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Development of energy-saving technologies for the food processing industry
B. L. Amla and V. H. Potty
Central Food Technological Research Institute, Mysore, India
Awareness of the importance of energy saving in manufacturing processes was kindled only when fossil fuels registered dramatic price increases in 1973. These increases led to evolving strategies to conserve energy resources, especially exhaustible sources, by reducing their consumption and developing renewable sources of energy. To achieve any significant savings in energy consumption in manufacturing processes, the food industry must reliably assess energy consumption at each unit operation. Estimation of gross energy requirement can be used for deciding on technology options. Two approaches for achieving significant savings in energy consumption in the food industry could be: (a) improving the efficiency of each unit operation by design improvement; (b) developing new processes or products that consume less energy than traditional processes. The latter approach may be suitable for developing countries like India, which is promoting its processed food industry on a priority basis. A few technologies that require considerably less energy to process products developed in India are highlighted in this paper.
The abilities to control and use energy sources were important milestones in man's progress and civilization. The development from a primitive hunter-gatherer society to the present has progressed through the use of various energy options: fire, animal power, water, wind, fossil fuels, and nuclear energy.
Throughout history the generation of surplus has been the fundamental purpose of any economic activity. The use of newer energy systems also followed this rule and helped to generate surpluses of time, resources, and energy. Curtailing the gross energy expended in the food production and delivery system in developing economies is critically important in any long-term strategy for energy conservation. An intense awareness has been generated in most of the developed countries regarding the acute need for energy conservation in all sectors and has resulted in both voluntary and statutory steps to cut down on energy cost and conserve scarce energy resources. In the developing world, not much activity is evident in this critical area, and even the availability of vital data regarding energy generation and use is doubtful. If any worthwhile practical programme of energy conservation is to be planned and implemented, it is necessary to have (al a reliable database concerning production and consumption of various types of energy sources by different users and (b) energy auditing at various levels to provide a firm basis for identifying options for saving energy.
APPROACHES TO ENERGY CONSERVATION
Industry is generally more aware of energy conservation today than it was when the oil crunch started in 1973. The degree of response to energy problems can be expected to vary among industries and would be higher in the case of energy-intensive industries. It is reported that many major industries in the developed countries have initiated efforts to effect immediate savings by improving operating procedures requiring comparatively smaller capital investments. Energy conservation in the food industry on a national scale can be achieved with two approaches:
a. improving the efficiency of the conversion processes in various operations through different techniques; these include:
- waste-energy recovery from plant equipment such as cookers,
driers, compressors, waste service, and hot water;
- improved use of electrical energy by optimizing plant power factors, motor and pump sizes, and light sources; replacement of electric motors with back pressure steam turbines; and use of multiple capacity compressors for refrigeration;
- increased boiler and steam efficiency by such measures as minimizing boiler blow-down, use of better feed-water, recovery of heat from hot blow down, returning more steam condensate to boiler, recovery of heat from flue gases, optimizing combustion conditions, improving oil atomization, more frequent descaling of boiler tubes;
- more extensive use of efficient insulation;
- minimizing refrigeration and air conditioning and using improved designs;
- use of improved or additional equipment such as multiple effect evaporators, mechanical vapour compressors, ring driers, screw and pneumatic dewaterers before drying, matched air compressors, microwave driers and cookers to eliminate long steamheating, agitators in the vacuum pan of evaporators, and a scraping device in evaporation to improve heat transfer;
b. developing alternative technologies that are more energy-efficient in terms of quantum of consumption, cost, and use of scarce energy sources.
A major factor that may be an obstacle to improving the efficiency of conversion processes is the relatively small percentage of the direct cost to industry of energy in the overall production cost. Though considerable variations exist for these cost ratios among different industries, it is generally less than 2 per cent of the value of production (table 11. Even if all available and known techniques are adopted by the industry to effect a net reduction in direct energy consumption, the savings would be only on the order of 0.1 per cent of the total value of their production. Those savings would be almost imperceptible in the context of rising food prices and increasing energy costs. Though the United States food industry is reported to have been able to achieve energy-efficiency improvements to the extent of 10 to 26 per cent in different sectors by judicious energy management, generally, progress is considered difficult because of factors such as technological feasibility, economic practicability, and rigid government regulations involving environmental protection and exceptional safety and quality parameters (table 2). Similarly, frequent shifts in product mixes within the industry to keep pace with the changing consumer needs make it difficult to adhere to any rigid format of operations aimed at energy saving.
