Nowadays, the predominant paradigm in conventional agriculture establishes that "technology is adequate whenever an increment in input produces an increase in output". This point of view usually results in an over-simplification of agricultural systems and loss of biodiversity in rural space. The output of the main product may be greater but the systems develop an enormous increase in internal stock losses and induce costs in others.

In this study, by means of a systems approach, we studied three different soybean production systems (including transgenic) and identified and measured (in terms of emergy) the contributions of biodiversity to the productivity of the cultivars, making it possible to substitute industrial inputs.

Also, in this preliminary research, the way in which emergy methodology deals with agricultural systems and the changes necessary to represent and correctly study conventional and agro-ecological systems was examined. The agroecological techniques (biological control, crop rotation, green manure, composting, mulching, incorporation of shrubs and trees in mixed cultures, use of manual labor) reduce losses of soil and preserve biological stocks, which if destroyed would take a very long time to recover. In conventional agriculture, the internal stock losses, the input wastes and the externalities need to be quantified in order to use their flows in emergy and economic indexes.

The prepared emergy diagrams and analyses are rather different from those of the simplified systems of modern agriculture in the USA and Europe in order to represent the complexity inherent in agroecological projects.

The organic, chemical and herbicidal systems show emergy favorable indices to the organic alternative. However, on the other hand, the economic index is favorable to herbicidal technology, which receives a high subsidize from the low petroleum price.

The data is still under collection, but we can say that the emergy indexes for agroecological projects, using the more complex point of view, are quite different from those obtained from chemical agriculture. They show higher values in relation to renewability (56% vs. 11%) and yield ratio (2.4 vs. 1.65) and lower values for investment (0.7 vs. 1.9), loading (0.8 vs. 8.2) and exchange (about 0.8 against 1.6). and similar values for transformity (80000 vs. 91500). Values for the annual profit ratio, defined as net income divided by expenses, are 1.1% against 1.6%, respectively.

Up to now, results have shown that both the studied agrochemical alternatives are neither ecological nor social equitable, but are more economically advantageous to farmers, inducing them to adopt non-sustainable procedures in opposition to Agenda 21´s agreements. Public policy needs to consider taxes to externalities and biodiversity losses produced by agrochemical technology and, at same time, incentives to promote agroecological projects according with the social and environmental benefits they produce.

Keywords: Soybean production, Transgenic, Biodiversity, Agriculture, Emergy.

Agenda 21, the world agreement established in 1992, recognized the lack of sustainability of our economic system and promoted the creation of new standards to evaluate human achievements. After that, the economic science won a new variable for the evaluation of ecological performance: "Sustainability".

What characteristics could define a system as sustainable? Sustainability depends on the capacity of analysis of the systems behavior, on the perception of the economic system dependence on different kinds of external and internal energy sources and on the recognition that many of these sources have an ephemeral character. As a result, social conscience and capacity for self-government can be developed.

How to measure sustainability? Neo Classic Economy, although thoroughly used, has become obsolete due to its deficiencies in measuring sustainability (Ulgiati et al., 1998). New approaches are necessary, like energy analysis. First of all, it is necessary to identify all the system’s energy sources, after that, to classify the flows as renewable or non-renewable and, finally, to obtain the "renewability", an index fitted to quantify energy sustainability:

		Renewable energy
Renewability	=	---------------------------
		Total energy used

The above mentioned sustainability can be calculated in several forms:

1. Measuring the caloric energy common to all things. This method leads to erroneous results, because it does not take into account all the energy required in the production of the materials, nor the energies consumed in the processes;
2. Using the concept of embodied energy, which consists of identifying all the energy flows in a system, starting from its raw materials, and measuring them in terms of one kind of energy. For many years, this methodology used the barrel of petroleum as the unit of reference, because it was applied to industrial systems, which have their raw materials clearly linked to the consumption of petroleum. This methodology does not consider neither nature services nor human work;
3. Measuring exergy, the capacity for work production of materials and energies for processes. This methodology is derived from Mechanical Thermodynamics and now confronts the measurement of biological energy, a problem difficult to solve;
4. Using emergy. This methodology was developed in energy analysis of natural systems and uses Thermodynamics. It was successful in the measurement of the biosphere energy required to produce the natural resource flows (rain, sediments, biomass, chemical substances, fossil energies, etc.). It measures flows in terms of equivalent solar energy (sej). It moved its focus from natural to anthropic systems; the human economy is being studied as a sub-system of the biosphere, with laws of restricted validity. Research is needed to measure the transformity of different types of human works;
5. Using the ecological economy. Some economists decided to confront the challenge of evaluating nature's services in order to complement the economic analysis, without altering the present values of economic inputs. This methodology has already produced some important results, disclosed in the press, such as the values of biosphere’s services in economic terms, but, up to now, it has few examples of calculations in terms of local or specific projects.

