Energy Use in Wisconsin s Dairy Industry and Options for Improved Energy Efficiency

Transcription

1 Energy Use in Wisconsin s Dairy Industry and Options for Improved Energy Efficiency By Adriano Sun with Douglas Reindl Douglas Reinemann 1

2 Table of Contents PART 1 WISCONSIN DAIRYING: BACKGROUND AND TRENDS... 3 Introduction... 3 Wisconsin Dairy Farms and Milk Cows... 4 Number of Dairy Farms by Herd Size... 7 Milk Production: per Cow and Herd Size Wisconsin Dairy Manufacturing Wisconsin Cheese Final Remarks References PART 2 DAIRY PROCESSING OVERVIEW Background On-Farm Operations Milk Transportation Manufacturing of Dairy Products PART 3 ENERGY USE IN DAIRY PROCESSING Introduction Dairy Market and How It Influences Wisconsin Energy in Wisconsin On-Farm Operations Milk Transportation Dairy Manufacturing PART 4 - Membrane FILTRATION in Cheese production Introduction On-Farm Concentration Microfiltration of Raw Milk Use of UF Milk in Cheesemaking RO in Cheesemaking Energy Requirements References PART 5 CASES OF Energy process improvement Understanding the Analysis Case Scenarios Case Current Case Case Case Case

3 PART 1 WISCONSIN DAIRYING: BACKGROUND AND TRENDS Introduction Wisconsin holds the title of America s Dairyland as dairy farming and cheesemaking have been a practice and culture for more than 150 years. The dairy industry is of great importance generating nearly $20 billion a year for the states economy and employing over 128,000 dairy-related jobs, which represents $5.5 billion of the states income (Wisconsin Milk Marketing Board-WMMB, 2006). These numbers result a total milk production of 22,866 million pounds of milk produced in more than 17,000 dairy farms, ranking second in 2005 just behind California with 37,564 millions (USDA National Agricultural Statistics Services). Wisconsin is considered the Cheese State leading the rank of cheese production with 2,405,699 thousand pounds of cheese last year. The state is also the leader in production of specialty cheeses with 15% of Wisconsin s cheese production. In addition, Wisconsin ranks first in the number of organic farms and number of cheese plants in the country (WASS and Wisconsin State Journal). Despite these achievements, the trend developed over the years has been of concern to Wisconsin dairy industry. The number of milk cows and dairy farms in Wisconsin has declined continuously over the last 15 years and milk production has been flat to decreasing since 1988 (Jesse, 2002). On top of that, California achieved two billion pounds of production compared to 2.4 billion pounds of cheese produced in Wisconsin last year, and the Western state is expected to get ahead of Wisconsin in total cheese production in a near future. 3

4 The following discussion corresponds to background information and forecasts of the dairy industry in Wisconsin, based on the current dairy market and trends developed over the years. Wisconsin Dairy Farms and Milk Cows According to Wisconsin Agricultural Statistics Services (WASS), there are currently 14,717 dairy herds licensed in the state. Recent studies also show that Wisconsin has approximately 1,241,000 dairy cows with an average of 84 dairy cows per dairy farm. Total monthly milk production is estimated to 1.96 billion pounds with 1,580 pounds of milk produced per cow monthly (WASS, 2006). The trend on dairy farming in Wisconsin is emphasized in a 2002 report Rethinking Dairyland, developed by the Department of Agricultural and Applied Economics at the University of Wisconsin-Madison. About 1.3 million milking cows was reported in February of 2002 and 17,711 dairy farms wide spread within the state, as shown in Figure 1.1. Figure 1.2 illustrates the distribution of number of cows throughout the state in Figure 1.1 Wisconsin Dairy Herds by County, Figure 1.2 Wisconsin Cow Number by County, (Source: Jesse, 2002) (Source: WASS and Jesse, 2002) 4

5 In December of 2004, WASS published results of a dairy producer survey from selected dairy operators in Wisconsin. Among the results, the survey compares the number of herds and milk cows from 1999, 2004, and a projection for 2009, which is shown in Table 1.1. Figure 1.3 is a representation of the trend for dairy farms and number of cows per farm until 2002 from Jesse (2002) Rethinking Dairyland report. Table 1.1 Wisconsin Dairy Herds, 1999, 2004, and 2009 Projection. (Source: WASS) Year Number of Herds Number of Milk Cows Milk Cows per Herd ,000 1,370, ,400 1,240, * 14,717 1,241, ,300 1,260, * Current numbers inserted from WI Agricultural Statistics Service Figure 1.3 Wisconsin Dairy Farms and Average Herd Size. (Source: Jesse, 2002) Jesse (2002) shows that despite the number of cows per farm increased over the years, the number of dairy farms has fallen steadily. The number of WI dairy farms lost each month in 2004 was near 50, where about 100 milking operations were lost each month between 1993 and 2001 (WASS 2004 Dairy Producer Survey). In addition, same trend is indicated in a previous research conducted in 2001 by the Program on Agricultural Technology Studies (PATS), in 5

6 which it is characterized an increase in the net loss (7 to 10% per year) of dairy farm numbers, while there has not been a significant number of farmers entering the sector (Figure 1.4). Figure 1.4 Estimated Annual Numbers of Entrants and Exiters in WI Dairy Sector. (Source: PAT, 2001) It is interesting to point out that the average age of farmers response from the WASS survey was 52 years old; 68% of dairy producers are in the age range of 40 to 60, 20% are over 60 years old, and only 12% are under 40. From the WASS survey and the study by PATS, it can be concluded that both herd operations with less than 40 cows and 43% of the late-career farmers are the most likely to exit the industry. The reality, however, is that the total number of U.S. farms has also been decreasing for the past century as shown by census information from USDA and WASS. There are currently 100,000 U.S. dairy farms, in which 18% of them (17,000) are situated in Wisconsin. Thus, it can be said that the state is one of the few in the U.S. with over 10,000 farms. To make matter worse, the total number of cows in the state fell by 26% (approximately one-half million) from 1980 to 2000, where the highest losses were in the Northwest, Southeast, and Southwest regions of Wisconsin (Jesse, 2002). The concern is more stressed by observing the fluctuation of milk cows in WI since 1924, and the sharp reduction since 1980 s (Figure 1.5). 6

7 Yet, it is believed that California and other states in the West gained almost as many cows as Wisconsin and other Eastern and Midwestern states lost (Figure 1.6). These trends indicate that as the number of cows is lost by states in both the East and the Midwest and taken by the Western states, 55% of U.S. milk will be produced by the West in a 2015 projection, with 35% to the remaining regions (Jesse et al., 2002). Figure 1.5 WI Milk Cows from 1924 to Figure 1.6 Change of Milk Cows from 1985 to (Source: Jesse et al., 2002) (Source: Jesse et al., 2002) Number of Dairy Farms by Herd Size As the number of dairy farms in Wisconsin tends to decrease in the following years, the dairy herd size tends to increase. It becomes more difficult to small farmers to compete and produce at certain level to be economically profitable. Thus, new production strategies of largerscale milking parlor/free stall housing systems and farm modernization are taken into consideration. Herd size distribution data can be found in the USDA National Agricultural Statistics Services. As shown in Figure 1.7, herd sizes vary greatly across the state, where the East Central region has the largest herd size. In addition, Barham et al. (2005) states that the average herd size in Wisconsin grew at a rate of about 3% a year. From 1990 to 2002, the average herd size 7

8 jumped from 50 cows to nearly 71 cows (shown in Figure 1.8), indicating that moderate size dairy farms is the predominant type of dairy operation in Wisconsin. Likewise, 93% of the state s dairy farms were under 200 cows and 80% were under 100 cows, in Note that the average dairy herd size in California is approximately 860 cows and 46% of all dairies are over 500 heads (California Milk Advisory Board/California Department of Food and Agriculture), and the average in the U.S. corresponds to 135 cows per farm and 77% of the dairy farms have less than 100 cows (America s Dairy Farmers). Figure 1.7 Average Dairy Herd Size by Region. (Source: Turnquist et al., 2004) Figure 1.8 Average Dairy Herd Size in Wisconsin, (Source: Barham et al., 2005) 8

9 Number of Herds In Table 1.2 the number of dairy farms by herd size from 2000 until 2005 in shown, while Figure 1.9 illustrates this trend. Also, a 2009 herd projection is shown from the 2004 Dairy Producer Survey by USDA-WASS. Table 1.2 Wisconsin Dairy Herds by Herd Size. (Source: NASS and WASS) Milk Cow Herd Size Year Total ,700 6,200 8,300 2, , ,150 5,300 7,800 2, , ,700 4,700 7,500 2, , ,500 4,500 7,100 1, , ,300 4,100 6,700 1, , ,200 3,900 6,400 1, , ,150 2,300 4,700 1, ,300 8,000 7,000 6,000 5,000 4,000 3, Figure 1.9 Illustration of Wisconsin Dairy Herds by Size. (Source: NASS and WASS) 2,000 1, Milk Cow Herd Size Based on the information shown above, some observations can be taken. The expansion in dairy herd size in Wisconsin has been noticed in the early years, and historically, farms under 100 cows were responsible for the majority of cows and milk production in the state. However, special attention has been taken to herds with more than 200 cows as it grew rapidly between 9

10 1997 and 2002, and as a result, this farm size accounts for the majority of cow number, not to mention milk production. Meanwhile, herds with 100 or less cows accounts for 20% of the farms only. Barham et al. (2005) indicate trends in dairy farming over the past five years, where almost 2/3 of the dairy farms remained constant in regards of herd size. Furthermore, farms under 100 cows were more likely to grow at moderate rate, whereas herds with 100 or more were quite rapid. Also, it was pointed out that rapid herd expansion took place in already larger dairy herds. Furthermore, PATS posted the highlights of a poll from about 700 dairy farmers in Wisconsin. As shown in Figure 1.10, it is observed that the largest percentages (total of 12.4%) of the farmers who will be unable to continue farming or have already quit fall in the 100 cows and less herd size category. An interesting observation is that dairy farms with 100 or more cows have a lower percentage than small farmers regarding expectation to continue farming for one more year, which is explained by considering that they will be more likely to be in the sector for longer years (2 to 10 years). Figure 1.11 stresses tendency of smaller dairy herds to exit farming in the next five years, compared to larger herds that will focus in expanding their operations. In addition, the survey shows that herds with more than 100 heads are expected to grow and increase their milking operation at higher rate than farms with less than 100 milk cows. 10

