Scientific and Technological Management Advisor – SECT-MG.
The Program for Improvement of the Energy Efficiency of Equipment and Systems of the Minas Gerais state, approved by the Science and Technology State Council, proposes to approach the efficiency question of energy conversion systems by studying all phases that constitute each one of the large systems, considering those of interest to the Minas Gerais state. Initially, the charcoal production and use in metallurgy production, the use of ethanol fuel and electricity generation systems are focused.
The present Technical Report aims at describing the present state of the technology and evaluating the potential of producing ethanol from sugarcane in order to help the analysis of P& D project applications in the area. In order to systematize the treatment, this study considers the agricultural productivity and the industrial efficiency in the conversion of the total reducing sugars (TRS) of ethanol. The efficiency of the hydrated ethanol fuelled engine, the gain of the motors fuelled with gasoline to which anhydrous ethanol was added and the co-generation potential (electricity and process vapor ) will be considered in another work.
The data used in the present study were taken from DATAGRO and from the COPERSUCAR Technology Center. Since this work is an exercise concerning the application of the technology forecast methodology that was proposed as a management instrument to the SECT, the author intends to ask for the help of the above mentioned institutions in order to verify the consistency of the results relative to the projections already elaborated by those institutions that, besides the pertinent technical information, have the economic perspective of this important Agro-industrial Sector.
Sugar and alcohol production data.
Graphic 1 shows the production evolution from 1975 on. Until 1985 alcohol production has grown considerably, driven by Proálcool, while that of sugar has remained constant. The decrease of oil price in the middle eighties resulted in the stagnation of the alcohol fuel industry, interrupted only at the beginning of the nineties, when the sugar production has also grown, an effect that apparently is connected with the ascending phase of the Real Economic Plan.
The production data are shown in anhydrous equivalent through the reduction of the hydrated alcohol by a factor of 0.93 corresponding to the average alcohol content of fuel alcohol. The coexistence of the two types will be analyzed in the item that handles the alcohol engine.
Graphic 1 – Sugarcane , sugar and alcohol production.
The production evolution was nor merely quantitative, since the productivity indexes shown in graphic 2 show expressive efficiency gains.
Graphic 2 – Productivity.
The productivity gains are reflected in the production cost, shown in graphic 3, and were calculated from data obtained from a ÚNICA report.
Graphic 3 – Evolution of fuel alcohol production cost .
The main objective of the present study is to evaluate the productive limits, starting with the t TRS/t sugarcane, a function of the agricultural practice (in its turn, a function of sugarcane prices, of inputs, alcohol demand, etc.), of the sugarcane variety used and water availability, evaluated here by rainfall of each year, since irrigation is not a common practice in the Sector. In order to evaluate even coarsely the effect of water availability, graphic 3 was elaborated and it shows the rain amount and the corresponding variation of TRS content (in the following year).
Graphic 4 – TRS productivity versus water availability.
A reasonable conformity is observed between the maximum rainfall and that of TRS productivity, except notably those of 77/78, 80/81 and 93/94, when the indexes have varied in opposite directions, explainable by the exceptional variation of alcohol demand in these periods.
Water availability affects farming productivity in the way shown in graphic 4 where it can be seen that this correlation is weaker than the TRS productivity (graphic 3). The lack of clear correlation between water availability and farming productivity hinders the projection of this productivity according to the methodology described in the previous Technical Report. In that case the data fitting to the logistic differential equation presented poor correlation coefficients as shown in graphic 5.
Based on the adjustment shown, it was estimated that the limit-productivity is 120t/ha.year; therefore there is room to gains regarding this parameter.
However, by examining the productivity curve, shown in graphic 6, where the equation written in the legend corresponds to the adjusted curve, one observes that it does not coincide with the expected curve (logistic curve), suggesting that factors external to the system, mainly encouraging the use of fuel alcohol, are strong factors that determine productivity because they condition the farming renewal and the use of fertilizers and pesticides. The three plateaus seen in the graphic correspond respectively to the gasoline-anhydrous alcohol mixtures (1975), to the introduction of hydrated alcohol (1980) and the increase of anhydrous alcohol content in its mixture with gasoline (1988).
Industrial productivity should start from the mass of TRS/t necessary to obtain one unit of anhydrous alcohol (m3). However we have been informed that the TRS content has been calculated, when sugarcane is bought , through the amount of sugar or alcohol produced from 1 t of sugarcane, that is, the TRS content is not directly measured. Due to this limitation, we have preferred to calculate the alcohol volume corresponding to 1 t of sugarcane.
The following graphics show the sequence of the logistic study concerning the alcohol production productivity.
Graphic 8 – Productivity variation rate.
Graphic 9 – Linear logistic productivity curve.
Graphic 10 – Evolution of the industrial productivity .
The analysis suggests that there is room for the industrial productivity growth, since the maximum foreseen value (graphic 7) is about 113 liters/t of sugarcane while the value reached in 1999 is 75l/t. Recent study carried out by UNICA (Union of the Sugarcane Growers from São Paulo) concerning the co-generation potential mentions a 83l/t productivity. Possible gains would come, from our point of view, from irrigation and from a better TRS extraction. However, we have no notice of studies of economical viability concerning the possible improvements. A source from the Sector mentions as a drawback to irrigation the taxation of water for industrial purposes, recently introduced in Brazil.
Fuel alcohol production presented considerable increase together with important productivity gains since the establishment of the Pro-Álcool. Studies show that the Sector has reacted positively to external incentive, both from the government, now scarce, and from the fuel market. Production cost has systematically decreased, a remarkable fact in the energy market where almost all costs are growing.
The study shows that there is still room for increasing farming and industrial productivity that could decrease costs even more. We believe that the definition of a energetic, clear and permanent policy that takes into account the effects of alcohol use on creation of jobs, on external trade balance, on technological development, on atmospheric carbon abatement and on the possibility of co-generation will be sufficient to fix the alcohol position in the Brazilian energy matrix.
 We want to thank Drs. Plínio Mário Nastari (DATAGRO) and Manoel Régis Lima Verde Leal (CTC-COPERSUCAR) for their priceless help.
 “Potencial de co-geração com resíduos da cana-de-açúcar: sua compatibilidade com o modelo atual” União das Indústrias Canavieiras de S. Paulo-UNICA/2002.
Graphic Edition/Edição Gráfica:
Tuesday, 10 May 2011.