Use of renewable resources from biodiversity in agriculture:

Biodiversity contribution is diminishing due to degradation of the rural structure (previous systems were based on multiple crops and animal husbandry in diversified farms) and the use of energy intensive inputs with high environmental impact (chemical fertilizers, pesticides, herbicides). Furthermore, modern technology had lead to higher losses of soil and decrease in its fertility (through erosion, leaching, salinization and sterilization); loss of species and cultivars that do not provide high yields (some could be useful in the future). The agrochemical system loses soluble chemicals to watercourses and subsoil, polluting aquifers. People are also lost, as well as their cultural values, since they leave the area due to mechanization. For soybean production using transgenic seeds and herbicides, the costs must include human and nature health risks. Agricultural accounting and public policy might consider all these losses and additional costs.

In this study, we use the emergy methodology proposed by Odum (1996). This technique has been used to analyze conventional agricultural systems (intensive in non-renewable energy) of the United States and Europe (Odum, H.T., 1984; Brandt-Williams, S. & Odum, H.T., 1998). However, as a function of peculiar characteristics of ecological agriculture, Ortega and Polidoro (1998), after observing very low values of renewability for agroecological projects, proposed several modifications to the emergy current approach for including biodiversity contributions and losses:

1. The environmental contributions (nitrogen from the atmosphere, nutrients obtained from sub-soil rocks, biological control, etc.);
2. The ecosystem losses (top soil, water, biodiversity, people);
3. The system's waste of purchased inputs;
4. Some externalities (effluent treatment, medical treatment, health risks, etc.).

This study tries to assist the methodological concepts suggested by those authors. Some approaches and results from other researchers were considered, mainly one from Brown (1998), who made an emergy analysis of our Biosphere. He discovered that in a hundred years the rate of global renewability dropped from 95 to 27%. In industrialized countries this fall is more drastic, now having a renewability of 5 - 15%. Under-developed countries are more sustainable (50-60%).

In our work it was reviewed the diagram of the Biosphere, identifying the different stocks of internal energy (Figure 1).

Figure 1. A detailed energy flow diagram of the terrestrial biosphere showing internal stocks.

As well as the global system it is possible to analyze sub-systems. Our main research interest is emergy analysis of agricultural and agro-industrial systems. We prepared a general diagram of energy flows of an agro-ecological farming system (Figure 2).

Figura 2. Energy flow diagram of an agroecological system.

In Brazil's main soybean areas (Rio Grande do Sul and Parana States) it is common to plant soybean's in the summer and corn in the winter, forming a complementary system. The three main systems of production were studied: (a) agrochemical, (b) herbicide; (c) organic).

1. Capture of atmospheric nitrogen (nitrifying bacteria);

2. Intensive use of soluble chemical fertilizers (phosphates and potassium);

3. Losses from leaching of 50% of the soluble fertilizers;

4. Intensive use of pesticides;

5. Soil, feed and water contamination with pesticides;

6. Externalities (traditional and new) are not accounted.

1. Huge soil losses;

2. Intensive use of agricultural machinery;

3. Intermediate use of human labor.

1. Reduced soil losses (due to the use of the direct plantation technique);

2. Low use of agricultural machinery;

3. Minimum use of human labor;

4. Intensive use of herbicides,

5. Leaching of surfactants (used in the herbicide formulation).

1. Minimum soil losses (due to the use of direct plantation and recomposition);

2. Capture of atmospheric nitrogen (nitrifying bacteria);

3. No-soluble chemical fertilizers, animal and vegetable manure use;

4. No use of pesticide or herbicide;

5. Moderated use of agricultural machinery; and wide use of family work labor;

6. Minimum losses from leaching of the input use;

7. No soil, feed nor water contamination;

8.Pratically has no externalities.

		Sales – Costs of Economic Inputs
ER Economic Rentability	=	-----------------------------------------
		Costs of Economic Inputs

		Sales – Environmental, social and economical Costs
SE Systemic Rentability	=	----------------------------------------------------------------
		Environmental, social and economical Costs

Table comparing the results of the evaluation systems

Indices	Standard Method			Complex Method
	Org.	Chem.	Herb.	Org.	Chem.	Herb.
Transformity (sej/J)	49 000	59 000	81 000	80 000	76 000	107 000
R Renewability	0.33	0.16	0.12	0.56	0.11	0.10
EYR Yield Ratio	1.56	1.49	1.23	2.40	1.93	1.37
EIR Investment ratio	1.8	2.1	4.4	0.7	1.1	2.7
ELR Environmental Loading	2.0	5.4	7.8	0.8	7.7	8.6
EER Exchange ratio	0.5	1.9	1.0	0.8	2.4	1.3
ER Economic Rentability	4.3	2.1	10.6	1.1	1.5	1.7
SR Systemic Rentability	4.3	0.4	4.4	1.0	-0.3	0.6

See data and calculation procedures at following web pages:

http://www.unicamp.br/fea/ortega/curso/planilha-simples.htm
http://www.unicamp.br/fea/ortega/curso/planilha-complexo.htm
http://www.unicamp.br/fea/ortega/cyted/software.htm

Figura 3. Comparison of organic, chemical and herbicide soybean production systems.

