From the energy point of view, for granting purposes of enterprises in the energy sector, biomass is every renewable resource originating from of organic matter (of animal or vegetable origin) that can be used in the production of energy. As well as the hydraulic energy and other renewable sources, the biomass is an indirect form of solar energy. The solar energy is converted in chemical energy, through the photosynthesis, base of the biological processes of all the live beings.
That chemical energy can be liberated directly by combustion, or converted through some process in other energy sources such as alcohol and vegetable coal. Taking advantage of 1% of the total of the incident solar radiation approximately on the Earth, it is considered that annually are produced, for the photosynthesis process, about 220 x 109 tons of biomass, what is equal to an energy of 2 x 1015 MJ, or is more than 10 times the global energy consumed a year in our planet (SMIL,1985). THE total of the existent energy in the vegetable covering of the Earth is esteemed as being 100 times the current consumption of energy along one year in the Earth. Although the great part of the planet is without forests, the amount of existent biomass in the earth is in the order of two trillion tons; what means that about 400 per capita tons. In energy terms, that relatively corresponds to 3.000 EJ a year, in other words, eight times the world consumption of primary energy (in the order of 400 EJ a year) (RAMAGE; SCURLOCK, 1996).
One of the main advantages of the biomass is that, although the reduced efficiency, its use can be made directly, through the combustion in ovens, kettles, etc. For the raise of the efficiency of the process and to reduce impacts socioambientais, it has been developed and improved more efficient conversion technologies, such as the gasification and the pyrolysis, also being common to co-generation in systems that use the biomass as an energy source.
In the medium and long term, the exhaustion of non renewable sources and the environmentalpressures can leaverage larger energy use of the biomass. Nowadays, the biomass has been systematically used in the generation of electricity, mainly in co-generation systems and in the supply of electricity for isolated demands of the electric network system.
Types of Biomass
The firewood was the first energy source used by the man for the obtaining of the fire that, consequently, that passed to be used to heat up and to illuminate the atmosphere, to cook and even to defend from ferocious animals.
The development of the firewood combustion techniques became the energy base of the old civilization, taking to the development of important activities, such as: glass production, foundry of metals, ceramic among others.
The firewood has great importance in the Brazilian Energy Matrix, representing about 10% of the production of primary energy. The firewood can have native or reforestation origin.
The firewood can be obtained through the vegetable reforested areas extration or native forest. It is a raw material that is still being used today for, approximately, half of the population of the Earth in fireplaces, furnaces, firewood stoves, kettles in industries, because it is a low cost energy source. Consequently it has been receiving the denomination of the poor energy for being significant part of the energy base of the developing countries, getting to act up to 95% of the energy source in several countries. In the industrialized countries, the contribution of the firewood gets to the maximum of 4%.
About 40% of the firewood produced in Brazil is transformed in vegetable coal. The residential segment is the one that largely consumes the firewood (29%), after the coal production. Usually it is destined to meal cooking in the rural areas. An eight people family approximately needs of 2 m3 of firewood a month to prepare their meals. After that, the industrial section closely appears presenting about 23% of the consumption. The main consuming industries of firewood in the country are the food and beverage, further than ceramic, paper and cellulose.
The native forest has always been a firewood source, that seemed to be inexhaustible, due to the amount generated in the enlargement of the agricultural border. The devastating form which it was explored left the country in critical situation, in several areas where abundant forest coverings existed, concerning the degradation of the soil, alteration of the system of rains and resulting desertification. The substitution of the native forest firewood by reforestation firewood have been growing every year, being the eucalyptus the main tree cultivated for this purpose. After that, comes the pine wood, commonly used because it has low amount of water in its composition, being characterized as good heat producer. The sawdust and the shavings (vestiges produced in the sawmills or resulting the cut of wood) present better combustion because they are small in relation to the trunks.
In the firewood production for commercial ends, a part of the tree (trunks and fine branches) is rejected constituting the forest residues. Besides, the industries that do not use the wood for energetic purposes, such as the sawmills and the industries of furniture, produce industrial residues like tips of logs, and sawdust in different sizes of particles and densities, that can have energy uses.
