Energy Conservation in the Food Processing Industry A.L.RIPPEN Department Offood Science and Human Nutrition Michigan State University, East Lansing, Michigan 48824

715

Energy Conservation in the Food Processing Industry A.L.RIPPEN Department ofFood Science and Human Nutrition Michigan State University, East Lansing, Michigan 48824

(Received for publication June 2, 1975)

ABSTRACT requirements for production, transportation and The food system utilizes 12.8o/o of the total energy consumed in the processing to a stable form before distribution is Downloaded from http://meridian.allenpress.com/jfp/article-pdf/38/11/715/2396907/0022-2747-38_11_715.pdf by guest on 29 September 2021 United States. Higher fuel costs increase the need for operating only presented in Fig. 1. For many fruits and vegetables can efficient steam systems in food plants. Checking combustion efficiency 6 by monitoring flue gases and maintaining an exhaust gas temperature ning plants use about 3.5 x 10 BTU per ton of finished no higher than 150 F above that of the saturated steam helps save fueL product. Milk processing operations were found to The importance of insulating pipelines, buildings, and some equipment consume about 1.3 x 106 BTU per ton of raw product. is increased as available energy sources become limited. Enlarging a Electrical energy requirements, however, are higher for regenerator of a milk pasteurizer from 80 to 90% reduces steam requirements by one-half. Inserting a heat exchanger to capture heat processing one ton of milk than to can or freeze either lost through liquid or air discharges saves energy. Infra-red systems can peaches or green beans, as indicated in Fig. 2. reduce fuel consumption SO% in heating poorly insulated or partially A wide variation may exist in the energy required to exposed shipping, receiving, or similar areas. The energy efficiency ratio is an important consideration in selection convert raw products into different processed forms. of a refrigeration unit. When operating at low temperatures such as Nielsen (14) compared the heat needed to pasteurize and -28 F. a two stage ammonia system can save about 25% of the package fluid milk with the amount necessary to electricity used by a single stage installation. Modern light sources use manufacture cheese and dry whey. To convert 100 lb of electric energy more efficiently than some older systems. Employee milk to cheese and spray dried whey requires 81,620 involvement and cooperation is necessary for an energy conservation program to reach its potential. BTU whereas 15,600 BTU are used to process the bottled product. Food plants performing similar processing functions Growth in energy consumption without adequate vary in their energy requirements as influenced by expansion of supply suggests the need for conservation. location, physical arrangement, and overall efficiency. Rising costs of the energy sources now available have Data obtained from one relatively large dairy plant greatly increased the economic impetus for initiating provide some information on usage. This dairy processes conservation measures for both the private and industrial over 500,000 lb of milk per day into fluid products, ice sectors. In energy consumption the food processing cream, and cottage cheese and utilized 29.5 Kwh and 3 industry ranks fourth behind metals, chemical and 215.3 ft of natural gas per 1,000 lb of milk during the petroleum refining in the Standard Industrial first 6 months of 1974. Classification grouping (15). Since the impact of the energy situation in 1973 many Estimating the energy consumption by various food plants have made considerable effort to reduce segments of our food system is complex, therefore, some utility consumption. For example, one dairy achieved the inconsistencies in the estimated values reported may be following reductions during Jan., Feb .. and March, 1974 expected (6). Steinhart (18) reported that all of the compared with the same period of 1973: functions involved in the food system from production Kwh------·--· 9.5 o-/o reduction through consumption accounted for about 12.8% of the Natural gas------·- 4.5o/oreduction total energy used in the United States in 1970. Hirst (8) Water------15.0 o/o reduction reports that on a per capita basis we are approximately 6 The reduction in water usage was achieved mainly by 32.4 x 10 BTU (British thermal unit) annually in the recycling the discharge water from compressed air food system. The ratio of energy input into the system to after-coolers and ammonia compressor heads over a food energy consumed has increased from approximately cooling tower permitting its reuse as a coolant. Careful 3:1 to 7: 1 between 1940 and 1970. use of power and steam also reduced electricity and fuel consumption in this plant. FOOD INDUSTRY ENERGY REQUIREMENTS Another medium size dairy operation significantly A 1972 survey of the California food industry (2) decreased the natural gas burned through conservation indicates that for some agricultural products the measures beginning in 1972. Steps taken included combined production and transportation energy installation of a water softener for boiler feedwater, requirements exceeded the amount needed for thorough boiler descaling, discontinuance of direct processing one ton of product. The relative energy steam injection processing of fluid milk, lowering steam 716 RIPPEN

GREEN BEANS PRODUCTION AND TRMlSPORT CANN I ~IG

PROD. PEACHES AND CANNING ENERGY FORI'-1S INCLUDE: LP GAS.~ TRANS. GASOLINE; NATURAL GAS Arm ELECTRICITY

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0 2 If 6 8 10 12

Figure 1. Energy required to produce, transport and can one ton a_{ three products in California in 1972.

