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Industrial Crops and Products 54 (2014) 175–184

Contents lists available at ScienceDirect

Industrial Crops and Products

jo ur nal home p age: www.elsev ier .com/ locate / indcrop

echno-economic and environmental assessment of essential oilxtraction from Citronella (Cymbopogon winteriana) and LemongrassCymbopogon citrus): A Colombian case to evaluate differentxtraction technologies

onathan Moncadaa, Jhonny A. Tamayob, Carlos A. Cardonaa,∗

Instituto de Biotecnología y Agroindustria, Departamento de Ingeniería Química, Universidad Nacional de Colombia sede Manizales, Cra. 27 No. 64-60,anizales, ColombiaInstituto de Biotecnología y Agroindustria, Departamento de Ingeniería Industrial, Universidad Nacional de Colombia sede Manizales, Cra. 27 No. 64-60,anizales, Colombia

r t i c l e i n f o

rticle history:eceived 7 October 2013eceived in revised form 15 January 2014ccepted 17 January 2014vailable online 9 February 2014

eywords:ssential oilemongrassitronella

a b s t r a c t

In this study a techno-economic and environmental assessment of essential oil extraction from Citronellaand Lemongrass is presented for the Colombian case. Extraction by water distillation was used to evaluateexperimental yields (Lemongrass: 7.50 kg/t, Citronella: 8.27 kg/t). Samples obtained from the experi-mental procedure were analyzed to determine the essential oil composition and use this information asstarting point in the technical analysis. After this, three extraction technologies (i.e. supercritical fluid, sol-vent, and water distillation) were assessed from the techno-economic and environmental points of view.All technologies were evaluated using Aspen Plus, Aspen Process Economic Analyzer, and WAR GUI, carry-ing out simulation, economic evaluation, and environmental assessment, respectively. Besides, to analyzethe effect of energy consumption in each technology, two scenarios were proposed considering different

olvent extractionupercritical fluid extractionater distillation-extraction

levels integration (i.e. without integration, fully integrated). The lowest production cost was obtainedfor extraction by water distillation with full energy integration for both Citronella and Lemongrass (Cit-ronella: 6.48 USD/kg, Lemongrass: 7.50 USD/kg). Additionally, the lowest potential environmental impact(Citronella: 0.017 PEI/kg, Lemongrass: 0.016 PEI/kg) and lowest carbon footprint (Citronella: 0.79 kg CO2-e/kg oil, Lemongrass: 0.73 kg CO2-e/kg oil) were obtained for extraction by water distillation with fullenergy integration.

© 2014 Elsevier B.V. All rights reserved.

. Introduction

Colombia, a country located in the tropical region is a verynteresting biomass source at high productive levels. In this sense,he Colombian government is looking forward to increase biomassroductivity, and propose technological schemes to obtain newroducts on a biorefinery concept (Moncada et al., 2013). Consider-

ng this, essential oils are bio-based products with wide variety ofpplications in different industry sectors (e.g. food, pharmaceutics,osmetics) (Burt, 2004; Danh et al., 2009). Therefore, many plantsontaining essential oils can be cropped and harvested in differ-

nt regions (Burt, 2004). In Colombia, varieties such as CitronellaCymbopogon winteriana), Oregano (Origanum vulgare), RosemaryRosmarinus officinalis), Orange (Citrus sinensis), Mandarin (Cit-

∗ Corresponding author. Tel.: +57 6 8879300x50417; fax: +57 6 8859300x50199.E-mail address: ccardonaal@unal.edu.co (C.A. Cardona).

926-6690/$ – see front matter © 2014 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.indcrop.2014.01.035

rus reticulate), and Lemongrass (Cymbopogon citrus), among manyothers, are now harvested and used in different areas as thecase of traditional syrups. Nevertheless, these uses have not beenwidely exploited to obtain essential oils at high productive levelsin Colombia.

