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Contents lists available at ScienceDirect

Food and Bioproducts Processing

j ourna l ho me page: www.elsev ier .com/ locate / fbp

conomic feasibility of a pilot-scale fermentativeuccinic acid production from bakery wastes

oon Fung Lama, Cho Chark Joe Leungb, Ho Man Lei c, Carol Sze Ki Linb,∗

Department of Chemical Engineering, University College London, Torrington Place, WC1E 7JE London, UnitedingdomSchool of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Hong KongDepartment of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clearater Bay, Kowloon, Hong Kong

a b s t r a c t

In this paper, the techno-economic study for a pilot-scale production of succinic acid from food waste via fermen-

tation was evaluated. The pilot plant was based in Hong Kong and designed for converting 1 tonne/day of bakery

waste into succinic acid. The mass and energy balance of the process was simulated by computer package Super-

Pro Designer®. The total capital investment for the plant and the total production cost were US$ 1,118,243 and US$

230,750/year respectively. Overall revenue generated from the process was US$ 374,041/year. The return on invest-

ment, payback period and internal rate of return of the project were 12.8%, 7.2 years and 15.3% respectively. The

findings indicated that the fermentative succinic acid production from bakery waste was feasible. This is important

for attracting investment and industrialization interest on the biorefinery process using domestic wastes as raw

materials.

© 2013 The Institution of Chemical Engineers. All rights reserved.

Keywords: Biorefinery; Food waste; Fermentation; Platform chemical; SuperPro Designer®

recent research focused on utilizing it as an energy source

. Introduction

isposal and utilization of food waste, which is defined as anyneaten food or food preparation residues from residences orommercial establishments, is one of the major global chal-enges, particularly in Southeast Asian countries (Ngoc andchnitzer, 2009). Adhikari et al. (2006) carried out a study whichorrelated the gross domestic product (GDP) of a country andhe quantity of the food waste generated. The authors fore-asted that the food waste problem of Asian countries in theoming decade is worse than elsewhere in the World due tohe rapid economic development in the region. For instance, ineijing, generation of municipal solid waste (MSW) increasedy almost 4 times over the past three decades and the contri-ution of food waste was doubled between 1989 and 2006 (Lit al., 2009).

Similar to many other metropolitan cities, Hong Kong is

Please cite this article in press as: Lam, K.F., et al., Economic feasibilitywastes. Food Bioprod Process (2013), http://dx.doi.org/10.1016/j.fbp.2013.09

acing an imminent and serious waste management problem.

∗ Corresponding author. Tel.: +852 3442 7497; fax: +852 3442 0688.E-mail address: carollin@cityu.edu.hk (C.S.K. Lin).Received 10 February 2013; Received in revised form 4 September 201

960-3085/$ – see front matter © 2013 The Institution of Chemical Engittp://dx.doi.org/10.1016/j.fbp.2013.09.001

In 2009, 3,300 tonnes of food waste, as the second largest wastecategory, was produced and it contributed to 25% of the wastedisposed to landfill (HKCAS, 2010). A worse situation is that theamount of food waste arising from the commercial and indus-trial sectors has been increasing steadily based on the fact thatthe food waste amount in 2009 was doubled as compared tothe amount in 2002 (Lin et al., 2013).

Landfill, incineration and composting are common, maturetechnologies for waste disposal. However, they are not satis-factory for treating food waste due to the generation of toxicmethane gas and bad odour, high energy consumption andslow reaction kinetics respectively. In fact, research effort hasalso been put on the new technology for decomposition offood waste (Yun et al., 2000). However, no valuable productis generated from the decomposition process.

Instead of disposing and decomposing the food wastes,

of a pilot-scale fermentative succinic acid production from bakery.001

3; Accepted 13 September 2013

(Iacovidou et al., 2012). Similar to the production of

neers. All rights reserved.

