1) Introduction
2) Energy integrated systems
3) The SAU'S energy integrated system
4) Comments about the SAU'S energy integrated system
5) Proposals for future activities in the project
6) Conclusions
7) Bibliography
C. C. de Carvalho Neto (NATRONTEC Estudos e Engenharia de Processos)
Rio de Janeiro - RJ - Brazil
Paper No. 9413
The Northeast region of China has approximately 1.99 million square kilometers and is formed by the Provinces of Heilongjiang, Jilin, Liaoning and Inner Mongolia. Almost 110 million people live there and the region's economy is heavily based on agriculture, with major cultures being corn, wheat, sorghum, rice, soybean, potato, sugarbeet, tobacco, cotton and bean. The Liaoning Province is one of the most important provinces in the region, since it is the most populous and industrialized and produces approximatelly 12 million metric tons of grains per year (1) .
The Northeast region is very cold from November until March, with temperatures variyng in the range from -5° C to -32° C. Energy supply in the region is scarce and the energy prices are very high. The energy shortage makes living conditions there very difficult and is a big constraint for the regional development. The rural area is more affected by the energetic problem and it is very common the utilization of tractors and trucks by less than 200 h per year due to the lack of liquid fuels. Approximatelly, 50% to 75% of the crop residues are used for home heating, which is causing serious problems related with decreased land fertility, increased air pollution and soil erosion. Electricity availability is not reliable and black outs are very common in the region. All these energetic problems strongly affect its economic and social developmental).
To increase local energy availability is a important task for the. Chinese government and a rational explotation of the biomass can play a key role in these efforts, since will strengthen the natural inclination of the region for agriculture.
Biomass utilization in the Northeast region of China needs also to meet the requirement for higher food production. Due to the large population, it does not seem reasonable to grow, like in some European projects (2, 3), cultures only for energy production or industrial utilization. Food production is a very important matter for China, mainly in the Northeast region, where adverse weather conditions make possible to carry out agricultural activities only from April to October.
To increase the food and energy availability in the Northeastern provinces, the Chinese government is developing a large research and development programme, which involves institutions like the States Ministries of Agriculture and Education, the Liaoning Province Ministry of Agriculture and the Liaoning Provincial Committee for Science and Technology (PCST&T).
The Shenyang Agricultural University (SAU) has been supported for more than 10 years by those institutions and research programmes were carried out trying to develop new sources of energy for rural regions.
In April 1989, the UNITED NATIONS DEVELOPMENT PROGRAMME (UNDP), as the financial agency and the FOOD AND AGRICULTURAL ORGANIZATION OF THE UNITED NATIONS (FAO), as the executing agency, signed a contract with the Chinese government to develop a new project, entitled "Establishment of an Energy Integrated Demonstration Base for China's Cold Northeastern Region".
The main project purpose was the establishment of a farm, in SAU's campus, to be used as a demonstration site for the concept of integrated food and energy production, using only direct sun light and biomass as energy sources.
The development of the integrated concept and its dissemination throughout the whole Northeast region of China is expected to be a great contribution to increase the production and utilization of non-fossil energy in rural areas. At the same time, it will be possible to contribute for the regional economic and social development. Benefits are also expected in soil fertility and ambiental pollution.
The large population and unfavorable climate increase the requirement for a better utilization of the available agricultural land in the region. As consequence, its explotation needs to be optimized and the association of food and energy production can give a strong contribution to attain this objective.
Use of more efficient technologies for energy production and explotation will allow the reduction, by the Chinese farmers, of direct biomass burning for home heating. Consequently, more crop residues can be returned to the soil and, as result, land will be ameliorated due to the higher organic matter content. Nowadays, the low organic matter content in the soils of the Northeast region, lower than 2%, is causing serious reduction in the agricultural productivity and decreased food production.
Other advantage from reduction in biomass burning for home heating is the abatement of the serious air pollution problems, which are caused by the enormous quantities of biomass burnt and are make heavier by the inefficient technologies currently used by the farmers.