11 Percent (%) Percent (%) 45 Unable to Continue 1 more year 2 to 3 years 4-10 years Indefinetely cows cows cows cows 200+ cows Dairy Farms by Herd Size Figure Dairy Farm Poll: Years Expect to Continue Farming. (Source: PATS, 2004) 60 Expand by 25% or more Expand by 50% or more Exit in the next 5 years cows cows cows cows 200+ cows Dairy Farms by Herd Size Figure Dairy Farm Poll: Expansion/Exit plans for the next 5 years. (Source: PATS, 2004) 11

12 Number of Farms (in Thousands) Milk Production (Millions of lbs) Milk Production: per Cow and Herd Size Milk production information by Wisconsin s county and per cow are currently available and can be found in the USDA-NASS website. Figure 1.12 gives a representation of milk production by county and indicates the 5 top counties in 2004 and Figure 1.13 by region. Figure 1.14 illustrates a steady milk production as the number of dairy farms is constantly decreasing. Figure Change in Milk Production, (Source: Turnquist et al., 2004) Figure 1.12 WI Milk Production by County in (Source: Wisconsin 2005 Agricultural Statistics, WASS) Legend in million lbs: white- 0 to 99; black ; grey- 400 to 599; and light grey * 28,000 21,000 14,000 7,000 Figure 1.14 WI Milk Production and Number of Dairy Farms Trend. (Source: NASS and WASS) 0 Farms Production 12

13 In 2005, the state of Wisconsin represented 13% of the milk produced from the total billion pounds in the U.S. (WMMB, 2006). Jesse (2002) points out a 4% gain in the state milk production between 1980 and 2000, where the East Central region contributed with 19% increase whereas both Northwest and Southeast regions were down about 7% and 6%, respectively. In addition, milk production per cow in Wisconsin increased almost 40% (equivalent to 5 thousand lbs) between 1980 and 2000 (Jesse, 2002). Currently, the monthly milk production per cow is estimated to 1,580 lbs of milk, and the daily production is 52.7 lbs of milk per cow (WMMB, 2006). As shown in Figure 1.14 (above), even though the number of dairy farms decreased considerably, not only has the milk production in the state increased over the years but has also kept steady in the past few years. In fact, dairy producers are able to increase their production per cow by implementing strategies, such as milking three times a day, breeding cows that produce more milk and using specific feeds that allow increase of production. Another strategy lied on implementing large scale milking systems as mentioned earlier, by increasing the herd sizes. For instance, dairy herds with represented 19% of the milk produced in 2005; herds with and 500+ heads represented 18 and 16%, respectively (USDA-NASS). Thus, greater herd sizes allow farmers to achieve higher milk yields per cow as compared to smaller farms. Other forms for growth and viability in Wisconsin dairying are pointed out in Rethinking Dairyland 2 report. From the available data by USDA-NASS (shown in Table 1.2 and Figure 1.9), it is shown that the number of dairy farms with herd size has held nearly constant with 19% of milk produced since 1993 (when data was first available). Thus, as observed by Jesse et al. (2002), 13

14 the dairy producers that cannot longer compete are the ones in the herd size category below 100 cows. Furthermore, a projection study indicates that the dairy herds with 100 or more cows will be responsible for the majority of milk produced in 2010 compared to the actual number from 2001 (Jesse et al., 2002). The following table reproduces a summary of this forecast. Table 1.3 WI Milk Production Forecast by Herd Size. (Source: Jesse et al., 2002) Cow Numbers Milk per Cow (lbs) Total Milk (bi. lbs) Year > > > , , ,000 15,532 16,278 18, , ,818 1,082,731 18,809 18,333 21, Wisconsin Dairy Manufacturing According to the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP), there are 379 dairy-related operating facilities in the state of Wisconsin reported in last September of Jesse (2002) reported 364 dairy plants from 2001 DATCP information. The Wisconsin Milk Marketing Board indicates currently 202 manufacturing plants of dairy products. Independently of the exact number of dairy plants in Wisconsin, there are currently 115 cheese plants spread within the state (Figure 1.15). These 115 plants were responsible for manufacturing 2,405,699 pounds of Wisconsin cheeses in 2005 (USDA-NASS), which represents about 26.4% of the total U.S. cheese production (WMMB). In addition, Wisconsin contains 11 buttter factories producing the second highest production in the U.S., behind only of California. In fact, little milk is actually used directly in butter-making, where most of the cream is obtained from standardizing milk for cheese-milk or it 14

15 is imported from other states (DATCP and Jesse, 2002). Moreover, from the 2005 DATCP dairy plant directory, there are still 29 processed cheese plants, 31 ice cream facilities, 39 of the plants process whey, and other dairy operation plants. Figure 1.15 Wisconsin Dairy Plants in (Source: Jesse, 2002) Wisconsin Cheese Nearly 90% of the 22,866 million pounds of milk produced in the state are used in the manufacturing of cheese in Figure 1.16 illustrates the states cheese production by variety for Today, Cheddar and Mozzarella account for almost 2/3 of the production, with 28.4% and 33.0% respectively. From 2000 until now, the major change corresponds to the increase in the production of specialty cheeses from 10% to 15%, which is equivalent to 355 million pounds. Indeed, 77 of the state s 115 cheese plants make at least one specialty type of cheese. 15

16 Number of Cheese Plants Cheese Production (Millions of Pounds) Figure 1.16 Wisconsin Cheese Production for (Source: Jesse, 2002) Although Wisconsin is the leading state in cheese production, the number of cheese plants in the state fell more than 60% between 1980 and 2000, and has kept steady since then (Figure 1.17). The largest fall corresponded to Cheddar cheese plants, whereas the number of plants of Mozzarella and other Italian cheese varieties remained constant (Jesse, 2002). Similarly to the dairy farms, where the number fell while milk production remained the same, average plant scale increased and consequently, the average cheese volume per plant increased as well , , , , , Number of Cheese Plants Cheese Production * Figure 1.17 Wisconsin Cheese Plants and Cheese Production. (Source: WMMB, 2006) Final Remarks From the discussion above on the dairy industry in Wisconsin, some remarks can be summarized as follows: 16

17 Number of dairy farms has fallen since 1965; Smaller dairy herd tend to disappear, while it is expected to have more farms with 100 or more milk cows; Number of milk cows decrease, but milk production keeps steady due to milking strategies; It is difficult to predict an increase on milk production, because number of milk cows is not going up; Large herd sizes will be responsible for the majority of milk produced; Number of cheese plants has decreased over the years and there are 115 plants now in 2006; and Cheese production has been constant, but California and other Western states will pass Wisconsin in the coming future. References America s Dairy Farmers. Milk Facts. Available online at: Barhma, B.L., Foltz, J., Aldana, U Expansion, Modernization, and Specialization in the Wisconsin Dairy Industry. Department of Agricultural and Applied Economics, Program on Agricultural Technology Studies (PATS), University of Wisconsin-Madison. California Milk Advisory Board/California Department of Food and Agriculture. Milk and Dairy Farm Facts. Available online at: Jesse, E Rethinking Dairyland: Background for Decisions about Wisconsin s Dairy Industry. Marketing and Policy Briefing Paper, Department of Agricultural and Applied Economics, University of Wisconsin-Madison. Jesse, E., Barham, B, and Jones, B Rethinking Dairyland Chapter 2: Wisconsin and U.S. 17

18 Dairy Industry Trends. Marketing and Policy Briefing Paper, Department of Agricultural and Applied Economics, University of Wisconsin-Madison. Leaf, N Top Stories: State Signs on to Signature Cheese. Wisconsin State Journal. Available online at: PATS Wisconsin Family Farm Facts: Dynamics of Entry and Exit on Wisconsin Dairy Farms in the 1990s. PATS Research Report No. 7, The Changing Face of Wisconsin Dairy Farms: A Summary of PATS Research on Structural Change in the 1990s. PATS Highlights from the 2003 Wisconsin Dairy Farm Poll. Program on Agricultural Technology Studies (PATS), University of Wisconsin-Madison. Turnquist, A., Foltz, J., Roth, C Land Use Fact Sheet No. 1: Wisconsin Dairy Industry. Program on Agricultural Technology Studies (PATS), University of Wisconsin-Madison, University of Wisconsin-Cooperative Extension. USDA-Wisconsin Agricultural Statistics Services (WASS)/Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP) Dairy Producer Survey. Available online at: USDA-National Agricultural Statistics Services. Census information of U.S. dairy farms, milk production, and cheese production. Available online at: USDA-Wisconsin Agricultural Statistics Services (WASS). Agricultural Statistics Database. Available online at: Wisconsin Milk Marketing Board (WMMB)/Wisconsin Dairy Producers. Dairy and Cheese Statistics. Available online at: Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP). Statistics information. Available online at: 18

19 PART 2 DAIRY PROCESSING OVERVIEW Background Milk production began as early as 6,000 years ago during the Agricultural Revolution. This was also the period in which ancient man learned to domesticate animals and recognized the nutritive value of their milk. From the early years until now, milk is a source of both energy and necessary nutrients for growth, and it is the only food of a young mammal in its first period of life. Milk also contains antibodies that are responsible to protect the young mammal against infection and diseases. Fermented products were discovered accidentally in attempting to preserve and store milk. Bacteria present in milk would have produced acid during storage, leading to coagulation of milk proteins (caseins) and entrapment of fat, forming a gel-like structure. Fermented milk, sour cream and lactic butter were the three fermented products originated from this acid development, and cultures of lactic acid bacteria are used nowadays to promote acidification. Cheese was also discovered as a mean of preserving milk and its principal constituents. By breaking the gel developed through acid coagulation, curds and whey were separated, and the shelf-life of curds was extended by dehydration and salting. It was also observed that stomach of slaughtered animals would have been used to preserve milk in the form of curds. It is now known that milk extract enzymes (chymosin) from the stomach tissue of slaughtered animals resulting in the coagulation of milk during storage. The current availability and distribution of milk and milk products are a result of technological advances, allowing the transition between making fermented products as a mean of preservation into a commodity. This section of the reports gives a general overview of the three stages of dairy processing: on-farm operations, transportation, and cheese manufacturing. 19