Development and use of alternative technologies based on less energy consumption can be a better proposition for countries that, like India, are on the threshold of industrialization, since this option gives sufficient opportunity to use scarce resources more judiciously. While less expensive techniques for energy savings in the existing food industry can be made acceptable by governmental regulatory mechanisms, their enforcement on a national scale becomes an impossible task. Many developing countries with predominantly agriculture-based economies are just in the planning stage of industrialization with a very insignificant percentage of their raw-material production undergoing any value addition. Thus, the availability of viable technologies with lower energy requirements can be of considerable significance to their developmental efforts.
TABLE 1. Energy Costs in the Processing of Cocoa Beans in India
|Administration and management||4.4|
TABLE 2. Energy Savings for the US Food Industry through Conservation Techniques (1972-1980)
THE FOOD PROCESSING INDUSTRY
The food industry in India is characterized by a production pattern geared to meet three types of demand: demand in areas with a high rate of consumption, urban demand, and export demand. The industry itself can be broadly classified into the following two groups: (al the basic food industries, comprising units engaged in rice milling, flour milling, legume milling, oilseed milling, sugar and jaggery; and (b) the processed-food industries, manufacturing bakery products, confectionery, hydrogenated fats, meat and fish products, canned fruit and vegetable products, breakfast foods, dairy items including infant and weaning foods, starch and its derivatives, and malt-based products. The organized sector of the food industry for which economic data are available has an investment of US$2.5 billion (2,500 million! in the basic food industries, for 7 per cent of the total investment in industry, and an investment in manufactured goods worth US$6.5 billion annually, which is about 16 per cent of the total production by all industry. The potential for growth of the food processing industry is very high in view of the following facts: (a) the food industry provides maximum employment per unit investment; (b) although 41 per cent of India's GNP is derived from agriculture, which is equivalent to about US$50 billion, the value addition by processing is only about US$0.65 billion at present; and (c) the Indian share in international food export of US$70 billion is hardly 2 per cent. Therefore, India has accorded a high priority to development of its food industry, and as a major input appropriate technologies are required for development. While there may be many factors that will influence technology selection, energy requirement should be a major one deserving attention. The indigenous development and availability of energy-saving technologies will go a long way in reducing future energy consumption by the food industry to significantly low levels.
Estimates of Gross Energy Requirement
The methodology adopted in this study is slightly different from that adopted by the US Federal Energy Administration, in that the present model focuses on only two of the components in the food system, namely capital inputs and process inputs, for the following reasons.
Indian agriculture is predominantly human-labour-oriented, and hence the major share of the gross energy requirement (GER) for primary agricultural production consists of photosynthetic energy and human power. Energy levels from primary production input are, therefore, not considered in the computation of the GER. The components of capital inputs, viz., building and equipment, are amortized for 20 years and 10 years respectively. The process inputs include material inputs, viz., processed materials and chemicals used in the course of manufacturing, primary packaging, manpower, and utility services. Merchandizing or trade and transportation inputs and consumption inputs are not included in the food-system model, as the GER is intended to be computed as a tool for evaluating processing technology. (A sample computation-for the tamarind powder process discussed below-is shown in table 3.1
FIG. 1. Process Flow-sheet for Tamarind Powder
As a part of research and development in the post-harvest technology sector, the development of energy-saving, alternative technologies has been receiving attention in India. The GERs of some comparable groups of processed foods manufactured in accordance with the technology standardized by the Central Food Technological Research Institute (CFTRI) have been estimated to indicate the relative energy consumption patterns of these processes. An analysis of comparable technology systems producing products of similar end-use with respect to GER and energy efficiency can be an important tool in technology development and assessment. It is increasingly being realized that, if energy requirement is kept in mind during the development stage itself, it should be possible in the long run to make available to the industry low-energy-consuming technologies that can be taken up by new manufacturing ventures. Such a concept is valid as exemplified by the experiences of CFTRI described below.
Technologies for Tamarind Processing
Tamarind fruit is extensively used in Indian homes as an acidulant and flavouring ingredient. Considering the difficulties involved in handling and marketing these fruits in pulp form, CFTRI first developed a process to extract the solubles and make a concentrate having a good shelf-life and hygienic standard. Subsequently, a simpler and less energy-consuming process was developed to convert the pulp into a free-flowing powder. Figures 1 and 2 outline the two processes.
