COMPUTER-AIDED PROCESS ANALYSIS, ECONOMIC EVALUATION AND ENVIRONMENTAL IMPACT ASSESSMENT FOR UTILIZATION OF CHEESE WHEY

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1 COMPUTER-AIDED PROCESS ANALYSIS, ECONOMIC EVALUATION AND ENVIRONMENTAL IMPACT ASSESSMENT FOR UTILIZATION OF CHEESE WHEY Athanassios Kotoupas and Fotis Rigas School of Chemical Engineering, National Technical University of Athens Athens, Greece ABSTRACT Cheese whey is the yellow-green liquid remaining after the precipitation and removal of milk casein during cheese making. It presents an important environmental problem due to the high volumes produced and its high organic matter content, with lactose being largely responsible for its high BOD and COD values. Cheese whey utilization has been the subject of a great deal of research. About 50% of total world cheese whey production is now treated and transformed into various food products. In this work an efficient software was used for the comparison of three alternative scenarios for the utilization of cheese whey resulting from a 214 tons/d capacity factory of Cheddar cheese producing 1812 tons/d of cheese whey. The alternatives were investigated for the purpose of determining the most economical as well as the least polluting scenario of them. INTRODUCTION Polluting material Cheese whey is the yellow-green liquid remaining after the precipitation and removal of milk casein during cheese making. This by-product represents about 85-95% of the milk volume and retains 55% of milk nutrients. Among the most abundant of these nutrients are lactose (4.5-5% w/v), soluble proteins ( % w/v), lipids ( % w/v) and mineral salts (8-10% of dried extract). Whey represents an important environmental problem due to the high volumes produced and its high organic matter content, exhibiting a BOD 5 equal to ppm and COD equal to ppm, with lactose being largely responsible for the high BOD and COD (Gonzalez, 1996). Recovery products Condensed or powered cheese whey: In this form, the quality of fresh cheese whey is maintained for a longer period of time, facilitating manipulation and transport. The principal market for these products is animal feeding whereas smaller quantities may be used in human foods, such as ice creams, baked goods, and milky derivatives. Whey protein concentrate (WPC): The most commonly used methods for the recovery of the protein proportion are ultrafiltration and diafiltration (Barba et al, 1998). The protein concentrate is free of salts, thus making it suitable for all kinds of human foods, even dietetic or baby foods. Lactose: It is used as a supplement in baby milks and as an excipient for pharmaceutical products. Alternative uses are being sought, with most of them based on the direct Corresponding author. Tel.: ; fax: address: rigasf@central.ntua.gr

2 fermentation of lactose or the fermentation of the glucose and galactose obtained by hydrolysis of lactose (Gekas & Lopez-Leiva, 1985). Computing tools The successful design and evaluation of integrated material reclamation, waste treatment and disposal process is a challenging task that can be facilitated by the use of computeraided process design and simulation tools. SuperPro Designer is a process simulator developed at the Massachusetts Institute of Technology in collaboration with Intelligen, Inc by D.P. Petrides. The code is written in Visual C++ and enables the user to concurrently design and evaluate manufacturing (Petrides et al., 1995) with end-of-pipe treatment processes and practice waste minimization (Petrides et al., 1994) as well as pollution prevention. SuperPro Designer is currently used in many universities worldwide as a teaching tool and has found application in economic evaluation and environmental impact assessment for many industrial and municipal by-products (Rigas and Kordoutis, 2005). MATERIALS AND METHODS In this work part of a relevant flowsheet found in the literature (Petrides, 2002) was used in which the production of 214 tons/d of Cheddar cheese results in the production of 1812 tons/d of cheese whey (Fig. 1). Two other alternatives were investigated for the purpose of determining the most economical as well as the less polluting scenario of them. SuperPro Designer (ver. 4.9) was used for the computations. Process Description (Scenario 1) On a daily basis the plant processes 1812 tons of whey and produces 9 tons of butter, 211 tons of WPC, and 33.5 tons of 95% (by mass) ethanol. The plant operates around the clock for 330 days a year. Process modification (Scenario 2) This plant produces Manouri (cream cheese) instead of butter, whey protein concentrate (WPC), and ethanol. The ethanol section is similar to the basic process (scenario 1). Process modification (Scenario 3) On a daily basis, the plant produces butter, two types of WPC and pure lactose. The Butter-Making and WPC sections are similar to the basic process (scenario 1). RESULTS AND DISCUSSION Economic comparison of the three scenarios The reports of SuperPro Designer can be used for the selection of the most profitable plant. Table I facilitates this approach. Table I. Economic comparison of all scenarios. Cost Item Total Capital Investment ($) Breakeven Point NPV ($) 7% interest Scenario 1 101,167,000 F: 49,500 kg/h CR: 59,226,000 $/year Scenario 2 104,707,000 F: 38,000 kg/h CR: 60,500,000 $/year Scenario 3 54,916,000 F: 20,200 kg/h CR: 28,937,036 $/year 162,310, ,599, ,802, Payback time (Years)

