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Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey
Journal of Cleaner Production xxx (2015) 1e12
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Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey Parimal Pal*, Jayato Nayak Environment and Membrane Technology Laboratory, Department of Chemical Engineering, National Institute of Technology Durgapur, 713209, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 25 February 2015 Received in revised form 12 June 2015 Accepted 15 July 2015 Available online xxx
A multi-stage membrane-integrated hybrid reactor system was developed and investigated for fermentative production of high purity acetic acid and whey protein from waste cheese whey. Integration of largely fouling-free membrane modules with traditional fermenter allowed fermentation with product withdrawal in a continuous scheme. Provision for recycling microbial cells, unconverted sugars and nutrients through cross flow membrane modules resulted in high yield (>98%) and productivity (96 g L1 h1) under high cell density. The final forward osmosis stage concentrated dilute acetic acid to 962 g L1. The environmentally friendly modular design of the membrane integrated system ensured continuous production of more than 98% pure acetic acid in a very simple, compact and flexible plant configuration reflecting all the major characteristics of high process intensification essential to sustainable production and business. Concentrated whey protein (955 g L1) recovered as a by-product added to the economy of the process raising the possibility of enhanced profit margin. The developed new design fulfills the major expectations of a sustainable technology in terms of benefits to the planet, people and profit. The sustainability parameters in terms of cost of equipment, and production, reduced consumption of material and energy, flexibility, profitability and environmental friendliness have been analyzed in the paper. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Acetic acid Whey protein Green processing Energy reduction Waste reduction Sustainable technology
1. Introduction In an environmentally conscious global market amidst tough competition, the chemical, pharmaceutical and allied process industries are witnessing paradigm shift in their production strategy embracing the concepts of sustainable technology and sustainable development. All currently practiced energy-intensive and polluting processes and technologies will have to eventually leave the space for green production technologies (Biswas and Roy, 2015). Such production strategy fostering clean production in more efficient, more energy-saving, compact, flexible yet small plant configuration in other words is termed process intensification (PI) (Bruggen et al., 2004). Chemical and allied process industries can only move towards sustainability through such process intensification. The emerging new production regime is opening wide the gateway for innovations in a plethora of new products and processes. Along with other benefits, intrinsic safety of a process also improves dramatically in smaller and compact plants. The two
* Corresponding author. Tel.: þ91 343 2755055; fax: þ91 343 2754088. E-mail addresses: [email protected], [email protected] (P. Pal).
main categories of process intensification are unit intensification and plant intensification. Unit intensification could be achieved by minimizing hold-up and maximizing the throughput for a given size and process performance in terms of selectivity, yield, productivity and energy consumption. Plant intensification could be achieved by minimizing inventory and feedstock while maximizing the throughput (Ponce-Ortega et al., 2012). Among the different approaches of process intensification, replacement of traditional separationepurification devices by membrane filtration modules is considered one effective approach (Pal et al., 2009; Pal and Dey, 2013; Drioli et al., 2011). Integration of membrane based separation with traditional processes like fermentation can culminate in hybrid processes that eliminate the need for several other downstream unit operations such as centrifugation, crystallization, acidification, neutralization, carbon adsorption, ion-exchange and drying (Dautzenberg and Mukherjee, 2001; Becht et al., 2009; Choe et al., 2006; Lutze et al., 2010; Babi et al., 2014). Contrary to conventional chemical separation and purification involving phase change, product purification using membranes does not involve phase change (except pervaporation) and drastically brings down energy requirement. Such membrane-based processes also hold the potential of turning hazardous wastes and by-products into
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Please cite this article in press as: Pal, P., Nayak, J., Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey, Journal of Cleaner Production (2015), http://dx.doi.org/10.1016/j.jclepro.2015.07.085
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useful and value-added products in many cases (Kumar and Pal, 2013). The possibility of high degree of fractionation of target molecules using tailor-made membranes has opened up new routes to production of high purity organic acids and other thermosensitive biomolecules (Cheung et al., 2005). In this context, process intensification in acetic acid manufacture assumes significance in view of its huge market demand in production of vinyl acetate monomer, acetic anhydride polyethylene terephthalate, terephthalic acid, food grade vinegar, paints, adhesives, foods, textiles and photographic products. Annually 95% of acetic acid is produced by exploiting petroleum resources like methanol (carbonylation reaction) and ethylene or acetaldehyde (oxidation reaction) (Babi et al., 2014). Whey protein powder which is an essential constituent of whey has demand for its excellent nutritional and functional properties. It is conventionally recovered by evaporation and spray drying of cheese whey which involves substantial energy consumption (Cheung et al., 2005; Jayaprakasha and Yoon, 2005). More than half of the total production cost in such conventional chemical synthetic routes is involved in a large number of separation and purification steps. Those processes not only involve harsh chemicals and highly energy consuming steps like evaporation and distillation but also end up with generation of mixture of waste nez et al., 2012). Studies with batch or acids and chemicals (Jime fed-batch systems employing microfiltration or ultrafiltration membranes in tubular or hollow fiber modules for downstream processing have been reported (Jones, 2000; Esymondt et al., 1990; Grzenia et al., 2008; Rodríguez et al., 2006). But single-step membrane integration does not help in reaping the possible manifold benefits of membrane-integration. For example microfiltration module can help separate microbial cells for recycle; nanofiltration can separate acid product from the broth and forward osmosis can concentrate the products and by-products further be removing the water part without involving much energy consumption (Park and Toda, 1990; Phuntsho et al., 2013; Emadzadeh et al., 2014; Zhang et al., 2013; Wang et al., 2011, 2014; Kong et al., 2014; Yanga et al., 2009; Sant'Anna et al., 2012). But a fully membraneintegrated hybrid system for simultaneous production of acetic acid and whey protein in concentrated and highly purified form from a cheap carbon source needs to be investigated with analysis of culminating process intensification leading to sustainability. This manuscript fills this technology gap.
maintained at about 448e460 K but the dryers need to be so well engineered that gentle heat treatment (338e343 K) is provided to the heat-sensitive material (cheese whey) to produce whey protein avoiding denaturation. Provisions for such sensitive heat treatment in a conventional technology get reflected in overall cost of production of whey protein. Requirement of high temperature and high pressure inside the reactors for different phase changing phenomena makes the process highly energy-intensive. Capital investment on equipment is also very high. Catalyst constitutes other significant cost component. Highly skilled professionals are necessary for safe and successful operation of such plant. Disposal of wastes like propanoic acid and other high boiling impurities (like mixture of acetaldehyde, butyric acid, butanone, ethyl acetate, formic acid, dichloroacetic acid) is a big problem in conventional plants as these wastes are generated in substantial quantities and can lead to air pollution (through VOC emission), soil pollution (through hydrocarbon contamination) and water pollution through the escaped acidic substances and other hydrocarbon unless very effectively treated before disposal. Escaped acidic substances may significantly lower pH of the concerned water bodies and increase COD and BOD loading. Often alkali treatment is resorted for neutralizing acidic wastes, which though neutralizes the waste, generates enormous quantities of sludge. Land filling or dumping of these waste hydrocarbons in open atmosphere can create air pollution (due to increase in volatile organic carbon) while reducing soil fertility and increasing bio-hazard due to rise in biological oxygen demand and chemical oxygen demand of the water bodies where such wastes eventually escape. The plant has to make provisions for biological and chemical treatment along with options for final disposal of solid or semi solid sludge. Provisions for such treatment obviously add to the overall cost of production. Such elaborate treatment of waste streams will not be necessary in the proposed new membrane-based scheme. The total number of unit operations involved in a conventional acetic acid production plant is much higher than those required in a membrane integrated acetic acid production system which as shown in Table 1.
2. Overview of the current technologies
Sweet cheese whey containing 4.5e5% lactose and 0.6e0.65% whey protein was used as the starting raw material for the production of both acetic acid and whey protein (Yang, 2007). Acetobactor Aceti (NCIM-2116), an aerobic acetic acid producing strain, procured from National Collection of Industrial Microbes (NCIM), NCL Pune, India, was used in the work for production of acetic acid. Flat sheet cross flow membrane modules with membranes like Nylon-0.22 (Membrane Solutions, U.S.A.) for microfiltration, PES-5 (Membrane Solutions, U.S.A.) for ultrafiltration, NF-1 and NF-2, NF3 (Sepro Membranes Inc, U.S.A.) for nanofiltration and forward osmosis were used for the downstream purifications in a multistage membrane-integrated reactor system. 1.0 M MgSO4 solution was used as the draw solution for forward osmosis as it could generate sufficient driving force without much problem of reverse salt flux. Finally small service of a vacuum dryer was utilized in getting dry whey protein powder from concentrated liquid form.
Despite the presence of eco-friendly fermentative routes for acetic acid production (like Orleans process and German method) hardly any of those processes has been commercialized (Sokollek et al., 1998) due to low productivity. Cativa process involving ethylene or aldehyde oxidation has been commercialized successfully and caters to almost 65% of the global demand of acetic acid. In this process, acetic acid is produced by the reaction of carbon monoxide and methanol employing iridium as a catalyst and hydrogen iodide as promoter (Yoneda et al., 2001; Howard et al., 1993). This method consists of a number of downstream treatment units like distillation, condensation, drying, recovery of catalysts as presented in Fig. 1. A typical cheese whey treatment plant as presented in Fig. 2 also involves a series of evaporators and spray driers to extract the whey powder. Whey protein concentrate obtained after dehydration of cheese whey in evaporators is treated in spray dryers to obtain the commercial form of whey protein. A typical cheese whey treatment plant as presented in Fig. 2 also involves a series of evaporators and spray driers to extract the whey powder. Whey protein concentrate obtained after dehydration of cheese whey in evaporators is treated in spray dryers to obtain the commercial form of whey protein. Inlet air temperature of hot air is
3. Materials and methods 3.1. Materials
3.2. Experimental procedure 3.2.1. Pretreatment of raw cheese whey The raw material (sweet cheese whey) was first microfiltered with a Nylon-0.22 membrane (operated at 3 bars) for separation of coarse suspended matters and microbial cells. Next an
Please cite this article in press as: Pal, P., Nayak, J., Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey, Journal of Cleaner Production (2015), http://dx.doi.org/10.1016/j.jclepro.2015.07.085
P. Pal, J. Nayak / Journal of Cleaner Production xxx (2015) 1e12
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Fig. 1. Schematic diagram of a conventional acetic acid production (Cativa) plant.
ultrafiltration module fitted with ultrafiltration membrane PES-5 was operated at 6 bars, for separation of whey protein and whey lactose. 3.2.2. Fermentation of microfiltered cheese whey The whey permeate had a lactose concentration of 48.8 g L1 which was used for acetic acid production. Cell recycle fermentation with microfiltration membrane was run at a dilution rate of
0.1 h1. The separated whey lactose was subsequently subjected to fermentation in a membrane integrated fermenter made of high quality stainless steel (SS316) with a working volume of 30 L under non neutralizing conditions. Downstream product withdrawal and nanofiltration stage was made on-line after allowing an initial lag phase of around 15 h (as arrived through prior separate investigation) of fermentation to exploit the exponential growth of the life cycle of the microbes. Continuous cell separation and recycle
Fig. 2. Schematic diagram of a conventional whey protein production plant.
Please cite this article in press as: Pal, P., Nayak, J., Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey, Journal of Cleaner Production (2015), http://dx.doi.org/10.1016/j.jclepro.2015.07.085
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Table 1 Unit operations involved in a conventional Cativa Plant and a membrane integrated fermentation based acetic acid production plant (10,000 tonnes per year). Conventional Cativa plant
Membrane integrated fermentation system
Sl. no. Unit operations
Sl. no.
