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Workshop on energy-conserving technologies for the post-harvest system

A workshop on Energy-Conserving Technologies for the Postharvest System, organized by the United Nations University and the Institute of Agricultural and Food Economics in Warsaw, was held from 26 May to 1 June 1984 in Przysiek, Poland, near Toruń, about 250 km northwest of Warsaw. The conference facilities were provided by the Agricultural Progress Centre in Przysiek, which specializes in extension work and the training of farmers. Thirty-two scholars and specialists from 18 countries participated. All the papers presented during the workshop will be published, after editing in co-operation with the authors, by the Institute of Agricultural and Food Economics.

The workshop followed earlier work in the field of energy-conserving technologies organized by the UN University in co-operation with other organizations, including workshops on the following topics:

- Bioconversion of Organic Residues for Rural Communities (November 1978),

- Organic Residues in Rural Communities (December 1979),

- Traditional Food Technologies: Their Development and Integrated Utilization with the Emerging Technologies (July 1983),

- Need-Based Information Service in Appropriate Food Science and Technology for Developing Countries (January 1983), as well as the work of the Need-Based Information Service and material available in the UNU-published ASSET: Abstracts of Selected Solar Energy Technology.

The following purposes were set out as guidelines for the workshop:

a. identification and assessment of energy-conserving technologies for the post-harvest agricultural and food systems— both traditional technologies and others known today and technologies requiring further research and extension in order to make them appropriate for utilization in the agricultural and food systems of the developing countries,

b. identification and assessment of institutions, scholars, and research staff active in the field of energy-conserving technologies for the post-harvest system and of the research and development work being done in various countries and regions of the world;

c. provision of an opportunity for an interchange of ideas and experience and a collective assessment of the state of research and development in the field of energy conservation in the post-harvest systems,

d. formulation of future research and development thrusts in the field of energy-conserving technologies for the post-harvest system, on the basis of past and present experience, anticipating research and staff training requirements, taking into consideration the technical feasibility of the technologies and their economic viability and social acceptance,

e. proposals for directions and methods for the dissemination of available information and technologies.

The workshop was opened by Professor Augustyn Wos, Director of the Institute of Agricultural and Food Economics, who stated that research on energy-conserving postharvest technologies must take into consideration, first, the fact that energy spent in the food production system constitutes a major part of total energy use and, second, the cumulative impact of losses and costs in the consecutive stages of food production. This means additional loss of the inputs used in previous stages. While it is generally recognized that technologies developed in the industrialized countries are not suitable for the developing countries-for economic, social, and strictly technical reasons-appropriate technologies have yet to be developed.

Participants in the workshop were addressed by Dr. Henryk Burczyk, Under-Secretary of State in the Ministry of Agriculture and Food Economy in Poland, who presented the view of the policy-maker. Equally important as the work done on particular technologies for the various stages of agricultural and food production is a systems approach, oriented towards seeing food production as a whole, with its elements closely linked and interacting, including a macroeconomic analysis of the whole food production network. A recent conference on energy management in Polish farming pointed not only to the possibilities of energy-saving within existing technologies, but also to the urgent need for an impartial analysis of future prospects for various crops, livestock breeding systems, and food processing techniques. The policy-maker should thus not limit himself to providing incentives for improved efficiency of the present food systems, but search for future solutions as well.

On behalf of the United Nations University, Dr. Miguel Urrutia, Vice-Rector, Development Studies Division, welcomed the participants and the present representatives of the regional administrative and political authorities and outlined the following as the objectives of the workshop:

- an interchange of information among scientists and researchers present and a discussion of prospective technologies that are promising in the field of energy conservation and that require international co-operation;

- the elaboration of particular concrete projects that would make possible the development and adoption of energy-efficient technologies for food production in lowincome countries, with special attention to the problems of Africa;

- help in identifying individuals, institutions, and programmes of research to contribute to a joint international effort in research, dissemination, and extension of energy-conserving technologies, to propose research programmes in this area that are particularly promising and in need of attention. The United Nations University intends to continue its efforts and interest in the field of energy-conserving technologies for post-harvest systems.