Through this project, SAU's staff will be kept in contact with advanced technologies of biomass utilization for energy production, in an integrated approach. At the same time, new knowledge will be generated and valuable information disseminated throughout the Chinese farmers, mainly those situated in the Northeastern provinces.
The energy integrated systems are under investigation in various parts of the world, like USA, European Comunity (EC) and Brazil (2, 3, 4, 5, 6). In these systems, different technologies are associated in the same productive site to get the more efficient biomass utilization, according to the purposes of each project. In this way, pyrolysis units, 'biodigestors, ethanol plants, solar energy collectors, boilers, mills and other equipments are putting to work together and out streams from one is, many times, the raw material for the other.
USA and the European countries are now facing serious problems (high subsidies and ambiental pollution) related with excessive production of several agricultural commodities. To keep the commodities prices in a satisfactory level, the governments are supporting theirs farmers with strong subsidies and, at the same time, reducing the agricultural area dedicated to food production. A good example of this situation is the 40 millions tons of agricultural commodities surplus in Europe, in 1988, which required a global amount of 25 billion ECU in subsidies (2).
It is estimated that EC will need to take out about 20 million hectares from food production. Wishing to keep this land productive and to avoid worstening of the social problems of rural people (unemployment and lower incomes), EC decided to launch a big programme for cultivation of energy and industrial crops in that area (2-). This programme is called "Large European Biomass Energy Network" (LEBEN) and is supporting the development of projects, at pilot and industrial scales, in many European countries (Italy, Scotland and other). LEBEN's proposal is the increasing of biomass utilization, at regional scale, for energy production, associated with the production of industrial products like paper pulp, paper, sugar, ethanol, organic fertilizers, animal feed stocks, metallurgical charcoal, activated charcoal and others (2, 6, 7).
The LEBEN project at Basilicata (Italy) plans to produce pulp for paper (250 m3/day), ethanol (500 m3/day) and eletricity (400 MW), using sweet sorghum as the main raw material. Sweet sorghum will be cultivated in 30, 000 ha of irrigated land and 20, 000 ha of land now used for cereal growing. Construction of a sea-water desalination plant (350, 000 m3/day) is also planned (7).
Other LEBEN project based on the utilization of sweet sorghum, as one of the raw materials, is being developed in the Abruzo region (Italy). Sweet sorghum, miscanthus, Cynara, Robinia and short rotation forests are being investigated as raw materials for future industrial production of pulp for paper. charcoal pellets (12 t/day) and eletricity (up to 50 MW) (8).
An alternative fuels programme, based on biomass utilization, is being carried out by the United State Department of Agriculture and aims at the increasing of petroleum substitution, the improving of air quality, the mitigation of global warming and the stregthening of weak farm economy (5). Universities and private companies has also been engaged in the demonstration, at pilot and industrial levels, of the technical and economical feasibility of energy integrated projects using biomass as raw material. As examples, it is possible to list the Ranch Energy System (6), the Bioenergy System (9) and the Nebraska University System (10).
The Ranch Energy System was projected to produce bovine meat, dried distillers grains, anhydrous alcohol and carbon dioxide. Methane produced through anaerobic fermentation of cattle manure was selected to be used as energy source to run the ethanol plant. Sweet potato was choosen to be used as raw material in the summer time, while fodder beets and fodder turnips were selected as winter crops. The Ranch System was designed to produce, in a yearly basis, 50 MM gallon of alcohol and 120 million pounds of beef. All the raw material required for ethanol production can be produced in a farm with 60, 000 acres of area.
The University of Nebraska (Lincoln - Nebraska - USA) is testing an integrated system (pilot scale) based on the utilization of corn as raw material. Ethanol, greenhouse products, dried distillers grains and pork were selected to be produced in the demonstration farm. Methane from animal manure biodigestion and solar light provide energy for the project, which contains one ethanol plant, one biodigestor and one greenhouse.