The vegetable coal is obtained from the burn of the wood in special ovens, done of masonry, that reach a medium temperature of 500ºC. Unlike what it happened at the industrialized countries, in Brazil, the industrial use of the vegetable coal continues being broadly practiced. Brazil is the largest world producer of that energy input, assisting about a quarter of all energy consumed in the Brazilian blast furnaces. In the industrial sector (almost 85% of the consumption), the iron-cast, iron, steel and iron-leagues are the main consumers of the coal firewood, that work as reducer (vegetable bun) and as energy at the same time. The residential sector consumes about 9% followed by the commercial sector containing the barbecue restaurants, pizzerias and bakeries suming 1,5%. It is also used, in the locomotives to obtain steam still existent in some places of Brazil ..30% of that coal is obtained through reforestation and 70% came from the deforestation of large areas of the savannah in the north of Minas Gerais, south of Bahia, and in the area of Carajás, Pará and in Maranhão.
It is important to notice that the output in mass of the vegetable coal in relation to dried firewood put into the oven is of approximately 25% in the masonry furnaces.
Inside of the tissues existent in the leaves or stem of some vegetate, there is an oily substance that can be used to burn. Also, it can be obtained the substance of some seeds that, when passing for a mechanical process of pressure, they are broken. After this mechanical process, it is applied a chemical process that uses a liquid solvent to extract only the oil. Later, that oil will be refined, clarified and deodorized losing, as a consequence, the unpleasant odor.
Brazil has a great diversity of oleaginous vegetable species which can extract oils for energy purposes. Some of these species are native (buriti, babassu, castor oil plant, etc.), some are of short cycle cultivation (soy, peanut, etc.) and there are others of long cycle or perennial cultivation (palm oil). Among them can be mentioned: Avocado, Cotton, Peanut, Coconut, Palm oil, Castor oil plant, Corn, Soy and Urucum.
Nowadays, it is studied the possibility to substitute the diesel by different amounts of vegetable oil that represent an alternative to the diesel oil use in interns combustion, automotive and stationary motors. Mainly, the use of the castor oil plant oil and palm oil in the automotive motors, contributes significantly, to the decrease of the pollution. Besides the socioeconomic aspects implicated, this practice can make possible the maintainable development, especially in the rural communities.
The sugarcane is original from Asia and it was introduced in America, by Christopher Columbus, in the middle of 1492. Historically, the sugar cane has become one of the main agricultural products of Brazil, and has been cultivated since the colonization. It is affirmed that Souza's Martins Afonso fit the installation of the first mill, in São Vicente's captaincy - SP, in 1533. The second was installed in Pernambuco, by Jerônimo of Albuquerque, in 1535. Brazil is the second producer country of the world with huge sugar cane plantations, including the states such as: São Paulo, Paraná, Alagoas, Minas Gerais, Pernambuco, Mato Grosso do Sul, Mato Grosso, Rio de Janeiro and Paraíba. Brazil stands bellow below India that is still the first world producer of cane.
Due to the greatness of the numbers of the alcohol and sugar cane production sector in Brazil, the sugar cane is treated as the main type of biomass energy, base for the whole agri business, containing 350 industries of sugar and alcohol and 1.000.000 direct and indirect jobs throughout Brazil.
With the extracted broth, through mills, sugar cane juice can be produced, pinga (alcoholic beverage), sugar, raw brown sugar, tractors alcohol combustible for, cuisine alcohol, vinasse and pulp.
Nowadays, the pulp of the cane is used as fuel for the electric power generation in turbines of steam.
Recently, with the entrance of the Kyoto Protocol , the sugar cane disclosed another attention,due to peculiar characteristics related to the capture of carbon. Some studies seems to be developed in Unifei aiminf determine the percentile of capture of the sugar cane.
In Brazil, the use of the alcohol begun in 1975 with the creation of "Pro alcohol" by the Federal Government, program that incentivates the plantation and controlled exploration of the sugar cane. The initiative resulted from the consequences faced by Brazil after the Crisis of the Petroleum that happened in 1973, when the producting countries such as Iraq, Kwait, Iran and Saudi Arabia overvalued the purchase of the petroleum, in other words, they increased a lot the price avoiding, as a consequence, that many countries could import it. With that, Brazil was forced to begin several research studies on alternative sources of energy, and due to it since 1978, the alcohol has been used as fuel for motors.