The representative of the regional Toruń government, St. Trokowski, and R. Kaminski, Director of the Agricultural Progress Centre, stressed in their statements during the opening session the interest of local farmers and extension workers in receiving from research and development institutions technologies and assistance that would be acceptable from an economic point of view and that would fit well into existing agricultural and food-processing systems.


Assessment of the Present Situation in Research and Development

It was recognized that the post-harvest system in food production, particularly in developing countries where the economies are primarily agricultural, is a major single consumer of energy. The papers and discussions brought out the social and economic importance of the need to give sufficiently high priority to improving energy efficiency, especially in traditional technologies that are responsible for the processing and preservation of a major portion of the food in developing countries. Research efforts have already been initiated to upgrade existing technologies to reduce the use, especially the waste, of energy, and also to utilize nonconventional sources of energy where possible.

It was recognized that most of the technologies currently in use were not developed with the primary objective of energy efficiency, and in many cases they did not comprise a large share of the final cost of the product. The awareness of the need to make the agricultural system more energy-efficient has begun to receive attention only since the energy crisis of the 1970s that led to sharp increases in the price of fossil fuels.

The problems of developing countries with little or inadequate petroleum and coal resources, who are also depleting other renewable energy resources such as forests, have assumed serious dimensions and this necessitates the use of nonconventional energy resources, such as solar, geothermal, wind, and a combination of these with conventional fuels for greater efficiency.

Studies aimed at making the existing food conservation and processing technologies more energy-efficient and integrating them with the emerging new technologies, as well with current social and economic conditions, have become very important. This is true especially in developing countries as a means to accelerate their development towards selfsufficiency in food.

The efforts so far aimed at improvement of existing technologies and the development of new ones have already contributed to a significant improvement in energy management. Case studies have shown that energy efficiency can be increased by as much as 50 per cent.

Investment in improved or new energy-efficient technologies has to consider the availability of funds, the technologies' impact on employment, their contribution to increases and improvements in food supplies and better nutritional standards, and their impact on the population's incomes as well as the infrastructural constraints.

It was found that in both research and economic technological policy it is difficult-if not impossible-to separate sharply and definitively the energy conservation targets from general energy management practice. This is an important obstacle if energy conservation in post-harvest systems is to receive due attention in both research and policy. Expertise is required to secure the recognition of this problem at the policy level, to consider the potential impact on the economy and the standard of living, including food quality, and to create and stimulate structural development. A system for communication of research and development indicators to policy-makers would be appropriate, as this is often lacking. The post-harvest system is a complex network of links between agricultural production, food processing and storage, cooking, and serving food, with strong upstream and downstream interactions; in order to understand its functioning we must analyse its composition and the links within it.

A very promising approach would be to include nutrition policy considerations at the very beginning of work on energy conservation in agricultural and food systems.

Agricultural resources available today could feed more people if the recommendations from nutrition scientists were incorporated at the beginning of production, processing, and storage operations. Conceptual and methodological improvements and work on making research material uniform are required.

Principal Points of Discussion and Proposed Directions for Research and Development

Research is urgently required on the economic and social aspects of the appropriateness and adoption of new or improved traditional technologies in the post-harvest system oriented towards energy conservation. Experience has clearly, and in some cases dramatically, shown that without adequate economic and social analysis even the best new technologies may fail. The complexity of the impact of the new or modified technologies on the economic and social fabric of societies calls for close scrutiny of these effects. The experience in this field, both positive and negative, should be studied and guidelines offered to countries embarking towards change.

Research and development either on new technologies or on upgraded traditional ones ought to take into consideration

- the appropriateness of the technology to the conditions of the developing countries (e.g., should developing countries consider refrigeration techniques for storage, even though these have originated in the fundamentally different conditions of Europe and the United States?);

- the potential of mixed technologies, drawing on traditional local experience, incidentally frequently rediscovered today.

Nutritional implications should be included in plans for production, processing, and storage technologies, as it is believed that vast reserves could be tapped if the effect of technology on nutrition were considered from the very start.