Brazil is carrying out an intensive programme of ethanol production using biomass (sugar cane) as main raw material, with approximatelly 12. billions of fuel ethanol being produced each harvesting season (11). Different of some European projects, associated food production has been a major concerning of many research projects in Brazil, since sugar cane cultivation is reducing availability of good land for food production. At the same time, it is being more and more economically important to associate the ethanol production with manufacture of food (bovine cattle, fish and other) and other products, like biogas and bio-fertilizers (4).
Associated production of energy and food is a very important matter for the underdeveloped countries, where large areas of land are frequently used for cultivation of energy crops and commodities for exportation. Simultaneously, soil fertility needs to be improved, together with environmental protection strengthening. The SAU's Energy Integrated System (SEIS) was designed taking into consideration these aspects (see figure 1) and a detailed description of the project is now presented.
3.1) The concepts of the system
PETS was conceived to be a demonstration site of the technical and economical feasibility of the energy integrated concept, wishing to spread it, in the near future, throughout the rural areas of the Chinese Northeast region.
The system was designed to operate year around as a typical Chinese farm, with all the energy required for farming operations being provided by biomass and sun light. No other sources of energy, such as petrol, coal and diesel oil are expected to be used at the project site.
Production of liquid and solid fuels was considered of great importance, as it makes easier energy handling and storing in high density forms.
According to this principle, an ethanol factory and a pyrolysis unit were selected to be erected in the demonstration farm, to supply carburant fuels for cars, tractors, trucks and agricultural machines. Charcoal from the pyrolysis plant will be used as fuel for steam production in the ethanol distillation apparatus. Electricity for equipment operation will be provided by a biogas fueled cogenerator, while solar energy and steam, produced in the cogenerator and in the ethanol unit, will be used for houses heating,
Ethanol has been, since 1975, largely used as fuel in Brazil as hydrated alcohol (92.6% w/w) or as anhydrous alcohol mixed with petrol. Approximatelly 12 billions liters of alcohol are produced annually in Brazil and more than 4.5 millions cars are powered by hydrated ethanol. Almost all the petrol used in Brazil is mixed with anhydrous alcohol, with ethanol concentrations varying from 30 to 20%. Many countries, such as U.S.A. and Latin American and Caribbean countries, are using ethanol as fuel, in fossil fuels substitution and environmental protection programmes (12, 13),
Pyrolysis is an advanced technology under intensive development in many countries (14) and domination of this technology by China would give a good contribution to solve its energetic problem
Animal, green- and humanhouses were constructed in the project site and will be used for farming activities and training. Insulation materials were used in the construction of almost all houses to reduce heat losses, mainly in the winter season. Temperature profiles, inside and outside, of some houses will be measured in a whole year basis These data will be used to evaluate the buildings efficiency in energy preservation and also to analyze the performance of the heating systems used.
A glasshouse, made in Italy and equiped with a carbon dioxide admission system, was erected at the project site. It was equiped with instruments for solar radiation (global and direct), temperature and ground humidity measurement and will be fed by carbon dioxide produced in the ethanol unit. Firstly, diesel oil will be used as energy source for the glasshouse, since it was not possible to purchase a biogas fueled one. It is intention of the project staff to adapt the glasshouse engine for biogas utilization. By this way, it will be possible to preservate the basic concept of the project, that is the no utilization of external sources of energy.
Sorghum, grain and sweet varieties, maize and potato will be sowed in the project land and used as raw material for ethanol and meat production, while the lignocellulosic residues will be processed in the pyrolysis plant and/or left in the land, to improve soil fertility.
Sweet sorghum utilization in the context of energy integrated system will be specially investigated in the SEIS, since it can be used, simultaneously, as energy source (ethanol) and as feedstuff (grains). SAU developed new and more productives sweet sorghum varieties. The best one is called number 2 variety and can produce up to 70 t/ha of stems and 5 t/ha of grains. Sorghum grains can also be used to produce a typical and expensive Chinese liquor.
Sweet sorghum harvesting period begins, normally, at the end of September and is, approximatelly, three weeks long. This short period is a restriction for a more intensive utilization of sweet sorghum and makes necessary to process other raw materials in the demonstration farm.