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0 CAN f::RZN FRESH CArl FRZN FRES:I OR DRY Figure 2. Electrical energy required to process one ton of three different products in California in 1972. pressures, and boiler shut-down on weekends. The effect of natural gas in 1973 and $1.55 in 1975 indicating the on gas purchases is given in Fig. 3. An indication of the sharp increase in the cost of fuel. Higher fuel costs monetary savings which was a direct benefit to this plant virtually mandates the operation of only efficient is evident from the data in Table 1. combustion and heat transfer systems. A comparison of the cost of steam produced by two hypothetical boilers THE STEAM SYSTEM with fuel to steam efficiencies of 70 and 80 o/o serves to A food processor in Michigan paid $0.82 per 1000 ftl illustrate the need to operate efficient units. Table 2 ENERGY CONSERVATION 717

A - SCALED BOILER B SO Ef~ ~·1ATER C - SHUTDOW~J 130 I LER ~vK ENDS 30 D DISCONTINUED DIRECT STEAM INJECTION

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1969 197::3 1971 1972 1973 197!+ YEAR Figure 3. Reduction in natural gas consumption in a Michigan dairy plam.

TABLE 1. Amount paid for natural gas by a Michigan dairy plant

6 mo. period Year Rate per 1000 ft3 Jan. through June 1971 $0.82 $9,740 1972 0.82 9,115 Excellent 10.0 12.8 l3.8 1973 0.82 5,691 Good 9.0 11.5 13.0 1974 0.92 5,243 Fair 8.5 10.0 12.5 1975 est. 1.55 8.400 Poor 8.0 9.0 12.0

TABLE 2. Cost qfproducing 1.000 lb of steam with boilers of70 and 80% and two fuel prices ciency rating for three different fuels as determined by the amount of C02 in the flue gas (13). Efficiency Natural gas Cost advantage 3 cost per 1000 !t of 80% boiler declines with a decrease in C02• Carbon monoxide is zero $0.82 $1.13 $1.00 $0.13 with complete combustion. Exhaust gases should contain 1.55 2.15 1.89 0.26 1 to 2% oxygen to assure an adequate amount to completely burn the fuel. Manufacturers of boilers can shows that the boiler with an 80 o/o fuel to steam assist in obtaining testing equipment for regularly conversion efficiency has a cost advantage of $0.13 per checking flue gases. 1000 lb of steam when gas costs $0.82 per 1000 ft 3• Boilers should obviously be kept clean and free of scale However, the cost advantage increases to $0.26 per 1000 (7). An increase in the stack temperature is an lb of steam when fuel costs $1.55 per 1000 ft3• Careful indication of scale buildup. A general guide used by some evaluation of the steam system is recommended with food plant operators is to avoid having exhaust gas special consideration of the effect of higher fuel prices. temperatures exceed the saturated steam temperature by Some plant operators have discovered that the time for more than 150 F (16). This figure can generally be recovering the cost of a new boiler to replace an older, applied in the operation of most common fire tube inefficient unit has been shortened substantially. boilers. A heat exchanger installed to recover some of the The burner on any boiler must be adjusted to obtain heat from exhaust gases for preheating incoming air complete combustion and maximum heat from the fuel. before combustion also saves fuel. Each 100 F rise in the An analysis of the flue gas for C02 (carbon dioxide) temperature of the air entering the burner results in a content is important. Table 3 gives the combustion effi- fuel saving of approximately 2 to 2.5% (10). 718 RlPPEK

Steam condensate returned to the boiler saves principle in energy conservation. For example, over an approximately 1 o/o in fuel cost for every 11 F increase in 8-h period at night, a fuel saving of 1 o/o or more results fecdwater temperature. Condensate also will usually for each degree F the temperature is lowered (12). Fuel reduce the amount of chemicals needed for feedwater savings diminish if the thermostat is lower than about treatment. 60 F at night.