There is a need to exchange views and experiences on the subject of translation of energy management and conservation requirements and indications into the language of social and economic policy; production and household decisions are made on the basis of tradition, cost calculations, and demonstrated effects, not on the basis of energy input-output relations. The translation of energy management indications into everyday incentives, e.g., economic, is a vital and urgent need, and the experience of all in this area ought to be disseminated. Most enlightening would be establishment of a standard procedure for measuring energy consumption in agricultural production, food processing, storage, distribution, and food preparation (including cooking) systems that would be applicable to all countries at different stages of development. The development of such a methodology would permit, on the basis of a world-wide survey, the most efficient energy use in various agricultural and food systems. Thus, research is required on energy input-output relationships and on their translation into social and economic policy.

The material and experience of the workshops on energy organized so far by the United Nations University now permit the assembling of an impartial listing and classification of institutions and research done in the field of energy conservation in post-harvest systems, oriented towards assisting the developing countries in their efforts to select the most suitable methods and course of action. It is recommended that the United Nations University assemble such a list. It is hoped that the following listing of prospective technologies will be useful in this respect.


The Use of Energy in Food Processing and Distribution: Selected Problems. Piotr Lewicki, SGGW-AR Agricultural Academy, Warsaw, Poland, and Wlodzimierz Kamiński, Institute of Agricultural and Food Economics, Warsaw, Poland

Statistics on global use of energy discussed in the paper clearly point to a deficit in traditional resources of energy in the near future. A spatial analysis further shows the differentiation between regions and countries, depending highly on the stage of economic development.

The food economy, i.e. agricultural production, food processing and distribution, storage and marketing, is central in energy use; figures discussed for the Polish economy indicate the cumulative use of energy as the most important aspect, e.g., losses in food processing also mean waste of the preceding agricultural inputs. The Polish experience in food processing, with particular regard to the choice of technologies from the point of view of energy management, and the spatial adjustment of the links of the food economy network are discussed. This choice is exemplified by three technologies of pea processing, varying in energy input and requirements. The energy requirements of some food products are shown, as are methods used by the Polish food industry to limit energy costs.

Use of Food Energy in Human Nutrition-World Overview. Stanislaw Berger and Grazyna Dybowska

A quantitative analysis of energy input-output ratios in nutrition is a most promising field of research. Energy units may be used both as basic information regarding the nutritive value of foods and in the determination of human nutritional needs. The present and future world consumption of energy in foods is extensively discussed on the basis of the Food and Agriculture Organization statistics and methodology, with its far-reaching social and economic impacts and health implications. The overriding effect of the demographic factor in developing countries is considered. Thus, one has to consider not only the total dietary energy supply, but its sources as well, correlated both to the costs of production of nutrients, their utilization, and their effects on the population's incomes. Nutrient composition varies throughout the world, the basic indicator being the protein source. Unless the above problems of data collection and analysis are resolved-and it is notable that they are far from solved in the developed countries as well-no important progress can be made in food and agricultural production systems. Once nutritional considerations are included in food production and processing systems from the start, the goals of upgrading the latter will become much clearer.

Development of Energy-Saving Technologies for the Food-Processing Industry. B. L. Amla and V. H. Potty, Central Food Technological Research Institute, Mysore, India

A reliable assessment of energy consumption in particular units and operations of the food industry may be obtained through an estimation of the gross energy requirement and provide a basis for choice of technology options. One approach for energy saving in food processing could be the improved efficiency of each unit of operation by design improvement. A more promising alternative is the development of new products or technologies that consume less energy than traditional ones. The impact of the first approach is limited by the fact that direct energy costs as a rule constitute a small share of the total costs. Estimates of the gross energy requirement for various Indian food industries are discussed. Energy-saving technologies and calculations for tamarind processing, for weaning foods technologies, for rice milling and preparation, for legume processing using traditional versus modern techniques, and mango-based beverage production are discussed and illustrated within the Indian context. In research, but particularly in extension, the trade-off between energy-saving and other economic consideratios must always be examined.