3 According to the breakeven point analysis the second technological proposal seems to have satisfactory economic flexibility due to its low production rate (40% of the full production rate). Although the third scenario has higher net present value and lower payback period from the second, the last one is the most profitable due to its breakeven point. SCENARIO 1 WHEY SERUM S-126 Butter-Making Section TOP CREAM S-117 S-101 P-14 / V-101 Whey Storage S-105 P-11 / DS-101 Cream Separation SEPARATED WHEY P-12 / V-102 Cream Storage S-114 P-13 / HX-101 Pasteurization S-118 P-15 / HX-102 Cooling S-119 S-120 S-122 BUTTER CARTONS P-18 / FL-101 Butter Packaging CARTONS P-17 / CSP-101 Splitter BUTTER WASTE S-121 P-16 / V-103 Cream Storage WPC Section S-130 S-132 S-135 S-129 S-128 P-19 / UF-101 Ultrafiltration S-137 P-20 / V-104 Retentate Storage S-131 S-134 P-21 / SDR-101 Spray Drying S-133 P-22 / SL-101 Powder Silo S-136 DEMIN. WATER WPC S-138 P-26 / RO-102 Reverse Osmosis LIQ. WASTE 1 Ethanol Section BAGS P-23 / FL-102 WPC Packaging GAS S-155 S-147 S-115 S-146 S-124 P-25 / RO-101 Reverse Osmosis P-28 / V-105 Beer Well P-29 / DS-102 Biomass Removal LIQ. WASTE 2 S-140 P-1 / V-107 Stoich. Fermentation S-154 LIQ.WASTE 3 S-145 S-142 P-30 / HX-104 S-141 P-27 / HX-103 ETHANOL P-32 / V-106 Cooling P-31 / C-101 Heat Exchanging Ethanol Storage S-143 Distillation Figure 1. Process flowsheet for scenario 1

4 For the second scenario the breakdown of the operating cost on a per-process section shows that 55.6% of the total operating cost is associated with the production of ethanol, the Manouri-making section account for 42.4% and the WPC section for only 2.0% of the total operating cost. For the third scenario the breakdown of the operating cost on a perprocess section shows that 47.3% of the total operating cost is associated with the production of WPC, the lactose crystallization section accounts for 34.8% and the buttermaking section for 17.9% of the total operating cost Figure 2. Process flowsheet for scenario 2 Figure 3. Process flowsheet for scenario 3

5 Environmental impact comparison Table II shows the amounts of the components that flow out of the plants and provide information about their environmental impact. Table II. Environmental parameters Com. Name OUT (tons/year) Scenario 1 Scenario 2 Scenario 3 COD 42,105 42,083 42,501 BODu 34,720 34,999 29,751 BOD5 31,248 31,500 26,776 TKN NH TDS 2,302 2,432 0 The values for the environmental parameters (COD, BOD etc) are quite close for scenarios 1 and 2. The third scenario is more environmentally friendly in comparison with the other plants due to the negligible quantities of nitrogen and solids in the effluent. The quantities of total Kjeldahl nitrogen (TKN) and ammonia nitrogen (NH 3 ) in the effluent of the three plants depend on the amount of biomass (yeast) that is rejected to the environment. The overall approach shows that none of the scenarios is both the most profitable and most environmentally friendly. The choice of the most suitable scenario will depend on other factors such as the national regulations and the financial demands of the investors. REFERENCES 1. Barba D., Beolchini F., Veglio F. Water saving in a two stage diafiltration for the production of whey protein concentrates Desalination, 119, , Gekas V. & Lopez-Leiva, M. Hydrolysis of lactose: a literature review Proc. Biochemistry, 20, 2-12, Gonzalez S.M.I. The Biotechnological utilization of Cheese whey: A review Bioresource Technology, 57, 1-11, Kordoutis K., Rigas F., Municipal Sewage Sludge Treatment Alternative Technologies: Economic and Environmental Evaluation, IASME Transactions, 4(2), , Petrides D.P., Aelion V., Mallick S.K. Pollution prevention through process simulation, Industrial Pollution Prevention handbook, Freeman ed.1994, Petrides D.P., Elpida Sapidou, and Jon Calandranis Computer-Aided Process Analysis and Economic Evaluation for Biosynthetic Human Insulin Production- A Case Study Biotechnology and Bioengineering, 48(5), , Petrides D.P., Integrated Cheese Plant. Example in SuperPro Designer User Guide, v. 4.9, Rigas F., Kordoutis K., Economic and environmental evaluation of municipal sewage sludge treatment methods International Conference on Energy, Environment, Ecosystems and Sustainable Development, WSEAS, Athens, July 12-14, 2005