20 On-Farm Operations Milk Production Milk production takes place during lactation. Milk is secreted into the cow s udder shortly before calving, and at parturition, a yellowish colored fluid is secreted from the mammary gland. This fluid is known as colostrums and contains a high content of serum protein that provides antibodies to protect the newborn. Milk returns to its fresh composition within 72 hours and it can then be used as a food supply. The cow continues to give milk for an average of 305 days producing approximately 15,500 pounds of milk. However, milk production decreases throughout the lactation period to about 15-25% of the peak volume (Figure 2.1). As a result, the highest milk yield corresponds to the first 2-3 months post-parturition, and at the reduction stage, milking is interrupted to give cow a non-lactating period of up to 60 days prior to calving again. Figure 2.1 Lactation Cycle. (Source: Goff, D.) Machine Milking In the late 19 th century, milking machines were introduced to replace conventional hand milking on medium and large dairy farms. As shown in Figure 2.2, the basic milking components are: a vacuum pump, a vacuum vessel for milk collecting pail or milk pipeline, teat 20

21 cups connected by hoses to the vacuum vessel, and a pulsator to alternate vacuum and atmospheric pressures applied to the teat cups. Figure 2.2 Machine Milking and Milking Pipeline System. (Source: Tetra Pak, 1995) The teat cup unit contains a teat cup liner, which is an inner tube of rubber attached to the teat cup, so that during milking, the inside of the line is under a constant vacuum of about 0.5 bars when in contact with the teat. The objective of the pulsator is to alternate 0.5 bar vacuum pressure during suction and atmospheric pressure during the massage stage. During the massage stage, the teat cup liner is pressed together to stop milk suction. A period of teat massage takes place again and another one to allow new-milk to come to the teat cistern. The suction stage is followed next and this alternation continues through milking. The pulsator alternates between 40 to 60 minutes to avoid accumulation of blood and fluid in the teat, which can be painful to the cow. In the past few decades, automatic (or robotic) milking systems were introduced as potential resource to enhance the quality of life for dairy operators and their cows as well as to increase both milk production and quality. Helgren and Reinemann (2006) reported that in 2004 there were over 2200 farms using automatic milking systems worldwide, mostly in Europe. In the U.S., however, these new systems are considered experimental only, according to the U.S. Food and Drug Administration (FDA) through the Pasteurized Milk Ordinance (PMO). 21

22 One of the main concerns regarding these automatic milking systems lies on milk quality, because bacteria count can be higher due to possible contamination opportunities. However, Hengren and Reinemann (2006) reported no significant difference in somatic cell count (SCC) nor in total bacterial count (TBC) between milk from conventional systems and automatic milking systems. In addition, there were recent improvements on washing and pre-cooling of the milk, resulting in acceptable bacteria counts (Rotz et al., 2002). Another possible drawback is on lower solid content of the milk, once milk protein and fat concentration may be lower than normal due to frequent milking. Moreover, the system requires reliable in-line sensors to assess health of the cow and quality of milk that was previously done by the dairy producer. A list of publications that further elucidates advantages and disadvantages of automatic milking systems are available in the literature. Figure 2.3 Automatic Milking System. (Source: UW-MRIL) Milking Center Milking center is the facility designed to milk cows and handle milk on a dairy farm. The minimum features of a milking center are (Graves and Reineman): holding area, milking parlor, milk room, and utility area. Other sections can also be designed in the facility, but the major component is the milking parlor. 22

23 The milking parlor corresponds to the area where cows are brought from the feeding and resting housing area to be milked. A proper designed milking parlor has an organized assembly line type, milk procedures and systematic work routines, so that cows spend an hour or less in the parlor. Basically, the position of how the cow stands in relation to each other and to the milker categorizes the type of milk parlor. For instance, elevator parlors have cows elevated above the milker in comparison to flat parlors. Moreover, as shown in Figure 2.4, cows can stand at an angle to the operator (herringbone), side by side facing to the operator (parallel), or cows can stand in a rotary platform that moves around while milkers stay in one location. Milk parlors can also be organized according to how cows enter and leave the milking area. (More information can be found in Graves and Reinemann.) Figure 2.4 Milking Parlors: Herringbone (left), Parallel (center), and Rotary (right). (Source: Schutz, M.) Milking Operations In on-farm operations, cows are brought to the milking center to be milked. The general operation is to milk twice per day, but it is quite common to milk cows three times per day, and sometimes four times a day. This operational strategy increases milk production in up to 12%, 23

24 but it can be labor intensive as cows are milked in three 7-hours shifts with a couple of hours gap used for washing and cleaning of the milking equipment. Cooling of the fresh milk is essential for milk quality. Milk itself is an excellent substrate for bacteria containing a wide range of nutrients. Milk leaves the cow s udder at a temperature of about 98.6 F (37 C), which is an optimum temperature for bacteria growth. Therefore, milk must be chilled to approximately 45 F (7 C) immediately. In fact, the FDA s Agriculture, Trade & Consumer Protection (Chapter ATCP 60) along with the Pasteurized Milk Ordinance (PMO) determines that milk shall be cooled to 45 F (7 C) or less within 2 hours after milking. It also points out that if cooled milk is mixed with uncooled milk, the blend temperature should not exceed 50 F (10 C) at any time. In dairy farms with milking machine operations, direct expansion tanks are used for cooling and storage of milk. The item ATCP (3) states that a bulk milk tank should be capable of cooling all milk placed in tank to a temperature of 45 F (7 C) within one hour. However, in large milking operations, the bulk tank is inadequate and it is only used to maintain the required storage temperature. Therefore, cooling of milk is carried out by pre-cooler. The pre-coolers are heat exchangers where water flows in opposite direction of the warm milk to obtain the greatest reduction in milk temperature. As the water (from wells) and the warm milk pass each other through the heat exchanger, heat is transferred from the warm milk (98 F) to the well water (50-55 F in Wisconsin), as shown in Figure 2.5. The cooling rate to be obtained depends on flow rates, heat transfer area, milk residence time, and well water temperature. (Other milk cooling units are discussed later in the report in regards of energy use.) 24

25 Figure 2.5 Milk Cooling with Well Water Pre-Cooler. (Source: WI Public Service) Milk in the pipelines is driven by pumps and they control the flow rate of milk through the pre-cooler, so that cooling efficiency can be regulated. Variable Speed (VS) milk pumps are being more often used by dairy producers to lower the average milk flow through the pre-cooler to meet the water: milk ratio and water demand, while obtaining maximum cooling efficiency. As milk cooling is important to prevent bacteria growth, maintaining milking machines and other milk equipments in clean and sanitary conditions is vital. Fortunately, most dairy equipments are provided with circulation cleaning systems (Cleaning-In-Place, CIP) with application of proper cleaning cycles, with detergents, and sanitizers. The FDA determines that dairy equipments, including bulk tanks and milk pipelines, to be washed at least once in 24 hours. Most dairy producers schedule their CIP applications around the 7 hours milking operation to avoid contamination and detriment of milk. A pre-rinsing cycle is a rule of thumb in CIP systems to flush remaining milk and residues from pipelines and equipments. Water temperature during pre-rinsing is usually warm, but not higher than 131 F (55 C) to avoid coagulation of protein. A detergent cycle is next followed by sanitizer flush. It is usually recommended to heat the water to temperatures of 161 F (70 C) for cleaning with acid detergents and at the same temperature of the milk when 25

26 washing with alkaline detergents. While heating the water for washing is necessary to guarantee safe and asceptic operations, energy costs to heat water is a concern. (Methods and systems for water heating will be further discussed in the following sections.) Milk Transportation Milk haulers collect milk from dairy farms to a collecting centre or to dairy processing plants. Bulk milk tankers, according to Chapter ATCP 82, can transport not only fluid milk, but also whey or whey cream in bulk from a dairy farm, and fluid milk products. Licensed milk haulers are as cautious as the dairy farmers in regards of milk quality and contamination. Thus, milk is unloaded or transferred from/to a bulk milk tank in a manner to avoid contamination of milk. For instance, air entering a bulk milk tanker is filtered to prevent addition of contaminants or microorganisms. Milk tankers can usually hold 48 to 55 thousand gallons of milk per load in stainless steel tankers, which allow milk temperature to be kept at proper levels during transportation. In addition, some tankers contain vacuum pumps instead of electric pumps, and as a result, milk can be pumped faster from the dairy s bulk tank. This way, a gallon of milk takes approximately 20 minutes rather than an hour half when using electric pumps. Collection from the dairy farms on alternate days is a common practice, but it varies widely depending on the amount of milk available by the dairy producer and the demand by the dairy plant. Consequently, a tanker can collect milk from several dairy farms to be delivered for dairy processing. 26

27 Manufacturing of Dairy Products Cheese Manufacturing of cheese started out as an accidental curdling of milk for storage stability and it now represents one of the most popular manufactured food products due to the refining of cheesemaking practices. It is estimated that there are over 2000 varieties of cheese and the list continues to grow. Cheese can be classified based on several attributes, e.g., according to milk source, firmness, moisture, ripening, and many others. Due to the difficulty in classifying cheeses, the United States Coded of Federal Regulations (CFR, 1998) determines standards of identity for cheeses so that cheeses can be classified according to their consistency: hard, semi-soft, or soft. The manufacturing processes of most cheeses follow several common steps. As shown in Figure 2.6, the essential steps in cheesemaking are illustrated and description of each step is provided below. Figure 2.7 shows a detailed flow diagram for the manufacture of Cheddar cheese. a.) Milk Receiving The raw milk received from the dairy farms must be at or below 45 F (7 C). At the dairy plant, the raw milk is tested for antibiotics, milk composition, temperature, and bacterial count before being unloaded. Once the federal regulations are met, the raw milk in unloaded into sanitized storage silos, where it would be kept at cooled temperatures until use. It is very common for the dairy plants to use the stored raw milk within less than 2 days. b.) Standardization From the milk composition test, the raw milk may be added with cream, skim milk, or skim milk powder (non-fat dry milk) to achieve a specific fat-to-protein ratio and fat content for certain cheeses. 27