Processing of Foodstuffs and Vegetables by Energy-Saving Enzymic Technologies. 1. Varsanyi, Central Food Research Institute, Budapest, Hungary

The utilization of different enzymes in food processing and the application of various enzyme systems in processing technologies offer promising potential for energy saving.

Enzymes used in industry permit either limited use of energy with identical output or an even lower energy requirement. The enzymes and enzyme systems used on a large scale in the Hungarian food industry are listed, the most important of these being pectolytic enzymes. The effects are quality improvement and decreased energy utilization.

The endo-polygalacturonase enzyme was successfully used in the production of fruit and vegetable juices and in machine-harvested tomato processing. Energy saving and quality improvement resulted. The Hungarian experience has demonstrated that biotechnologies may effectively conserve energy.

Energy-Saving Technologies for the Post-harvest System: The Possibility of Energy-Saving in Food Processing. Augustyn Jakubowski, Meat Processing Institute, Warsaw, Poland

Various methods are employed in food processing, ranging from mechanical to biological, and they offer many choices of energy-conserving technologies. Recommendations for energy conservation emanate from the Polish sugar processing industry (the most energy-intensive of all food industries), from the meat-processing industry, and from improved storage technologies.

The introduction of new techniques in potato processing are also presented. The scale of raw materials processed in cereal milling and in dairy plants makes even minor energy savings important, the former conserving energy in bread baking, the latter using less energy in storage. Spirit- and beer-making offer an opportunity to save energy through use of by-product energy, as does fat processing. The different ways energy is used per product unit in various plants point to considerable reserve potential yet to be explored.

Fermented Foods in Hungary. P. A. Biacs and J. Beczner, Central Food Research Institute, Budapest, Hungary

The fermenting activity of microbes is extensively utilized in the dairy industry, where different starter cultures are used in the production of cheese, butter, sour milk products, cottage cheese, etc. Starter cultures result in safer and more controllable technology and decreased waste, and they save labour and lower the amount of raw materials required. The biological and nutritive values of the products are also higher. The various starter cultures used in the dairy industry are listed. An addition of CITOPAN improves bread quality along with another additive that improves leavening with positive effects on product quality.

Microbiological processes are used in the meat industry, in ripening, curing, brining, and all improve product quality, making the products more reliable technologically and safer. The resulting pH decrease inhibits the propagation of non-desirable bacteria and increases the water evaporation of the product so that drying time is shortened. Mycelium offers the most promising potential for production of valuable protein and as a flavouring agent.

Whole or Cut Fruits and Vegetables as Semi-finished Products in Large Packs. I. Kafedshiev, Canning Research Institute, Plovdid, Bulgaria

The experience of some countries indicates that the spoilage of fruit and vegetable products at pH 4.5 is caused by moulds and yeast and that spoilage by spores occurs only in cases of extremely high contamination of the raw material. Accordingly, a hot filling system was designed that would not require aseptic conditions in filling and sealing operations. This simplified both process and equipment. An investigation established the optimum heating conditions for destroying undesirable microflora and inactivating enzyme systems. Research has resulted in the construction of a commercial production line that reduces production costs without changing product quality. As heating and cooling temperatures were crucial, this is an important contribution to energy management.

Energy-Conserving Technologies for the Post-harvest System. Cheikh Ndiaye, Institute of Food Technology, Dakar, Senegal

This paper gives a comprehensive review of the African experience in traditional food systems, including the central place of agriculture in the national economy. It discusses the impact of low incomes and high population growth, of a ground-nut monoculture oriented towards exports, the effects of drought, etc. Traditional food processing methods are described, including those for cereals, oilseeds, drying and dehydration, and traditional technologies for fish processing (salting, drying, smoking, fermenting).

Improved techniques of drying with the solar dehydrator made with black HOPE sheets resulted in higher temperatures and shorter drying time. Various conservation agents are also described. Improved grain storage structures at the farm level are vital and require the utmost attention. Traditional structures, underground silos, mud granaries, interwoven wickerwork baskets, various kinds of small containers, and sheet metal silos are reviewed and their appropriate use is explained. Extensive farm-level research has resulted in recommendations for improved storage, pest control, and conservation techniques.