A grain sorghum variety commonly cultivated in China requires less than 100 days for growing and can be sowed at the end of June. As a consequence, land can be previously destinated for potato growing, since this culture is harvested at the middle of June. In the periods where sorghum and potato are not being harvested, gamed corn grains will be processed in the ethanol plant.
Sequencial utilization of maize, potato and sorghum is expected to make possible a whole year operation of the ethanol plant. The major concern is the winter season due to its very low temperatures, which makes plant operation a very hard, but, at the same time, challenging task for the project team.
A methodology for economical analysis of all activities in the demonstration farm was established and is being applied to verify SEIS's economical aspects. This is a very important project activity, since results from the economical studies will be considered for the final definition of the demonstration farm's conception.
At the present moment, China is developing a great effort to construct a more efficient economy and the project needs to take this into consideration. Otherwise. it will be much more difficult, if not impossible, to spread out the energy integrated concept and correlate technologies to the farmers.
Products from the demonstration farm (meat, vegetables, flowers, liquor, medicines and other) are being sold at market prices and funds used for farm supportation. Through these procedure, the project staff has an excellent opportunity to obtain reliable data for the economic analysis and also can contribute to support the demonstration farm's operation.
Past and current activities yet carried out at the project site show that production of pork is more economically advantageous than beef or milk production. Flowers growing also generates higher profits, when compared with vegetables cultivation. Preliminar analysis indicated that liquors manufacturing is more interesting, from the economical point of view, than production of fuel ethanol. All these results can not be considered as final ones, as they were obtained from non integrated operations arid studies; in fact they can change significativelly, when those activities come to be developed in an integrated system.
3.2) Components of the demonstration farm
The demonstration farm has 30 ha of arable land and an area of 10, 290 square meters was destinated to the erection of the operating units and buildings. According to the preliminary mass balance, it will be possible to produce, each year, 500 liters of carburant alcohol, 1100 liters of liquors, 3, 900 m3 of biogas, 145 ton of coal, 4, 380 liters of bio-oil, plus meat and other farm products. -
To satisfy the project requirements, the demonstration farm was equiped with the following components: one ethanol plant, one pyrolysis unit, three biodigestors, one cogenerator, one glasshouse, three green-houses, three animal houses, two human houses and one training building.
One of the human houses is a 55 square meters construction and is being used as watching house. It has one meeting room, one sleeping room and one bathroom and was designed to be an energy saving building, with insulation materials (polyurethane and residual charcoal) being used in its construction. Water and air active heating systems accomplished with solar energy collectors were installed in the watching house.
The second human house was constructed at the West side of the pig house and is very simple and small. It has only two rooms and insulation materials were not used in its erection. Hot air from a stove placed in this house is used to warm the pig house North wall.
The training building is a two floors construction and has a total area of 267 square meters. It was designed to be an energy saving building, with insulation materials being used in the North wall. It has two solar energy collectors in the South wall and one in the West wall. These systems are passive ones and will be used for air heating. Two small green-houses were constructed in the South wall, at the first floor. The training building will be used, mainly, for classes, training and research. The research will include a whole year temperature recording, to check if the concepts applied in the building design are sufficient to keep it habitable, mainly in the winter times.
Two of the three animal houses were constructed with insulation materials in the North wall, while the third one is very simple and was designed without take into consideration any energy saving principle. The animal house attached to the human house is 100 square meters large and has capacity to raise up to 70 pigs. The second insulated house and the simple one can receive 50 sheep, each one.
The green-houses were erected according a typical Chinese design using plastic sheet as South wall and straw blanket to cover it. The North, East and West walls were made with bricks. The total area of the green-houses is 360 square meters and two of them have systems for air circulation between the internal atmosphere and the underground. At day, the air heated by the sun light is used to increase the underground temperature and, at night, the reversal process occurs. All green-houses are being used for cultivation of vegetables and flowers. Based in market conditions, other plants will also be cultivated.
The glasshouse is 50 square meters large and will be destinated for plant growing experiments using air enriched with carbon dioxide. Products from the glasshouse will also be sold.