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bio-ethanol from agricultural wastes which has been provento be economically feasible (Bohlmann, 2006; Dutta et al.,2010). Food wastes can also be easily assimilated by micro-organisms, because they are rich in sugars, vitamins andminerals. This makes food wastes suitable as raw materi-als for the production of secondary metabolites of industrialsignificance by microorganisms in controlled environments.For instance, Kapdan and Kargi (2006) reviewed the produc-tion of bio-hydrogen from various organic materials includingfood waste. Techno-economic evaluation of hydrogen produc-tion using potato steam peels (Ljunggren and Zacchi, 2010a)and beverage wastewater (Li et al., 2012) showed that the fer-mentation process was economically feasible. Ljunggren andZacchi (2010b) further improved the economic attractivenessof the hydrogen production from starch-based food waste bydigesting anaerobically the un-utilized biomass for produc-ing methane. On the other hand, methane production frommixture of dairy manure and food waste was also reported(El-Mashad and Zhang, 2010).

In addition to the energy application, organic waste is use-ful for production of commercialized organic chemicals viabiorefinery or white biotechnology, which defines as the pro-duction by means of fermentation or enzymatic conversionon a larger scale (Hermann and Patel, 2007). For instance, low-value by-product, glycerol, from bio-diesel production wassuccessfully converted into value-added products via fermen-tation process such as succinic acid (Vlysidis et al., 2009, 2011a,2011b) and bio-plastic (Posada et al., 2011). It is found thatthe co-production of the succinic acid increases the profit ofa biodiesel plant by 60% (Vlysidis et al., 2009). Meanwhile,Wensel et al. (2011) reported an industrial-scale process designfor production of succinic acid from agricultural wastes.

From the viewpoint of food waste management, Hang(2004) has suggested making use of the large quantities of liq-uid and solid wastes (food processing residues, FPR) from foodindustry for production of valuable bio-products. For exam-ple, fermentative production of lactic acid from a mixture ofrestaurant food waste, bakery by-product, barley and wheatbran was demonstrated (Yang et al., 2006). Also, a membraneintegrated process for lactic acid production from sugarcanejuice was economically evaluated using pilot plant scale tech-nical data (Sikder et al., 2012). Production of biopolymerfrom various food industry wastes and agricultural crops isshown to be technically and economically feasible for replac-ing petroleum-derived plastics (Lopez Garcíaa et al., 2012).Similarly, our previous research shows that succinic acid couldbe produced from wheat-based and cereal-based renewablefeedstocks (Du et al., 2008; Dorado et al., 2009; Lin et al., 2012).

Recently, we demonstrated that succinic acid (SA) can beproduced by fermentation of bakery waste and the overallyield (1.16 g SA/total sugar) is the highest among other foodwaste-derived media (Leung et al., 2012; Zhang et al., 2013). Inthe light of the technical feasibility, the objective of this workis to evaluate the economic feasibility of the whole productionprocess including down-stream separation and purificationusing computer simulation. Profitability of a pilot-scale facilityto be built in Hong Kong for treating bakery waste is assessed.

2. Methodology

To evaluate the economic feasibility of succinic acid (SA) pro-

Please cite this article in press as: Lam, K.F., et al., Economic feasibilitywastes. Food Bioprod Process (2013), http://dx.doi.org/10.1016/j.fbp.2013.09

duction from bakery waste, the total capital investment, totalproduction cost and profitability of the production process

were estimated. Mass and energy balance required for the esti-mation was simulated using the computer software SuperProDesigner 8.0. The process began with feeding 1 tonne/day ofbakery waste, which was the quantity of the bakery wastecollected by the Hong Kong Organic Waste Recycling Cen-tre (HKOWRC). The plant was to be built in Hong Kong andthe construction phase of the plant was 1 year. The oper-ating lifetime of the plant was assumed to be 20 years andit operated for 312 days/year (85% of the plant utilization).The down time was for regular maintenance and engineer-ing work. The cumulative cash flow diagrams were generatedusing Microsoft Excel 2010.

2.1. Process description

The proposed succinic acid production process in this studywas reported in our previous publication (Leung et al., 2012)and the process flow is depicted in Fig. 1.