Unit operations
1 2 3 4 5 6 7 8 9 10 11 12
1 2 3 4 5
Ultrafiltration Fermentation Microfiltration Nanofiltration Forward osmosis
Main reactor Flash drum Secondary reactor Bubble loop reactor Recovery unit for feed Recovery unit for catalyst Distillation column Condenser Reboiler Dryer Evaporator Iodide recovery unit
through cross flow microfiltration membrane module (Nylon-0.22 membrane operated at 2.5 bars) ensured high concentration of viable cells in the fermenter resulting in high productivity. 3.2.3. Downstream purification The subsequent stages consisted of cross flow nanofiltration and forward osmosis membrane modules. Composite polyamide membrane NF-2 operated at 12.5 bar transmembrane pressure was used as the second filtration unit. A high pressure pump (Hydracell, 2.2 kW, Minneapolis, USA) circulated fermentation broth through NF modules. Permeate collected after nanofiltration was again filtered at the final stage forward osmosis unit with NF-3 membranes at 1.2 bar transmembrane pressure using draw solution of 1.0 M MgSO4 for the concentration enrichment of acetic acid. A side stream containing raw cheese whey which is rich in whey protein was also first concentrated by forward osmosis (using NF-3 membrane) using the same draw solution and was finally subjected to mild vacuum drying to get the powder form. The whole system was operated completely in continuous mode from where the whey protein was recovered as a by-product of the process. The diluted draw solution streams coming out from both the forward osmosis systems were recovered by a nanofiltration membrane module employing NF-1 membrane operated at 14e15 bar transmembrane pressure. Membranes were sterilized with 200 mg L1 NaOCl solution followed by rinsing with Milli-Q water. Characteristics of the membranes used for nanofiltration have been presented in Table 2. Schematic diagram of the new technology is presented in Fig. 3. 4. Results and discussion 4.1. Improvement in production process and product quality The first stage nanofiltration with NF-2 membrane under a pressure of 12.5 bar yielded a flux of 80 L m2 h1 with the acetic acid concentration of 43.2 g L1. Breakthrough curves of rejection and flux of acetic acid with respect to transmembrane pressure during first stage nanofiltration (using NF-2 membrane) have been represented in Fig. 4. Forward osmosis was used for concentration enrichment of acetic acid. Counter current flow of feed and draw solutions in flat-sheet cross-flow membrane modules fitted with NF-3 membrane rejected acetic acid by more than 99% at an operating pressure of 1.2 bar and whey protein by 100% at an operating pressure of 1.5 bar. Flux of around 40 L m2 h1 was achieved as presented in Fig. 5. Forward osmosis stage significantly dehydrated the acid product as well as whey protein powder. Fig. 6 indicates how in forward osmosis, concentration of
Table 2 Typical characteristics and performances of investigated membranes: NF-1 and NF-2 during nanofiltration and NF-3 membrane during forward osmosis. Characteristics Operating pressure (bar) For acetic acid separation For whey protein separation
NF-1
NF-2
NF-3
15
12.5
1.2 1.5
Filtration purpose
Nanofiltration
Nanofiltration
Module type Membrane geometry Membrane material Thickness (cm) Temp ( C) resistance pH resistance Pure water flux (L h1 m2) Acetic acid rejection (%)
Cross flow Flat-sheet Polyamide 0.0165 50 2e11 110
Cross flow Flat-sheet Polyamide 0.0165 50 2e11 130
Forward osmosis Cross flow Flat-sheet Polyamide 0.0165 50 2e11 120
89
10
99.5
Investigated solute rejection (%) MgSO4 NaCl MnSO4 MnCl2
99.8 95 99.2 98.6
99 92 98 98.2
99.2 94.3 98.6 98.4
final acetic acid solution reaches 962 g L1 after 30 h of continuous operation. Fouling study of the membranes reveals that the very flat sheet module with tangential fluid flow over the surface can substantially overcome fouling problem. After prolonged operation, simple rinsing could recover the lost flux significantly. Protein estimation (Lowry's method) and detection (SDSePAGE) showed that the protein concentration after forward osmosis reached 954.5 g L1. The final nanofiltration stage (NF-1) could recover draw solute (MgSO4) by more than 99% at an operating pressure of 12e14 bars. Produced acetic acid in membrane-integrated system was tested to be 98.7% pure as measured by HPLC (Agilent, 1200 series, USA) peak purity software tool. Yield (98.7%) achieved in this membrane integrated continuous production scheme is substantially higher than those achieved in conventional systems (Moulijn et al., 2013). Final product concentration (962 g L1) and density (1.11 g L1) are almost same for both the systems. Differences in flux and rejection of the used membranes are obviously attributed to the physical structures and charge repulsion properties of the membranes. NF-2 has the loosest structure (pore radius 0.57 nm) and the lowest membrane charge density whereas NF-1 possesses the most compact structure (pore radius 0.53 nm) and the highest membrane charge density during the nanofiltration of acetic acid fermentation broth. This explains the reason of obtaining high flux and low rejection (10%) in case of NF-2 and low flux but high rejection (89%) for NF-1 during nanofiltration. The purpose of filtration employing NF-3 membrane was dehydration by forwardosmosis technology. Due to the chemical potential difference between the feed and draw solution, the water molecules of the feed solution permeate out to the draw solution stream leaving the solute molecules into the feed solution. Moreover, membrane properties like pore radius (0.55 nm), membrane charge density also play important role that results in the observed behavior of that NF3 membrane in forward osmosis (resulting in a rejection of 99.5% of acetic acid). In the same Table 2, the investigated solutes are MgSO4, NaCl, MnSO4 and MnCl2 whose rejection (%) has already been provided. The overall production parameters and product characteristics for both conventional and membrane integrated system for
Please cite this article in press as: Pal, P., Nayak, J., Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey, Journal of Cleaner Production (2015), http://dx.doi.org/10.1016/j.jclepro.2015.07.085
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Fig. 3. Schematic diagram of membrane integrated hybrid fermentation system for continuous production of acetic acid.
direct production of acetic acid production have been presented in Table 3 for quick comparison. 4.2. Value addition for enhanced profit margin in the sustainable technology The by-products from the proposed plant are whey-protein and reusable water. Such a plant that can annually treat 5 108 L of cheese whey produces 3000 ton of dry whey protein powder as byproduct through forward-osmosis and vacuum drying. Conventionally the involvement of triple effect evaporators and spray
dryers for the sole production of whey protein powder involves huge energy consumption apart from involving high equipment cost, maintenance and man power expenses. Thus the configuration for whey protein regeneration section which is actually a byproduct recovery division of the main plant of acetic acid production stands to be very much simpler than the classical ones. As presented in Table 4, the estimated energy consumption for a conventional whey protein production plant stands at about 864 kWh for per ton whereas in membrane integrated system, it drops down to 40 kWh for per ton of whey protein. So the energy reduction parameter computes to around 0.05. The capital
Please cite this article in press as: Pal, P., Nayak, J., Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey, Journal of Cleaner Production (2015), http://dx.doi.org/10.1016/j.jclepro.2015.07.085
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100
90
90
80
Flux (L m−2 h−1)
100
70 60
80
50 60
40 30
40
20 20
10 0
0 0
5
10
15
20
25
Transmembrane Pressure (bar) flux from NF-2
rejection of acetic acid by NF-2
rejection of lactose by NF-2 Fig. 4. Separation of microfiltered fermentation broth: flux and rejection characteristics of nanofiltration membrane (NF-2) with respect to transmembrane pressure.
investment including total equipment and machinery costs along with indirect costs specifically for the whey protein production has been presented in Table 5. In the proposed system, the total installed equipment cost involved is about US $ 33.2 104 where
Space intensification ¼
120 100
80 70
80
60 60
50 40
40
30 20
Rejection (%)
120
100
Flux (L m-2 h-1)
140
Rejection of acetic acid (%)
6
20
10 0
0 0
0.5
1 1.5 2 Applied pressure (bar)
2.5
flux during acetic acid separation
flux during protein separation
rejection during acetic acid separation
rejection during protein separation
Fig. 5. Separation of acetic acid and whey protein using NF-3 membrane and 1 M MgSO4 as draw solution: flux and rejection characteristics with respect to transmembrane pressure during forward osmosis.
tonnes per annum, the space requirement compared to a conventional Cativa plant comes down to almost one-fifth (as presented in Table 6). Total space required for a conventional Cativa plant is about 5000 m2 whereas in the membrane integrated system, the space requirement comes down to 902 m2 for the same quantum of production. This space intensification may be expressed as:
total area required for membrane integrated hybrid fermentation system Overall area requirement for a conventional plant
the total production cost stands to be US $ 68.8 104 for 3000 ton/ year whey protein powder. The annual operating cost for that amount of whey protein production is US $ 25.8 104. Considering the same project life and interest rate as that of the main plant, the annual manufacturing cost of whey protein powder stands to be US $ 0.11/kg. To operate such a compact membrane based plant, a total water supply of 80.12 106 L/year is very much required as applications involving membranes require continuous supply of water. But in the proposed plant, due to presence of feed concentration enrichment units like forward osmosis, huge volume of water which is about 264 106 L/year could be recovered after nanofiltration treatment. Thus there is further cost saving on utility account. 4.3. Compactness of the new system A membrane integrated fermentation based process consists of only 5 unit operations as compared to 12 unit operations in a conventional Cativa plant for acetic acid production. For an acetic acid production plant with the production capacity of 10,000
Flexibility in application ¼
Such intensification computes to around 0.2 for the membrane-vis a conventional plant of the same prointegrated plant vis-a duction capacity. This establishes compact design of the new system. 4.4. Flexibility in plant capacity utilization The very modular design of a membrane-integrated plant results in high capacity flexibility as any number of modules can be made operational depending on the market demand. Due to the series and parallel adjustment of the microfiltration and nanofiltration modules (including excess modules) in the membrane integrated system, such flexibility is achieved. The modular plant also offers the flexibility of production of similar organic or amino acids or even the plant can be used for other fermentative or microbial productions. The flexibility in application in hybrid processes could be defined as the ratio of number of possible applications in the hybrid process to the number of possible applications in conventional process.
possible applications in membrane integrated hybrid process possible applications in conventional process
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120
1200
100
1000
80
800
60
600
40
400
20
200
Concentration of acetic acid (g/L)
Flux (L m−2 h−1)
P. Pal, J. Nayak / Journal of Cleaner Production xxx (2015) 1e12
0
0
0
20
40 Time (h)
60
80
flux from NF-3 during forward osmosis flux from NF-2 during nanofiltration Acetic acid concentration (g/L) during forward osmosis Fig. 6. Separation of acetic acid: a fouling study and enrichment of acetic acid concentration profile with respect to time using NF-3 (operating pressure 1.2 bar) and NF2 (operating pressure 12.5 bar) membranes.