The Status of Energy Utilization for the Post-harvest System and the Development of Energy-Saving Technologies in Japan. Nobuzo Tsumura, National Food Research Institute, Tsukuba, Japan

Japan's high dependence (over 50 per cent) on oil makes energy conservation a pressing problem, all the more so since the energy consumption in the post-harvest system, excluding production, represents 73 per cent of the total energy used in the food supply system, or 8 per cent of the total energy used in the national economy. Examples of technical developments in food processing affecting energy conservation are controlling the balancing water in pans in sugar refineries, the introduction of a non-cooking fermentation process in alcohol production (enzymes are used for saccharization of raw starch!, technologies using membranes in concentration of liquids, and isolation of solutes. Simple solutions such as the insertion of a heat pipe into the centre of brewing tanks are frequently very effective.

Low-Energy Post-harvest Technologies for Paddy Rice and Fruits in Korea. Tai-wan Kwon, Hyun-kyung Shin, and Key-sun Kim, Korea Advanced Institute of Science and Technology, Seoul, Republic of Korea

The development and extension of technologies suitable at the village level, such as in-bin drying and storage systems for paddy rice and an economical storehouse for fruits, were related to the small farm size dominating the Korean agricultural system. The appropriateness, simple construction, and economic benefits of these technologies made them acceptable to local farmers.

A system was developed to utilize the low temperature and humid air of the night to store fruits without expensive mechanical refrigeration. The construction of a standard storehouse with a capacity for 40 tons of fruit is described. It can be built with cement blocks, is low in cost, and simple. Emphasis on insulation and natural ventilation provide the required temperatures without the need for either electricity or refrigeration.

An in-bin drying system for paddy rice was developed along identical lines, based on a system of ventilation, to store and dry this staple crop. An economic analysis of these developments compared to conventional systems showed them to be superior in terms of energy use and general costs.

The Development of Energy-Conserving Technology for the Post-harvest Food System in Indonesia. F. G. Winarno and Hadi K. Purwadaria, Bogor Agricultural University, Bogor, Indonesia

One of the goals of research in post harvest systems in Indonesia is reduction of losses. Heavy dependence on imported kerosene as the principal cooking fuel is another concern. If firewood consumption continues at the present rate, in 15 years if would exceed the supply in Java twofold. Various kinds of cooking stoves have been tested with significant energy gains apparent. One possibility is use of charcoal made from rice husks. Small solar dryers that can be used by farmers for drying bananas and chips have been developed and have proved to be twice as effective as traditional solar drying. Agricultural wastes, waste wood, and biogas offer enormous potential, but technical difficulties are still encountered.

Numerous types of promising manually operated equipment, such as paddy threshers, cassava chippers and raspers, corn grinders, soybean roasters, and oil-pressing machines have been developed.

Energy Consumption Analysis in Selected Branches of Food Production and Consumption. A. Neryng, K. Biedrzycki, and J. Lecyk, Institute of Human Nutrition, SGGW-AR Agricultural University, Warsaw, Poland

Evaluation of the energy consumption necessary in food production and during distribution must be the basis for choosing technology in terms of type and quality. A dynamic method of comparing energy consumption with output was proposed. It was found that energy consumption per kilogram of food produced and per unit of energy in the food produced, calculated for the mean energy composition of food is the most objective method. The main method applied in determining energy use was the fuel and energy balance for particular plants, with the division by specific departments and machines, to ascertain the amount of different types of fuels used in different processes. Gross energy requirement is a more comprehensive measurement, as it includes all earlier energy inputs to obtain the raw materials and intermediate products. The experiences of a bakery plant and production of some ready-to-serve foods were analysed, as were differences in energy management in mass catering establishments in Warsaw. This revealed the importance of personnel training and motivation in energy management.