The process started by grinding of the incoming bakerywastes into pieces smaller than 1 cm3. The bread was thenblended in process water which provided a liquid medium forthe subsequent enzymatic reaction at 55 ◦C for 24 h. Industrial-grade glucoamylase was added to the vessel (R-101 in Fig. 1) tospeed up the hydrolysis of �-1,4 and �-1,6 glucosidic linkagesand eventually produce �-d-glucose from starch and otherpolysaccharides. Meanwhile, industrial-grade protease wasused to hydrolyse peptide bonds present in the bread waste torelease amino acids. After the hydrolysis process, solid con-tent of the paste was separated by centrifugation at 7000 rpmfor 15 min to produce bakery hydrolysate. Small amount ofoil (i.e. 3.8 wt% of the hydrolysate) was also removed. Theaqueous supernatant was transferred to a fermenter (FR-101) for SA production. Actinobacilus succinogenes was used forthe fermentative production of succinic acid. Before the fer-mentation, adequate quantity of A. succinogenes was obtainedvia laboratory-scale shake-flask incubation, followed by seedfermentation with supply of essential nutrients including glu-cose, vitamins and minerals. The required inoculum size forthe fermentative SA production was 5% (v/v). Based on our pre-vious finding, the optimal time for the fermentation at 37 ◦Cwas 44 h. Continuous supply of carbon dioxide was neededfor the anaerobic reaction. Also, magnesium carbonate andsodium hydroxide were used to control the pH of fermenta-tion broth. The experimental result showed that the overallyield of the production was 0.55 g SA per g bread. Indeed, theyield achieved using waste bread is so far the highest amongthe SA production using other food waste-derived media. TheSA concentration of the resultant broth was 47.3 g SA/L andSA crystals with purity >99% was obtained via a novel-resinbased distillation and crystallization process (Lin et al., 2010).

Solid–liquid separation by centrifugation is the first step ofthe down-stream process. Biomass (solid fraction of fermen-tation broth from both fungal and bacterial fermentations)was sold to the fish farm nearby the plant. Protein impuritiesand colour-like compounds that contributed to the dark browncolour of the fermentation broth was removed by adsorptionusing granulated activated carbon (GAC) and there was around0.5% of SA was lost at this stage (Wensel et al., 2011). Fur-thermore, organic acids produced as a waste product from themicroorganism were selectively removed via an ion-exchangeprocess in which the pH of the broth was fine-tuned so itwas above the pKa of the organic acids and below the pKa of

of a pilot-scale fermentative succinic acid production from bakery.001

SA. After the adsorption process, more than 97% of the waterin the clean broth was separated by a flash drum operated

Please cite this article in press as: Lam, K.F., et al., Economic feasibility of a pilot-scale fermentative succinic acid production from bakerywastes. Food Bioprod Process (2013), http://dx.doi.org/10.1016/j.fbp.2013.09.001

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at 105 ◦C and 1.2 atm, resulting in the raw SA product whichconsisted of 44 wt% of water. After cooling the raw product liq-uid stream to 4 ◦C, the supersaturated SA was crystallized toform the SA crystals. The residue solution was recycled andfed to the flash drum whereas the wet SA crystals were finallydried by a tray dryer (TDR-101) to obtain anhydrous SA crystalsas the final product. Since the operating conditions of mostequipment were mild, heat integration was not considered forsimplification in this study.

2.2. Economic analysis

With the mass and energy balance from the computer simu-lation, various economic variables were assessed in order toconclude the economic feasibility of the SA production facility.The following variables are considered in Section 2.2.

2.2.1. Total capital costTotal capital cost of the plant consists of two components:fixed capital investment (FCI) and working capital. Fixed cap-ital investment includes the purchase of equipment and theirinstallation, services building, land and other related costs.The free-on-board equipment quotations for this study werekindly provided by the Associated Engineers Limited in HongKong. For academic purpose, only major equipment of theplant is considered in this study. All costs were converted intoUS dollars for the ease of comparison and they were providedup-to-date (September 2012 basis), so they were not adjustedby the chemical engineering plant cost index. In addition tothe purchase of bare equipment, other related costs incurredsuch as installation, piping and construction were also consid-ered. The contribution of the component to the fixed capitalinvestment is estimated based on the suggested range pub-lished (Peters et al., 2003). It is worth noting that as the SAproduction is a kind of waste recovery project that is encour-aged by the Hong Kong Government, in which we target apilot-scale facility, governmental subsidize may incur and sowe do not account for the land cost here. Also, this assumptioncan be fully justified by personal communications with severallocal property management companies, whose have been longestablished to undertake construction business, property andenvironmental management in Hong Kong. These companiesare highly interested in collaboration in building a food wasteto succinic acid pilot plant in Hong Kong, and their manage-ment staff advised that the land cost of the pilot plant will notbe an issue to be considered. The working capital for the plantwas assumed to be 6.5% of the total FCI.

