1. Sugarcane production in Brazil
Sugarcane is grown on approximately 3.8 million hectares of land which represents only 0.76 percent of Brazil's arable land consisting of about 500 million hectares. The land actually used is only 5.9 percent of these values. From this area, 125 million tons of cane were harvested in the 1985/86 season. Sugar and alcohol production were respectively 7.8 million tons and 11.9 billion litres. Of the total sugar production only 1.8 million tons are sold outside the country.
Sugarcane cultivation represents the third working force of the country with 1 700 000 employees. Since 1979 alcohol production has represented an investment of Brazilian capital equivalent to US$ 6 billion and has represented an economy of US$ 9 billion.
The harvesting plan for 1986/87 has established a production target of 8.5 million tons of sugar and about 11.7 billion litres of alcohol. Alcohol production is dependent upon political decisions. Two factors have disturbed alcohol producers: the return of oil prices to the level of 1973 and a long, dry season that reduced production and influenced this year's yield. Some views were that it was necessary to stop the National Alcohol Programme. However, on 27 February, during a visit of the President of Brazil to Ribeirao Preto, State of Sao Paulo, it was confirmed that the Programme would continue. It is commonly agreed that some changes should be made but the reduction in yield will give them time to decide.
2. Sugarcane by-products
The 125 million tons sugarcane harvest in the 85/86 season gave 17 million tons of tops, 31 million tons of bagasse, 5 million tons of filter cake, about 5 million tons of molasses, 75 billion tons of stillage and 140 thousand tons of dried yeast.
Sugarcane tops are, in almost their totality, left in the field. In special situations they are used for feeding animals.
Fifty percent of the bagasse produced is burned for steam production. Some is burned for the production of electricity. From the remaining bagasse, about 100 thousand tons are used in the paper industry and about 140 thousand tons in furfural production which has a very large industrial application. Small amounts are used as a crop mulch and for animal feeding. In 1985 the southeast area had an unusual drought during the months of October to December, so emergency feeding for the animals on pastures consisted in low quality roughages (including bagasse) with the addition of urea plus oil cake proteins to cover the lack of green forages.
Filter cake has a very large variation in its chemical composition so it is difficult to recommend it for any specific use. Its final use is as fertilizer in sugarcane crops.
From 1979 to 1985 molasses has almost disappeared as an animal feed being partly exported and partly transformed into alcohol.
Stillage no longer causes problems for producers and consumers. Actually it is almost entirely used as a fertilizer, at least as a good source of K and water, increasing the sugarcane yield from 8 to 10 percent. After fermenting a batch of sugarcane juice, using the Mellet-Boinot process, some yeast milk is taken off giving about 40 g of dry matter per litre of alcohol.
3. The use of sugarcane and byproducts in animal feeding
The real amount of whole sugarcane given to domestic animals in the country is not known but it has certainly been widely used as green chopped forage in the majority of low production (less than 10 kg/cow/day) milking farms. A recent survey (1983) in a very representative area of milk production, the county of Campinas, in the State of Sao Paulo, showed that 70 percent of the farms have sugarcane as green stock. They cover 1.3 ha in an average area of 123 ha. The amount given, per animal, per day, on average is 14 kg (from 9.9 to 17.6). Whole sugarcane in some cases is given with cotton seed meal or soybean meal, raising protein levels to 11–12 percent (dry basis) which gives a daily gain of 0.7 to 0.8 kg. Lower gains have been obtained when urea, sulphur and rice polishings are given instead of oil cake protein.
Sugarcane tops in spite of their large availability are not commonly used and in fact are only used in very specific situations. One of the factors that limits their use is the collecting cost from the field after harvesting the sugarcane. Left on the soil when manually cut the mineral matter increases if the sugarcane tops are not properly managed. The common practice of burning the crop reduces production and the time available to transport them from the field without changing their composition. Burned sugarcane tops, plus soybean straw without pods are two kinds of residues found together in some areas of the State of Sao Paulo. Consumption of 6.6 kg dry matter composed of 2.6 kg of burned sugarcane tops and 4.0 kg of soybean straw is enough to maintain the liveweight of 350 kg steers during the dry season.