The ethanol unit has capacity to produce 500 liters/day of carburant alcohol using sweet sorghum stalks or grains as raw materials. Other grains and molasses can also be processed. The plant can also produce liquors from starchy materials (sorghum grains, maize, potato and other), but not simultaneously with carburant alcohol. Product selection will be made according to the market conditions.
Carburant ethanol will be produced by a continuous process developed by SAU and previously tested at pilot scale, which is based on the utilization of yeast immobilized in calcium alginate beads. The fermentation reactor has a special design to avoid beads compression and to facilitate gas flowing.
Liquor will be manufactured according a traditional Chinese technology, since preservation of product taste is a major concern. This tecnology is based in the enzymatic saccharification of starch, with fermentation and hydrolysis being carried out simultaneously. Sorghum grains will be the main raw material, as it gives a product with better quality, when compared with maize and potato.
The pyrolysis unit has capacity to process 1.2 t/day of lignocellulosic materials and was designed by the Biomass Technology Group (BTG - Enschede - The Netherlands). The BTG's technology was selected due to its high level and price compatibility with the project budget. The plant erection at the project site is expected to be finished at the end of 1994. Sorghum bagasse, maize straw and wood residues (Robinia) will be the main raw materials of the pyrolysis unit.
The total volume of biodigestion is 61 m3 (two reactors with 8 m3 and one with 45 m3) being sewage and vinasse produced in the ethanol unit the main raw materials. The biggest biodigestor was designed with a new biological heating system developed by the SAU team. In this system, the biodigestor pipes are warmed by heat generated in the natural fermentation of solid residues from the beer industry. Biodigestor heating is an important question, since at the winter time biodigestors are not used in the Northeast region of China due to the very low temperatures. With the heating system, it is expected an extension of the biodigestors operation period.
The biodigestors were constructed based on traditional Chinese design, since China has more than 10, 000 medium and large size biodigestors in operation (15) and, together with India, has the largest experience in biodigestors design, construction and operation in the world. The main difference of SAU's biodigestors, when compared with the traditional Chinese design, is the new biological heating system. A cogenerator, fueled by biogas, was purchased from TOTEM (Italy) and installed at the demonstration farm.
3.3 - The energy network
The energy network of SEIS now presented is not yet the final conception, as it can be modified to be in agreement with the technical and economical information generated by the project.
Carburant ethanol will be used to run an ethanol fueled van made in Brazil and also a tractor, which diesel engine was adapted, by the project staff, to consume diesel oil mixed with ethanol. Ethanol will substitute petrol completelly in the project site and will also contribute to reduce diesel oil consumption by the agricultural machines.
The ethanol fueled van is being used for persons and materials transportation, while the tractor is being tested, in bench and field experiments, at the demonstration farm.
Solid residues from sweet sorghum and other raw materials will be sent to the pyrolysis unit for bio-oil, charcoal and gas production. Gas will be consumed in the self pyrolysis unit, while charcoal and bio-oil will be used, respectivelly, for ethanol distillation and diesel oil substitution.
The vinasse generated in the ethanol unit will be used, together with human and animal manure, as raw material for the biodigestion unit. Vinasse can also be used as fertilizer. Eletricity produced in the biogas fueled cogenerator will be used to run some equipments, while steam will be consumed in house heating and/or ethanol distillation. Biodigestor heating is another option for steam utilization. Solar energy from collectors will be used at homes for air and water heating.
When compared with other similar systems, SEIS has a more complex and integrated network of processes, raw materials, energy and products. According to the principles of the SAU's system, the farm is expected to work the whole year using only energy provided by the sun in a direct way (solar energy collectors) or indirect way (biomass growing and utilization).
Other key point of SEIS is its capacitation for simultaneous production of food and energy. Food is also a strategical question for China, since it has the largest population in the world and low availability of new arable land.
Utilization and integration of various production processes in the demonstration farm may be of great value for China, as will allow to bring it up to date with advanced technics of biomass explotation. As good examples, it is possible to list the pyrolysis, the ethanolic fermentation, the cogeneration and the plant growing in glasshouses.