2.2.2. Total production costThe major components of the total production cost includeraw materials such as the bakery waste and other neces-sary chemicals for the SA production, utilities and operatinglabours. It was given that the bakery waste and its collectionand transportation were sponsored by the Hong Kong OrganicWaste Recycling Centre and the chemical costs were obtainedfrom major chemical suppliers. The charges for hiring engi-neers and operators were assumed to be US$ 23,000/year andUS$ 11,000/year respectively. In addition to the currently avail-able staff, two extra engineers and six operation labours (i.e.3 shifts per day) were required for operating the SA produc-tion facility. Utility cost was estimated based on the mass andenergy balance from the computer simulation which deter-

Please cite this article in press as: Lam, K.F., et al., Economic feasibilitywastes. Food Bioprod Process (2013), http://dx.doi.org/10.1016/j.fbp.2013.09

mined the quantities of each type of utility required. Accordingto David (2007), it was assumed that the waste management

cost was negligible as the waste streams of this plant weremainly sold as fish feed (animal feed). It is worth noting thatthe financial charges included depreciation, insurance andlocal tax. The depreciation of the fixed capital investment withnegligible savage values was calculated based on the 20-yearsstraight-line method. The insurance was assumed to be 2% ofthe FCI and the local tax of Hong Kong is 16.5%. As the plantwas to be invested using internal fund of the sponsored com-pany or with the potential governmental support. There wasno incurred interest charge.

2.2.3. ProfitabilityThe market price of SA in 2012 was US$ 9 kg−1 (Wensel et al.,2011). Solid waste streams from the centrifugation includingthe undigested bakery waste and the fermentative biomasswere sold as fish feed which price was set at US$ 0.45 kg−1.Waste waters from the ion-exchanger, adsorption column,flash drum and the tray dryer were collected and undergonebiological digestion before discharge if the biological oxygendemand exceeded the regulation limit.

Revenues generated from the SA production comprise thesales of the high-purity succinic acid, solid by-product andthe service charge for treating the bakery waste to the wastesupplier. The annual profit was the difference between therevenue and the total production cost. Return on investment(ROI) was defined in Eq. (1) (Towler and Sinnott, 2012).

Return on investment(%) = Annual profit after taxInitial total investment

× 100%

(1)

Furthermore, the annual cash flows were determined for thewhole operating life. A cumulative cash flow diagram was plot-ted accordingly and the diagram indicated the payback period(PBP), which was the time required for breakeven of the invest-ment. Effect of the discount rate on the plant economics wasaccounted by calculating the overall net present value (NPV)generated from the investment and operation. Internal rate ofreturn (IRR) was determined by setting the overall NPV to bezero.

2.2.4. Sensitivity analysisAs the operating life of the plant was 20 years, uncertainty wastherefore existed and it was evaluated by sensitivity analysis.Variables such as the quantity of bakery waste treated, utilitycost and SA price were set to be varied with ±20% while allother variables were kept constant. The effects on the NPV ofthe plant were then plotted and compared.

3. Results and discussion

3.1. Capital investment

Estimation of capital investment was based on the number ofequipment required for the SA production. Based on the massand energy balance simulated using SuperPro Designer 8.0,the quantity of each main plant components, together withthe bare equipment cost, was estimated and listed in Table 1.The total equipment cost was US$ 314,998. In fact, additionalcosts for setting up the plant were anticipated before startingup the production and they were summarized in Table 2. Thepercentages of the associated costs of the fixed capital invest-

of a pilot-scale fermentative succinic acid production from bakery.001

ment were determined based on Peters et al. (2003). The totalfixed capital investment was US$ 1,049,993. It is equivalent

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Table 1 – Free-on-board equipment cost of the fermentative succinic acid production plant.