Energy-Conserving Measures in the Malaysian Post-harvest System. Dhiauddin bin Mohd. Nour/Jantan, Malaysian Agricultural Research and Development Institute, Serdang, Selangor, Malaysia

The use of crop residues has made the oil palm mills in Malaysia self-sufficient in energy. The additional use of the oil palm mill effluent, as a pollution control method through biogas generation, presents a potential for turning these mills into net exporters of energy.

Pilot plants using rice husk wastes as fuel have been set up and appear to offer considerable promise. Research has shown that a dryer combining a solar collector and a diesel burner for a heat energy source along with electricity for air circulation within the dryer is cheaper for most crops. Technical details of these trials are presented in the paper together with cost calculations.

An Overview of Energy-Efficient Technologies for Food-Processing Industries in Thailand. Wiboonkiet Moleeratanond, Thailand Institute of Scientific and Technological Research, Bangkok, Thailand

The need for energy conservation is heightened by the high cost of petroleum imports. Current government programmes concentrate more on utilization of indigenous sources of energy than on improved energy efficiency. There are energy losses and waste in the food processing industries, the latter accounting for a major part of total energy use using traditional technologies.

The Thailand experience of energy management in truck transport, in cassava production, in case studies of a transparent noodle factory, and in cold storage operations is discussed, showing considerable energy-conserving potential. An energy-saving project in monosodium glutamate production that has significantly improved energy management is discussed.

Resource Requirements in the Use of Refrigeration. Mogens Jul. Department of Food Preservation, the Royal Veterinary and Agricultural University, Copenhagen, Denmark

The high losses observed of perishable food products, especially milk, meat, and fish, encourage consideration of refrigeration as a storage and preservation technique. A simplified calculation shows that to preserve fish by freezing may cost more than acquiring the same food energy on international markets. This is based on the fact that cereals form a major part of the diet in developing countries. A review of the capital and energy requirements for various forms of preserving food by chilling or freezing shows the costs involved to be high enough to become a problem for the developing countries, though chilling is less expensive. While the benefits of Western-style cold storage or cooling are easily appreciated, the high capital and energy costs must be taken into consideration when introducing these methods in developing countries.

Attempts to Develop New Energy-Saving Starch-Production Technologies. A. Neryng, D. Kolozyn-Krajewska, and J. Lecyk, Institute of Human Nutrition, SGGW-AR Agricultural University, Warsaw, Poland

Starch, an important food-industry product, is obtained from potatoes, corn, and rice. The United States experience in new methods of starch production from corn has constituted the basis for research on a new method for starch production from potatoes, a staple crop in Polish farming. The change from a wet milling process for corn to the use of ensiled corn permitted a change from the former energy-intensive process to one that is less so without deterioration of product quality. It was proposed that, after grinding, potatoes could as well undergo lactic acid bacterial culture fermentation. This would solve the problem of storage in silos. This new method of starch production from potatoes means less capital investment, less energy use, and no loss in quality.

Utilization of Renewable Energy in Post-harvest Technology. T. A. Lawand and J. LeNormand, Brace Research institute, Faculty of Engineering, McGill University, Quebec, Canada

Several ideas are presented in the paper for the use of simple renewable sources of energy in post-harvest systems. The concepts were selected for their simplicity and for the possibility of construction with local resources without importation of technology or expertise.

Experience with solar drying and solar cooling is presented, in the former the potential of greenhouse-type solar dryers and in situ barn dryers is discussed. Research on an in situ solar dryer with a roof solar collector and temperature-forced air circulation is described, as well as a dryer that uses heat pipes for heat transfer. The conditions for successful implementation of such dryers are listed. Solar refrigeration and cooling using nocturnal cooler chambers with liquid ammonia as the medium is discussed, together with ideas for energy conservation, such as early morning harvesting when temperatures are still low, thus limiting heat respiration in the harvested crops.

A nocturnal cooler has been developed based on the heat pipe principles, linking a cooler box and roof top emitter. While this system requires reliable sky temperature data, its merit is its simplicity and reliability.