FIG. 2. Process Flow-sheet for Tamarind Juice Concentrate
A computation of the GER for production of the powder is given in table 3 (with the accepted conversion factors employed and the assumptions made in the absence of reliable data shown in table 4). Table 5 compares the GERs for the two processes. The process for producing tamarind powder requires significantly less investment for plant than does the process for the concentrate, and the packaging requirements are also minimal and less exacting. In addition, the powder has 1.22 times the acidifying effect of the concentrate. To supply 9 per cent acidity, the GER for users would be 2,955.53 kcal/kg for the powder and 10,780.70 kcal/kg for the concentrate. Assuming a total conversion of 1.65 million tons* of tamarind pulp produced in India by the two alternatives to supply an equivalent quantum of acidity, the GER would be 4,876.62 x 109 kcal for tamarind powder and 12,705.83 x 109 kcal for tamarind juice concentrate.
Weaning foods play an important role in the growth of children in the age group of one to four years. Assuming that approximately 9.75 per cent of the population in India falls in that age group, the need for weaning food will be about 2.56 million tons annually (with a total population of 717.22 million, 70.14 million children aged one to four, and a quantity intake of 100 g/day to supply 390 calories). A choice of three technologies developed at CFTRI is available to the industry: simple roasting (energy food), a malting technique, and a roller-drying technique (figs. 3, 4, and 5). From a comparative analysis of the GERs for these technologies (table 6) we can determine that, to produce 2.56 million tons annually, 5,767.78 x 109 kcal would be needed for the energy food 14,050.43 x 109 kcal for the malted weaning food, and 10,512.49 x 109 kcal for the rollerdried weaning food. The energy-food process is also the most efficient technology as a protein delivery system, as it has the lowest GER per gram of protein delivered.
TABLE 3. Model Calculation of Gross Energy Requirement: Production of Tamarind Powder(Basis: capacity, 500 kg per day; working three shifts, 300 days per year)
|A. Capital Input (amortized)|
|Total energy for building = 375 m2 @ 694.25 x 103 kcal/m2||=260,343.75 x 103 kcal|
|Energy input/day =
||43.39 x 103 kcal|
|a. Fabricated mild steel, 3.01 tons @ 11,940 x 103 kcal/ton||=35,939.40 x 103 kcal|
|b. Electric motors, 1 hp, 5 @ 45 x 103 kcal||=225.00 x 103 kcal|
|Total energy input for equipment||=36,164.40 x 103 kcal|
|Energy input/day =
||=12.05 x 103 kcal|
|B. Process Inputs (per day )|
|a. Water for process, 1 m3 @ 477.70 kcal/m3||=0.48 x 103 kcal|
|b. Electricity, 300 kWh @ 2,863 kcal/kWh||=858.90 x 103 kcal|
|Total||=859.38 x 103 kcal|
|19 persons working 8 hours @ 540 kcal/hr||=82.08 x 103 kcal|
|a. Starch for diluent, 200 kg @ 983.8 x 103 kcal/ton||=196.76 x 103 kcal|
(for 500 kg powder), polythene bags, 200 g
capacity, 2,500 @ 245 kcal
|=612.50 x 103 kcal|
|Total||=809.26 x 103 kcal|
|Gross energy requirement to produce 500 kg tamarind powder||=1,806.16 x 103 kcal|
|GER per ton||=3,612.32 x 103 kcal|
TABLE 4. Energy Input Factors Used for the Calculation of Table 3
|Unit||Energy per Unit|
|Building||m2||694.25 x 103|
|Mild steel (including fabrication and castings)||ton||11,940 x 103|
|Fabricated stainless steel||ton||21,735.35 x 103|
|Electric motors (1 hp)||each||45x 103|
|Polythene bags (200 g)||each||245|
|Bottles (200 g)||each||449 7|
FIG. 3. Process Flow-sheet for Roasted Weaning Food (Energy Food)
Normally, paddy is milled in single-huller mills or in the
organized sector in modern rice mills to polished rice, which is
cooked in households before consumption. Rice is also consumed in
a ready-to-use form after precooking of paddy, flaking, drying,
and milling by a number of small-scale processors in southern
India. Assuming an annual production of 53.6 million tons of
milled rice in the country, the GER for delivery as cooked rice
is 146,498.98 x 109 kcal while, by using an energy-saving
technology producing rice flakes, the same quantities could be
delivered at 61,072.38 x 109 kcal (table 7 and figs. 6 and 7). In
order to supply 70 per cent of the caloric needs of an average
Indian adult (2,400 kcal), the GER expended by the alternative
technologies will be 1,345 kcal for cooked rice and 595 kcal for
TABLE 5. Gross Energy Requirement: Tamarind Processing Systems
for End Product,
|Capital inputs (amortized)|
end use (providing 9% acidity)
FIG. 4. Process Flow-sheet for Malted Weaning Food
TABLE 6. Gross Energy Requirement: Weaning
|System Component||Foods GER for End Product, 103 kcal/ton|
|Roasted (energy food)||Malted||Roller-dried|
|Capital input (amortized)|
|GER to provide 400 cal of nutritional energy in end use||225 kcal||549 kcal||410 kcal|
|GER to provide 12 g protein||169 kcal||549 kcal||246 kcal|
Energy food provides 394 cal nutritional energy and 16 g
protein per 100 g.