1. Emergy Yield (EYR), Investment (EIR) and Environment Loading (ELR) using both analyses


2. Renewability versus Economic Rentability for simple and complex emergy analyses

The emergy methodology, as used in other countries to study conventional agricultural systems (intensive in the use of non-renewable resources), does not show adequate results in the evaluation of ecological agricultural systems (intensive in renewable resources). The modifications in the methodology led to more coherent results (Figure 3). The data is still under collection, but we can say that the emergy indexes for agroecological projects, using the more complex method are quite different from those obtained with simple approach.

Using simple method, comparing agroecolgy against agro-chemical agriculture:

Using complex method, comparing agroecolgy against agro-chemical agriculture:

5. PRELIMINARY CONCLUSIONS (BASED ON COMPLEX METHOD)

The results obtained (Ortega & Miller, 2000) came from the data of other researchers and expert opinions (FNP, 1999; IEASP, 1999). They need to be confirmed by field research to be done the next months. As final stage the results will be confronted with results obtained by Pimentel et al. (1996), Merico (1966) and other researchers of Ecological Economics.

These conclusions most be considered as hypothesis to be tested and refer only to results obtained with complex method.

1. The transformity measures the amount of solar energy necessary to obtain the products. Agricultural products based on herbicides need more energy (106616). The transformities of chemical (75516) and agro-ecological (80359) products are rather small and close.
2. Analyzing the renewability percentage we noticed that more than half of the necessary resources for organic agriculture production came from renewable resources (0.56). For this index, the values for chemical agriculture (0.10) and herbicide agriculture (0.11) are very low, indicating low renewability or sustainability.
3. The yield ratio (EYR) indicates that the three systems return more energy than they receive from the economy. However, organic agriculture has the best return to economy (2.40) indicating that it incorporates a great deal of ecological energy. The value for herbicide agriculture (1.37) indicates that the system uses a lot of non-renewable resources from urban economy and, therefore, it is a less ecological agriculture. The value for agro-chemical (1.93) is an intermediate value.
4. The emergy investment ratio (EIR) is the relationship between economy resources and those from nature. Organic agriculture obtained the best index (0.72) in relation to chemical agriculture (1.08). Herbicide agriculture is very dependent on resources from the economy (2.74) which in the present situation, are basically non-renewable.
5. In the case of the environmental loading ratio (ELR), herbicide agriculture (8.6) causes a great environmental impact, close to that of chemical agriculture (7.7). The index for organic agriculture (0.8) indicates that it hardly produces damage to the environment.
6. The emergy exchange ratio (EER) measures the relationship between emergy transferred by the system (through products) and emergy received from the surroundings by sales (such as money flow). Agriculture usually transfers energy to urban systems and its internal stocks (natural and human resources) decrease. This is the case for systems based on herbicides (1.3) and chemical products (2.4) but not for the organic system which gets a surplus (0.8).
7. The ecosystem price is the price that the product should have in order to pay for all the environmental and economic expenses. Chemical agriculture has the smallest value (0.38) closely followed by organic agriculture (0.40). It would be necessary to charge 0.53 dollars per kilogram of product to pay for all the damage caused by the herbicide option.
8. Considering just the economic aspects, agriculture based on herbicides has the greatest profitability (ER or economic rentability), but if the system losses are considered, the situation is inverted, and in this case the organic agriculture is the best option of all.
9. When the analysis takes into consideration the system costs (losses of stocks, wastes, treatments, etc.) in SR (systemic rentability index), the option with greater profitability is also the system that has the largest renewability ratio (agroecology).

6. RECOMMENDATIONS

The agrochemical and herbicide options require greater investment of non-renewable resources and they put at risk the access of energy resources for future generations. Organic agriculture is by far the most sustainable technique studied, and must be promoted. It is necessary to establish new public policies to tax and incentive the agriculture systems:

• decrease of system stocks (losses),
• decrease input wastes;
• increase recycling and soil biomass production;

• preserve and increase biodiversity in rural areas;
• include externalities as additional services;
• promote the capacity to use more renewable resources in agriculture;
• increase job generation.

Thus Renewability and Systemic Rentability will show the same behavior, otherwise Economic Rentability will oppose and always defeat Sustainability.

REFERENCES