28 Figure 2.5 Major Steps in Cheesemaking. (Source: Gunasekaran and Ak, 2003) 28

29 Figure 2.6 Flow Diagram for the Manufacture of Cheddar Cheese. (Source: Fox et al., 2004) 29

30 c.) Heat Treatment In most dairy operations, the raw milk is pasteurized with HTST (high temperature short time) at 161 F (72 C) for at least 15 seconds, and then cooled to 88 F (31 C) to reduce protein damage. The pasteurization temperatures are designed to kill pathogens, including the most resistant pathogen oxiella burnetti, and to inactive many enzymes. Instead of pasteurization, some cheese-milk are only heat treated at 150 F (65 C) for texture and flavor improvement, but these cheeses are required to be hold in storage for a minimum of 30 days. d.) Make Vats After being pasteurized, the milk is pumped into large vats (known as Double O ), where color, starter bacteria, and later rennet are added. After that, the mixture is heated to 101 F (43 C) and held until coagulation takes place and a gel-like structure is formed. The cheesemaker determines whether or not is ready to cut. Cutting is done by knives already built into the vats as the blades cut the gel structure into cubes of curd while agitates it. Further cooking, mixing and cutting induce syneresis, a phenomena where whey is expelled from the gel coagulum. e.) Cheddaring After a period of agitation and whey expulsion, the mixture is pumped into a continuous cheddaring machine equipped with three or four conveyors. Curds are knitted together, matted, and milled while whey is drained. Salting occurs in the last conveyor and after a determined ph (~ 5.4) has been achieved from acidification by the starter bacteria. f.) Packaging The salted and stirred curds are fed into an auger hopper from where are placed in vacuum towers block former. Curds are then knitted together and additional whey is pulled off, resulting in well-formed uniform 40 pounds blocks of cheese. These blocks of cheeses are sealed in moisture proof bags, enclosed in cardboard boxes, and then placed on pallets. 30

31 g.) Ripening and Storage The cheese blocks, originally at F (32-38 C) are placed in storage for curing and aging at F (4-12 C). In some cheese plants, the cheese blocks are cooled for seven days and then maintained at 38 F (4 C), while in others, blocks are cooled for 24 hours at 38 F (3 C) and then aged at 40 to 42 F (4 to 6 C) Whey Whey is the by-product in the manufacturing of natural cheeses. It consists of 80 to 90% of the total volume of milk and contains about 50% of the nutrients of the original milk. Caseins are essentially the only milk protein used in cheesemaking, whereas only a few percentages of whey proteins are actually incorporated into the cheese and the rest is discarded into whey. The composition of whey products varies according to the milk, type of cheese, and manufacturing process. Whey extracted from the manufacture of enzyme-produced cheese, such as Cheddar, is called sweet whey. In recent years, whey became a valuable by-product of cheese as separation technologies evolved allowing the fractionation of both nutrients and high quality protein from whey, which includes α-lactalbumin, β-lactoglobulin, and glycomacropeptide. In large cheese operations, whey is stored in cold silos and concentrated using a series of operations to obtain high-quality whey powders, whey protein concentrate (WPC), whey protein isolates (WPI), reduced-lactose whey, or demineralized whey. Figure 2.7 illustrates alternative processes for whey treatment. In addition, the following describes common operations and concentration processes of whey. a.) Whey Storage Liquid whey collected from drainage of cheese curd during cheddaring is stored in cooled storage silos. Whey is processed as soon as possible because the starter culture bacteria continue to grow. 31

32 b.) Cheese Fines and Whey Cream Separation Whey is centrifuged with bowl separators (two) to remove cheese fines and whey cream. The cheese fines can be utilized again and incorporated into the cheese, but it is often discarded because of contamination problems. Whey cream is pasteurized before use or shipping, and it can be used in ice cream and butter making. d.) Concentration Whey can be concentrated through membrane filtration (reverses osmosis-ro and/or ultrafiltration-uf) or evaporation (falling film evaporators). c.) Heat Treatment Skim whey is then pasteurized (HTST) in order to inactivate both enzymes and the starter culture to continue to grow. Further concentration can be done after being heat treated, but it depends on the type of final product to be obtained. e.) Drying: Drying of the concentrated skim whey is carried out by spray dryers and/or fluidized bed dryers. 32

33 Figure 2.7 Whey Processing Alternatives. (Source: Tetra Pak, 1995) 33

34 2.1 References alfa Laval/Tetra Pak Dairy Processing Handbook. Tetra Pak Processing Systems: Lund, Sweden. Gunasekaran, S. and Ak, M.M Cheese Rheology and Texture. CRC Press: Boca Raton, FL. Fox, P.F., McSweeney, P.L.H, Cogan, T.M., Guinee, T.P Cheese: Chemistry, Physics, and Microbiology, Vol. 1, General Aspects. 3 rd Edition. Elsevier Academic Press. Goff, D. Introduction to Dairy Science, Milk Production and Biosynthesis. Dairy Science and Technology Education Series, University of Guelph. Available online at: Graves, R.E. and Reinemann, D.J. Layout and Components for Modern Milking Center. Available online at: Helgren, J.M. and Reinemann, D.J Survey of Milk Quality on U.S. Dairy Farms Utilizing Automatic Milking Systems. Applied Engineering in Agriculture 49: Roltz, C.A., Coiner, C.U., Soder, K.J Economic Impact of Automatic Milking Systems on Dairy Farms ASAE Annual International Meeting. University of Wisconsin Milking Research and Instruction Laboratory. General Information. Online web site: Schutz, M. Agricultural and Biological Engineering, Purdue University. Milking Parlors. Available online at: Zehr, S Process Energy Efficiency Improvement in Wisconsin Cheese Plants. Master of Science Thesis, University of Wisconsin-Madison. 34

35 PART 3 ENERGY USE IN DAIRY PROCESSING Introduction In the past few decades, the U.S. government has taken increasing effort in advising the population to use energy more efficiently. The reason for this growing concern lies on the recent spikes on energy costs, mainly due to the heavily dependency on imported oil over the years. Rising of energy prices has affected all economy s sector, including the industry who accounts for the largest consumption. The food industry is not only one of the largest industries in the U.S., but it is also one of the largest groups in use of energy. The food group can be identified as code 20 by OSHA s Standard Industrial Classification (SIC) or 311 by North America Industry Classification System (NAICS); and dairy products/manufacturing corresponds to code 202 and 3115, respectively. On-farm production and processing shared, respectively, 18% and 29% of energy used in the U.S. food system, according to Singh (1986). The remaining of the share corresponds to distribution (10%), in-home preparation (26%), and out-of-home preparation (17%). In dairy processing, specifically, energy consumption for cooling and heating consists of nearly 1/3 of all energy used. Both unit operations are essential to quality of raw milk and milk products throughout the stages of processing. Cooling preserves the quality of milk by reducing microbial growth, while thermal processing can be used to kill pathogens and inactivate enzymes (pasteurization) or to concentrate milk (evaporation). Storage and distribution, though not directly, also influence the overall energy used in dairy and food processing. 35

36 The goal of this section is to describe energy consumption in dairy processing and provide information of energy flows and efficiency improvement in regards of on-farm operations, transportation, and manufacturing. Dairy Market and How It Influences Wisconsin The dairy processing industry in Wisconsin is undergoing major changes in the last 20 years. One of the major changes has been on the increasing competition from the Western states, especially in milk production and the cheese market. Wisconsin is the leading cheese production state in the U.S. justifying the long tradition of being the Cheese State and maintaining its reputation of producing high quality cheeses. Cheese demand in the U.S. continues to increase and most of the cheeses are currently used as commodities (i.e. Cheddar and Mozzarella) in foodservice or in food processing (Cropp and Jesse, 2003). Customers tend to demand competitive prices and Wisconsin has a reputation of being a reliable supplier. Nevertheless, milk production has been flat to decreasing over the last 15 years (Jesse, 2002) making difficult for cheese plants to acquire cheese-milk due to a high demand. Conversely, milk prices in Wisconsin tends to be higher than in other states, including the Western states, where prices are lower, milk production is increasing, and cheese are produced in high-volume. Competitive threats on cheese combined to increased energy costs are forcing cheese plants in Wisconsin to reduce operational costs at any means. Yet, recent spikes in energy cost have affected the variability of cheesemakers gross margins, once prices for cheese-milk (Class III) accounts for a fixed make allowances that include production costs (Jesse and Gould, 2005). As a result, prices of Wisconsin s cheese tend to increase, which reinforce the threatening competition from the Western states on the cheese market. 36

37 Energy in Wisconsin Increasing of energy prices has affected all economy s sector: industrial, commercial, residential, agricultural, electrical utility, and transportation. As shown in Figure 3.1, industries, such as of papermaking, printing, and food processing, consumed 31% of all energy used in Wisconsin in The industry sector is primarily dependent on natural gas (39.4%) and electricity (23.1%), as observed in Figure 3.2. Figure Resource Energy Use by Sector in Wisconsin (in trillion of Btu and Percent total). (Source: Wisconsin Energy Statistics, 2005) According to the 2005 Energy Statistics published by the State of Wisconsin Department of Administration, the end use consumption by the agriculture sector has kept nearly constant (2%) over the years (Figure 3.3), though it decreased 1.1% from 2003 to

38 Electricity is the main type of energy used in agriculture with 32% of electricity s share (Figure 3.4). Also shown in Figure 3.2, the overall energy used by transportation increased 1.9% accounting for 34.5% of the state s total end use energy, where 83.1% corresponds to petroleum use and 12.4% for renewable energy end use, such as ethanol (Figure 3.5). Diesel fuel, which is the primarily fuel for trucking and freight, was at the highest due to increase of distribution and shipments through the State. Figure End Use Energy by Sector in Wisconsin (in trillion of Btu vs. year). (Source: Wisconsin Energy Statistics, 2005) Energy use is indicated by either resource energy or end use energy. The difference lies on that resource includes all energy content to generate electricity, whereas the latter refers to energy content of electricity and other fuels at the point of use. The resource energy consumption will be higher than the end use, because about 70% of energy is lost during generation and distribution of electricity. Taking energy source into consideration, five sources in Wisconsin can be pointed out. Coal is the most relied fuel since 1966 and over 86% are used by electric utilities. Transportation consumes approximately 83% of all petroleum, followed by residential sector (7%), industrial (4%), and agriculture (3%). Petroleum is the energy source of most dependency from other 38