It is valid to stand out that in the beginning of the "Pro alcohol" there was a mixture of alcohol in the gasoline reducing the quality of the fuel and causing, in most of the cases, damages like accentuated corrosion in some parts of the motor, for instance, tank of fuel, carburetors and exhaust.
To surprass the relative problems to the wear of components by corrosion, the automobile industry tries to present to the market alcohol powered vehicles as efficient as the ones powered by petrol, besides the advantage of being less pollutant due to the fact they emit less carbon gas.
The alcohol becomes, though, an important agent for the decrease of the atmospheric pollution when compared with other petroleum derived combustible.
Now it is in study phase the application of the ethanol as a source of power for the fuel cells. Japan, a defensive country of this technology, sought Brazil recently for definition of a bilateral agreement about the application of the alcohol in the fuel cells.
The Pro alcohol, National Programs of the Alcohol, is the largest commercial program of biomass used for the production of energy in the world. It presented the initiative of larger world success, in the substitution of the petrol powered automotive sector, by the use of the alcohol as the only fuel in the vehicles moved by moisturized alcohol. Nowadays there are about 4 million vehicles that use this exclusively sugar cane derived fuel, representing 40% of the national fleet. And do not forget the important paper carried out in the solution of the problem of the octane boostering of the gasoline, substituting the lead tetraetile, highly harmful to the human health, in the mixture gasoline-alcohol (gasohol), today well accepted and used everywhere.
In 1975, as an attempt of softening the energy problem, Pro Alcohol was created by the Brazilian Government with the objective of reducing the importation of petroleum. In that time, the world lived the first crisis of the petroleum. Brazil bought 80% of the consumed petroleum and with the discharge of prices between 1973 and 1974, the country had to face the growth of the import that passed from US$ 600 million for more than US$ 22 billion. The program made possible the continuity of the provisioning of automotive fuels based in the use of the biomass, through the incentive of the alcohol production of in the sugar plants, in independent distilleries, and the leaverage of the appropriate motors development for the automobile industry, and of an extensive net of distribution of the fuel.
Later, the decline of the prices of the petroleum became alcohol a little more competitive, demanding subsidies for the maintenance of the program. In the last 3 years the politics of elimination of subsidies, motivated a certain disorganization that has been lived and discussed, in search of a new balance among the several actors of the national energy scene. Now, it is low the production of new vehicles to alcohol, but the recent elevation of the international prices of the petroleum creates promising perspectives for the alcohol combustible. Further alcohol has been having its recognition in the international community as one of the possible solutions to the environmental problems standing out as one of the best candidates to be supported with financing politics (Mechanisms of Clean Development - MDL), according to the established in the Kyoto Protocol.
Now Brazil faces a retaking of the alcohol powered automobiles with the creation of the bifuel"cars," known as "Flex". The experience comes if showing quite productive the fleet of vehicles "bicombustivel" presents significant growth taxes.
Cogeneration in the sugar and alcohol sector
From its implantation in larger scale starting from the half of the century XX, the industries of the sector developed their own facilities of electric generation, from small hydroelectric uses, diesel oil, and later face to the electric power unavailability and their costs, generation systems were adopted, in cogeração process, fitting to the needs of the industrial processing of the cane of sugar, using the pulp.
However, as the amount of the pulp produced is very high (approximately 30% of the cane), a great potential exists for generation of electricity for commercial sale.
In agreement with several accomplished studies, the potential of generation of electricity starting from cane pulp in Brazil is esteemed in approximately 4.000 MW with technologies commercially available. The alterations in the rules of the electric power market are creating better conditions for the offer of energy for independent producers, what could be attractive for the sector that is experiencing changes and accompanying the technological development little by little, to increase its production of electricity.
The rural residues include all of the types of residues generated by the productive activities in the rural areas, which are: the agricultural residues, forestal and cattle derived. The agricultural residues are those produced in the field, resultants of the collect activities.
The quantification of the rural residues is based in the crop indexes, that expresses the percentile relationship between the total amount of biomass generated by planted hectare of a certain culture and the amount of product economically lucrative.
The great part of the agricultural residues is left in their own cultivation land, serving as protection to the soil or as nutrient supplying fertilizer for the soil.