The parameter describing the flexibility in application will be greater than 1 for this kind of membrane integrated process. A comparative description of system flexibility for both the processes has been presented in Table 7. Capacity flexibility may be expressed in terms of total throughput as below:
Capacity flexibility ¼
7
(50e70 bars) ranges are also quite high in conventional plants. These reflect not only high operating costs but high capital cost as well. Expensive catalysts such as rhodium or iridium based catalyst with methyl iodide in methanol carbonylation and cobalt, chromium or palladium based catalysts in ethylene oxidation and acetaldehyde oxidation add to the cost of production. Moreover a number of chemical or physical treatment operations are required to regenerate catalysts and recover the products. Involvement of several phase changing phenomena under high temperature and pressure regimes demands extra care for plant safety. This again raises cost. On the other hand, a membrane integrated reactor system involves only one phase (liquid phase). With minimum consumption of power and raw materials under non-neutralizing conditions, production process in this system represents an entirely green technology. Table 8 presents a comparative description of the two types of production schemes. 4.6. Energy consumption in the membrane based hybrid process -vis current technology vis-a In a classical Cativa plant of 10,000 tonnes per year acetic acid production capacity, the total annual energy consumption stands at 550 105 kW h. In those plants high temperature and high pressures are maintained to carry out reactions. Energy required for chemical reactions and downstream processing is very high. In conventional production route, downstream processing stages like distillation, evaporation, drying involve the maximum electrical energy. But while using membrane integrated fermentation tech-
variations in production capacity by hybrid process variations in production capacity by conventional system
Advantage of a hybrid plant is obvious as flexibility is always greater than one. This analysis indicates that in situations of fluctuating market demand, the new system can be operated by switching on to the desired number of modules and thus ensuring continuity in plant operation. 4.5. Benefits to the environment The downstream separation and purification does not involve any phase change and thus the overall energy consumption reduces significantly in the new system. In the illustrated scheme, ecofriendliness compared to the conventional ‘Cativa’, ‘Ethylene Oxidation’ or ‘Acetaldehyde Oxidation’ based plants is clearly evident. Disposal of acid or alkali-bearing wastes leads to environmental pollution in the currently practiced technology. Operating temperature (often exceeding 425e475 K) and pressure
nology, the power consumption could be effectively minimized. Acetic acid is produced through bio-reactions and the downstream processing steps involve only pumps. Power consumption at each stage of a conventional acetic acid production plant (Cativa plant) as well as membrane integrated system has been shown in Table 9. Total annual power consumption in a membrane integrated acetic acid production plant of similar capacity has been computed to be approximately 55.76 104 kW h only. Membrane-integrated acetic acid system thus turns out to be quite energy efficient system as power consumption is negligible compared to a conventional system. Energy involvement in a scaled up plant can be arrived at using sixetenth-factor rule (Peters and Timmerhaus, 1991) and power number equations (Doran, 2008). Thus energy consumption per ton of acid production is about 5500 kWh in a conventional plant against only 55 kW h in a membraneintegrated system.
Table 3 Production parameters: comparison of conventional plant with new membrane based plant for acetic acid (capacity: 10,000 tonnes/year) and whey protein (capacity: 3000 tonnes/year). Parameters
Membrane integrated plant
Conventional acetic acid production plant
Product yield Product concentration Productivity of the process Product purity
98.2% 961.72 g L1 (96%) 96.1 g L1 h1 98.7%
85e90% (Moulijn et al., 2013) 850e980 g L1 (85e98%) e 95e99%
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Table 4 Comparison of total energy consumption in a conventional process with respect to the proposed plant for whey protein production (capacity: 3000 tonnes/year). Conventional acetic acid production system Equipment
Membrane integrated system Energy (kWh) 5
Pasteurizer Evaporator (4 in number) Spray drier Pumps
1.15 10 12.60 105 6.48 105 5.68 105
Total energy requirement Energy requirement for per unit acetic acid production
25.91 105 (approximate) 863.7 kWh/ton acetic acid
Equipment
Energy (kWh)
Pumps Vacuum drier
3.5 104 8.5 104
12 104 (approximate) 40 kWh/ton whey protein
The energy reduction parameter can thus be expressed as:
Parameter of energy reduction ¼
energy required for per unit production in hybrid system energy required for per unit production in conventional system
The energy intensification parameter here computes to around 0.01 reflecting high energy intensification achievable in the new hybrid system. This analysis shows that the investigated membrane based process can be operated with huge energy saving compared to the currently practiced processes.
Table 5 Investment costs for production of whey protein powder in membrane integrated systems (capacity: 3000 tonnes/year). Item
Cost (US $)
A) Capital investment 1. Direct costs 1.1. Installed equipment 1.1.1. SS 316 membrane modules (nanofiltration) 1.1.2. Perspex modules (Forward osmosis) 1.1.3. Pumps (peristaltic and hydra-cell) 1.1.4. Holding tank for concentrated whey protein 1.1.5. Holding tanks for draw solution 1.1.6. Vacuum drier 1.1.7. Vessel for collection of whey protein powder
4.5 104 2.1 104 4.3 104 1.5 104 1.8 104 18 104 1.0 104
Total installed equipment
33.2 104
1.2. Piping 1.3. Electrical connections 1.4. Instrumentation
8.6 104 2.3 104 3.5 104
Total direct costs
47.6 104
2. Indirect costs 2.1. Engineering and supervision 2.2. Contractor's fee 2.3. Contingency
1 104 3.2 104 2 104
Fixed capital investment Working capital
53.8 104 15 104
Total capital investment ($/year)
68.8 £ 104
B) Operational cost i. Membrane replacement ii. Membrane cleaning iii. Draw solute (MgSO4) iv. Electrical v. Man power vi. Overhead charges vii. Maintenances
15.5 10 3 104 2 104 0.8 104 2.5 104 1.7 104 0.5 104
Total annual operating cost ($/year)
26 £ 104
4.7. Economic evaluation Scale up has been done following standard procedure to assess the capital investment cost of a plant for annual production of 10,000 tonnes of acetic acid. This assessment includes equipment installation cost and instrumentation cost for both the systems taking into account the new design as shown in Fig. 3. The total capital investment cost involved for a conventional acetic acid production is huge which stands about 86 106 US$ for 10,000 tonnes/year capacity whereas it drops to 3.0 106 US$ for a membrane integrated acetic acid production plant of same capacity (as evaluated in Table 10). Direct capital investments costs were calculated considering equipment purchase cost, equipment installation cost, piping cost, building cost, electrical instrumentation cost, yard improvements cost, service facilities and land purchase cost. Total equipment purchase cost for conventional system was calculated as 52 106 US$ which is about 36 times higher than the membrane integrated acetic acid system for same production capacity of acetic acid. Similarly, other associated costs and indirect costs like engineering supervision, contractor's fee and contingency are in the same way on the higher side for a conventional system. For membrane integrated system, costs for pumps and membrane modules contributed about 8.1% and 15.7% respectively to the total equipment cost. Cost of every equipment and process has been calculated using the standard equation below (Peters and Timmerhaus, 1991):
Cost of higher capacity equipment
4
¼ Cost of lab scale equipment capacity of high capacity equipment n capacity of lab scale equipment where n represents the scale-up factor and differs for different equipment, standard values of n were taken from the list mentioned by Peters and Timmerhaus (1991). Table 11 presents a comparative economic evaluation. This indicates involvement of huge material cost in a conventional plant vis-a-vis a membraneintegrated plant for the same capacity. Cost saving on carbon source raw could be effectively done here as the cost of transportation of cheese whey is the only cost factor for raw material involved in the proposed system. When around
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Table 6 A comparison of space required in a conventional and membrane integrated system for production of acetic acid (plant capacity: 10,000 tonnes per annum). Conventional acetic acid production system
Membrane integrated system
Sr. no.
Processing stages
Area required (m2)
Sr. no.
Processing stages
Area required (m2)
1 2 3 4 5 6 7
Main reactor Secondary reactor Bubble loop reactors Flash drum Recovery unit for feed Recovery unit for catalyst Distillation column (including condenser and reboiler) Dryer Evaporator Iodide recovery unit
535 267 1062 244 222 273 1250.4
1 2 3 4 5 6 7
Microfiltration Ultrafiltration Fermentation Forward osmosis Storage tanks Fresh feed supply tank Nanofiltration
245 90 31 180 50 31 210
152 743 252
8 9
Collection tanks Vacuum dryer
45 20
8 9 10
5000 m2 (approximate)
Total area required (including installation spaces and pipe lines)
902 m2 (approximate)
Table 7 Comparison of flexibility of systems for production of acetic acid. Parameters of flexibility
Membrane integrated system
Conventional production technique
Steps of operation Capacity of production
Only a few Flexible and could be modified as per market demand Membrane modules are highly flexible in size and numbers according to requirements Membrane units (ultra, micro, nano or forward osmosis) and modules are highly flexible to be arranged in parallel or series
Too many in numbers Fixed capacity of production
Plant configuration Arrangements of downstream purification
Fixed configuration Downstream purification arrangements are fixed
Table 8 Comparison of eco-friendliness for production of acetic acid. Parameters of eco-friendliness
Membrane integrated system
Conventional production technique
Raw material
Use of dairy waste cheese whey, a renewable resource
Exploitation of non-renewable petroleum stock.
Reaction phase
No phase change is encountered. Operations involve only liquid phase.
Multiphase process includes operations with solid, liquid, gas phases.
Reaction temperature
Reactions are highly exothermic and high temperature controlled (150e250 C).
Energy
Bio-reaction occurs within mesophilic range (30 C) and no exothermic process is involved. Microbes are the biocatalysts used here. No chances of formation of toxic chemicals as by product. Energy consumption is low.
Use of harsh chemicals
No harsh chemical is used.
Reaction catalyst By product
High cost iridium based catalyst is used. Generation of a mixture of propanoic acid, butyric acid, butanone, ethyl acetate, formic acid, dichloroacetic acid. Energy consumption is very high due to involvement of energy intensive red processes. All the chemicals used in this process are harsh in nature.
Table 9 -vis proposed plant for acetic acid production (capacity: 10,000 tonnes/year). Comparison of total energy consumption in a classical vis-a Conventional acetic acid production system
Membrane integrated system
Equipment
Energy (kWh)
Equipment
Energy (kWh)
Main reactor Secondary reactor Bubble loop reactors Flash drum Recovery unit for feed Recovery unit for catalyst Distillation column (including condenser and reboiler) Dryer Evaporator (4 in number) Iodide recovery unit
59.32 105 33.56 105 84.28 105 31.68 105 32.65 105 75 105 172 105
Fermentation Energy requirement for pumps
44.26 104 11.5 104
Total energy requirement Energy requirement for per unit acetic acid production
550 105 (approximate) 5500 kWh/ton acetic acid
6.48 105 12.60 105 42.44 105 55.76 104 (approximate) 55.76 kWh/ton acetic acid
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Table 10 Calculation of investment costs, including installation and instrumentation for membrane integrated systems (capacity: 10,000 tonnes/year). Item
Cost (US $)
Direct costs Installed equipment SS 316 membrane modules (microfiltration, ultrafiltration and nanofiltration) Perspex modules (forward osmosis) Pumps (peristaltic and hydra-cell) Holding tank for raw cheese whey Holding tank for microfiltered whey Sterilization Fermentation vessel Holding tank for fresh feed Holding tank for microfiltered broth Holding tank for nutrients Seed culture tank Holding tank for concentrated acid Holding tanks for draw solution Vessel for collection of reusable water
4.2 104 24.3 104 7.3 104 2.3 104 15 104 28.2 104 2.0 104 2.5 104 0.52 104 2 104 4 104 3 104 1.5 104
Total installed equipment
141.82 £ 104
Piping Electrical connections Instrumentation Buildings Land and yard improvements
18.6 104 8.6 104 14.5 104 25 104 8.2 104
Total direct costs
216.72 £ 104
45 104
achieve this production capacity in conventional acetic acid production system, the cost involvement for methanol, carbon monoxide, hydrogen iodide and iridium estimates to about US $ 4.87 106, whereas a membrane-integrated continuous process plant saves on such huge costs as such harsh chemicals need not be used. Simultaneously, labor cost and annual maintenance cost are much lower for membrane integrated reactor system due to involvement of a few operating units and simplicity of the overall design. Total annual production cost in Cativa process, stands at around $ 1.36/kg of acetic acid. In a conventional plant, pretreatment of cheese whey also involves substantial expenses which very drastically come down in membrane-based plant where a simple ultrafiltration module does the work. During final stage concentration using forward osmosis, the pure water produced is subsequently recycled and reused within the plant thus significantly bringing down utility cost. Operating cost for such membrane integrated system including all nutrients cost, electricity and maintenance costs like membrane replacement, labor; water supply was evaluated as US $ 4.028 106 for production of 10,000 tonnes of acetic acid per annum. In this work, a project life of 15 years and interest rate of 7% were considered according to the realistic present market conditions in India.