Some Post-harvest Energy-Saving Technologies. L. D. G. Coward, Caversham, Reading, Berkshire, UK

Upgraded technologies can contribute to a more favourable trade-off between energy costs of drying and the improved product quality effected by this process. Experience with sophisticated cassava-drying plants in Brazil revealed potential reserve in proper personnel training and in correct fuel preparation; e.g., fuel chips of even size improve energy efficiency.

Fiji experience with temperature control in drying cocoa beans showed that energy efficiency could be improved if thermometers were provided to farmers. A cashew-processing plant designed by the Tropical Development and Research Institute (TDRI) is discussed, and the benefits of this design are described. Biomass sources of energy and the need to reduce energy wastage in charcoal production and utilization have caused the TDRI to develop an energy-efficient and very successful transportable metal kiln. Special training programmes permitted its introduction into 20 countries. For instance, the kiln may be used to produce coconut-shell charcoal; in turn, gas can be made from charcoal using a gasifier. A trial was conducted using this equipment in electric energy generation. The TDRI experience in assessment of biogas production is presented. This institution has also proposed an improved forced convection solar drier for areas without electricity. This method improves product quality, shortens drying time, and lowers moisture content.

Technology for Drying Grain Applied in China. Deng Keyun, Chinese Institute of Energy, China Association for Science and Technology, Sanlihe, Beijing, People's Republic of China

Losses of grain because of poor weather during the drying period and the availability of an abundant supply of labourers resulted in development of an appropriate drying system. Cut grain is first stored in bundles stacked vertically so as to protect it from rain, and bundles are then piled. Grain is further dried on barn floors and turned over manually. A shortage of fuels prohibits warm aeration drying. A small multi-purpose dryer has been developed using a gas burner fueled with coal, but more often with rice husks, firewood, fruit shells, crop residues, or animal manure. Research is under way on practical and technically feasible biogas installations and solar driers.

Constraints to the Diffusion of Small-Scale Solar Dryers and Policy Implications. Armand F. Pereira, Technology and Employment Branch, Employment and Development Department, International Labour Office, Geneva, Switzerland

Inefficient technology is only one among many factors responsible for post-harvest losses. Energy-efficient food drying technologies also depend on many factors. These may be classified as income-related constraints for producers if the additional costs are prohibitive or products of higher quality are not in demand. There may be market-related constraints, such as price, product demand, and supply limitations because of improper organization of producers and distributors. Technology-related constraints are illustrated by the difference between industrial and artisan technologies. ILO experience points to the importance of correct training and extension programmes, a prerequisite to successful technology implementation.

Energy input-output relationships are rarely decisive in management and investment; economic considerations and human reasoning usually are more important. Solar dryers using direct radiation and others using heat transport features are discussed, illustrated with ILO experience in their implementation, with particular regard to economic aspects. An annex presents ILO research and technical assistance in post-harvest technologies.

The Potential for the Use of Solar Energy for Drying in Nigeria. M. A. O. Kehinde, Federal Institute of Industrial Research, Oshodi, Lagos, Nigeria

Preservation of agricultural produce by sun-drying is an age-old practice in Nigeria, as in other parts of the world. However, it is evident that a substantial part of such produce dried in the open air is lost to animals, birds, and insects, and the system is unhygienic. Recent innovations in solar drying technologies have not yet been commercially exploited in Nigeria, but research is under way aimed at the construction of solar dryers, adapted to local conditions, providing controlled exposure to radiation and wind.

Some Observations on Post-harvest Energy-Saving Practices in Brazil. Adhemar Brandini, EMBRAPA - Brazilian Agricultural Research Organization, Brasilia, Brazil

Following an introduction describing Brazilian farming, including figures on fuel consumption, the discussion then turns to maize losses in traditional harvesting and storage technologies, with a description of the potential of underground plastic silos as a remedy. Their construction and results of their use are illustrated. Post-harvest stages of cassava production, including storage techniques, grating, and other methods are discussed in terms of their effect on product quality. Statistics concerning the Brazilian post-harvest system are quoted, together with relevant storage experience.