Forest residues are considered those generated and left at the forest as a result of the activities of extraction of the wood. It is inferred that are left at the forest about 20% of the mass of a tree. It is considered that a big potential of energy use of forest residues exists in Brazil, once the extractive activities of the wood not only for the production of coal but also other non energetic use, are developed in an intensive way from the North to the South of the country.
The residues of the cattle are constituted by manures and other resulting products of the biological activity of the bovine swine, bovid and other kinds of cattle, whose local relevance justifies their energetic use. This residue type is important raw material for the biogas production that can have a relevant paper in the energy supply, mainly for the cooking in the rural areas.
We lived in a society that stimulates the consumption and the production in great scale. The philosophy of the disposable and of the excess of packings prevails in several sectors of the market that means more waste directly. In 1995, Brazil produced 241.614 tons of garbage a day, and 76% were exposed to open door garbages spots (IPT / CEMPRE). According to a public company of sanitation, there is a growth around 5% a year in the amount of generated garbage. Great part of the garbage is still not collected staying in the residences. The production per capita of garbage today rotates around 600g for inhabitant/day and there are few sanitary embankments or controlled embankments in Brazil. In São Paulo, for instance, it is considered that each inhabitant produces 1 kg of garbage a day. This value tends to grow, turning the problem of the relentless and irreversible garbage, legitimating the need of effective and effective alternatives.
Serious problems caused by the precarious final disposition of the garbage are the spread of diseases, the contamination of the soil and of underground waters by the pollution of the gas methane (generated in the decomposition of the present organic matter in the garbage), and the lack of space for the storage, among others. The tenor of organic matter (C, H, THE, N) of the Brazilian garbage is about 60% assotiating to it a good energy potential. The medium Inferior Calorific Power (ICP) of the residential residue is about 1.300 kcal/kg (5,44 MJ/kg) According to the used technology and to the physiochemical composition of the residues, it is considered the production of 0,035 MW/tonelada of garbage, through incineration.
The recovery of energy starting from the garbage has two great slopes:
1. The recovery of the gas methane for generation of energy (the anaerobic decomposition can generate 350 to 500 m3 of gas methane per Brazilian garbage ton), with investments in controlled embankments, that it can be complemented by the selective collection or after-collection selection seeking the recycling and the decrease of the volume to be covered with earth.
2. Incineration of the garbage seeking their reduction, with recovery of energy.
Industrial residues: They are considered the ones coming from the agricultural and forest products developement and the residues of the use of vegetable coal in the metallurgical sector of iron-cast iron and steel, the furnace gas to vegetable coal.
The wood sawmills and furniture industries produce residues from the handling of logs. The types of produced residues are peel, shavings, slabs, sawdust, and others. The industries of food and beverage produce residues in the manufacturing of juices and liquors (orange, cashew, pineapple, sugar cane, etc), in the handling of rice, coffee, wheat, corn (corn-cob and straw), peanut, chestnut, etc.
In the paper and cellulose sector there are paper manufacturers and cellulose industries, and also integrated industries, in other words which produce not only paper but also cellulose. There will be in these cases differences in the types of produced residues, however, in general this sector produces residues like peel, shavings and leaching. There are 220 companies in Brazil with industrial plants located in 16 states, using reforestation wood, of the species eucalyptus (62%) and pinus (36%).
The metallurgical sector powered by vegetable coal also possesses units of iron-cast, iron and of steel, and integrated units, that produce iron-cast, iron and steel. The iron-cast is an intermediate product for the production of the steel, and an important exportation product. The blast furnace gas is produced during the reaction of the carbon of the vegetable coal with the iron of the iron ore, and is introduced again in the process, being its heat reuse availabe. The metallurgyof the vegetable coal is responsible for about 30% of the Brazilian metallurgical production and it is concentrated mainly in the State of Minas Gerais, with some units in the Espírito Santo, Maranhão, Pará, Pernambuco, Rio Grande do Norte and Mato Grosso do Sul.
Nogueira, Luiz Augusto Horta & Lora, Electo, Dendroenergy: foundations and applications
DÉFÈCHE, J., The urban residues: a fuel – how to burn it and to recover its energy. "Energy - Alternative Sources" periodical, vol. VI