" Capital recovery factor ¼
Indirect costs Engineering and supervision Contractor's fee Contingency
12.5 104 11 104 20 104
Fixed capital investment Working capital
260.22 £ 104 40 104
Total capital investment
300.22 £ 104
5.8 108 L of cheese whey is consumed to produce 10,000 tonnes of acetic acid the same volume of waste gets disposed in one of the best possible ways. By assuming a conventional plant continuously working for 300 days a year, the annual production of same amount of acetic acid is dependent on the continuous supply of methanol of about 2.1 104 ton, 1.8 102 ton carbon monoxide as an active reactant and 0.8 102 ton hydrogen iodide as a promoter. Iridium is used as the catalyst in the reaction which is required at the rate of 18 ton for a yearly production of 10,000 tonnes of acetic acid. To
#
ið1 þ iÞn ð1 þ iÞnþ1 1
¼ 0:099
‘n’ and ‘i’ were considered to be is the project life of the plant and the rate of interest as per market statistics. So, the annualized capital cost is evaluated as:
"
# 300:22 104 0:099 z0:03 $=kg 107 The annualized operating cost was evaluated as:
Total annual operating cost ð$Þ 4:028 106 ¼ z0:4 $=kg Output per year ðkgÞ 107 It is observed that process, the major cost like yeast extract with comprises about 36% of
in membrane-integrated fermentation contributor is the cost of the nutrients combination of other nutrient salts. It the total operating cost. However, there
Table 11 Operational cost comparison for the conventional and membrane integrated systems (capacity: 10,000 tonnes/year). Membrane integrated plant
Conventional acetic acid production plant
Sl. no
Item
Quantity/year
Cost (US$)
Item
Quantity/year
1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12 1.13
Cheese whey Supplementary nutrients Membrane replacement Membrane cleaning Electrical Man power Maintenances Overhead charges Depreciation Insurance General and administrative expenses
5.8 108 L 7.1 105 kg 1100 m2 1500 kg 55.76 104 kWh 50 persons
0.365 106 2 106 0.35 106 0.01 106 0.04 106 0.25 106 0.1 106 0.2 106 0.6 106 0.003 106 0.11 106
Methanol Hydrogen Iodide Carbon monoxide Iridium catalyst Fuel (solid and liquid) Electrical Water Man power Maintenances Overhead charges Depreciation Insurance General and administrative expenses
2.1 0.8 1.8 1.8
Total annual operating cost ($/year) for production
4.028 106
107 105 105 104
kg kg kg kg
55 106 kWh 0.6 107 L 180 people
Cost (US$) 0.0756 106 1.1 106 0.114 106 3.58 106 2.2 106 3.5 106 0.028 106 0.8 106 0.9 106 0.5 106 0.25 106 0.035 106 0.48 106 13.56 106
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is scope for reduction of this cost with the use of cheap nitrogen sources like corn steep liquor (CSL), ultra filtered ethanol stillage, and hydrolyzed soy flour (Witjitra et al., 1996). Membrane replacement and cleaning charge was calculated considering the reusability of the membranes (ultra, micro and nano) in a year through chemical treatments. Depreciation cost and insurance costs have been considered to be 17% and 0.08% respectively, of fixed capital investment as a standard practice. Considering all the factors including maintenance, operating supplies, depreciation and insurance in membrane integrated plant, the annualized production cost of 98.7% pure 962 g L1 of acetic acid was evaluated by adding annualized operating cost to the annualized capital cost which was found out to be $ (0.03 þ 0.40) z 0.5 $/kg of acetic in the Indian market, where similar grade acetic acid costs about US $ 1.6 per kg. The cost advantage factor may be computed as below.
Cost advantage parameter ¼
11
Acknowledgment The authors are thankful to the Department of Science and Technology (DST) (SR/FST/ETi-204/2007 & SR/S5/GC-05/2008) and Ministry of Human resource Development (MHRD), Government of India for providing funds for necessary infrastructure and research materials procured for the present research under DST-FIST and DST, Green Chemistry/Technology program.
References Babi, D.K., Lutzeb, P., Woodley, J.M., Gani, R., 2014. A process synthesisintensification framework for the development of sustainable membranebased operations. Chem. Eng. Process. 86, 173e195. Becht, S., Franke, R., Geißelmann, A., Hahn, H., 2009. An industrial view of process intensification. Chem. Eng. Process. 48, 329e332.
Cost involved by hybrid system for per unit production Cost involved by conventional system for per unit production
Cost advantage parameter computes to 0.27 indicating major cost advantage in the new system over the conventional type. Economic advantage of the developed membrane-integrated process lies in involvement of less number of unit operations, less equipment cost, less material and energy consumption. Use of microbes enables eco-friendly production and high selectivity of membranes ensures higher purity of the desired product. Continuous production and fast separation in this kind of a compact plant leads to higher yield, productivity and purity of the product at significantly reduced cost.
5. Conclusion It transpires from the study that extensive process intensification and thus production sustainability could be achieved in manufacturing acetic acid in a membrane-integrated hybrid reactor system where multi-stage membrane separation modules are judiciously integrated with conventional fermentation device. Selection of appropriate membrane module that can overcome the fouling problem considered the major hurdle in membrane separation can culminate in a very eco-friendly, small, compact, energy-saving yet flexible plant with the promise of high yield, productivity, and purity of the desired product. After a long operation period, membrane integrated hybrid fermentation system may witness drop in flux to some extent but the same could be recovered through appropriate intervention of simple rinsing of the membranes. However, the quality of product need not be compromised. The system fulfills almost all the expectations of a sustainable system for production of high purity acetic acid and whey protein at a reduced cost. Amidst growing environmental awareness and stringent discharge regulations, this green technology is likely to be welcomed as a sustainable one by the chemical and allied process industries in an era of emaciated profit margin in the competitive global market.
Biswas, A., Roy, M., 2015. Green products: an exploratory study on the consumer behaviour in emerging economies of the East. J. Clean. Prod. 87, 463e468. Bruggen, B.V., Curcio, E., Drioli, E., 2004. Process intensification in the textile industry: the role of membrane technology. J. Environ. Manag. 73 (3), 267e274. Cheung, H., Tanke, R.S., Torrence, G.P., 2005. Acetic acid. In: Wiley-VCH (Ed.), Ullmann's Encyclopedia of Industrial Chemistry. Wiley, Weinheim, pp. 1e20. Choe, W.S., Nian, R., Lai, W.B., 2006. Recent advances in biomolecular process intensification. Chem. Eng. Sci. 61, 886e906. Drioli, E., Stankiewicz, A.I., Macedonio, F., 2011. Membrane engineering in process intensification e an overview. J. Membr. Sci. 380, 1e8. Dautzenberg, F.M., Mukherjee, M., 2001. Process intensification using multifunctional reactors. Chem. Eng. Sci. 56, 251e267. Doran, P.M., 2008. Bioprocess Engineering Principles, second ed. Elsevier, New York. Emadzadeh, D., Lau, W.J., Matsuura, T., Rahbari-Sisakht, M., Ismail, A.F., 2014. A novel thin film composite forward osmosis membrane prepared from PSfeTiO2 nanocomposite substrate for water desalination. Chem. Eng. J. 237, 70e80. Esymondt, J., Vasic-Racki, D., Wandrey, C., 1990. Acetic acid production by Acetogenium kivui in continuous culture e kinetic studies and computer simulations. Appl. Microbiol. Biotechnol. 34, 334e349. Grzenia, D.L., Schell, D.J., Wickramasinghe, S.R., 2008. Membrane extraction for removal of acetic acid from biomass hydrolysates. J. Membr. Sci. 322, 189e195. Howard, M.J., Jones, M.D., Roberts, M.S., Taylor, S.A., 1993. C1 to acetyls: catalysis and process. Catal. Today 18, 325e354. Jayaprakasha, H.M., Yoon, Y.C., 2005. Production of functional whey protein concentrate by monitoring the process of ultrafiltration. J. Anim. Sci. 18 (3), 433e438. nez, X.T., Cuenca, A.A., Jurado, A.T., Corona, A.A., Urista, C.R.M., 2012. Traditional Jime methods for whey protein isolation and concentration: effects on nutritional properties and biological activity. J. Mex. Chem. Soc. 56 (4), 369e377. Jones, J.H., 2000. The Cativa™ process for the manufacture of acetic acid. Platin. Met. Rev. 44 (3), 94e105. Kong, F., Yang, H., Wang, X., Xie, Y.F., 2014. Rejection of nine haloacetic acids and coupled reverse draw solute permeation in forward osmosis. Desalination 341, 1e9. Kumar, R., Pal, P., 2013. Turning hazardous waste into value-added products: production and characterization of struvite from ammoniacal waste with new approaches. J. Clean. Prod. 43, 59e70. Lutze, P., Gani, R., Woodley, J.M., 2010. Process intensification: a perspective on process synthesis. Chem. Eng. Process. 49, 547e558. Moulijn, J.A., Makkee, M., Diepen, A.E., 2013. Chemical Process Technology, second ed. Wiley, United Kingdom. Pal, P., Dey, P., 2013. Process intensification in lactic acid production by three stage membrane-integrated hybrid reactor system. Chem. Eng. Process. 64, 1e9. Pal, P., Sikder, J., Roy, S., Giorno, L., 2009. Process intensification in lactic acid production: a review of membrane based processes. Chem. Eng. Process. 48, 1549e1559.
Please cite this article in press as: Pal, P., Nayak, J., Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey, Journal of Cleaner Production (2015), http://dx.doi.org/10.1016/j.jclepro.2015.07.085
12
P. Pal, J. Nayak / Journal of Cleaner Production xxx (2015) 1e12
Park, Y.G., Toda, K., 1990. Simulation study on bleed effect in cell-recycle culture of Acetobacter aceti. J. Gen. Appl. Microbiol. 36 (4), 221e233. Peters, M.S., Timmerhaus, K.D., 1991. Plant Design and Economics for Chemical Engineers, fourth ed. McGraw-Hill, New York. Phuntsho, S., Sahebi, S., Majeed, T., Lotfi, F., Kim, J.E., Shon, H.K., 2013. Assessing the major factors affecting the performances of forward osmosis and its implications on the desalination process. Chem. Eng. J. 231, 484e496. Ponce-Ortega, J.M., Al-Thubaiti, M.M., El-Halwagi, M.M., 2012. Process intensification: new understanding and systematic approach. Chem. Eng. Process. 53, 63e75. lez-Mun ~ oz, M.J., Luque, S., Alvarez, J.R., Coca, J., 2006. Rodríguez, M., Gonza Extractiveultrafiltration for the removal of carboxylic acids. J. Membr. Sci. 274, 209e218. Sant'Anna, V., Marczak, L.D.F., Tessaro, I.C., 2012. Membrane concentration of liquid foods by forward osmosis: process and quality view. J. Food Eng. 111, 483e489. Sokollek, J.S., Hertel, C., Hammes, W.P., 1998. Cultivation and preservation of vinegar bacteria. J. Biotechnol. 60, 195e206.
Wang, K.Y., Teoh, M.M., Nugroho, A., Chung, T.S., 2011. Integrated forward osmosisemembrane distillation (FOeMD) hybrid system for the concentration of protein solutions. Chem. Eng. Sci. 66, 2421e2430. Wang, L., Chu, H., Dong, B., 2014. Effects on the purification of tannic acid and natural dissolved organic matter by forward osmosis membrane. J. Membr. Sci. 455, 31e43. Witjitra, K., Shah, M., Cheryan, M.,1996. Effect of nutrient sources on growth and acetate production by Clostridium thermoaceticum. Enz. Microb. Technol. 19, 322e327. Yanga, Q., Wanga, K.Y., Chung, T.S., 2009. A novel dual-layer forward osmosis membrane for protein enrichment and concentration. Sep. Purif. Technol. 69, 269e274. Yang, S., 2007. Bioprocessing for Value-added Products from Renewable Resources: New Technologies and Applications, first ed. Elsevier Science Publishers, Amsterdam. Yoneda, N., Kusano, S., Yasui, M., Pujado, P., Wilcher, S., 2001. Recent advances in process and catalysts for the production of acetic acid. Appl. Catal. 22, 253e265. Zhang, X., Ning, Z., Wang, D.K., Costa, J.C.D., 2013. A novel ethanol dehydration process by forward osmosis. Chem. Eng. J. 232, 397e404.