Despite the positive influence expected in the energy and food production, the dissemination of energy integrated systems may also contribute to reduce air pollution and to increase land fertility. Biomass utilization in a more efficient way can reduce agricultural residues requirements for home heating and cooking purposes. As a consequence, more residues will be available for field fertilization and lower quantities of gases will contaminate the atmosphere.
The economic studies under development by the project are of great importance and may give a good contribution for the Chinese efforts for modernization of its economy. The knowledge generated by the project will be valuable for researchers and farmers and would provide them with a better understanding of economic analysis of agro-business. They will also be essential to select the most appropriate scales for the ethanol and pyrolysis plants, when components of energy integrated systems.
A positive impact on job opportunities and incomes, in rural areas, is also expected as an other benefit resulting from the project development and consequent dissemination of integrated energy systems.
Chinese researchers and farmers are receiving training in planning, construction, operation and analysis of energy integrated systems. At the first project phase - characterized mainly by the farm erection - the SAU's team was trained in many areas of knowledge, such as: ethanol production, pyrolysis technology, solar energy utilization, engine adaptation for ethanol utilization and economic analysis of integrated systems.
Operation of the animal and greenhouses erected at the project site is under responsability of farmers, which are sharing the profits with SAU. Farmers training is an essential requirement to spread out SEIS principles throughout the country. Without a good knowledge of the technical and economical advantages provided by food and energy production in a synergistic way, it will be very difficult, if not impossible, the assimilation, by the farmers, of the new concepts and technologies.
Requirement for high price units, such as the ethanol and pyrolysis plants, may be a serious constraint to spread out SEIS's concepts. An ethanol plant, with capacity to produce 500 liters per day, costs approximatelly US$ 10, 000 in China, while a pyrolysis unit, with capacity to process 1.2 t/d of cellulosic materials, costs, at least, US$ 180, 000. These prices are very high for individual Chinese farmers and investment sharing with neighbour farmers, in a cooperative way, may be a good solution. In this case, raw material for the ethanol and pyrolysis units may be supplied by the cooperative members, that will receive back the products and will share the profits.
In such a case, the idea of central pyrolysis and ethanol units, erected by an association of farmers, is strengthened. The biofuel and the ethanol produced in these units can be transported to the farms and used there, while the gas and the charcoal can be consumed by the plants themselves. Steam can be used for heating and eletricity generation purposes. These points are intended to be clarified by the technical and economical studies, under development in the project.
The glasshouse purchased by the project is also expensive and complex to operate. Its dissemination throughout the Chinese farmers will be dependent of aspects such as higher productivity and capacity to satisfy the requirements of special plants for more controlled ambients.
The other components of the demonstration farm (biodigestors, cogenerator and houses) require lower investment and are, probably, affordable by individual farmers.
Sweet sorghum has lower productivity, when compared with sugar cane, that can produce more than 6, 400 liters of ethanol/ha.yr, while the best sweet sorghum variety of SAU produces approximatelly 5, 200 1/ha.yr, if grains are destinated for ethanol production. These data show that SAU must keep a research programme to develop more productive sweet sorghum varieties. Probably, SAU capacitation in genetic engineering techniques will be required for this target.
Future activities of SEIS needs to be focused in the main objective of giving contributions to solve the serious problems of energy shortage and high prices in the Northeast region of China. Associated production of food is also a major question.
The aspects of environmental protection and land fertility must always be a great concern of the project, since without a good management of these matters, it will not be possible to have a sustained development of the agriculture, agro-industry and correlated activities. The enormous Chinese population requires a capacity of food and energy production, by China, that can not be impaired by fertil land sterilization. Pollution problems can not also bring threats for the desired improvement in the standard of life of the people.
The project staff needs to be increased should to keep a strong integration with national and abroad institutions which are carrying out research programmes on biomass explotation. Through this interchange, the project team will be up to date with the new knowledge and technologies. Information dissemination to the farmers needs to be also a normal procedure, since without this it will not be possible to spread out the energy integrated concepts and the project will be meaningless.
