.

C MATERIAL CONTRIBUTIONS

SEEDS:

An agricultural production uses between 60 and 90 kilogrammes of seeds per hectare per year (kg/ha/year).

We distinguish three types of seed :

Organic seed manufactured by the agriculturists (Transformity: 1.0 E12 sej/kg);

Hybrid seed or controled by the companies (Transformity: 1.0 E12 sej/kg);

Transgenic seed resistant to the weedkillers (Transformity (estimate): 1.0 E13 sej/kg);

Calculation of the soybean Transformity value per kg :

5400 kcal * 4186 Joules = 1.8 E7 Joules

kg of seed         kcal               kg seed

1.8 E7 Joules * 66000 sej = 1.05 E+12 seJ

kg dry seed        Joule          kg dry seed

We consider that the technological and commercial investment and the propaganda are significant in the production of the transgenic seed, which is therefore ten times bigger, and especially prohibited in the country.

Seeds (continuation):

The equivalent monetary flow is obtained by multiplying emergy flow of seeds by the emergetic value of the dollar in Brazil in 1998 (3.70 E+12 sej/US\$). This value was estimated from Transformity values of dollar in Brazil existing in the table of Transformity which had been calculated from values of the economic censuses of 1981,1989 and 1995.

(0.85- 8.5) sej * 3.7 E12 US\$ = 23-230 emergetic US\$

ha. ano               dollar                     ha year

Seeds price used in calculations varies between 0,20 and 0,40 US\$/kg. Real monetary flow (in US\$/ha/year) is obtained by multiplying the unit cost by the used seeds amount.

CONVERSIONS:

For some cultures, conversions are carried out. If the emergy value of an inoculating agent is not priced in table, it is necessary to use the monetary value and the dollar Transformity in Brazil.

X kg    * y dollars * 3.7 E12 sej = Z US\$ emergetic

ha. year           kg            dollar               ha. year

Consumed volume (kg/ha/year) is multiplied by unit price of product (US\$/kg) and by Transformity (3,70E+12 sej/US\$). In this case, equivalent monetary flow (in emergetic/ha/year US\$) is identical to real monetary flow, because Transformity has been used in money.

INOCULATING AGENT:

In soybean production , weedkillers with 1.7 kilogrammes of inoculating per hectare per year are usually used. If the emergy value of an inoculating agent is not priced in table, it is necessary to use monetary value and his conversion factor in Brazil in terms of emergy. The volume consumed is multiplied by the unit price of product and by the currency Transformity.

1.7 kg    * 0.86 dollar * 3.7 E12 sej = 5.45 E12 sej

ha. year           kg              dollar             ha. year

The equivalent monetary flow, 1.46 US\$ emergetic/ha/year, is identical to the real monetary flow because Transformity has been used in money. Comment : the emergetic expense of inoculating agent is small in relation to the benefit that it brings to the system in capturing atmospheric nitrogens.

LIMESTONE:

The grounds of diverse brazilian areas are acid and react well (in terms of productivity) to the addition of limy material. The tables provide Transformity values of calcareous rock in terms of solar emergy per mass (seJ/kg).

2000 kg of limestone *    1.0 E12 sej    = 2.0 E+15 sej

ha. year               kg of limestone       ha year

MANURES:

Various types of nutriments can be used:

(a) Soluble artificial fertilizers;          (b) Manures;       (c) Ground rock;

(d) Green manures;           (e) Composites;            (f) Residues (agricultural and urban).

The soluble chemical fertilizers can be:

(a) Diverse types of phosphates;         (b) Nitrates and ammonia;            (c) Potassium salts;

(d) Mixtures of various components (N, P, K).

MANURES (continuation):

Tables provide Transformity of three forms of manures :

(a) seJ/J of manure;             (b) seJ/kg of manure                           (c) seJ/kg of active element.

Transformities

 seJ/J of manure seJ/kg of manure seJ/kg of active element Nitrogenics (1 860 000) 38.0 E11 46.0 E11 Potassics (3 000 000) 11.0 E11 17.4 E11 phosphatics (10 100 000) 39.0 E11 178.0 E11

Most used Transformities are given in terms of mass (seJ/kg of manure).

300 kg of phosphate *     39 E11 seJ     = 11.7 E+14 seJ

ha. year                kg of phosphate          ha year

It can be used balanced values according to the proportion of each type of chemical salt. The proportion of N, P, K is usually indicated in the fertilizer name.

MANURE (continuation):

Example:

Manure (10.20.20). Values indicated between brackets are the percentages of N, P2O5 and K2O in manure.