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Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey Parimal Pal*, Jayato Nayak Environment and Membrane Technology Laboratory, Department of Chemical Engineering, National Institute of Technology Durgapur, 713209, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 25 February 2015 Received in revised form 12 June 2015 Accepted 15 July 2015 Available online xxx
A multi-stage membrane-integrated hybrid reactor system was developed and investigated for fermentative production of high purity acetic acid and whey protein from waste cheese whey. Integration of largely fouling-free membrane modules with traditional fermenter allowed fermentation with product withdrawal in a continuous scheme. Provision for recycling microbial cells, unconverted sugars and nutrients through cross flow membrane modules resulted in high yield (>98%) and productivity (96 g L1 h1) under high cell density. The final forward osmosis stage concentrated dilute acetic acid to 962 g L1. The environmentally friendly modular design of the membrane integrated system ensured continuous production of more than 98% pure acetic acid in a very simple, compact and flexible plant configuration reflecting all the major characteristics of high process intensification essential to sustainable production and business. Concentrated whey protein (955 g L1) recovered as a by-product added to the economy of the process raising the possibility of enhanced profit margin. The developed new design fulfills the major expectations of a sustainable technology in terms of benefits to the planet, people and profit. The sustainability parameters in terms of cost of equipment, and production, reduced consumption of material and energy, flexibility, profitability and environmental friendliness have been analyzed in the paper. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Acetic acid Whey protein Green processing Energy reduction Waste reduction Sustainable technology
1. Introduction In an environmentally conscious global market amidst tough competition, the chemical, pharmaceutical and allied process industries are witnessing paradigm shift in their production strategy embracing the concepts of sustainable technology and sustainable development. All currently practiced energy-intensive and polluting processes and technologies will have to eventually leave the space for green production technologies (Biswas and Roy, 2015). Such production strategy fostering clean production in more efficient, more energy-saving, compact, flexible yet small plant configuration in other words is termed process intensification (PI) (Bruggen et al., 2004). Chemical and allied process industries can only move towards sustainability through such process intensification. The emerging new production regime is opening wide the gateway for innovations in a plethora of new products and processes. Along with other benefits, intrinsic safety of a process also improves dramatically in smaller and compact plants. The two
* Corresponding author. Tel.: þ91 343 2755055; fax: þ91 343 2754088. E-mail addresses: [email protected], [email protected] (P. Pal).
main categories of process intensification are unit intensification and plant intensification. Unit intensification could be achieved by minimizing hold-up and maximizing the throughput for a given size and process performance in terms of selectivity, yield, productivity and energy consumption. Plant intensification could be achieved by minimizing inventory and feedstock while maximizing the throughput (Ponce-Ortega et al., 2012). Among the different approaches of process intensification, replacement of traditional separationepurification devices by membrane filtration modules is considered one effective approach (Pal et al., 2009; Pal and Dey, 2013; Drioli et al., 2011). Integration of membrane based separation with traditional processes like fermentation can culminate in hybrid processes that eliminate the need for several other downstream unit operations such as centrifugation, crystallization, acidification, neutralization, carbon adsorption, ion-exchange and drying (Dautzenberg and Mukherjee, 2001; Becht et al., 2009; Choe et al., 2006; Lutze et al., 2010; Babi et al., 2014). Contrary to conventional chemical separation and purification involving phase change, product purification using membranes does not involve phase change (except pervaporation) and drastically brings down energy requirement. Such membrane-based processes also hold the potential of turning hazardous wastes and by-products into
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useful and value-added products in many cases (Kumar and Pal, 2013). The possibility of high degree of fractionation of target molecules using tailor-made membranes has opened up new routes to production of high purity organic acids and other thermosensitive biomolecules (Cheung et al., 2005). In this context, process intensification in acetic acid manufacture assumes significance in view of its huge market demand in production of vinyl acetate monomer, acetic anhydride polyethylene terephthalate, terephthalic acid, food grade vinegar, paints, adhesives, foods, textiles and photographic products. Annually 95% of acetic acid is produced by exploiting petroleum resources like methanol (carbonylation reaction) and ethylene or acetaldehyde (oxidation reaction) (Babi et al., 2014). Whey protein powder which is an essential constituent of whey has demand for its excellent nutritional and functional properties. It is conventionally recovered by evaporation and spray drying of cheese whey which involves substantial energy consumption (Cheung et al., 2005; Jayaprakasha and Yoon, 2005). More than half of the total production cost in such conventional chemical synthetic routes is involved in a large number of separation and purification steps. Those processes not only involve harsh chemicals and highly energy consuming steps like evaporation and distillation but also end up with generation of mixture of waste nez et al., 2012). Studies with batch or acids and chemicals (Jime fed-batch systems employing microfiltration or ultrafiltration membranes in tubular or hollow fiber modules for downstream processing have been reported (Jones, 2000; Esymondt et al., 1990; Grzenia et al., 2008; Rodríguez et al., 2006). But single-step membrane integration does not help in reaping the possible manifold benefits of membrane-integration. For example microfiltration module can help separate microbial cells for recycle; nanofiltration can separate acid product from the broth and forward osmosis can concentrate the products and by-products further be removing the water part without involving much energy consumption (Park and Toda, 1990; Phuntsho et al., 2013; Emadzadeh et al., 2014; Zhang et al., 2013; Wang et al., 2011, 2014; Kong et al., 2014; Yanga et al., 2009; Sant'Anna et al., 2012). But a fully membraneintegrated hybrid system for simultaneous production of acetic acid and whey protein in concentrated and highly purified form from a cheap carbon source needs to be investigated with analysis of culminating process intensification leading to sustainability. This manuscript fills this technology gap.
maintained at about 448e460 K but the dryers need to be so well engineered that gentle heat treatment (338e343 K) is provided to the heat-sensitive material (cheese whey) to produce whey protein avoiding denaturation. Provisions for such sensitive heat treatment in a conventional technology get reflected in overall cost of production of whey protein. Requirement of high temperature and high pressure inside the reactors for different phase changing phenomena makes the process highly energy-intensive. Capital investment on equipment is also very high. Catalyst constitutes other significant cost component. Highly skilled professionals are necessary for safe and successful operation of such plant. Disposal of wastes like propanoic acid and other high boiling impurities (like mixture of acetaldehyde, butyric acid, butanone, ethyl acetate, formic acid, dichloroacetic acid) is a big problem in conventional plants as these wastes are generated in substantial quantities and can lead to air pollution (through VOC emission), soil pollution (through hydrocarbon contamination) and water pollution through the escaped acidic substances and other hydrocarbon unless very effectively treated before disposal. Escaped acidic substances may significantly lower pH of the concerned water bodies and increase COD and BOD loading. Often alkali treatment is resorted for neutralizing acidic wastes, which though neutralizes the waste, generates enormous quantities of sludge. Land filling or dumping of these waste hydrocarbons in open atmosphere can create air pollution (due to increase in volatile organic carbon) while reducing soil fertility and increasing bio-hazard due to rise in biological oxygen demand and chemical oxygen demand of the water bodies where such wastes eventually escape. The plant has to make provisions for biological and chemical treatment along with options for final disposal of solid or semi solid sludge. Provisions for such treatment obviously add to the overall cost of production. Such elaborate treatment of waste streams will not be necessary in the proposed new membrane-based scheme. The total number of unit operations involved in a conventional acetic acid production plant is much higher than those required in a membrane integrated acetic acid production system which as shown in Table 1.
2. Overview of the current technologies
Sweet cheese whey containing 4.5e5% lactose and 0.6e0.65% whey protein was used as the starting raw material for the production of both acetic acid and whey protein (Yang, 2007). Acetobactor Aceti (NCIM-2116), an aerobic acetic acid producing strain, procured from National Collection of Industrial Microbes (NCIM), NCL Pune, India, was used in the work for production of acetic acid. Flat sheet cross flow membrane modules with membranes like Nylon-0.22 (Membrane Solutions, U.S.A.) for microfiltration, PES-5 (Membrane Solutions, U.S.A.) for ultrafiltration, NF-1 and NF-2, NF3 (Sepro Membranes Inc, U.S.A.) for nanofiltration and forward osmosis were used for the downstream purifications in a multistage membrane-integrated reactor system. 1.0 M MgSO4 solution was used as the draw solution for forward osmosis as it could generate sufficient driving force without much problem of reverse salt flux. Finally small service of a vacuum dryer was utilized in getting dry whey protein powder from concentrated liquid form.
Despite the presence of eco-friendly fermentative routes for acetic acid production (like Orleans process and German method) hardly any of those processes has been commercialized (Sokollek et al., 1998) due to low productivity. Cativa process involving ethylene or aldehyde oxidation has been commercialized successfully and caters to almost 65% of the global demand of acetic acid. In this process, acetic acid is produced by the reaction of carbon monoxide and methanol employing iridium as a catalyst and hydrogen iodide as promoter (Yoneda et al., 2001; Howard et al., 1993). This method consists of a number of downstream treatment units like distillation, condensation, drying, recovery of catalysts as presented in Fig. 1. A typical cheese whey treatment plant as presented in Fig. 2 also involves a series of evaporators and spray driers to extract the whey powder. Whey protein concentrate obtained after dehydration of cheese whey in evaporators is treated in spray dryers to obtain the commercial form of whey protein. A typical cheese whey treatment plant as presented in Fig. 2 also involves a series of evaporators and spray driers to extract the whey powder. Whey protein concentrate obtained after dehydration of cheese whey in evaporators is treated in spray dryers to obtain the commercial form of whey protein. Inlet air temperature of hot air is
3. Materials and methods 3.1. Materials
3.2. Experimental procedure 3.2.1. Pretreatment of raw cheese whey The raw material (sweet cheese whey) was first microfiltered with a Nylon-0.22 membrane (operated at 3 bars) for separation of coarse suspended matters and microbial cells. Next an
Please cite this article in press as: Pal, P., Nayak, J., Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey, Journal of Cleaner Production (2015), http://dx.doi.org/10.1016/j.jclepro.2015.07.085
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Fig. 1. Schematic diagram of a conventional acetic acid production (Cativa) plant.
ultrafiltration module fitted with ultrafiltration membrane PES-5 was operated at 6 bars, for separation of whey protein and whey lactose. 3.2.2. Fermentation of microfiltered cheese whey The whey permeate had a lactose concentration of 48.8 g L1 which was used for acetic acid production. Cell recycle fermentation with microfiltration membrane was run at a dilution rate of
0.1 h1. The separated whey lactose was subsequently subjected to fermentation in a membrane integrated fermenter made of high quality stainless steel (SS316) with a working volume of 30 L under non neutralizing conditions. Downstream product withdrawal and nanofiltration stage was made on-line after allowing an initial lag phase of around 15 h (as arrived through prior separate investigation) of fermentation to exploit the exponential growth of the life cycle of the microbes. Continuous cell separation and recycle
Fig. 2. Schematic diagram of a conventional whey protein production plant.
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Table 1 Unit operations involved in a conventional Cativa Plant and a membrane integrated fermentation based acetic acid production plant (10,000 tonnes per year). Conventional Cativa plant
Membrane integrated fermentation system
Sl. no. Unit operations
Sl. no.