REDUCIXG HEAT LOSSES PROCESSING OPERATIONS Heat passing from buildings to the outside atmosphere Food processing usually requires heating or cooling or that radiate from pipe lines or equipment from which and often both in many plants. Because heating and no benefit is gained represents a loss. Installing cooling are frequently used in an operation, insulation at the interface between where heat is desired opportunities are provided to employ the regenerative and where it yields no benefit is one of our principal heat exchange principle. The dairy industry has approaches to reducing heat losses. Most food processing successfully used milk-to-milk regeneration in the Downloaded from http://meridian.allenpress.com/jfp/article-pdf/38/11/715/2396907/0022-2747-38_11_715.pdf by guest on 29 September 2021 plants can probably benefit from a study of the various pasteurization process for about 25 years. During this areas of the building to determine insulation time the industry has saved a huge amount of steam with recommendations for each area. Because of variations in the milk-to-milk regenerator. All processes where processes, climate, location, and many other factors, a heating or cooling is involved should be analyzed for the general recommendation will not be attempted. In colder possibility of utilizing regeneration (17). In the analysis of climates where space heating is done for comfort or to an operation the discharges of hot or cold wastes should facilitate operations, some insulation will save fuel. be considered as a possible heating or cooling medium. Storm windows cut heat losses through a single pane of Using a suitable heat exchanger the heat may be glass in half. For a climate with 7,000 winter degree days transferred directly to a product or to another medium storm windows save about $17.00 annually per 100 ft2 of useful to the process. Passing warm water discharges glass area assuming steam costs $1.90 per 1000 lb. Heat from a blancher through a heat exchanger to preheat transfer through a single glass window is given as 1.13 incoming fresh water or boiler feed water is an example of BTU /h/ft2/c F temperature differential (1). recovering heat which would probably be lost. Uninsulated steam pipes radiate more heat than may Increasing the amount of regenerative heating and be realized. For example, a bare 2-inch pipe 100 ft long cooling of an existing regenerator can result in additional carrying steam at 1000 psig (Ib per in2 gage) will lose fuel savings. More heat exchange surface must be added 1.25 x 106 BTU in 24 h (13). Recovering the cost of steam to increase the amount of regeneration. Perhaps pipe insulation through fuel savings may require no more additional controls will be necessary for satisfactory than 1 or 2 years in industrial plants. performance. There is a practical limit of around 87 to Insulating refrigeration lines saves energy and is 90o-/o regeneration for present milk pasteurizers to avoid economically feasible in most food processing plants. operational difficulties. However. it should be noted that Approximately 43 BTU/F/ft2 of bare pipe is added to the increasing the regeneration of a HTST (high temperature refrigeration load in 24 h (7). This amounts to 3.8 tons of short time) pasteurizer from 80 to 90% reduces the steam refrigeration per year if the pipe is maintained at 0 F in consumed by one-half. an atmosphere of 70 F. Processing temperatures must obviously be adequate Heat flow from higher to lower temperature can be to achieve food safety and preservation. But there may be reduced if the temperature difference is decreased. Plant occasions where some temperatures could be adjusted operators can take advantage of this pinciple by reducing slightly without sacrificing quality or safety. An example the system steam pressure to the minimum necessary for is the possibility of lowering the pasteurization processing. The extent to which lower pressures reduce temperature of milk a few degrees in those instances heat losses is shown for 80 and 120 psig steam pressures where the actual processing temperature greatly exceeds in Table 4. Gradually lowering the steam pressure to the the legal minimum requirement. With a typical HTST unit, 8 to 9% saving in steam results by lowering the TABLE 4. Ejf'ect of' steam pressure on heat losses from 100ft of two .1ize pipes with 1 'lz in of' imulation process temperature from 176 to 165 F. The refrigeration requirement also is reduced 7% while processing at the lower temperature. If a program of lowering the 80psig 324F Difference temperature is undertaken, it should be done gradually 7,400 8,200 800 and with alertness to detect any adverse changes which 3-inch 9.700 10.700 1,000 ------might develop affecting product quality, particularly * In ambient 70 F. shelf life. point where processing functions begin to be affected helps to determine the minimum pressure required to SPACE HEATING operate the plant. Dialing down room thermostats in Space heating requirements differ between areas of a winter and up a few degrees in air conditioned rooms in food processing plant depending on the design and the summer takes advantage of the temperature differential kind of operation conducted in each area. But at times ENERGY CONSERVATION 719 during cold weather, most areas need some heat. production interruptions are inefficient and also tend to Infra-red heating systems offer economy and comfort increase power consumption. with less fuel in rooms with high, poorly-insulated Utility companies may insist on adjustments in ceilings or where there is considerable exposure to equipment if the power factor becomes too low. A power outside weather conditions. Loading or receiving docks factor below 0.85 causes concern for utility firms. which are not tightly enclosed, warehouses and supply Artificial lighting represents about 5% of the nation's storage rooms and:in some instances, processing areas total energy consumption. However,lighting accounts for lend themselves to infra-red heating systems. In some approximately 40% of the electrical energy used in the instances fuel consumption by gas type infra-red heaters commercial and institutional sector of our economy (3). was observed to be about SO% less than that for direct For this group effective application of lighting systems is gas fired space heaters for heating comparable industrial an important consideration. Some general areas which buildings (JJ). have been suggested for conserving energy in commercial