Item code Equipmenta Description Quantity Cost (USD)

GR-101 Grinder Max. working capacity: 1000 kg h−1 1 26,282V-101 Blender Stirrer with sharp paddles 1 24,167Bioreactor Reactor Oil jacket with stirrer 2 44,615Seed fermenter Fermenter (Small) Oil jacket with stirrer 2 13,012

Vessel volume = 2.84 LAS fermenter Fermenter (big) Oil jacket with stirrer 3 61,538

Vessel volume = 14 LBC-102 Bowl centrifuge (small) Working capacity: 670 L h−1 1 9,423C-101 Bowl centrifuge (big) Working capacity: 3200 L h−1 1 17,115SFR-104 Shake flask rack Growth of A. succinogenes 2 33,333GAC-101 Adsorber Activated carbon column 1 22,052INX-101 Ion-exchange column Ion-exchange column 1 3205V-102 Flash drum – 1 10,256CR-101 Crystallizer – 1 20,513TDR-101 Tray dryer Heating agent: electricity, heating power:

9 kW, blower power: 1.5 kW2 11,538

Auxiliary Sterilization tank (big) Power 2.2 kW 1 16,667Auxiliary Sterilization tank (small) Power: 0.37 kW 1 1282

Total 314,998

a Equipment is made of stainless steel SS316.

taritet1

3

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to

o around 3.33 times of the bare equipment cost and this is reasonable estimation. Working capital, which included theaw materials required for initializing the production, train-ng for operating labours, etc., were expected. It was assumedo be 6.5% of the total fixed capital investment. Thus, it isquivalent to US$ 68,250. Therefore, the total investment forhe fermentative succinic acid production required was US$,118,243.

.2. Total production cost

he SA production facility was designed for treating tonne/day of bakery waste generated in Hong Kong. Byccounting for the yield of the SA and lost throughout the pro-ess, 81.4 kg of succinic acid crystals were produced from eachonne of bakery waste per day. As the facility was designed toerform 312 batches of fermentation annually, this is equiva-

ent to an annual production of 25,388 kg SA/year.Supplementary chemicals were required for the produc-

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ion. The quotations of the industrial-grade chemicals werebtained. Table 3 summarized the annual material cost.

Table 2 – Total fixed-capital investment for the plant.

Type Component

Direct Purchased equipment

Purchased-equipment installation

Instrumentation and controls (installed)

Piping (installed)

Electrical systems (installed)

Buildings (including services)

Yard improvements

Service facilities (installed)

Land

Indirect Engineering and supervision

Construction expenses

Legal expenses

Contractor’s fee

Contingency

a The percentages are estimated based on Peters et al. (2003).

According to Novozymes® (2010), the cost of glucoamylasewith an activity >100,000 U/g was USD 1,258/tonne. One ofthe saccharification enzymes often used for the extraction offermentable sugars from starch in saccharification and fer-mentatiotion processes is Spirizyme Excel. In this process, weassume it is used to digest food waste with an enzyme load-ing ratio of 0.055% (w/w) food waste (Novozymes®, 2010). Sincethere are 312 batches of SA fermentation, there will be 0.172tonnes/year. Therefore, the cost of enzyme is US$ 216 per yearas shown in Table 3. Whereas the inoculum producing costhas been taken into account in the total raw material cost.

It is noted that 95% of the expenses was used for pur-chase of carbon dioxide while the other chemicals contributedinsignificantly to the cost. In fact, this expense can be reducedfurther by making use of the carbon dioxide generated fromother production facilities such as power plants. Utilities forheating and cooling of the streams and equipment werealso estimated from the energy balance of the computersimulation. Table 4 summarizes the consumption of various

of a pilot-scale fermentative succinic acid production from bakery.001

utilities for the production. As a biochemical process, the plantrequires large quantity of steam for both sterilization, and

Percentage of FCIa (%) Cost (USD)

30 314,99810 104,999

4 42,0006 63,0004 42,000

10 104,9992 21,0005 52,5000 –

6 63,0008 83,9992 21,0003 31,500

10 104,999Total 1,049,993

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Table 3 – Annual consumption of supplementary chemicals for the fermentative succinic acid production from bakerywaste.