Malted food provides 396 cal nutritional energy and 12 g protein per 100 g.
Roller-dried food provides 390 cal nutritional energy and 20 g protein per 100 g.
FIG. 5. Process Flow-sheet for Roller-Dried Weaning Food
FIG. 6. Process Flow-sheet for Parboiled Rice
FIG. 7 Process Flow-sheet for Flaked (Instant) Rice
Legumes are consumed in India after a process of dehusking and splitting carried out in the traditional sector using simple but time-consuming manual techniques (fig. 8). The legume splits are normally cooked in the household for long periods to make them soft and consumable. The major drawbacks in the traditional method are a high degree of dependence on the weather for the process to be completed, a high rate of breakage, and long cooking time for the splits to soften. Sustained efforts to modernize this sector have yielded fruitful results in the form of the development of a modern mill with improved productivity, higher yield of unbroken splits, and quicker cooking quality imparted to the final product (fig. 9). The GER profiles of the conventional and modern methods show a marked reduction in the energy requirement for the latter (table 8). To obtain one kilogram of cooked splits through the conventional technology, the GER is 6,467.15 kcal, while the modern mill gives the same product at 3,326.74 kcal/kg.
TABLE 7. Gross Energy Requirement: Paddy Rice Systems
|System Component||GER for End Product, 103 kcal/ton|
|Capital input (amortized)|
|GER to provide 1,700 cal nutritional energy|
|(70% of average adult daily need)||1,345 kcal||595 kcal|
Cooked rice provides 346 cal nutritional energy per 100 9. Flaked rice provides 325 cal nutritional energy per 100 g.
FIG. 8. Process Flow-sheet for Traditional Legume Milling
FIG. 9. Process Flow-sheet for Modern Legume Milling
TABLE 8. Gross Energy Requirement: Dhal (SpIit Pulses) Processing Systems
|System Component||GER for
(Cooked Dahl), 103 kcal/ton
|Capital inputs (amortized)|
Mangoes are extensively consumed in the form of ready-to-serve beverages, either mango juice or squash. For this study these products are compared for their caloric values and energy requirements for production as alternative food systems (table 9 and figs. 10 and 11). On this basis, canned mango juice is 1.57 times as energy-consuming as mango squash.
Considerable scope exists in developing and employing energy-saving technologies in the food industry as illustrated by the studies in this paper. The world-wide shortage of fuel for cooking and heating is beginning to receive attention from everyone concerned with development planning. It has been stated that even if India is able to grow enough food to feed its people by the year 2000, the people would not be able to cook it because energy sources are being depleted rapidly. Energy-resource depletion may be a fact for almost all developing countries aspiring to reduce the gap between the living styles of their population and that of the industrially advanced nations. Therefore, it is imperative that all available energy resources be judiciously and efficiently used. Since most developing countries are on the threshold of industrial development, they can afford to choose technologies based on minimum consumption of nonrenewable energy.
TABLE 9. Gross Energy Requirement: Processing Mangoes
|System Component||GER for
|Canned juice||Bottled squash|
|Capital inputs (amortized)|
|GER to provide
of beverage, supplying
|1,153 kcal||733 kcal|
Mango juice (TSS 20%) provides 21 cal nutritional energy per 100 g. Mango squash (TSS 40%) provides 42 cal nutritional energy per 100g.
FIG. 10. Process Flow-sheet for Canned Mango Juice
FIG. 11. Process Flow-sheet for Bottled Mango Squash
It is often debated whether industry in general can adjust to the energy situation by readily accepting fundamentally new processing methods or whether it would be better to be more conservative, making only minimal adjustments as needed, selecting first from the relatively well-tested and predictable alternatives currently available. While many feel that the traditional concept of economic viability should be the main criterion for industries in deciding whether to adopt energy-saving practices, many others hold the view that energy problems are sufficiently serious to consider energy consumption as the most important factor in the design of future processing systems. In any future research and development programme, while energy can be given an important place, other factors that contribute to economic feasibility should also be given serious consideration so that these programmes will have a better chance of being acceptable to the ultimate users, namely industry.
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