Certain processing operations can be a heat source for lighting systems are as follows: (a) Survey present Downloaded from http://meridian.allenpress.com/jfp/article-pdf/38/11/715/2396907/0022-2747-38_11_715.pdf by guest on 29 September 2021 space heating by directing warm exhaust air through a lighting levels by area or operation and establish heat exchanger. If conditions warrant, it may be minimum requirements consistent with good lighting satisfactory to discharge high quality warm air directly practices. The survey should also note location and type into an adjacent room. Humidity and condensation of light source including switches and other controls. (h) control become important considerations, however, when Develop recommended changes in fixture locations, type, utilizing warm moisture-laden air for space heating. controls, light intensity, and others as appropriate. (c) Follow a maintenance program for regular luminaire ELECTRICITY cleaning, lamp replacement, and fixture ventilation. (e) Sharp increases in the fuel cost adjustment portion of Develop a program to obtain employee cooperation in electric bills during 1974 reflects directly the fuel turning off lights when not in use. situation and probably portends things to come. Plant operators may discover economic advantages by Projections of electric power demand in the United replacing a portion or all light sources with newer, more States indicate the need to increase generating capacity efficient systems. In any event, the potential for energy from the present 450,000 to 650,000 megawatts by 1985 saving warrants investigation. Comparative efliciencies (19). The steady rise in construction costs of generating of some commonly used light sources are given in Table plants leaves little doubt that further price increases for 5. electrical energy lies ahead. sources The refrigeration system is the biggest electrical load in many food plants. It is, therefore, necessary to keep the system performing efficiently. Good overall Incandescent 10-20 Mercury 40·60 maintenance is required with particular emphasis on Fluorescent 50-70 eliminating any obstructions to heat flow at all heat Metal halide 70-90 transfer surfaces. sodium 90-120 Ammonia systems used for cooling low temperature storages or for rapid freezing of food should be the two EMPLOYEE INVOLVEMENT stage type. Single stage type ammonia systems using reciprocating compressors are not recommended for Energy conservation will usually require some suction pressures of 0 psig (-28 F) or below. Even at 0 engineering, scheduling, or operational changes; but psig the two stage system has about 25 o/o lower brake unless employees are motivated in an energy saving horsepower requirement than a single stage installation effort, the goals may not be reached. Employee (5). The difference increases to approximately 40o-/o in suggestions should be solicited. Their voice in planning favor of the two stage system when operated at 5.4 inches and goal setting and their sincerity in executing a Hg vacuum (-35 F). In this comparison condensing conservation program may well determine the success or pressures to 185 psig were considered. failure of the project. Some firms have effectively utilized The energy efficiency ratio (electrical energy required a committee of employees to develop and conduct a per unit of capacity) should be considered when selecting conservation program (9). Prominently displaying a a freon condensing unit for a specific refrigeration job. sizeable chart showing the amount of the various utilities Most manufacturers can provide data on power used each month per unit of production helps maintain consumption (BTU/kwh) under given operating the interest and cooperation of everyone. conditions. A slight change in the bore size, for example, can make a difference in excess of 15% in the energy used CONCLUSION when performing under certain conditions (4). Food processing is a necessary function in our food Electric power requirements can generally be lowered system. Those performing this important function must by carefully scheduling operations so that equipment is assume the responsibility of using the available energy doing productive work when running. Frequent wisely. Although progress appears to have been made, 720 RIPPEN additional efforts and changes are needed to reduce 69.428,000 BTU's and $86,656. 