Raw materialsa Quantity Unit cost (USD) Cost (USD/yr)

Hydrochloric acid 2 metric tonnes 580 1160Carbon dioxide 1949 metric tonnes 35 68,215Magnesium carbonate 6942 kg 0.051 354Sodium hydroxide 5 metric tonnes 350 1750Enzymes 0.172 metric tonnes 1258 216

Total 71,695

a Inoculum producing cost is included in the raw material cost.

Table 4 – Utility cost for the plant operation.

Utilities Quantity Unit cost (USD) Cost (USD/yr)

Steam 1029 metric tonnes 12 12,348Electricitya 25,631 kW h−1 0.115 2957NaCl brine 381 metric tonnes 0.25 95Heating oil 85,937 kg 0.0082 705Process water 2974 metric tonnes 0.173 515

Total 16,620

a The costs of electricity and process water already took account of the cooling cost for this process.

thus, it contributed the most (i.e. 74%) to the utility cost. Partof the operating cost (US$ 112,000/year) spent on hiring oper-ating two engineers and six operators for operation of thisSA production facility. On the other hand, the annual main-tenance and repair cost was assumed to be 1% of the fixedcapital investment and the laboratory charges were relatedto the operating labour costs. Other costs such as distribu-tion cost and waste treatment cost were assumed to be anadditional 5% of the total production cost. Table 5 summa-rizes the annual total production cost, which was US$ 230,750.It is found that the raw material and operating labours arethe highest expenditure for the fermentative SA productionfacility.

3.3. Profitability

The main revenue of the plant was from the sales of the suc-cinic acid crystals and the by-products. In addition, as the pilotplant provided service for treating the bakery waste, wastetreatment charge was received from the supplier. The over-all revenue generated from the facility is US$ 374,041/year, asshown in Table 6. By accounting for the production cost, theannual profit of the plant is US$ 143,559. Thus, the return oninvestment (ROI) of this project is 12.8%. Although the ROIshowed positive economic attractiveness, further economicanalysis is required in order to determine the time required

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for breakeven and the overall net present value to be earnedby the plant. Fig. 2a shows the cumulative cash flow diagram

Table 5 – Total production cost of the fermentative succinic acid

Component Descriptiona

Raw materials See Table 3

Utilities See Table 4

Operating labour cost Engineers and operators

Maintenance & repair 1% of FCI

Laboratory charges 8% of operating labour cost

Other costs 5% of total production cost

Total

a The percentages are estimated based on Peters et al. (2003).

constructed using the above-mentioned economic data. Thenet present value of the whole project was equivalent to US$2,577,000 and the payback period was 7.22 years when thediscount rate was not accounted for. In fact, discount rateis a key variable to discount future cash flows to the presentvalue. Increasing the discount rate allows adjusting for risks orother uncertainty throughout the plant operation. As shown inFig. 2a, the higher discount rate resulted in a lower overall NPV.This implied that the project became less attractive when thediscount rate increased. This is also reflected from the longerpayback period. However, as long as the NPV remained posi-tive, the project is economically viable. Fig. 2b shows a plot ofthe NPV against the discount rate. The NPV became zero whenthe discount rate was 15.3%, which is also known as inter-nal rate of return (IRR). Indeed, these economic parametersdemonstrated that the project is economically feasible.

3.4. Sensitivity analysis

Investment of a chemical plant requires years for reasonablereturns. Meanwhile, it poses to considerable risk throughoutthe operating life of the plant due to the variation of thetechnical performance of the plant or economically changingenvironment. In this study, sensitivity analysis was used toevaluate the effects of key variables on the economic perfor-mance of the SA production plant. The results are shown in

of a pilot-scale fermentative succinic acid production from bakery.001

Fig. 3a. In general, the change of the variables within ±20% didnot result in any negative NPV, thus, the project was viable.

production plant.