39 countries, such as OPEC, once over 62% of petroleum was imported in Meanwhile, the major markets for natural gas are space heating in residents and industrial process, with 36% and 37% total energy, respectively. The industrial sector has the largest share on electricity usage in the state. Lastly, nuclear power contributes with 19.7% of energy to produce electricity. Table 3.1 summarizes these facts. Figure 3.3 Industrial Energy Use, 2004 (in trillion of Btu and Percent of total). (Source: Wisconsin Energy Statistics Highlights, 2005) Figure 3.4 Agriculture Energy Use, 2004 (in trillion of Btu and Percent of total). (Source: Wisconsin Energy Statistics Highlights, 2005) 39

40 Figure 3.5 Transportation Energy Use, 2004 (in trillion of Btu and Percent of total). (Source: Wisconsin Energy Statistics Highlights, 2005) Table 3.1 Energy Sources and Usage by Economic Sectors (in %). (Source: Wisconsin Energy Statistics Highlights, 2005) Energy Source Industrial Residential Commercial Agriculture Transportation Electric Utilities Coal Petroleum Natural Gas Electricity Nuclear On-Farm Operations Overview of Energy Use The agriculture sector is a major part of the U.S. economy with 1.8% of the national gross domestic product (GDP) (Brown and Elliott, 2005a). This trend is not different for Wisconsin, where dairy farming is the major contributor to the State s economy, followed by oilseed and grain farming. Energy usage in agriculture accounts for about only 3% of the total energy consumed in the U.S. (Edens et al., 2003), but up to 6% of farm production costs are related to energy costs (Brown and Elliott, 2005a). The constant increasing in energy prices over the last decades has drawn much interest in monitoring and promoting efficiently energy use on farms. Dairy farms are able to operate with lower production cost and obtain higher profit margins, once unnecessary energy use has been eliminated. 40

41 Brown and Elliott (2005a) states that gasoline an diesel are the largest fuel energy type in the agriculture sector for the U.S. and to Wisconsin as well, shown in Figure 3.4 above. In addition, the authors report that the end-uses of these fuels in on-farm operations are machinery, transport, and motors. Table 3.2 reproduces the end-use of energy in dairy farming in Wisconsin from Brown and Elliott (2005a). The authors mention that some of the unavailable data was filled with data from Canada due to similar farming practices and climate. Fuel Type Table 3.2 End-Use Energy in Wisconsin (in million Btus). Total Motors (Reproduced from Brown and Elliott, 2005a) Total Lighting Onsite Transportation Machinery Others Total Gasoline 1,508, , ,411 3,035 1,733,750 Diesel 120, ,164,619 3,726,502 6,011,348 Natural Gas 3, , ,547 Other 158, ,819,464 1,977,679 Electricity 645,215 65, ,334,891 4,045,235 Total Petroleum 1,790, ,941 2,298,31 5,769,894 9,947,324 Total Energy 2,435,673 65,128 88,941 2,298,31 9,104,785 13,992,558 Following diesel fuel, electricity itself accounts for 2 to 5% of a dairy farm s production costs in Wisconsin, which is equivalent to kwh per cow or kwh per hundredweight (cwt) of milk produced, annually (Farm Energy Management Handbook, DATCP). In other words, dairy farmers spend an average of $62 to $96 per cow on energy that includes electricity, natural gas, LP gas, and heating oil. Table 3.3 reproduces utility costs paid in 2003 by dairy producers in the State. Table 3.3 Utility Costs vs. Farm Size. (Reproduced from 2003 study by Jenny Vanderlin) Herd Size Avg Cost/Cow Max / Min 50 or less $ 96 $ / to 75 $ 95 $ / to 100 $ 94 $ / to 150 $ 84 $ /

42 151 to 250 $ 71 $ / or more $ 62 $ / In regards of electric use, it is recognized that milk cooling and water heating along with vacuum pumps for milking are the major consumers of electrical energy in a milking center. Milk cooling and water heating together can account for 40 to 60% of the total dairy farm electric use, and it is estimated that milking (through vacuum pumps) can take up to 15% of the electric load in the State (Peebles and Reinemann, 1994; Edens et al., 2003). Figure 3.6 shows the distribution of energy use on Wisconsin dairy farms. Figure 3.6 Energy Use by Equipment on Wisconsin Dairy Farms. (Source: Dairy Farm Energy Management Handbook, DATCP) Based one estimates by Singh (1986), Peebles et al. (1994), and Edens et al. (2003) energy consumption of milk coolers, water heaters, and vacuum pumps for milking are: Milk Cooling: 0.8 to 1.1 kwh/cwt of milk or approximately 140 kwh/cow/yr; Water Heating: 131 kwh/cow/yr with heat recovery or 203 kwh/cow/yr without heat recovery; and Vacuum Pumps: 0.4 to 1.19 kwh/cwt of milk or 49 to 190 kwh/cow/yr. 42

43 The amount of energy consumed by these three units varies with farm size, once milking procedures and equipments differs accordingly. Similarly, selection of equipment also varies with farm size, once a key factor is whether the capital investment outweighs future energy savings. Commonly in Wisconsin, smaller dairy farms (100 milk cows or less) operate only with heat recovery for energy savings. Meanwhile, heat recovery tends to be a better option for medium herds (100 to 150 heads), and a combination of heat recovery and pre-cooling tends to be more energy efficiently for larger dairy herds (200 and more) (Sanford, 2003; and Peebles and Reinemann, 1994) Technologies for Energy Conservation a.) Pre-Cooler One of the ultimate goals of a dairy producer is to be able to cool milk for quality assurance purposes, while saving energy by reducing the demand on the bulk tank compressor. Pre-coolers are installed in the milk discharge line between the receiver and the bulk tank, so that well water cools the milk before it reaches the bulk tank. A well designed pre-cooler can reduce milk temperature originally from F (35-37 C) at milking to up to 40 F (4.5 C), which represents approximately 56 Btu/lbs of milk of energy removal before storage. As a result, precoolers can reduce refrigeration energy by about 60% not to mention lower the overall farm electrical energy requirement to 15% (Sanford, 2003a). A pre-cooling system (Figure 3.7) is designed as a heat exchanger with well water as the coolant. The water flows in opposite directions of the milk (counter-flow) though the plate heat exchanger, transferring heat from the milk to the well water. Concentric heat exchanger is also 43

44 used as a pre-cooler, but the plate type tends to be more popular as it is able to expand by adding more plates depending on the flow requirements. In addition, the pre-coolers may be designed as a single pass (Figure 3.8) or multiple circuits (Figure 3.9), where the latter is more often used on larger farm operations once milking is longer. In this configuration, well water serve as the primary coolant, while chilled water or glycol solution as the secondary coolant. Figure 3.7 Plate-type Pre-cooler (single circuit). (Source: Sanford, 2003a) Figure 3.8 Single Circuit Plate Heat Exchanger. (Source: Sanford, 2003a) 44

45 Figure 3.9 Multi-Circuit Plate Heat Exchanger: 2 coolants. (Source: Sanford, 2003a) After heat from milk has been transferred to the coolant, the used and warm cooling water can be stored and re-used for watering cows and/or for cleaning. Sanford (2003a) points out that on farms with more than 500 cows, water storage tank can be avoided by having well water flowing through the pre-cooler and then directly to cow waterers. However, a variable speed milk pump is needed in order to regulate the milk flow rate to maintain a sufficient waterto-milk ratio. A 1:1 1 ratio is able to achieve considerable amount of cooling, but ½:1 are very common in practice, though manufactures recommend ratios up to 3:1. The average daily water flow rate is estimated to be 1.9 gpm per 100 milking cows (Sanford, 2003a). Addition of a variable speed (VS) milk pump allows a water-to-milk ratio to 1.0 to 1.5:1 or even higher, as compared to 0.5:1 ratio without it. The VS milk pumps increase energy efficiency by slowing the milk flow rate through the pre-cooler, resulting in higher water-to-milk ratios and therefore cooling. It is recommended the use of VS pumps on farms with limited water system flow rates (Sanford, 2003d). Moreover, many VS controllers contain Milk and Wash modes, so that milk pumps can operate at the lowest speed or full speed, respectively. In general, variable speed milk pumps are able to cool milk to an addition 15 F. b.) Refrigeration Heat Recovery (RHR) 45

46 The basic purpose to heat water is for washing and cleaning. Refrigeration heat recovery (RHR) units remove heat from the refrigerant that would be lost into the air, and uses this captured heat to pre-heat water before it enters the water heater. RHR, shown in Figure 3.10, is able to reduce water heating energy requirements, once up to 50% of the energy require to heat water is captured from the refrigerant. As shown in Figure 3.11, a RHR unit contains a storage tank and a heat exchanger. In a common refrigeration system, a compressor pressurized the hot refrigerant into high pressure steam, so that a condenser cools and condense it to a high pressure liquid. However, with the RHR, the hot refrigerant gas is piped through the heat exchanger in the RHR and cooled, and heat is transferred to the water. The temperature of the hot refrigerant gas can reach 200 F (94 C) when entering the RHR and F (24-30 C) exiting after heat has been transferred to the water (Sanford, 2003b). Moreover, an air-cooled or water cooled condenser unit is placed in series with the RHR heat exchanger to remove remaining heat from the refrigerant before it passes through the evaporator of the refrigeration system. 46

47 Figure 3.10 Refrigeration Heat Recovery (RHR) and Water Heater. (Source: Sanford, 2003b) Figure 3.11 Description of RHR Unit. (Source: Sanford, 2003b) c.) Vacuum Pumps During milking, an air pump removes air from the milking system to reduce pressure to kpa vacuum. In conventional vacuum systems, motors run at constant speed and admit air to regulate the vacuum systems. On the other hand, variable speed (VS) vacuum pump is capable of adjusting the motor speed instead of admitting air. This change in speed uses less electricity, and therefore, VS vacuum pump can reduce consumption by 50%. d.) Effects on Farm Size 47