Relations of molecular weights are: [P/P2O5]=0.437 e [K/K2O]=0.83
46E11(1.0)(0.1)+17.4E11(0.437)(0.2)+178(0.83)(0.2) = 4.6 E11 + 1.53 E11 + 29.54 E11 = 35.7 E11 seJ/kg

300 kg manure (10,20,20) * 35.7 E11 seJ = 10.7 E+14 seJ

ha. year                                kg                ha year

PESTICIDES AND WEEDKILLERS:

The tables provide pesticides and weedkillers Transformity in two forms:

(a) seJ/J of manure;             (b) seJ/kg of manure

Transformities

 seJ/J of substance seJ/kg of substance Pesticides (general) 1 970 000 1.48 E13 Weedkillers (general) - 1.48 E13

Most used Transformities are given in terms of mass (seJ/kg of manure).

10 kg of pesticide *   1.48 E13 seJ   = 1.48 E+14 seJ

ha. year              kg of pesticide          ha year

1.5 liters of weedkiller * 0.7 kg *    1.48 E13 seJ    = 1.55 E14 seJ

ha. year                1 liter     kg of weedkiller         ha year

The emergetic density of agrotoxics is high because its very intensive manufacturing process doesn’t use renewable energy resources. For the moment, we cannot find in the Emergy Methodology (Odum, 1996), the Transformity values specific to diverse types of pesticides (insecticide, acaricide, fungicide, etc), therefore, a general value for all the pesticides is used.

FUEL:

80 liters of fuel per hectare per year are usually used in the soybean production. It is there still necessary to use a conversion factor. This factor corresponds to the following operations :

0.75 kg * 10000 kcal * 4186 J = 3.14 E+07 J

liter              kg           1 kcal           liter

This factor (in J/litro) allows to convert the fuel flow (litros/ha/year) into energy flow (J/ha/year). Then, it is multiplied by the Transformity found in table (6,6 E+04 sej/J). Thus, we obtain the emergy flow, in our case: 2,07 E+12 sej/ha/year. The equivalent monetary flow is worth 56,00 US\$ emergetic/ha/year. The fuel price was estimated at 0.36 US\$/liter. The corresponding monetary flow is 28,80 US\$/ha/year.

The emergetic value is generally greater that the economic one, this fact can be interpreted as a temporary subsidy to the economy, caused by low price of oil and its derivatives, consequence of an unjust situation forced by politic and military intervention in the Middle East.

MACHINERY AND INFRASTRCTURE :

It can be considered that, on average, a tractor of 3000 kilogrammes of steel covers 300 ha. And the tractor is depreciated over 10 years.

3000 kg        = 1 kg of steel

300 ha 10 years        ha year

Transformity of worked steel is used to obtqin emergy flow.
Transformities

 steel produced (seJ/J) steel produced (seJ/kg) Machinery in steel, vehicles (75 E6 - 139 E6) 67.0 E11

kg of steel * 67 E11 sej = 6.7 E12 seJ

ha. year      kg of steel        ha.an

Knowing that 1 dollar corresponds to 3.7 E12 seJ, to get the equivalent monetary flow, the value obtained has to be multiplied by 1/3.7E12.

6.7 E12 sej *    1 dollar    = 1.8 in dollars

ha. year       3.7 E12 sej         ha year

Thus, equivalent monetary flow is worth 1,8 US\$ emergetic/ha.year. The unit price of a tractor is 2 US\$/kg. Real monetary flow is worth 2 US\$/ha.year.

D. ECONOMIC SERVICES:

HUMAIN LABOUR

Manpower forms a subset of the agricultural system, that can be located inside the agricultural unit or in the city. To work, the family head has to obtain enough money to pay expenditures of his family. If the worker and his family live in rural area and if environment provides good conditions, they can get some free resources from nature; in town they should pay to obtain  them. The life quality of agricultural workers depends on what the natural reserves can provide to them : fruits, hunting, entertainment, shade, drinkable water, fish, remedies, etc... The minimum wage must be sufficient so that the family of the worker can live with a minimum of dignity, safety and comfort, and releases the family head 8 hours per day to provide agricultural work of good quality. The employer pays wages and assumes some social contributions, in return, he gets some services from government for the workers (preventive education, communications, research, care of health, medical care).

CALCULATION OF THE TRANSFORMITY OF MANPOWER

Considerations for the calculation of Transformity in emjoules solar per Joule (sej/J):

In 2001, the minimum wage of a Brazilian farm worker received is worth R\$ 180.00. The average tax of the exchange was 2,6 Reals/dollar.