Some aspects of SEIS need special attention for the technical and economical performance improvement of the system. Among them, it is convenient to emphasize: the increase of sweet sorghum productivity, the fermentation technologies improvement, the melioration of SAU's staff knowledge on pyrolysis technology, the extension of biodigestors operation period and the more intensive utilization of energy sources available at the project site.
Higher productivity of sweet sorghum will contribute to increase the demonstration farm's capacity of producing, simultaneously, food and energy, using the same cultivated area.
The fermentation technology selected for fuel ethanol manufacturing, based on the use of yeast immobilized in calcium alginate beads, seems not to be the less expensive one, since alginate is a expensive material (US$ 7/kg, in 1990) and has low resistance for long operation periods. More simple and lower cost technologies must be investigated under its technical and economical aspects and applied in the project, if favourable results are obtained.
Liquors will be produced according a traditional Chinese technology largely adopted by industries. SAU staff has no experience on liquors production and needs to receive an intensive training on this matter, since manufacturing of high quality liquor is desirable. Future improvements on this technology also must be pursued by the project team, to increase productivity and to reduce the production costs.
SAU staff needs also to receive a strong training on pyrolysis technology, including the plant operation. Pyrolysis is being intensivelly investigated in many countries and SEIS can give a good contribution for this development, as will have, probably, the single pyrolysis unit working in a such kind of energy integrated system in whole world.
Biodigestors operation by larger periods is a very important question for the project. Nowadays, the low temperatures do not allow biodigestors operation from November until the end of May. This is a serious constraint for the project success, since biogas generation, for home heating, is more desired at this period. As a consequence, the project is recommended to give emphasis on the development of new biodigestion systems with capacity to operate during longer periods and, even, the whole year.
The use of the biological heating system mentioned in the item 3.2 of this document can contribute for the biodigestors operation period increasing. Another possibility is the biodigestors heating by hot streams generated in other components of the demonstration farm, such as the ethanol and pyrolysis plants.
SEIS mass and energy balances optimization is a matter of great importance, as it can be determinant for the technical and economical success of the project. A better integration among the farm's components and use of more productive plants and animal species would- give a significant contribution for this optimization
Reliable economic analysis of the whole energy integrated system needs to be continuouslly developed and must consider the effects of present changes in the Chinese economy, as well as the technological evolution of the biomass utilization processes.
Government support will be essential to guarantee the widespread utilization of energy integrated systems, since institutional support, more strict environmental protection laws and incentives like favoured investments, better trading conditions and taxes reduction may be required. The Chinese government is suggested to consider the inclusion of SAU' s project in the context of the National Agenda 21, as this is a basic document for the sustained development of China, when the energetic and ambiental aspects are considered.
SAU has, through operation of its energy integrated system, an unique opportunity to give a strong contribution to reduce the energy shortage and prices in the Northeast region of China, mainly in the rural area. The project can also estimulate the regional socio-economical development, by increasing farmers profits and land fertility and by reducing ambiental pollution.
To be successfull, SAU must be continuously brought up to date with the new technologies of biomass production and explotation, as well as with the methodologies required for technical and economical evaluation of integrated systems. To hit this task, permanent contacts with other research institutions and scientist is required.
The mass and energy balances of SEIS need to be optimized, taking into account the technical and economical aspects. The main objective of such optimization is to allow a whole year operation of the demonstration farm, in a profitable basis. Improvement of the mass and energy balances will require the establishment of an efficient network linking the farm's components, so that effluents and by-products from one unit can be used as raw material or utility for other one.
To assure the dissemination, among the farmers, of the information generated by the project, SAU is recommended to give training courses and to carry out an intensive work of information disclosure, which will require visits to the farmers and edition and distribution of technical documents, wrote in a understandable style.
Political, financial and technical backing by the Chinese government is essential to assure a full operation of the demonstration farm. Support from foreign institutions and the United Nations Organization's system is also highly desirable and would give a significant contribution to attain a successfull project development.
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FIGURE 1 THE SAU'S ENERGY INTEGRATED SYSTEM