48 As mentioned earlier, energy distribution between milk cooling and water heating changes with farm size. In general, the contribution by milk cooling is greater as farm size increases, whereas it is smaller by water heating (Peebles et al., 1994; Peebles and Reinemann, 1994; and Sanford, 2003a). This is due to the fact that cooling requirements are proportional to the amount of milk to be cooled and hot water relates to washing and cleaning only. Consequently, water heating becomes less of an issue regarding total energy use on larger farms, once higher milk production requires more cooling, and thus more heating is available for heating water. Hence, heat recovery units (i.e. RHR) without pre-cooling units tend to be more advantageous and preferred on dairy farms of 150 or less cows. Meanwhile, combination of pre-cooling and heat recovery is recommended for larger dairy farms. Pre-cooling has less effect on heat recovery as the ratio of milk production to hot water use increases. Peebles et al. (1994) indicates that pre-cooling in fact reduces the quantity of heat covered for water heating by about 40% in farms with less than 100 milk cows, 15% on the 200 cow farm, and 10% on the 400 cow farm Energy Flow Table 3.4 shows estimates of electrical energy use on Wisconsin dairy farms. The energy model developed by Peebles and Reinemann (1994) indicates the energy end-use in 1994 and a 10-year projection, thus 2004, taking into consideration energy conserving technologies. Figure 3.12 illustrate a schematic of energy flow during milk cooling for small dairy farms operations (150 or less milk cows) using the refrigeration heat recovery unit. Figure 3.13 shows the flow for larger operations (200 and more milk cows) with pre-coolers and RHR unit together. 48

49 Table 3.4 Energy Use by Farm Size (in MWh). (Reproduced from Peebles and Reinemann, 1994) Farm Size Water Heating Milk Cooling Lighting Fans Vacuum Pumps Total Use * * * * * * ,461 96,359 85,791 39, ,119 46, , ,155 70,754 32, , , , ,483 81,800 69, ,437 96, , ,230 58,218 49, , , ,831 43,324 34,731 64,907 64, ,950 5,021 7,933 25,058 38, , ,426 * 10-year projection 49

50 Milking (milk at 98 F) Milk Refrigerant Water CIP Water Rinse: F Chemical Wash: F Acid/Sanitizer Rinse: cold or warm Hot Water, F 56 Btu/lbs of milk to be removed VS Milk Pump Energy: - electricity - propane - heating oil - natural gas Water Heater Tempered Water, 55 F Cold refrigerant Bulk Storage Tank (milk at 38 F) Compressor RHR De-super heated refrigerant Evaporator Exp. Valve Air Cooled Condenser Electricity Super heated refrigerant 200 F Figure 3.12 Energy Flow for Small Dairy Farms F Heated Air Potable Water Remove remaining heat 50

51 VS Milk Pump Precooler Bulk Storage Tank (milk at 38 F) Milk Refrigerant Water Milking (milk at 98 F) Hot Water Super heated refrigerant 200 F Cold refrigerant Water Heater Tempered Water, 55 F RHR Compressor Hot Water, F Energy: - electricity - propane - heating oil - natural gas CIP Water Rinse: F Chemical Wash: F Acid/Sanitizer Rinse: cold or warm F Air Cooled Condenser Heated Air Potable Water Remove remaining heat De-super heated refrigerant Exp. Valve Electricity Evaporator Figure 3.13 Energy Flow for Large Dairy Farms. 51

52 Predicting the average farm size in the state of Wisconsin will be over 1,000 dairy herds in the future, while the number of dairy farms will drop drastically, both milk production and energy flow are estimated. It is assumed that average milk production per cow is about 75 lbs of milk, though recent USDA reports indicated that in 2005, production was about 49.5 lbs of milk per cow. Moreover, farm design and operation are scaled up to meet milk production of a Wisconsin s dairy farm of 1,200 milk cows, shown in Table 3.5. Table 3.6 summarizes the energy consumption at the considered dairy farm (referred to as baseline) for milk cooling, vacuum pump, and water are analyzed, once they together represent about 60% of total energy use. The table also shows energy values obtained from Peebles et al. (1994), maximum and minimum values cited from Edens et al. (2003). Shown below are the equations and calculations to determine on-farm energy use. Figure 3.14 illustrates the energy flow. Average milk flow rate through preccoler = (2.0) x (total milk produced per day/ total milking time per day) (1) Precooler (thermal energy) = (lbs of milk/day) x (0.93 Btu/lbs F) x (98F-78F) x (1kWh/3413Btu) x (365days) (2) Bulk tank (thermal energy) = (lbs of milk/day) x (0.93 Btu/lbs F) x (78F-38F) x (1kWh/3413Btu) x (365days) (3) Electrical energy (cooling) = (Thermal energy) / (COP) (4) Vacuum pump = (20 hp) x (0.746 kwh/hp) x (0.95 motor load factor) x (hours of operation/day) x (1/motor efficiency) x (365 days) (5) Water heating (at 110F) = (3 washing/day) x (2 cycles/washing) x (85 gal/cycle) x (8.34 lbs/gal) x (1Btu/lbs F) x (110F-65.6F) x (1 kwh/3413 Btu) x (1/efficiency) x (365 days) (6) Water heating (at 160F) = (3 washing/day) x (1 cycles/washing) x (85 gal/cycle) x (8.34 lbs/gal) x (1Btu/lbs F) x (160F-65.6F) x (1 kwh/3413 Btu) x (1/efficiency) x (365 days) (7) 52

53 Table 3.5 On-Farm Operation. Design and Operations Milk Cooling Farm Size: 1,200 cows Milk production per cow per day: 75 lbs of milk/cow/day Milking per day: 3 Hours per milking: 7 Parlor design: Double 24 (48 milking units) Milk production per day: 90,000 lbs of milk/day Milk production per hour: 4,284 lbs of milk/hour Precooler: Average milk flow rate: 8,571.4 lbs/hour or L/min Number of plates: 35 (De Laval model BH PR-35) Water to milk ratio: 2 to 1 Milk temperatures: Initial (at milking): 98F Intermediate (after precooler): 78F Final (storage): 38F Well water temperatures: Initial: 55F Final (after heat transfer): 65.6 COP: 3.50 (estimated) Vacuum Pump Water Heating Size: 180 cfm Pipeline size: 3 in (diameter) Motor power: 20 hp Motor efficiency: 85% (estimated) Milking time: 21 hours of operation Washing time: 1.5 hours per day Washing and CIP: 3 cyles 2 cycles at 110F 1 cycle at 160F Temperature of washing water (well water): 65.6F Total water use after 3 cycles: 255 gal/washing Total water use per day: 765 gal/day Water heater efficiency: Gas: 80% Electric: 100% 53

54 Table 3.6 Energy Use in On-Farm Operation. Milk Cooling Vacuum Pump Water Heating Thermal Electric Electric Electric Gas Baseline 537, , ,505 41,667 52,083 Peebles et al. 128,115 46,072 Edens et al. (min) 262, , ,075 Edens et al. (max) 361, ,915 Well Water 55F Milking 98F Precooler 78F Bulk Storage 38F Tank Storage Q(c) = 51,162 kwh Q(c) = 102,325 kwh Vacuum Pump Drinking Water to Cows 65.6F Q(vp) = 145,504 kwh Water Heater 110F & 160F Washing / CIP Q(h,gas) = 52,083 kwh Q(h,elec) = 41,666 kwh Figure 3.14 On-Farm Operations Energy Flow. Milk Transportation Overview: Costs and Statistics Almost all milk produced in Wisconsin s dairy farms are marketed and processed within the State. According to Katie Neuser from Wisconsin Milk Marketing Board (WMMB), it is unlikely that milk is shipped far beyond Wisconsin s border once demand for milk is very high 54

55 nowadays, especially for cheese-milk. Many of the Wisconsin s dairy plants employ contract haulers to pick up milk at dairy farms, whereas only a few maintain their own milk trucks and hired drivers. Dairy producers in Wisconsin and some other states pay a subsidized rate, which are less than the actual costs to haul their milk. The remaining of the costs is normally paid by the dairy plants, who buy the milk and negotiate rates with haulers and pay them directly. The subsidized rates are often related to patron volume, where larger patrons are charged less for milk hauling, and they may be paid a volume premium to cover lower costs for hauling. In theory, the actual expenses in milk hauling involve costs that are fixed regardless of volume hauled per patron, and some that vary with volume (Jesse, 1985). The first one refers to fixed time-related costs that are the same independently on the amount of milk picked up, such as time to drive to the farm, sample, record weights, deliver supplies, clean the tank, and drive to the next farm. On the other hand, variable costs consist of pumping time, fuel, and driver time associated with volume. However, due to the difficulty in assessing and separating fixed and variable costs, the majority of handlers in the Upper Midwest Order charge dairy producers a flat hauling charge per hundredweight (cwt), regardless of the volume of milk (Jesse, 1985; Freije, 2005; and Natzke, 2006). According to the USDA Federal Milk Market Administrator s Office for the Upper Midwest Order, the average hauling charge portion paid by dairy producers in 2004 in Wisconsin was cents/cwt, compared to and cents/cwt in Minnesota and North Dakota, respectively (Freije, 2005). Variations of charges are highly influenced by both milk volume and dairy farm operations. In general, the lower the volume, the higher costs on a per hundredweight (cwt) 55