Emergy of annual wages:

180 Reals . 13 month . 1 dollar . 3.7x10E12 sej = 3.33x1015

sej/year       month         year         2.6 Real            1 dollar

Annual energy spent by a worker:

3200 kcal . 365 days . 4186 Joules = 48,89 x 108 J/year

day             year           1 kcal

Transformity of his work was thus:

Tr = 3.3 E15 sej = 673 469 sej/J

4.9 E09 J

TRANSFORMITY OF MANPOWER:

Considerations for the calculation of Transformité in sej/J (year 2001):

Hard worker manpower:                     1 SM: roughly 670000 sej/J * 1.0 = 6.7 X 105 sej/J

Manpower (operator):                        3 SM: roughly 670000 sej/J * 3.0 = 1.9 X 106 sej/J

Agricultural technician:                     5 SM: roughly 670000 sej/J * 5.0 = 3.3 X 106 sej/J

Qualified agricultural technician:     10 SM: roughly 670000 sej/J * 10 = 6.7 X 106 sej/J

Professor of University:                    25 SM: roughly 670000 sej/J * 25 = 16.7 X 106 sej/J

Considerations for the calculation of Transformité in emjoules solar per hour (sej/h):

Hard worker manpower:                     6.7E5 sej/J * (4186 J/kcal) * (3200 kcal/jour) * (1 day/8 H) = 1.1 E12 sej/H

Manpower (operator):                        1.9E6 sej/J * (4186 J/kcal) * (3000 kcal/day) * (1 day/8 H) = 3.0 E12 sej/H

Agricultural technician:                     3.E6 sej/J * (4186 J/kcal) * (2500 kcal/day) * (1 day/8 H) = 4.3 E12 sej/H

Qualified agricultural technician:     6.7E6 sej/J * (4186 J/kcal) * (2500 kcal/day) * (1 day/8 H) = 8.8 E12 sej/H Professor of University:                   1.7E7 sej/J * (4186 J/kcal) * (2500 kcal/day) * (1 day/8 H) = 2.2 E13 sej/H

HARD WORKER MANPOWER:

In the case of conventional soybean production with weedkillers, the agricultural technique doesn’t use hard worker manpower, therefore,  the number of hard working hours per hectare per year is considered as equal to zero.

The concept man-day, also called 8 men-hour, means 8 working hours per day. In these case, a conversion factor has to be used, because the quantity unit is hours/ha.year.

This factor is worth 1,67E+06 J/hour and is obtained in the following way :

3200 kcal * 4186 J * 1.0 man-day = 1.67 E+06 J

day         1 kcal      8 men-hour      man-hour

The multiplication of this factor by the number of hard working hours allows to get the energy flow in J/ha.year (if the value is different from zero) and the Transformity to use is 4,0 E+05 sej/J.

The emergy flow in sej/ha.year results of these operations.

We multiply this value by the ratio emergy/dollar for Brazil and for this year, and we would get the equivalent monetary flow, in dollar emergetic/ha.year. This value is also called macroeconomic value or in-dollar.

Therefore, the cost of  hard worker manpower is worth of 0,33 US\$/hour.

QUALIFIED MANPOWER :

In a conventional soybean production with weedkillers, 0,8 qualified working hour per hectare per year is necessary.

Moreover, we must use a conversion factor, because the quantity is given in hours/ha.an. This factor is worth 1,31E+06 J/heure and is obtained by the following formula:

2500 kcal * 4186 J *   1 day   = 1,31E+06 J

day         1kcal     8 hours         hour

The multiplication of this factor by the quantity of qualified working hours necessary allows to obtain the energy flow : 1,0Ë+06 J/ha.year. Transformity used is worth: 1.2 E+06 sej/J, this value is three times bigger than the one for hard worker manpower. The emergy flow results of these operations.

Therefore, the cost of  qualified manpower is worth of 0,33 US\$/hour.

In the production of soybean with weedkillers and direct plantation, this value is provided in dollar per hectare per year (4.28 US\$/ha.year). Consequently, Transformity used is worth 3.70E+12 seJ/dollar and the emergy flow is worth 1.58E+13 sej/ha.year.

The equivalent monetary flow and  the real monetary flow are equal (4.28 US\$/ha.year).

USE OF THE AGRICULTURAL MACHINERY:

The expenses value in soybean production with weedkillers and direct plantation is provided in dollar per hectare per year.

It corresponds to works of :

(a) Preparation;          (b) Sowing;          (c) Harvest.

It can also include:

(d) Improvement of the place;          (e) Transport;           (f) Cleaning, drying and storage.

We have two alternatives of calculation:

1. To use monetary value relating to various stages of the productive process. And to add the corresponding values in dollars/ha.year.