Post-harvest Systems at the Centres for Appropriate Technology in the Philippines. Romeo V. Alicbusan, National Institute of Science and Technology, Manila, Philippines

Present programmes oriented towards bringing technology to villages are based on active partnership between industry and villagers. Programmes emphasize technology transfer, skills development, and institution-building. Details of the work the national centres are doing to bring progress to farming and in the countryside are given, together with a list of commercial technologies employed. A solar dryer made of plastic sheets, wood, and aluminium with wire mesh for trays, was developed to dry fruits, vegetables, fish, and meat. Adjustable ventilators regulate the heat generated by solar energy, and drying time is radically shortened. A biogas digester, windmills, cooking stoves, and gasifiers (for producer gas and dendrogas) are discussed. A proposition is made to shift from motor-driven to manually operated equipment, the overriding consideration being the saving of imported petroleum.

Energy Systems Analysis in Food and Energy Crop Production Methodology Data Preparation and Analysis. Malcolm Slesser, University of Strathclyde, Glasgow, Scotland

An extensive study of methods of analysis, following data collection and processing, summarizes research on energy use in various agricultural and food systems. Input-output ratios, the gross-energy-requirement concept, and systems analysis methods in farming energy use are discussed, with different sources of energy included in the calculations. For macro-economic analysis, input-output balances of the Leontieff type may be used. Energy use, depending on the type of crop, and a comparison of economic and energy appraisal are some of the methodological ideas presented.

Energy-Conserving Technologies for Africa's Rural Areas: Background Problems, Realistic Options, Postharvest Energy-Saving Processes. Jiri Texler, Prague, Czechoslovakia

Africa has become the world's foremost problem region in terms of the population-to-resource ratio. Lagging agricultural productivity is one vital cause of the problem. A huge gap has opened between population growth and food supplies over the past few years. The exodus of peasants to cities cannot be called a symptom of modernization. Africa's food import bill and need for food aid are no longer supportable. Food problems are coupled with large-scale deforestation in parts of Africa.

The growing demand for food together with increased costs of imported energy have confronted African countries with a dilemma for which there are no viable solutions. Since the present generation of Africans will continue to live in the fuelwood era, the only solution is to develop fuelwood plantations. The Ethiopian experience in this area is described. Factors constraining the applicability of solar cookers are discussed, with the potential of production of safe drinking water an exception. Cultural factors, such as the effect of a permanent open fire on family life ought to be considered. Something of a renaissance of the traditional technologies for storage, drying, and threshing is currently being observed, and these are found to be most appropriate for local conditions.

Utilization of Solar Energy for Grain Drying. National Food Research Institute, Tsukuba, Ibaraki, Japan

Selected solar grain-drying systems were tested for the utilization of this resource for drying wheat and unhulled rice. The C-type solar grain-drying system is composed of a circulation-type dryer, 900 kg in capacity, with a flat-plate heat collector of the suspended, covered type. The V-type solar grain-dryer is composed of the same kind of circulation dryer combined with a plastic greenhouse, 19 m˛ in area, in which a black net is stretched to serve as the absorbing surface. The F-type is a forced-air dryer of the flat-bed type, 1,000 kg in capacity, built in the greenhouse and fan operated. Computer simulation techniques permitted observations of the capacities of these dryers, thus enabling construction of a better system that is described in this paper.

Simple, Low-Cost On-Farm Paddy Dryer-Thailand. ESCAP/UNIDO Division of Industry, Human Settlements and Technology

A simple, low-cost, on-farm paddy dryer for Thailand was constructed in order to reduce losses and expand storage time. The relatively high cost of fossil-fueled dryers is a major constraint to their expansion. The method proposed entails the forcing of air that has not been artificially heated through the mass of paddy for six to nine hours during the daytime. The system consists of a gable roof-shaped paddy bed, an axial flow fan, and a gasoline engine. For mass production it will be constructed with local materials. The fan may be powered by a small tractor. Field experiments have yielded satisfactory results, as illustrated by the extensive data presented. Details of further research to upgrade the system are discussed.

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