56 basis, and having large dairy farms in the area usually helps decreased the local hauling rate as well. Hauling distances to dairy plants also tend to be a factor, along with competition among handlers (Freije, 2005). For instance, North Dakota had the highest average charge in 2004, as producers are spread over 35 counties, and are located by long distances to the core of dairy manufacturing sites. Overall, Freije (2005) reported that hauling rates tended to increase farther north and west from Chicago, and thus, Ohio, Wisconsin, and Michigan had the lowest hauling charges in addition to Illinois itself. In addition, hauling charges may vary within counties as well, according to Freije (2005). The range is considerably wide, charges range from 3 to 39 cents/wt in Wisconsin. For instance, it was shown that five counties in the State, though presented similar features regarding number of dairy producers, milk volume marketed, and location near manufacturing sites, hauling charges differed due to county s dairy farm size of operation and subsidies, such as premiums (Freije, 2005). As dairy farmers in the Wisconsin are charged a flat rate, dairy plants pay by zone rates, which tend to be a better representative of the costs to haul milk in comparison to flat rates (Jesse, 1986). According to Roger Nordtvedt, a representative from Northwest Food Product Transportation, zone rates are calculated in relation to total expenses involved during milk hauling. Costs include labor (estimated pay rate of $22/hour plus benefits), maintenance and insurance of hauling trucks, fuel consumption (30-35% of total costs), which relates to milk density and geographic locations, and producer s size. Part of Land O Lakes Inc., the Northwest Food Products Transportation services in the Upper Midwest and other states around the U.S., and it currently works with some dairy industries in Wisconsin, such as Foremost Farms USA and Trega Foods. Their zone rates ranges 56

57 from 30 to 42 cents/cwt as said by Nordtvedt (2006). A stop charge is applied (about $20 minimum) in order to avoid inefficiency or discrimination between small and large producers, once number of pick ups may vary. For example, Nordtvedt mentioned that in East of Wisconsin, there are usually 4 stops for one load while in Greenwood, IL, there are 9 up to 12 stops per load, which represents a difference of three hours spent for milk pick up. Moreover, shown below are some estimates by Nordtvedt (2006) on distance traveled per load (equivalent to thousand gallons or thousand lbs of milk) to pick milk at the dairy farms, and bring it to the dairy plants: North and South Dakota: 200 to 400 miles/load Central and South Minnesota: 75 miles/load Southwest and East Wisconsin: 35 to 40 miles/load Central Wisconsin: 75 miles/load Alternatively, Jesse (1985) previously examined costs of milk hauling and milk volume from six dairy cooperatives in Wisconsin. It was found that actual hauling costs per cwt varied from 26 to 74 cents, with average falling between 32 and 42 cents, which seems to be similar to what is charged nowadays. Also, volume of milk picked up per stop ranged from 6 to 68 cwt, but most observation fell between 24 and 34 cwt per stop, and distance between stops were from 6 to 17 miles round trip per stop, which represents a route density of 0.06 to 0.16 stops per mile Energy The energy aspect on milk hauling can be accounted by the amount fuel consumption during milk pick ups. As discussed earlier, dairy farmers often pay a flat hauling charge of

58 cents/cwt thus far in 2004 (Freije, 2005), while dairy plants cover the remaining of the costs paid to contractor haulers by zone rates of 30 to 42 cents/cwt of milk (Nordtvedt, 2006). Consequently, it can be determined that the actual and total milk hauling costs in the state of Wisconsin ranges from to cents/cwt of milk, which is with accordance to cents/cwt paid in Minnesota from a survey on total milk hauling costs in the State (Ye, 2003). Furthermore, taking into consideration that the average distance traveled from dairy farms to milk plants fall in the range of 35 to 40 miles per load in both Southwest and Eastern, and 75 miles in Central region of the State, volume of fuel consumed for milk pick up is estimated for these regions, as well as the corresponding energies (Table 3.7). The equations used to calculate the energy values shown in Table 3.7 are illustrated below. Volume of fuel use = (distance) / (truck fuel efficiency, mpg) (8) Energy/load = (mass energy density of diesel) x (1 Btu/ J) x (fuel eff.) x (1 kwh/3413 Btu) x (fuel used) (9) Energy/lbs of milk = (energy/load) x (1 load/53,750 lbs of milk) (10) Energy for yearly production = (energy/lbs of milk) x (90,000 lbs of milk/day) x (365 days) (11) Transportation costs are also shown in Table 3.7. The equations used are described below, and in the calculations, it was assumed that price of diesel is $3/gal and one load corresponds to 53,750 lbs of milk. Costs per Load = (volume per load, gal) x (diesel price per gal) (12) Costs per lbs of milk = (costs / load) x (1 load / 53,750 lbs of milk) (13) Cost per year = ($ / lbs of milk) x (90,000 lbs of milk/day) x (365 days) (14) 58

59 Table 3.7 Milk Transportation: Energy and Costs. Location: Southwest East Central Distances (miles): Fuel volume (gal): Energy/Load (kwh/load): Energy/lbs of milk (kwh/lbs of milk): Energy for 1 year of production (kwh): 40, , , Cost/Load ($): Cost/lbs of milk ($): Cost per year ($): 10, , , Assumptions: o Truck fuel efficiency: 6 MPG o Mass energy density of diesel: 38.6 MJ/L o Fuel efficiency: 0.28 o 1 load: 53,750 lbs of milk o 1 day of milk production (1,200 cows): 90,000 lbs of milk o Price of diesel: $3/gallon Dairy Manufacturing Energy Use in the Food Industry Energy use in food industry has increased rapidly in the last 50 years, accounting to nearly 1/3 or more of total energy consumed by all industries nowadays (Singh, 1986; and Wilhem et al., 2004). The recent increase in energy costs has affected all food industries, including the dairy industries and cheese manufacturing plants, as utility costs jumped to as high as 11-15% of total production costs (Zehr, 1997; Jesse and Gould, 2005). 59

60 The food industry, in general, requires energy to operate a variety of equipments, such as electrical motors, steam boilers, and refrigeration equipments. Typical utility for operations in dairy plants consist of thermal energy, electrical energy, and water. Jesse and Gould (2005) estimated that both electricity and natural gas represent, respectively, 40 and 32% of total utility costs. Thermal energy is supplied in the form of natural gas, which is the dominant source of energy is food processing. Natural gas and distillate fuel are both mostly consumed as boiler fuel to generate steam for thermal processing and dehydration, and together can reach approximately 29% of total energy in the food industry, with about 62% and 42% share, respectively (Okos et al., 1998). Distillate fuel is also used for transportation. Moreover, electricity is consumed intensively by the food industry, whereby about 94% is purchased and the remaining is produced through co-generation (Okos et al., 1998). Over 80% of the electricity is used in processing, such as in mechanical power, refrigeration, and cooling, whereas the remaining accounts for lighting, ventilation, and air conditioning. Table 3.8 reproduces the data of purchased fuels and electric energy used by the dairy industry. In fact, the dairy industry uses about 12% of purchased electric energy of the entire food manufacturing group. Lastly, approximately 60% of water is used for energy-related operations, especially for cooling water or steam generation. The typical utilities and service demands in dairy processing is shown in Table 3.9, which was reproduced from the National Dairy Council of Canada. 60

61 Table 3.8 Purchased Fuels and Electric Energy for Heat and Power by Industry Groups and Industries. (Source: Annual Survey of Manufacturers, 2004). Cost of purchased NAICS Industry Group fuels and Cost of Code electric purchased Electric Energy Purchased energy fuels Quantity Cost ($1,000) ($1,000) (1,000 kwh) ($1,000) 3115 Dairy product manufacturing 892, ,718 9,141, , Dairy product manufacturing (except frozen) 800, ,503 7,672, , Cheese manufacturing 285, ,877 2,604, , Dry, condensed, and evaporated dairy product manufacturing 162,481 94,499 1,225,453 67, N - Fluid milk and butter manufacturing 352, ,127 3,842, , Ice cream and frozen dessert manufacturing 92,154 15,215 1,468,318 76, Ice cream and frozen dessert manufacturing 92,154 15,215 1,468,318 76,939 61

62 Table 3.9 Typical Utility and Service Requirements for Dairy Processing. (Source: National Dairy Council of Canada, 1997). Utility Type Cold Water (1-7C / 34-45F) Demand Requirements Rinsing, Washing, Recirculation, and Cooling. Hot Water (90C / 194F) Pasteurizer Heating Medium (70C / 158F) Mould Release (for Ice Cream Processes) (50C+ / 122F+) Washup/CIP Steam (790 kpa abs / 16,500 lbs/sqft) Pasteurizer Heating (via Hot Water) Dryer Air Heating Evaporation (Lower 790 kpa abs / lbs/sqft) Water Heating Thermal Furnace Boiler Heater Space Heating Hot Water/Space Heating Dryer Air Heating Refrigeration (-40C / -40F) Mould Brine (for Ice Cream Processes) (-30C / -22F) Freezer/Storage (-9C / 15F) Ice Cream Maker (-6C / 21F) Glycol for HTST Chilling (1C / 34F) Product Holding Cooler (4C / 39F) Milk/Product Cooling Compressed Air Valve Actuation, Air Blows, and Conveying Electrical (Direct Uses) Conveyor, Centrifuge, Homogenizer, Packaging, Unit Drives, Lights, and Refrigeration. 62

63 3.6.2 Energy Analysis in a Cheddar Cheese Plant The manufacture practices of the Cheddar cheese plant analyzed here were considered following common operations in a cheese plant. It was assumed that the plant processes about 1,551,500 lbs of milk daily, making 29 cheese vats per day, where each vat holds 53,500 lbs of milk. The by-product of cheese, whey, is processed in the plant. Nearly 85% of the total volume of cheese-milk is assumed to result in whey. Cheese fines and whey cream (0.05%) are separated, and skim whey is concentrated with both reverse osmosis (RO) and evaporator to reach approximately 21.5% and 52% of solids content, respectively. The remaining is made into dry whey by a spray dryer. Full description of process operation can be found in Part 2 of this report. The process flow is shown in Figure 3.15, and energy flow of each stage is shown in Table Energy analysis at the stage of HTST milk pasteurization was conducted by assuming a 60% heat recovery between incoming cold raw milk and hot pasteurized milk, so that milk originally at 38F is pre-heated to about 112F. Consequently, the heating section in the plate heat exchanger is responsible for the remaining 40% to pasteurize milk at 161F, while the regeneration also cools the milk to approximately 88F. After pasteurization, cheese-milk fills the make vats, where after steps of coagulation and cutting, cooking and stirring takes place. The temperature is raised from 88F to 101F, by steam injection. During the rest of the process until packaging, temperature drops to 75F, when 40 lbs block of Cheddar cheese are sealed and boxed, and it is assumed that neither heating nor cooling 63