Raw bagasse has been introduced in many situations as emergency feed. Diets including 30 percent of raw bagasse (± 50 percent dry matter) given to Nelore cattle and buffaloes were consumed in growing amounts in relation to time. Treatments with ammonia, sodium hydroxide and steam cooking have actually been tested in several places with variable results. Of these treatments, steam cooking seems to be the one that has a more promising application in the future. Currently more than 5 000 head of cattle are fed with one type of steam treatment representing about 50 percent of the daily dry matter consumption. There are still several questions to be answered before the release of the technique. Some of the equipment used for steam treatment does not have good control of temperature and time, so it is very difficult to know what are the real working conditions. It is well known that small variations in these parameters can change considerably the digestibility and probably the consumption of the steam treated bagasse.
Molasses was largely used before 1975 and it seems that, if no big changes occur in the oil price, it will again be available for animal feeding.
Dried yeast tested as a protein source for ruminants, totally substituted cotton seed and soybean meal for beef and dairy cattle. Consumption of up to 4 kg/animal/day was not detrimental to the animals. The possibility to take off 40 percent of dried yeast, without affecting alcohol production, opened a new set of opportunities for the utilization of this source of protein. The strategy towards yeast production in relation to alcohol will be decided by international prices and Brazilian internal policy. The “Usina Santa Luiza”, one of the alcohol producers in the State of Sao Paulo, has a daily production of 4 tons of dried yeast, which, over the entire sugarcane harvesting season, gives about 800 tons (1983). The producers mentioned export of 250 tons to UK in 1983 and about 1 000 tons in 1984.
Stillage as it comes after distillation (2 to 7 percent of dry matter) has also been used as a palatability agent for low quality forages. Corn husks and cobs 50 percent (W/W) and stillage 50 percent (W/W) had a 10 percent increase in nutritive value compared to the first one alone. Stillage has been used in mixtures with low quality forages and ensiled. Some mixtures balanced in nutrients can constitute a complete ration.
Concentrated syrup (± 48 percent of dry matter, pH = 4.5) has a detrimental effect on the animals when representing more than 7 percent of the total diet dry matter.
Two research projects dealing with sugarcane are presently in operation. One is the use of steam exploded bagasse in rations for beef and dairy cattle. The other is the establishment of an integrated system of sugarcane utilization, starting with direct fermentation in the plant without tops, distillation of the biomass and the residue given as a partial ration to the animals in the feedlot, faeces and urine producing biogas, biogas used to produce heat for distillation (or for any other kind of use) and the final residue returned to the field as fertilizer.
The use of steam exploded bagasse at temperatures of 200–210°C, pressure toward 18 kg/cm2 for 5 minutes has given promising results in terms of nutritive value measured in the laboratory and in short feeding trials with sheep and steers. Small feedlots receiving diets with 50 percent dry matter from steam treated bagasse for more than 100 days, have shown a constant drop in dry matter intake in relation to time. It was suspected that the furfural produced in the process was partially retained in the mass. Levels, in terms of free furfural in the filtrate, varied from 0.14 to 0.35 percent, the potential value varied from 0.42 to 0.66 percent and the potential furfural level in the solids varied from 0.37 to 7.59 percent. The representativeness of these figures is not yet known, but what is surprising is the large variability of the potential furfural in the solid, despite physical conditions being the same. This year it is planned to go deeper into the analyses of chemical residues produced during the process. Analyses of the fibre portion that represents 91.6 percent in the dry matter expressed as Neutral Detergent Fibre in the raw bagasse, drops to 67.2 percent in steamed bagasse.