Cost (USD/year) Percentage (%)

71,695 31.116,620 7.2

112,000 48.510,500 4.5

8960 3.910,975 4.8

230,750 100.0

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Table 6 – Overall annual revenue from the fermentative succinic acid production facility.

Product Quantity Unit price (US$/unit) Revenue (US$/yr)

Succinic acid crystals 25,388 kg 9.00 228,492Solid biomass (fish feeda) 270,108 kg 0.45 121,549Bakery waste treatment 312 batches 76.9 24,000

Total 374,041

a Assumption of solid biomass for fish feed application is based on David (2007).

IappIiccerblDm

b

Fds

the bakery waste fed also resulted in the decrease in quan-

t was found that the prices of products including succiniccid and biomass significantly affected the profitability of thelant. It is because they directly affected the revenue of theroduction plant and the prices change readily against time.

n fact, it was forecasted that the demand for succinic acid andts price will increase steadily in the future as it is an importanthemical intermediate for the production of various chemi-als (Cheng et al., 2012). A significant drop in its price was notxpected. On the other hand, increase in operating labour costeduced the profit of the plant considerably. This will pose theiggest risk to the operation due to the steadily increase in

abour wage in Asian countries in the recent years (Cai and

Please cite this article in press as: Lam, K.F., et al., Economic feasibilitywastes. Food Bioprod Process (2013), http://dx.doi.org/10.1016/j.fbp.2013.09

u, 2011). The NPV was much less affected by the costs of rawaterial cost and utility.

a

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ig. 2 – (a) Cumulative cash flow diagram at differentiscount rates and (b) the internal rate of return of theuccinic acid production from bakery waste.

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The proposed bio-refinery aimed to convert bakery wasteinto succinic acid. In fact, it is possible to face a shortage ofthe waste when the HK Government promote the reduction ofmunicipal solid waste. As the facility was designed for treatinga tonne of bakery waste per day, Fig. 3b plots the NPV againstthe quantity of bakery waste used for SA production. It wasassumed that fixed costs, such as utility cost, maintenance &repair cost, etc., remained unchanged for 1 tonne bakery wasteper day (i.e. the initial designed values) while the raw materialcost, operating labour cost and laboratory cost were linearlyproportional to the quantity of the bakery waste. Reduction of

of a pilot-scale fermentative succinic acid production from bakery.001

tities of products, and thus, the revenue was also affected

1500

2000

2500

3000

3500

20% -10% 0% 10% 20%

NPV x1 000 (US$)

Variat ion of th e parameter

Price of biomass

Raw materi al cost

SA price

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Operating labour cost

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Variable c ost

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Fig. 3 – (a) Sensitivity analysis and (b) the breakeven chartof the fermentative succinic acid production from bakerywaste.

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adversely, which was assumed to be changed linearly withthe bakery waste fed. Based on the result, the plant startedto have negative profit when the bakery waste fed was lessthan 0.26 tonnes/day. Therefore, the operation might requiresuspension below this quantity.

4. Conclusions

In this study, the techno-economic feasibility of the fer-mentative succinic acid production from bakery waste wasdemonstrated using SuperPro Designer®. The total capitalinvestment (US$ 1,118,243) and the total production cost(US$ 230,750/year) were estimated. The total revenue wasUS$ 374,041/year, which includes the sales of 28,533 kg suc-cinic acid/year, 270,108 kg solid biomass/year and the receivedwaste treatment charge. The return on investment (ROI) was12.8%, the breakeven of the capital investment was 7.2 yearsand the internal rate of return was 15.3%. The production plantreached shutdown point when the bakery waste feed was lessthan 0.26 tonnes/day.

Acknowledgements

The research was supported by the Industrial TechnologyFunding from the Innovation and Technology Commission(ITS/323/11) in Hong Kong, the donation from the Coffee Con-cept (Hong Kong) Ltd. for the ‘Care for Our Planet’ campaign, aswell as a grant from the City University of Hong Kong (ProjectNo. 7200248). We are also grateful for the industrial partnersthe Hong Kong Organic Waste Recycling Centre and the Asso-ciated Engineers Limited for providing valuable data of bakerywaste and acquiring the quotations of major equipment.

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