64 are applied. During storage, refrigeration is essential to cool cheese block to 42F, at which it remains during aging and ripening. 64

65 38F 161F F 84-95F 75-82F 42F Receiving HTST Make Vats Cheddaring Packaging Storage Cheese Production: - 29 vats per day - 1,551,500 lbs of cheese-milk/day 6.4% T.S. Sweet Whey Silo Whey Processing: - 1,318,775 lbs of sweet whey/day Skim whey Separators Cheese fines and Whey cream (660 lbs) HTST Concentrated skim whey 21.5% T.S. RO C.F. = 3.45 Permeate water (936,053 lbs) Figure 3.15 Process Flow 52% T.S. Evaporators Water vapor (~237,664 lbs) Dry whey Spray Dryer 65

66 Table 3.10 Energy Flow of Each Operation in Cheesemaking. Energy Location Temperatures Thermal Energy (electric/gas) (F) (kwh) (kwh) Receiving Storage 38 11,546,337 at Regeneration (heat transfer) 7,697,558 9,055,950 HTST at Pasteurization 161 (heating) 11,546,337 at Regeneration (cooling) 125,164 at Filling/Setting 88 Make Vats 2,033,908 2,392,832 at Cooking/Stirring 101 at "Pump Over" ,259 at Cheddaring 90 Cheddaring 337,807 at Milling ,903 at Salting ,903 at Hopper ,355 Packaging at Block Former ,807 Sealed and Boxed 75 2,786, ,259 Fast Cooling Storage Curing 42 Aging 66

67 Table 3.11 Energy Flow of Each Operation in Whey Processing. Energy Location Temperatures Thermal Energy (electric/gas) (F) (kwh) (kwh) Separators (removal of lbs of whey cream) at Regeneration (heat transfer) 4,505,887 5,301,044 HTST at Pasteurization (heating) at Regeneration (cooling) 6,758,831 RO Electricity consumption: 1,504, kwh/1000l of water removed Energy use: 9.6 kwh (6-20% solids) Evaporator Stage ,185,326 15,512,148 Stage ,933,798 Spray Dryer ,935, ,100,931 67

68 In the whey processing part, skim whey is pasteurized at 167F to inactivate both starter culture and enzymes, after cheese fines and whey cream have been separated. The thermal energy taken by pasteurization is estimated similarly to milk HTST pasteurization. The temperature of whey is assumed to be 95F, which is about the temperature at the pump over stage in cheddaring. Skim whey is pre-heated to 138.2F, and cooled to 123.8F. Following heat treatment, whey is pre-concentrated. In this analysis, whey consideration is carried out by reverse osmosis, once membrane separations are a common practice in large cheese operations. The concentration factor (C.F.) of whey by RO is 3.45, which removes about 70% of the water from skim whey, and the goal is to concentrate to approximately 21.5% total solids. The temperature of skim whey going through the RO was assumed to be 123.8F, though it might be much smaller in real conditions. Whey is then further concentrated with evaporators. In this analysis, information of temperatures and flow rates of product, vapor, and condensate were taken from Zehr (1997), who analyzed energy efficiency in the cheese plant at Marshfield, WI. The process operation described by Zehr is similar to the one estimated here, such that Marshfield processed about 1.6 million lbs of milk per day and 81,000 lbs/hr of whey. The evaporator consisted of 5 stages falling film. Moreover, at the end of stage 3, the solid content of whey was reported to be near 22%, which is close to the total solids content obtained with RO. Finally, the spray drying calculations were also based on Zehr (1997) from the cheese plant at Blair, WI. The calculated thermal energies for each stage of the process were calculated based on the following equations: Milk HTST Pasteurization Q = (lbs of cheesemilk/day) x (0.93 Btu/lbs F) x (161F 111.8F) x (1kWh/3413Btu) x (365days) (15) 68

69 Cooking in Make Vats Q = (lbs of cheesemilk/day) x (0.93 Btu/lbs F) x (101F 88F) x (1kWh/3413Btu) x (365days) (16) Cooling of Packaged Cheese Q = (lbs of cheese/day) x (0.502 Btu/lbs F) x (75F 42F) x (1kWh/3413Btu) x (365days) (17) Whey HTST Pasteurization Q = (lbs of skim whey/day) x (0.936 Btu/lbs F) x (1671F 138.2F) x (1kWh/3413Btu) x (365days) (18) Evaporator Q = [ (lbs of conc. whey/day) x (0.936 Btu/lbs F) x (ΔF) x (1kWh/3413Btu) x (365days) ] + [ (lbs of vapor/day) x (2,357,000J/kg) x (1kg/2.204lbs) x (1Btu/1055.6J) x (1kWh/3413Btu) x (365days) ] (19) Spray Drying Q = [ (lbs of conc. whey/day) x (0.936 Btu/lbs F) x (ΔF) x (1kWh/3413Btu) x (365days) ] + [ (lbs of vapor/day) x (2,357,000J/kg) x (1kg/2.204lbs) x (1Btu/1055.6J) x (1kWh/3413Btu) x (365days) ] (20) The calculated thermal energies above can be converted into electric (cooling) and gas (heating) energies. Also, energy use by RO was accounted as electric energy following Fellows (2003). Cooling Electric = (thermal energy, kwh) / (COP) (21) Heating Gas = (thermal energy, kwh) / (0.85) (22) Whey concentration with RO Electricity = (10 kwh/1,000l) x (1L/0.264 gal) x (1 gal/8.6 lbs) x (volume of H20 removed,lbs) (22) 69

70 3.7 References Brown, E. and R.N. Elliott. 2005a. On-Farm Energy Use Characterizations. Washington, D.C.: America Council for an Energy-Efficient Economy. Brown, E. and R.N. Elliott. 2005b. Potential Energy Efficiency Savings in the Agricultural Sector. Washington, D.C.: America Council for an Energy-Efficient Economy. Cropp, B. and Jesse, E Rethinking Dairyland Farm Level Milk Prices: Is Wisconsin Competitive? Marketing and Policy Briefing Paper, Department of Agricultural and Applied Economics, University of Wisconsin-Madison. Farm Energy Management Handbook, Department of Agriculture, Trade and Consumer Protection. Available online at: Edens, W.C., L.O. Pordesimo, L.R. Wilhelm, and R.T Burns Energy Use Analysis of Major Milking Center Components at a Dairy Experiment Stattion. ASABE 19(6): Freije, C Milk Hauling Charges in the Upper Midwest Marketing Area May USDA Federal Milk Market Administrator s Office, Staff Paper No Available online at: Jesse, E.V Analysis of Milk Hauling Costs as Related to Volume and Distance. Department of Agriculture Economics, University of Wisconsin-Madison. Agricultural Economics Staff Paper Series No Jesse, E Rethinking Dairyland: Background for Decisions about Wisconsin s Dairy Industry. Marketing and Policy Briefing Paper, Department of Agricultural and Applied Economics, University of Wisconsin-Madison. Jesse, E. and Gould, B.W Federal Order Product Price Formulas and Cheesemaker Margins: A Closer Look. Marketing and Policy Briefing Paper, Department of Agricultural and Applied Economics, University of Wisconsin-Madison. Peebles, R.W., D.J. Reinemann, and R.J. Straub Analysis of Milking Center Energy Use. Applied Engineering in Agriculture. ASAE Paper No Available online at: Peebles, R.W., and D.J. Reinemann Demand-Side Management/Energy Conservation Potential for Wisconsin Dairy Farms. ASAE Meeting Paper Presentation No Available online at: 70

71 Sanford, S. 2003a. Energy Conservation on the Farm: Well Water Precoolers. Wisconsin Focus on Energy Program. University of Wisconsin-Extension. Sanford, S. 2003b. Energy Conservation on the Farm: Refrigeration Systems. Wisconsin Focus on Energy Program. University of Wisconsin-Extension. Sanford, S. 2003c. Energy Conservation on the Farm: Vacuum Systems. Wisconsin Focus on Energy Program. University of Wisconsin-Extension. Sanford, S. 2003d. Energy Conservation on the Farm: Vacuum Systems. Wisconsin Focus on Energy Program. University of Wisconsin-Extension. Singh, R.P Energy in Food Processing, in Energy in World Agriculture. Vol. 1. Elsevier Publishing Company, Amsterdam. Vanderlin, J Milk Production Costs on Selected Wisconsin Dairy Farms. Center for Dairy Profitability, University of Wisconsin-Madison. Zehr, S Process Energy Efficiency Improvement in Wisconsin Cheese Plants. Master of Science Thesis, University of Wisconsin-Madison. Wilhelm, L.R., Suter, D.A. and Brusewitz, G.H Energy Use in Food Processing. Chapter 11 in Food & Process Engineering Technology, St. Joseph, Michigan: ASAE. Wisconsin Energy Statistics Wisconsin Department of Administration, Division of Energy. Available online at: Wisconsin Energy Statistics Highlights Wisconsin Department of Administration, Division of Energy. Available online at: Ye, S Milk Hauling Cost in Minnesota. Agricultural Marketing Services Division, Minnesota Department of Agriculture. Available online at: 71

72 PART 4 - Membrane FILTRATION in Cheese production Introduction Membrane filtration is a rate-based separation that uses an energy separating agent to generate miscible products of the same phase. A fluid stream, such as milk, is forced by hydraulic pressure to pass through a series of semi-permeable membranes that are typically made of a thin film of porous polymer. The membranes act as the filter media, and separates the dissolved solids, which is referred as to retentate, from the fluid that passes through the membranes, the permeate. Differently from conventional filtration, where flow is perpendicular to the filter, membrane separation is considered a crossflow system, once fluid flows under pressure and at high velocity (Dairy Management Inc., 2000). In addition, the extent of separation and fractionation is determined based on pore size of the membranes, allowing components to be selectively separated. Figure 4.1 (below) illustrates the spectrum of filtration for milk, and Table 4.1 provides more detail about the four types of membrane separations used in the dairy industry. It is interesting to note that overlaps between membranes occurs, once the retentate will always contain some material from the permeate. 72