Unit operations
1 2 3 4 5 6 7 8 9 10 11 12
1 2 3 4 5
Ultrafiltration Fermentation Microfiltration Nanofiltration Forward osmosis
Main reactor Flash drum Secondary reactor Bubble loop reactor Recovery unit for feed Recovery unit for catalyst Distillation column Condenser Reboiler Dryer Evaporator Iodide recovery unit
through cross flow microfiltration membrane module (Nylon-0.22 membrane operated at 2.5 bars) ensured high concentration of viable cells in the fermenter resulting in high productivity. 3.2.3. Downstream purification The subsequent stages consisted of cross flow nanofiltration and forward osmosis membrane modules. Composite polyamide membrane NF-2 operated at 12.5 bar transmembrane pressure was used as the second filtration unit. A high pressure pump (Hydracell, 2.2 kW, Minneapolis, USA) circulated fermentation broth through NF modules. Permeate collected after nanofiltration was again filtered at the final stage forward osmosis unit with NF-3 membranes at 1.2 bar transmembrane pressure using draw solution of 1.0 M MgSO4 for the concentration enrichment of acetic acid. A side stream containing raw cheese whey which is rich in whey protein was also first concentrated by forward osmosis (using NF-3 membrane) using the same draw solution and was finally subjected to mild vacuum drying to get the powder form. The whole system was operated completely in continuous mode from where the whey protein was recovered as a by-product of the process. The diluted draw solution streams coming out from both the forward osmosis systems were recovered by a nanofiltration membrane module employing NF-1 membrane operated at 14e15 bar transmembrane pressure. Membranes were sterilized with 200 mg L1 NaOCl solution followed by rinsing with Milli-Q water. Characteristics of the membranes used for nanofiltration have been presented in Table 2. Schematic diagram of the new technology is presented in Fig. 3. 4. Results and discussion 4.1. Improvement in production process and product quality The first stage nanofiltration with NF-2 membrane under a pressure of 12.5 bar yielded a flux of 80 L m2 h1 with the acetic acid concentration of 43.2 g L1. Breakthrough curves of rejection and flux of acetic acid with respect to transmembrane pressure during first stage nanofiltration (using NF-2 membrane) have been represented in Fig. 4. Forward osmosis was used for concentration enrichment of acetic acid. Counter current flow of feed and draw solutions in flat-sheet cross-flow membrane modules fitted with NF-3 membrane rejected acetic acid by more than 99% at an operating pressure of 1.2 bar and whey protein by 100% at an operating pressure of 1.5 bar. Flux of around 40 L m2 h1 was achieved as presented in Fig. 5. Forward osmosis stage significantly dehydrated the acid product as well as whey protein powder. Fig. 6 indicates how in forward osmosis, concentration of
Table 2 Typical characteristics and performances of investigated membranes: NF-1 and NF-2 during nanofiltration and NF-3 membrane during forward osmosis. Characteristics Operating pressure (bar) For acetic acid separation For whey protein separation
NF-1
NF-2
NF-3
15
12.5
1.2 1.5
Filtration purpose
Nanofiltration
Nanofiltration
Module type Membrane geometry Membrane material Thickness (cm) Temp ( C) resistance pH resistance Pure water flux (L h1 m2) Acetic acid rejection (%)
Cross flow Flat-sheet Polyamide 0.0165 50 2e11 110
Cross flow Flat-sheet Polyamide 0.0165 50 2e11 130
Forward osmosis Cross flow Flat-sheet Polyamide 0.0165 50 2e11 120
89
10
99.5
Investigated solute rejection (%) MgSO4 NaCl MnSO4 MnCl2
99.8 95 99.2 98.6
99 92 98 98.2
99.2 94.3 98.6 98.4
final acetic acid solution reaches 962 g L1 after 30 h of continuous operation. Fouling study of the membranes reveals that the very flat sheet module with tangential fluid flow over the surface can substantially overcome fouling problem. After prolonged operation, simple rinsing could recover the lost flux significantly. Protein estimation (Lowry's method) and detection (SDSePAGE) showed that the protein concentration after forward osmosis reached 954.5 g L1. The final nanofiltration stage (NF-1) could recover draw solute (MgSO4) by more than 99% at an operating pressure of 12e14 bars. Produced acetic acid in membrane-integrated system was tested to be 98.7% pure as measured by HPLC (Agilent, 1200 series, USA) peak purity software tool. Yield (98.7%) achieved in this membrane integrated continuous production scheme is substantially higher than those achieved in conventional systems (Moulijn et al., 2013). Final product concentration (962 g L1) and density (1.11 g L1) are almost same for both the systems. Differences in flux and rejection of the used membranes are obviously attributed to the physical structures and charge repulsion properties of the membranes. NF-2 has the loosest structure (pore radius 0.57 nm) and the lowest membrane charge density whereas NF-1 possesses the most compact structure (pore radius 0.53 nm) and the highest membrane charge density during the nanofiltration of acetic acid fermentation broth. This explains the reason of obtaining high flux and low rejection (10%) in case of NF-2 and low flux but high rejection (89%) for NF-1 during nanofiltration. The purpose of filtration employing NF-3 membrane was dehydration by forwardosmosis technology. Due to the chemical potential difference between the feed and draw solution, the water molecules of the feed solution permeate out to the draw solution stream leaving the solute molecules into the feed solution. Moreover, membrane properties like pore radius (0.55 nm), membrane charge density also play important role that results in the observed behavior of that NF3 membrane in forward osmosis (resulting in a rejection of 99.5% of acetic acid). In the same Table 2, the investigated solutes are MgSO4, NaCl, MnSO4 and MnCl2 whose rejection (%) has already been provided. The overall production parameters and product characteristics for both conventional and membrane integrated system for
Please cite this article in press as: Pal, P., Nayak, J., Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey, Journal of Cleaner Production (2015), http://dx.doi.org/10.1016/j.jclepro.2015.07.085
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Fig. 3. Schematic diagram of membrane integrated hybrid fermentation system for continuous production of acetic acid.
direct production of acetic acid production have been presented in Table 3 for quick comparison. 4.2. Value addition for enhanced profit margin in the sustainable technology The by-products from the proposed plant are whey-protein and reusable water. Such a plant that can annually treat 5 108 L of cheese whey produces 3000 ton of dry whey protein powder as byproduct through forward-osmosis and vacuum drying. Conventionally the involvement of triple effect evaporators and spray
dryers for the sole production of whey protein powder involves huge energy consumption apart from involving high equipment cost, maintenance and man power expenses. Thus the configuration for whey protein regeneration section which is actually a byproduct recovery division of the main plant of acetic acid production stands to be very much simpler than the classical ones. As presented in Table 4, the estimated energy consumption for a conventional whey protein production plant stands at about 864 kWh for per ton whereas in membrane integrated system, it drops down to 40 kWh for per ton of whey protein. So the energy reduction parameter computes to around 0.05. The capital
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100
90
90
80
Flux (L m−2 h−1)
100
70 60
80
50 60
40 30
40
20 20
10 0
0 0
5
10
15
20
25
Transmembrane Pressure (bar) flux from NF-2
rejection of acetic acid by NF-2
rejection of lactose by NF-2 Fig. 4. Separation of microfiltered fermentation broth: flux and rejection characteristics of nanofiltration membrane (NF-2) with respect to transmembrane pressure.
investment including total equipment and machinery costs along with indirect costs specifically for the whey protein production has been presented in Table 5. In the proposed system, the total installed equipment cost involved is about US $ 33.2 104 where
Space intensification ¼
120 100
80 70
80
60 60
50 40
40
30 20
Rejection (%)
120
100
Flux (L m-2 h-1)
140
Rejection of acetic acid (%)
6
20
10 0
0 0
0.5
1 1.5 2 Applied pressure (bar)
2.5
flux during acetic acid separation
flux during protein separation
rejection during acetic acid separation
rejection during protein separation
Fig. 5. Separation of acetic acid and whey protein using NF-3 membrane and 1 M MgSO4 as draw solution: flux and rejection characteristics with respect to transmembrane pressure during forward osmosis.
tonnes per annum, the space requirement compared to a conventional Cativa plant comes down to almost one-fifth (as presented in Table 6). Total space required for a conventional Cativa plant is about 5000 m2 whereas in the membrane integrated system, the space requirement comes down to 902 m2 for the same quantum of production. This space intensification may be expressed as:
total area required for membrane integrated hybrid fermentation system Overall area requirement for a conventional plant
the total production cost stands to be US $ 68.8 104 for 3000 ton/ year whey protein powder. The annual operating cost for that amount of whey protein production is US $ 25.8 104. Considering the same project life and interest rate as that of the main plant, the annual manufacturing cost of whey protein powder stands to be US $ 0.11/kg. To operate such a compact membrane based plant, a total water supply of 80.12 106 L/year is very much required as applications involving membranes require continuous supply of water. But in the proposed plant, due to presence of feed concentration enrichment units like forward osmosis, huge volume of water which is about 264 106 L/year could be recovered after nanofiltration treatment. Thus there is further cost saving on utility account. 4.3. Compactness of the new system A membrane integrated fermentation based process consists of only 5 unit operations as compared to 12 unit operations in a conventional Cativa plant for acetic acid production. For an acetic acid production plant with the production capacity of 10,000
Flexibility in application ¼
Such intensification computes to around 0.2 for the membrane-vis a conventional plant of the same prointegrated plant vis-a duction capacity. This establishes compact design of the new system. 4.4. Flexibility in plant capacity utilization The very modular design of a membrane-integrated plant results in high capacity flexibility as any number of modules can be made operational depending on the market demand. Due to the series and parallel adjustment of the microfiltration and nanofiltration modules (including excess modules) in the membrane integrated system, such flexibility is achieved. The modular plant also offers the flexibility of production of similar organic or amino acids or even the plant can be used for other fermentative or microbial productions. The flexibility in application in hybrid processes could be defined as the ratio of number of possible applications in the hybrid process to the number of possible applications in conventional process.
possible applications in membrane integrated hybrid process possible applications in conventional process
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120
1200
100
1000
80
800
60
600
40
400
20
200
Concentration of acetic acid (g/L)
Flux (L m−2 h−1)
P. Pal, J. Nayak / Journal of Cleaner Production xxx (2015) 1e12
0
0
0
20
40 Time (h)
60
80
flux from NF-3 during forward osmosis flux from NF-2 during nanofiltration Acetic acid concentration (g/L) during forward osmosis Fig. 6. Separation of acetic acid: a fouling study and enrichment of acetic acid concentration profile with respect to time using NF-3 (operating pressure 1.2 bar) and NF2 (operating pressure 12.5 bar) membranes.
The parameter describing the flexibility in application will be greater than 1 for this kind of membrane integrated process. A comparative description of system flexibility for both the processes has been presented in Table 7. Capacity flexibility may be expressed in terms of total throughput as below:
Capacity flexibility ¼
7
(50e70 bars) ranges are also quite high in conventional plants. These reflect not only high operating costs but high capital cost as well. Expensive catalysts such as rhodium or iridium based catalyst with methyl iodide in methanol carbonylation and cobalt, chromium or palladium based catalysts in ethylene oxidation and acetaldehyde oxidation add to the cost of production. Moreover a number of chemical or physical treatment operations are required to regenerate catalysts and recover the products. Involvement of several phase changing phenomena under high temperature and pressure regimes demands extra care for plant safety. This again raises cost. On the other hand, a membrane integrated reactor system involves only one phase (liquid phase). With minimum consumption of power and raw materials under non-neutralizing conditions, production process in this system represents an entirely green technology. Table 8 presents a comparative description of the two types of production schemes. 4.6. Energy consumption in the membrane based hybrid process -vis current technology vis-a In a classical Cativa plant of 10,000 tonnes per year acetic acid production capacity, the total annual energy consumption stands at 550 105 kW h. In those plants high temperature and high pressures are maintained to carry out reactions. Energy required for chemical reactions and downstream processing is very high. In conventional production route, downstream processing stages like distillation, evaporation, drying involve the maximum electrical energy. But while using membrane integrated fermentation tech-
variations in production capacity by hybrid process variations in production capacity by conventional system
Advantage of a hybrid plant is obvious as flexibility is always greater than one. This analysis indicates that in situations of fluctuating market demand, the new system can be operated by switching on to the desired number of modules and thus ensuring continuity in plant operation. 4.5. Benefits to the environment The downstream separation and purification does not involve any phase change and thus the overall energy consumption reduces significantly in the new system. In the illustrated scheme, ecofriendliness compared to the conventional ‘Cativa’, ‘Ethylene Oxidation’ or ‘Acetaldehyde Oxidation’ based plants is clearly evident. Disposal of acid or alkali-bearing wastes leads to environmental pollution in the currently practiced technology. Operating temperature (often exceeding 425e475 K) and pressure
nology, the power consumption could be effectively minimized. Acetic acid is produced through bio-reactions and the downstream processing steps involve only pumps. Power consumption at each stage of a conventional acetic acid production plant (Cativa plant) as well as membrane integrated system has been shown in Table 9. Total annual power consumption in a membrane integrated acetic acid production plant of similar capacity has been computed to be approximately 55.76 104 kW h only. Membrane-integrated acetic acid system thus turns out to be quite energy efficient system as power consumption is negligible compared to a conventional system. Energy involvement in a scaled up plant can be arrived at using sixetenth-factor rule (Peters and Timmerhaus, 1991) and power number equations (Doran, 2008). Thus energy consumption per ton of acid production is about 5500 kWh in a conventional plant against only 55 kW h in a membraneintegrated system.