1974. Food Processing 35(10):96- energy requirements. 98. 10. Kent's Mechanical Engineers' Handbook. 1954. Power volume. J. K. Salisbury, Editor. 12th ed. John Wiley and Sons. Inc .. New REFERENCES York. 1459 p. 1. /\mer. Society of Heating. Refrigerating and Air Conditioning En 11. Michigan Consolidated Gas Co., Detroit, Mich. 1972. Case his gineers, New York. 1968. Guide and data book-Applications. tory, Muskegon district. Chap. 4:51. 12. Michigan Department of Commerce, Lansing, Mich. 1973. How 2. Cervinka, V., W. J. Chancellor. R. J. Coffelt, R. G. Curley, and to heat your home with less fuel. Folder 2 p. J. B. Dobie. 1974. Energy requirements for agriculture in Cali 13. Milk Industry Foundation, Washington, D.C. 1967. Manual for fornia. Joint Study Calif. Dept. of Food and Agr. and Univ. of milk plant operators. 3rd ed. 919 p. Calif., Davis. 151 p. 14. Nielsen. V. H. 1974. Dairy industry contemplates future position .1. Consumers Power Co., Jackson, Mich. 1974. Energy saving tips in the energy picture. Amer. Dairy Rev. 36(4):46-49; 62, 63 . Lighting systems. Mimeo. 6 p. 15. Patterns of Energy Consumption in the United States. 1972. Re 4. Copeland Refrigeration Corp., Sidney. 0. Engineering Data on Z port prepared for Off. of Sci. and Tech. by Stanford Res. Inst., Downloaded from http://meridian.allenpress.com/jfp/article-pdf/38/11/715/2396907/0022-2747-38_11_715.pdf by guest on 29 September 2021 310 Units. Descrip. Broeh. Form No. 5530-Rl. 2 p. Supt. of Documents, U.S. Gov't. Printing Off., Washington, D.C., 5. Creamery Package Manufacturing Co .. Chicago. Ill. 1949. Per Stock No. 4106-0034. sonal Communication. 16. Rippen, A. L. 1975. Conserving energy in the dairy plant. Dairy 6. Economic Research Service. USDA. 1974. Appetite for energy. and Ice Cream Field. 158(2):36, 97. The Farm Index 13(11-12):4-6. 17. Rippen, A. L. 1974. Fuel-handle with care. Amer. Dairy Rev. 7. Farrall. A. W. 1963. Engineering for dairy and food products. 36(5):16, 17, 43, 44. John Wiley and Sons, Inc., New York. 674 p. 18. Steinhart, J. S., and C. E. Steinhart. 1974. Energy use in the U.S. 8. Hirst, E. 1974. Food-related energy requirements. Science 184 food system. Science 184(4134):307-316. (4134): 134-138. 19. Utilities: Weak Point in the Energy Future. 1975. Business Week. 9. Kaiser, R. J.. F. M. Stark, and W. S. Stinson. Swift plant saves (2364):46-54.

International Institute of Refrigeration Meeting

The Australian National Committee for the I.I.R. is in other countries. orgamzmg a Joint Meeting of Commissions in A Call for Papers for the meeting will be issued shortly, Melbourne in September 1976. This will be the first setting out the selected theme and a list of preferred occasion on which the Institute has held a meeting in topics. Papers will however also be invited in the general that country, and it is being arranged by the Committee areas of interest of the five Commissions. Limited funds in collaboration with local professional and technological will be available to assist selected authors with travel Societies. costs. The aim of the meeting is to bring Australian research The organizer of the meeting is Mr. F. G. Hogg, I.I.R. and development in the relevant fields to the notice of an Liaison Officer in Australia, from whom further details international audience, and to acquaint Australian can be obtained. His address is P.O. Box 26, Highett, science and industry with current work being carried out Victoria, 3190, Australia.