Hemicellulose in the first case is 29.1 percent and in the second only 10 percent. Steamed bagasse mixed with corn ground grain, urea, ammonium sulphate and several other ingredients, in such a way to give more or less 30 percent of dry matter was ensiled in small plastic silos. “In vitro” dry matter digestibility and “in situ” nylon bag technique gave higher figures when compared to non-fermented steamed bagasse. This year testing will be done with animals.
The integrated sugarcane system project has just begun. Some of the initial problems in relation to the sugar level in the mass and transportation of the material have been solved. The residue left after distillation had an increase in the protein level from 1.25 to 6.8 percent. The nutritive value will be better evaluated this year when routine work will be started.
4. Perspectives
At this point it is important to find out what is happening in the country now and what kind of strategies are under way. With this in mind a profile can be drawn of the type of residues available in the near future. It is well known that Brazil has a huge sugar-alcohol industry. Its survival is very dependent upon the efficiency of utilization of the sugarcane yielded and a better use of the residues produced. It was recently said that the new alcohol distillery will be a chemical industry using renewable sources of carbon. It will be based on the conversion of starchy and cellulosic materials to single sugars which will be transformed biologically to several chemical feedstocks now produced by petrochemistry.
The first and main factor that affects production is sugarcane and sugar yield per unit of area. Recent varieties produced 20 percent more than the older ones. The variety SP 70–1143 produces 21.1 tons of sugar per ha against 17.4 of the NA 56–79. The extension of the harvesting season and the payment for the amount of sugar in the harvested sugarcane are two new strategies that will increase productivity and total production.
At the industrial level new technologies have been applied and many others are under way in different sugar mills or distilleries. The Bagatex Industry installed in the “Usina Santa Lydia” in Ribeirao Preto - Sao Paulo, developed a project to reduce bagasse moisture from 50 to 20 percent and actually more than 20 new installations will be working this year. The stillage production with new techniques can be reduced from 13–16 1/per litre of alcohol to 3–4 1. Recycling stillage is now largely used. Centrifuged stillage gives a product very similar to the yeast produced in the fermentation bath.
Many other new developments have been tested on a small scale, such as: a) the use of a bacteria Zymomonas mobilis instead of Saccharomyces; b) use of immobilized enzymes; c) extraction of K, lactic and succinic acid and glycerine from stillage; d) reduction of water in distilled alcohol with absorption agents like Silicalitas ZSM-5 and ZSM-11; e) extraction of hemicellulose by-products specially D-Xylose and f) saccharification of cellulose with the yeast Pachysolen tannophilus.
One question that can be raised is, if these technologies will change the relation in many cases of product to byproduct or residue? What will remain for animal feeding will be the result of the new technologies applied. We can guess that whole sugarcane will still be largely used with the addition of some source of nitrogen. Sugarcane tops, if available, will only be used in very specific situations. The situation of molasses, a strategic byproduct, will be uncertain. Low moisture stillage (free of K), or centrifuged stillage, probably would substitute molasses and probably there will be plenty of yeast produced in different ways.
La zafra de 1985/86 produjo 125 milliones de toneladas de caña de azücar, 7,8 de azücar, 5 de melaza y 12 billones de Litros de alcohol.
La caña entera es empleada como forraje en lecherias y en unidades de engorde. El uso del cógollo es limitado en el periodo de sequia. El bagazo fresco se ha empleado en periodos criticos. La melaza era muy utilizada antes del 1975 y podria ser empleada de nuevo si el precio de petróleo se mantiene bajo. La producción de levadura como subproducto del alcohol ha brindado una fuente importante de proteina para los animales.
El proyecto más importante que se está desarollando ahora es el tratamiento del bagazo con el vapor a una temperatura de 200–210°C y una presión de 18 kg/cm2 durante 5 minutos. En ensayos con bovinos de engorde se ha notado una disminución constante del consumo de materia seca que podria ser debido al contenido de furfural.
En el futuro la utilización de la caña de azúcar y sus derivados en la alimentación animal en Brasil será dependiente de las nuevas tecnologías utilizadas en la industria azucarera particularmente dentro del marco del programa de producción de alcohol.