Table 3 Production parameters: comparison of conventional plant with new membrane based plant for acetic acid (capacity: 10,000 tonnes/year) and whey protein (capacity: 3000 tonnes/year). Parameters
Membrane integrated plant
Conventional acetic acid production plant
Product yield Product concentration Productivity of the process Product purity
98.2% 961.72 g L1 (96%) 96.1 g L1 h1 98.7%
85e90% (Moulijn et al., 2013) 850e980 g L1 (85e98%) e 95e99%
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Table 4 Comparison of total energy consumption in a conventional process with respect to the proposed plant for whey protein production (capacity: 3000 tonnes/year). Conventional acetic acid production system Equipment
Membrane integrated system Energy (kWh) 5
Pasteurizer Evaporator (4 in number) Spray drier Pumps
1.15 10 12.60 105 6.48 105 5.68 105
Total energy requirement Energy requirement for per unit acetic acid production
25.91 105 (approximate) 863.7 kWh/ton acetic acid
Equipment
Energy (kWh)
Pumps Vacuum drier
3.5 104 8.5 104
12 104 (approximate) 40 kWh/ton whey protein
The energy reduction parameter can thus be expressed as:
Parameter of energy reduction ¼
energy required for per unit production in hybrid system energy required for per unit production in conventional system
The energy intensification parameter here computes to around 0.01 reflecting high energy intensification achievable in the new hybrid system. This analysis shows that the investigated membrane based process can be operated with huge energy saving compared to the currently practiced processes.
Table 5 Investment costs for production of whey protein powder in membrane integrated systems (capacity: 3000 tonnes/year). Item
Cost (US $)
A) Capital investment 1. Direct costs 1.1. Installed equipment 1.1.1. SS 316 membrane modules (nanofiltration) 1.1.2. Perspex modules (Forward osmosis) 1.1.3. Pumps (peristaltic and hydra-cell) 1.1.4. Holding tank for concentrated whey protein 1.1.5. Holding tanks for draw solution 1.1.6. Vacuum drier 1.1.7. Vessel for collection of whey protein powder
4.5 104 2.1 104 4.3 104 1.5 104 1.8 104 18 104 1.0 104
Total installed equipment
33.2 104
1.2. Piping 1.3. Electrical connections 1.4. Instrumentation
8.6 104 2.3 104 3.5 104
Total direct costs
47.6 104
2. Indirect costs 2.1. Engineering and supervision 2.2. Contractor's fee 2.3. Contingency
1 104 3.2 104 2 104
Fixed capital investment Working capital
53.8 104 15 104
Total capital investment ($/year)
68.8 £ 104
B) Operational cost i. Membrane replacement ii. Membrane cleaning iii. Draw solute (MgSO4) iv. Electrical v. Man power vi. Overhead charges vii. Maintenances
15.5 10 3 104 2 104 0.8 104 2.5 104 1.7 104 0.5 104
Total annual operating cost ($/year)
26 £ 104
4.7. Economic evaluation Scale up has been done following standard procedure to assess the capital investment cost of a plant for annual production of 10,000 tonnes of acetic acid. This assessment includes equipment installation cost and instrumentation cost for both the systems taking into account the new design as shown in Fig. 3. The total capital investment cost involved for a conventional acetic acid production is huge which stands about 86 106 US$ for 10,000 tonnes/year capacity whereas it drops to 3.0 106 US$ for a membrane integrated acetic acid production plant of same capacity (as evaluated in Table 10). Direct capital investments costs were calculated considering equipment purchase cost, equipment installation cost, piping cost, building cost, electrical instrumentation cost, yard improvements cost, service facilities and land purchase cost. Total equipment purchase cost for conventional system was calculated as 52 106 US$ which is about 36 times higher than the membrane integrated acetic acid system for same production capacity of acetic acid. Similarly, other associated costs and indirect costs like engineering supervision, contractor's fee and contingency are in the same way on the higher side for a conventional system. For membrane integrated system, costs for pumps and membrane modules contributed about 8.1% and 15.7% respectively to the total equipment cost. Cost of every equipment and process has been calculated using the standard equation below (Peters and Timmerhaus, 1991):
Cost of higher capacity equipment
4
¼ Cost of lab scale equipment capacity of high capacity equipment n capacity of lab scale equipment where n represents the scale-up factor and differs for different equipment, standard values of n were taken from the list mentioned by Peters and Timmerhaus (1991). Table 11 presents a comparative economic evaluation. This indicates involvement of huge material cost in a conventional plant vis-a-vis a membraneintegrated plant for the same capacity. Cost saving on carbon source raw could be effectively done here as the cost of transportation of cheese whey is the only cost factor for raw material involved in the proposed system. When around
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Table 6 A comparison of space required in a conventional and membrane integrated system for production of acetic acid (plant capacity: 10,000 tonnes per annum). Conventional acetic acid production system
Membrane integrated system
Sr. no.
Processing stages
Area required (m2)
Sr. no.
Processing stages
Area required (m2)
1 2 3 4 5 6 7
Main reactor Secondary reactor Bubble loop reactors Flash drum Recovery unit for feed Recovery unit for catalyst Distillation column (including condenser and reboiler) Dryer Evaporator Iodide recovery unit
535 267 1062 244 222 273 1250.4
1 2 3 4 5 6 7
Microfiltration Ultrafiltration Fermentation Forward osmosis Storage tanks Fresh feed supply tank Nanofiltration
245 90 31 180 50 31 210
152 743 252
8 9
Collection tanks Vacuum dryer
45 20
8 9 10
5000 m2 (approximate)
Total area required (including installation spaces and pipe lines)
902 m2 (approximate)
Table 7 Comparison of flexibility of systems for production of acetic acid. Parameters of flexibility
Membrane integrated system
Conventional production technique
Steps of operation Capacity of production
Only a few Flexible and could be modified as per market demand Membrane modules are highly flexible in size and numbers according to requirements Membrane units (ultra, micro, nano or forward osmosis) and modules are highly flexible to be arranged in parallel or series
Too many in numbers Fixed capacity of production
Plant configuration Arrangements of downstream purification
Fixed configuration Downstream purification arrangements are fixed
Table 8 Comparison of eco-friendliness for production of acetic acid. Parameters of eco-friendliness
Membrane integrated system
Conventional production technique
Raw material
Use of dairy waste cheese whey, a renewable resource
Exploitation of non-renewable petroleum stock.
Reaction phase
No phase change is encountered. Operations involve only liquid phase.
Multiphase process includes operations with solid, liquid, gas phases.
Reaction temperature
Reactions are highly exothermic and high temperature controlled (150e250 C).
Energy
Bio-reaction occurs within mesophilic range (30 C) and no exothermic process is involved. Microbes are the biocatalysts used here. No chances of formation of toxic chemicals as by product. Energy consumption is low.
Use of harsh chemicals
No harsh chemical is used.
Reaction catalyst By product
High cost iridium based catalyst is used. Generation of a mixture of propanoic acid, butyric acid, butanone, ethyl acetate, formic acid, dichloroacetic acid. Energy consumption is very high due to involvement of energy intensive red processes. All the chemicals used in this process are harsh in nature.
Table 9 -vis proposed plant for acetic acid production (capacity: 10,000 tonnes/year). Comparison of total energy consumption in a classical vis-a Conventional acetic acid production system
Membrane integrated system
Equipment
Energy (kWh)
Equipment
Energy (kWh)
Main reactor Secondary reactor Bubble loop reactors Flash drum Recovery unit for feed Recovery unit for catalyst Distillation column (including condenser and reboiler) Dryer Evaporator (4 in number) Iodide recovery unit
59.32 105 33.56 105 84.28 105 31.68 105 32.65 105 75 105 172 105
Fermentation Energy requirement for pumps
44.26 104 11.5 104
Total energy requirement Energy requirement for per unit acetic acid production
550 105 (approximate) 5500 kWh/ton acetic acid
6.48 105 12.60 105 42.44 105 55.76 104 (approximate) 55.76 kWh/ton acetic acid
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Table 10 Calculation of investment costs, including installation and instrumentation for membrane integrated systems (capacity: 10,000 tonnes/year). Item
Cost (US $)
Direct costs Installed equipment SS 316 membrane modules (microfiltration, ultrafiltration and nanofiltration) Perspex modules (forward osmosis) Pumps (peristaltic and hydra-cell) Holding tank for raw cheese whey Holding tank for microfiltered whey Sterilization Fermentation vessel Holding tank for fresh feed Holding tank for microfiltered broth Holding tank for nutrients Seed culture tank Holding tank for concentrated acid Holding tanks for draw solution Vessel for collection of reusable water
4.2 104 24.3 104 7.3 104 2.3 104 15 104 28.2 104 2.0 104 2.5 104 0.52 104 2 104 4 104 3 104 1.5 104
Total installed equipment
141.82 £ 104
Piping Electrical connections Instrumentation Buildings Land and yard improvements
18.6 104 8.6 104 14.5 104 25 104 8.2 104
Total direct costs
216.72 £ 104
45 104
achieve this production capacity in conventional acetic acid production system, the cost involvement for methanol, carbon monoxide, hydrogen iodide and iridium estimates to about US $ 4.87 106, whereas a membrane-integrated continuous process plant saves on such huge costs as such harsh chemicals need not be used. Simultaneously, labor cost and annual maintenance cost are much lower for membrane integrated reactor system due to involvement of a few operating units and simplicity of the overall design. Total annual production cost in Cativa process, stands at around $ 1.36/kg of acetic acid. In a conventional plant, pretreatment of cheese whey also involves substantial expenses which very drastically come down in membrane-based plant where a simple ultrafiltration module does the work. During final stage concentration using forward osmosis, the pure water produced is subsequently recycled and reused within the plant thus significantly bringing down utility cost. Operating cost for such membrane integrated system including all nutrients cost, electricity and maintenance costs like membrane replacement, labor; water supply was evaluated as US $ 4.028 106 for production of 10,000 tonnes of acetic acid per annum. In this work, a project life of 15 years and interest rate of 7% were considered according to the realistic present market conditions in India.