2. To break up this value into basic elements:

a)       Depreciation of the equipment (60%); costing 6.00 dollars/kg, we can calculate the kilogramme of steel/ha.year.

b)       Fuel and lubricant (30%); costing 0.36 dollar/kg, we can calculate the kilogramme of fuel per hectare per year.

c)       Hard or qualified manpower (10%); costing 9.43 dollars/man-day, we can calculate the day/ha.year.

SPEND:

This value is provided in the local currency, 5.00 reals/ha.year. This amount corresponds to the production of common soybean. In this case, it is necessary to use a conversion factor: 0,59 dollar/real. Transformity used is 3.70E+12 sej/US\$. The equivalent monetary flow and the real monetary flow are equal (2.94 US\$/ha.year).

E PRODUCTS:

All products of the system must be considered. Some of them are easily identified as such, others not. Beyond the principal products, by-products are existing, with and without commercial value.

There are also solid, liquid and gaseous residues. The residues can produce benefit or expenditure. They can induce treatment and recycling , or special cares because of their toxicity and generate additional expenses.

In emergetic methodology we must take into account the system product(s) ; generally, in the case of agricultural raw materials, energy corresponds to their caloric value. We must know the centesimal composition of a product to calculate its caloric value. For calculation we have to consider the dry matter. Data to be used : Moisture : without caloric value ; Protein: 4500 kcal/kg; Carbohydrats: 5000 kcal/kg; Lipids: 9000 kcal/kg.

F. INPUTS LOSS :

Up to 50% of soluble chemical fertilizers are lost because of intense rains. They flow off superficially or infiltrate in phreatic tablecloth without interacting with plants. With agrotoxics and weedkillers options, it occurs the same phenomenon , but, it is less frequent. The ground hardening caused by weight of agricultural machinery and the loss of natural porosity caused by biota disappearance involve a reduction of water infiltration in the ground and a productivity loss.

G EXTERNAL SERVICES (SOCIETY EXPENSES) :

External negative works:

The expenditure due to the treatment of residues placed in the environment must be also considered. Health cares and death of farm workers and their family caused by agrotoxics use in the conventional leasing involve expenses that have to be considered. Expenses induced by treatment of residues placed in the environnement must also be considered.

Social exclusion:

We have to consider the direct and indirect costs of social exclusion induced by conventional agricultural projects that cities have to pay for : people leave the rural area and arrive in the cities to seek work and live in precarious suburbs. It is difficult to estimate values for these aditional services, however they exist and must be considered and paid by the companies which generate them. Perhaps, taxes are not sufficient to compensate expenses of the cities.

External positive works and social inclusion:

On the other hand, it is possible that the agricultural projects generate social inclusion by creating jobs and by integrating workmen. A project that promotes social organization and good interaction with nature is called positive external work. In this case, society could reward these enterprises with tax advantages and, why not, with subsidies for their contribution to the expenses reduction.

Capacity to exploit natural resources is much bigger in organic systems than in agrochemical systems and systems that use weedkillers - direct plantation. One of the significant factors which does this characteristic of organic systems is the fact that production is mainly familiar. When people live on the land that they cultivate, they have a much bigger preoccupation with the conservation of the land and its natural resources. Moreover, more people inhabit a property and contribute directly to work in the production, more they worry about health damages caused by agrotoxics.

Organic systems use much manpower, therefore, the conversion of agrochemical and/or weedkiller-direct plantation systems in organic systems (process called "agro-ambient transition") can create jobs in rural areas. This characteristic of organic process is significant for the Agrarian Reforms and the Employment Policy.

This explains why we find in the organic production diagram, symbols for agricultural families, people flow and regional and local biodiversity; these symbols do not exist in agrochemical and direct plantation systems. Moreover, in this thesis, ecosystems met are preserved in organic option and unfinished  in the two other systems ; that is because biological control is a necessary condition for organic systems.

It is possible to perceive in the organic diagram that materials are recycled, because owners (familiar production) inhabit in agricultural installations, and are thus interested in reusing by-products and try to implement this strategy in diverse ways. Therefore, they use to advantage to the maximum property resources. A well-known example is the use of organic substance resulting from the decomposition as fertilizers and green manure. These processes allow to decrease inputs purchase, by using natural nutrients without incidental costs (without counting human work).

Among virtues shown above, external services and materials, that have to be acquired or to be requested, are represented in lesser amount in the diagram of organic system than in the two others.

The important difference between organic system of production and agrochemical system with weedkiller - direct plantation is the relation with natural resources : more they are removed and more they are given. This is done in a more harmonious and less destructive way in organic properties that used conventional systems. These assertions can be proved by an analysis of spread sheets of emergy flow.