" Capital recovery factor ¼
Indirect costs Engineering and supervision Contractor's fee Contingency
12.5 104 11 104 20 104
Fixed capital investment Working capital
260.22 £ 104 40 104
Total capital investment
300.22 £ 104
5.8 108 L of cheese whey is consumed to produce 10,000 tonnes of acetic acid the same volume of waste gets disposed in one of the best possible ways. By assuming a conventional plant continuously working for 300 days a year, the annual production of same amount of acetic acid is dependent on the continuous supply of methanol of about 2.1 104 ton, 1.8 102 ton carbon monoxide as an active reactant and 0.8 102 ton hydrogen iodide as a promoter. Iridium is used as the catalyst in the reaction which is required at the rate of 18 ton for a yearly production of 10,000 tonnes of acetic acid. To
#
ið1 þ iÞn ð1 þ iÞnþ1 1
¼ 0:099
‘n’ and ‘i’ were considered to be is the project life of the plant and the rate of interest as per market statistics. So, the annualized capital cost is evaluated as:
"
# 300:22 104 0:099 z0:03 $=kg 107 The annualized operating cost was evaluated as:
Total annual operating cost ð$Þ 4:028 106 ¼ z0:4 $=kg Output per year ðkgÞ 107 It is observed that process, the major cost like yeast extract with comprises about 36% of
in membrane-integrated fermentation contributor is the cost of the nutrients combination of other nutrient salts. It the total operating cost. However, there
Table 11 Operational cost comparison for the conventional and membrane integrated systems (capacity: 10,000 tonnes/year). Membrane integrated plant
Conventional acetic acid production plant
Sl. no
Item
Quantity/year
Cost (US$)
Item
Quantity/year
1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12 1.13
Cheese whey Supplementary nutrients Membrane replacement Membrane cleaning Electrical Man power Maintenances Overhead charges Depreciation Insurance General and administrative expenses
5.8 108 L 7.1 105 kg 1100 m2 1500 kg 55.76 104 kWh 50 persons
0.365 106 2 106 0.35 106 0.01 106 0.04 106 0.25 106 0.1 106 0.2 106 0.6 106 0.003 106 0.11 106
Methanol Hydrogen Iodide Carbon monoxide Iridium catalyst Fuel (solid and liquid) Electrical Water Man power Maintenances Overhead charges Depreciation Insurance General and administrative expenses
2.1 0.8 1.8 1.8
Total annual operating cost ($/year) for production
4.028 106
107 105 105 104
kg kg kg kg
55 106 kWh 0.6 107 L 180 people
Cost (US$) 0.0756 106 1.1 106 0.114 106 3.58 106 2.2 106 3.5 106 0.028 106 0.8 106 0.9 106 0.5 106 0.25 106 0.035 106 0.48 106 13.56 106
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is scope for reduction of this cost with the use of cheap nitrogen sources like corn steep liquor (CSL), ultra filtered ethanol stillage, and hydrolyzed soy flour (Witjitra et al., 1996). Membrane replacement and cleaning charge was calculated considering the reusability of the membranes (ultra, micro and nano) in a year through chemical treatments. Depreciation cost and insurance costs have been considered to be 17% and 0.08% respectively, of fixed capital investment as a standard practice. Considering all the factors including maintenance, operating supplies, depreciation and insurance in membrane integrated plant, the annualized production cost of 98.7% pure 962 g L1 of acetic acid was evaluated by adding annualized operating cost to the annualized capital cost which was found out to be $ (0.03 þ 0.40) z 0.5 $/kg of acetic in the Indian market, where similar grade acetic acid costs about US $ 1.6 per kg. The cost advantage factor may be computed as below.
Cost advantage parameter ¼
11
Acknowledgment The authors are thankful to the Department of Science and Technology (DST) (SR/FST/ETi-204/2007 & SR/S5/GC-05/2008) and Ministry of Human resource Development (MHRD), Government of India for providing funds for necessary infrastructure and research materials procured for the present research under DST-FIST and DST, Green Chemistry/Technology program.
References Babi, D.K., Lutzeb, P., Woodley, J.M., Gani, R., 2014. A process synthesisintensification framework for the development of sustainable membranebased operations. Chem. Eng. Process. 86, 173e195. Becht, S., Franke, R., Geißelmann, A., Hahn, H., 2009. An industrial view of process intensification. Chem. Eng. Process. 48, 329e332.
Cost involved by hybrid system for per unit production Cost involved by conventional system for per unit production
Cost advantage parameter computes to 0.27 indicating major cost advantage in the new system over the conventional type. Economic advantage of the developed membrane-integrated process lies in involvement of less number of unit operations, less equipment cost, less material and energy consumption. Use of microbes enables eco-friendly production and high selectivity of membranes ensures higher purity of the desired product. Continuous production and fast separation in this kind of a compact plant leads to higher yield, productivity and purity of the product at significantly reduced cost.
5. Conclusion It transpires from the study that extensive process intensification and thus production sustainability could be achieved in manufacturing acetic acid in a membrane-integrated hybrid reactor system where multi-stage membrane separation modules are judiciously integrated with conventional fermentation device. Selection of appropriate membrane module that can overcome the fouling problem considered the major hurdle in membrane separation can culminate in a very eco-friendly, small, compact, energy-saving yet flexible plant with the promise of high yield, productivity, and purity of the desired product. After a long operation period, membrane integrated hybrid fermentation system may witness drop in flux to some extent but the same could be recovered through appropriate intervention of simple rinsing of the membranes. However, the quality of product need not be compromised. The system fulfills almost all the expectations of a sustainable system for production of high purity acetic acid and whey protein at a reduced cost. Amidst growing environmental awareness and stringent discharge regulations, this green technology is likely to be welcomed as a sustainable one by the chemical and allied process industries in an era of emaciated profit margin in the competitive global market.
Biswas, A., Roy, M., 2015. Green products: an exploratory study on the consumer behaviour in emerging economies of the East. J. Clean. Prod. 87, 463e468. Bruggen, B.V., Curcio, E., Drioli, E., 2004. Process intensification in the textile industry: the role of membrane technology. J. Environ. Manag. 73 (3), 267e274. Cheung, H., Tanke, R.S., Torrence, G.P., 2005. Acetic acid. In: Wiley-VCH (Ed.), Ullmann's Encyclopedia of Industrial Chemistry. Wiley, Weinheim, pp. 1e20. Choe, W.S., Nian, R., Lai, W.B., 2006. Recent advances in biomolecular process intensification. Chem. Eng. Sci. 61, 886e906. Drioli, E., Stankiewicz, A.I., Macedonio, F., 2011. Membrane engineering in process intensification e an overview. J. Membr. Sci. 380, 1e8. Dautzenberg, F.M., Mukherjee, M., 2001. Process intensification using multifunctional reactors. Chem. Eng. Sci. 56, 251e267. Doran, P.M., 2008. Bioprocess Engineering Principles, second ed. Elsevier, New York. Emadzadeh, D., Lau, W.J., Matsuura, T., Rahbari-Sisakht, M., Ismail, A.F., 2014. A novel thin film composite forward osmosis membrane prepared from PSfeTiO2 nanocomposite substrate for water desalination. Chem. Eng. J. 237, 70e80. Esymondt, J., Vasic-Racki, D., Wandrey, C., 1990. Acetic acid production by Acetogenium kivui in continuous culture e kinetic studies and computer simulations. Appl. Microbiol. Biotechnol. 34, 334e349. Grzenia, D.L., Schell, D.J., Wickramasinghe, S.R., 2008. Membrane extraction for removal of acetic acid from biomass hydrolysates. J. Membr. Sci. 322, 189e195. Howard, M.J., Jones, M.D., Roberts, M.S., Taylor, S.A., 1993. C1 to acetyls: catalysis and process. Catal. Today 18, 325e354. Jayaprakasha, H.M., Yoon, Y.C., 2005. Production of functional whey protein concentrate by monitoring the process of ultrafiltration. J. Anim. Sci. 18 (3), 433e438. nez, X.T., Cuenca, A.A., Jurado, A.T., Corona, A.A., Urista, C.R.M., 2012. Traditional Jime methods for whey protein isolation and concentration: effects on nutritional properties and biological activity. J. Mex. Chem. Soc. 56 (4), 369e377. Jones, J.H., 2000. The Cativa™ process for the manufacture of acetic acid. Platin. Met. Rev. 44 (3), 94e105. Kong, F., Yang, H., Wang, X., Xie, Y.F., 2014. Rejection of nine haloacetic acids and coupled reverse draw solute permeation in forward osmosis. Desalination 341, 1e9. Kumar, R., Pal, P., 2013. Turning hazardous waste into value-added products: production and characterization of struvite from ammoniacal waste with new approaches. J. Clean. Prod. 43, 59e70. Lutze, P., Gani, R., Woodley, J.M., 2010. Process intensification: a perspective on process synthesis. Chem. Eng. Process. 49, 547e558. Moulijn, J.A., Makkee, M., Diepen, A.E., 2013. Chemical Process Technology, second ed. Wiley, United Kingdom. Pal, P., Dey, P., 2013. Process intensification in lactic acid production by three stage membrane-integrated hybrid reactor system. Chem. Eng. Process. 64, 1e9. Pal, P., Sikder, J., Roy, S., Giorno, L., 2009. Process intensification in lactic acid production: a review of membrane based processes. Chem. Eng. Process. 48, 1549e1559.
Please cite this article in press as: Pal, P., Nayak, J., Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey, Journal of Cleaner Production (2015), http://dx.doi.org/10.1016/j.jclepro.2015.07.085
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P. Pal, J. Nayak / Journal of Cleaner Production xxx (2015) 1e12
Park, Y.G., Toda, K., 1990. Simulation study on bleed effect in cell-recycle culture of Acetobacter aceti. J. Gen. Appl. Microbiol. 36 (4), 221e233. Peters, M.S., Timmerhaus, K.D., 1991. Plant Design and Economics for Chemical Engineers, fourth ed. McGraw-Hill, New York. Phuntsho, S., Sahebi, S., Majeed, T., Lotfi, F., Kim, J.E., Shon, H.K., 2013. Assessing the major factors affecting the performances of forward osmosis and its implications on the desalination process. Chem. Eng. J. 231, 484e496. Ponce-Ortega, J.M., Al-Thubaiti, M.M., El-Halwagi, M.M., 2012. Process intensification: new understanding and systematic approach. Chem. Eng. Process. 53, 63e75. lez-Mun ~ oz, M.J., Luque, S., Alvarez, J.R., Coca, J., 2006. Rodríguez, M., Gonza Extractiveultrafiltration for the removal of carboxylic acids. J. Membr. Sci. 274, 209e218. Sant'Anna, V., Marczak, L.D.F., Tessaro, I.C., 2012. Membrane concentration of liquid foods by forward osmosis: process and quality view. J. Food Eng. 111, 483e489. Sokollek, J.S., Hertel, C., Hammes, W.P., 1998. Cultivation and preservation of vinegar bacteria. J. Biotechnol. 60, 195e206.
Wang, K.Y., Teoh, M.M., Nugroho, A., Chung, T.S., 2011. Integrated forward osmosisemembrane distillation (FOeMD) hybrid system for the concentration of protein solutions. Chem. Eng. Sci. 66, 2421e2430. Wang, L., Chu, H., Dong, B., 2014. Effects on the purification of tannic acid and natural dissolved organic matter by forward osmosis membrane. J. Membr. Sci. 455, 31e43. Witjitra, K., Shah, M., Cheryan, M.,1996. Effect of nutrient sources on growth and acetate production by Clostridium thermoaceticum. Enz. Microb. Technol. 19, 322e327. Yanga, Q., Wanga, K.Y., Chung, T.S., 2009. A novel dual-layer forward osmosis membrane for protein enrichment and concentration. Sep. Purif. Technol. 69, 269e274. Yang, S., 2007. Bioprocessing for Value-added Products from Renewable Resources: New Technologies and Applications, first ed. Elsevier Science Publishers, Amsterdam. Yoneda, N., Kusano, S., Yasui, M., Pujado, P., Wilcher, S., 2001. Recent advances in process and catalysts for the production of acetic acid. Appl. Catal. 22, 253e265. Zhang, X., Ning, Z., Wang, D.K., Costa, J.C.D., 2013. A novel ethanol dehydration process by forward osmosis. Chem. Eng. J. 232, 397e404.
Please cite this article in press as: Pal, P., Nayak, J., Development and analysis of a sustainable technology in manufacturing acetic acid and whey protein from waste cheese whey, Journal of Cleaner Production (2015), http://dx.doi.org/10.1016/j.jclepro.2015.07.085