On the other hand, technologies for the extraction of essentialoils had been widely studied from an experimental and modelingpoint of view. In the case of supercritical fluid extraction, Danhet al. (2009) optimized three extraction parameters for essen-tial oil from Vetiveria zizanioides roots, using a central compositedesign (Danh et al., 2009). Also, Danh et al. (2010) evaluate theeffects of temperature, pressure and ethanol concentration for theextraction of vetiver essential oil by ethanol-modified supercrit-ical carbon dioxide (Danh et al., 2010). Berna et al. analyzed the

effect of the height of the bed for the extraction of essential oilfrom orange peels from both experimental and modeling pointsof view (Berna et al., 2000). Mira et al. (1999, 1996) analyzedthe supercritical fluid extraction of essential oil from citrus peels,

1 ops an

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76 J. Moncada et al. / Industrial Cr

tudying the influence of operating conditions, the effect of par-icle size and the effect of mass flow of CO2 on the extractionate of essential oil. Additionally, Mira et al. (1999, 1996) applied

model to the experimental data in order to prepare a tool forhe scale up of the supercritical extraction process. Other work,eported by Khajeh et al. (2012), presented a three layer artificialeural network to predict the extraction yield of essential oils fromiplotaenia cachrydifolia by supercritical fluid extraction including

he effect of different parameters such as pressure, temperature,odifier volume and extraction time. In the case of solvent extrac-

ion and extraction by water distillation, different studies had beenonsidered from both the experimental and modeling point of view.or instance, Monsálvez et al. (2010) studied the antifungal effect ofn extract selected from the bark of Drimys winteri from n-hexanextraction. Jiménez-Carmona et al. (1999) compared the continu-us subcritical water extraction and hydro-distillation of essentialil from marjoram leaves showing that a subcritical extraction pro-ess resulted in less time and higher yields. Zhang et al. (2012),roposed a combination of solvent extraction and steam distil-

ation for the extraction of essential oil from discarded tobaccoeaves evaluating different operating conditions such as temper-ture and liquid–solid ratio and their influence on the extractomposition. Masango (2005) presented a new process design andperation for steam distillation of essential oils increasing extrac-ion yields and reducing the loss of polar compounds in wasteaters of the system. This work approximates an environmental

oncept by including indirectly a water footprint analysis. On thether hand, Cassel et al. (2009) evaluated a mathematical modelo predict the essential oil recovery by steam distillation of rose-

ary, basil and lavender comparing with experimental data onields.

Supercritical extraction technology shows to be a promisingechnology to extract components at high purity in a cleaner wayhan other technologies, however it is a demanding technologyn terms of energy consumption for the compression and decom-ression of supercritical systems (Danh et al., 2009, 2010). On thether hand, solvent extraction is a conventional technology thathows high yields due to the selectivity of solvents and inter-sting compounds to be extracted, however, hazardous solventseed to be used to guaranteed a proper extraction and therefore

t could represent an environmental issue (Fakhr Hoseini et al.,009; Yang et al., 2012; Zhang et al., 2012). Additionally, the qual-

ty of the extracted oil can be notoriously affected depending onhe organic solvent selected (Fakhr Hoseini et al., 2009; Yang et al.,012; Zhang et al., 2012). Finally, the water distillation extractionechnology is the oldest technology used to extract essential oilsith high yields and high purity of the extracts. However, one of itsisadvantages is the use of high amounts of water at high temper-ture, which notoriously affect the quality of the extracts, and theechnology also becomes an energy demanding one (Cassel et al.,009; Masango, 2005; Zhang et al., 2012). Considering the back-round described above, different extraction techniques and rawaterials had been tested for the production of essential oils. How-

ver, its techno-economic and environmental assessment of hasot been completely studied. Taking this into account, this studyonsiders supercritical fluid, solvent and water distillation as tech-ologies for the extraction of essential oils from Citronella andemongrass as case study. Additionally, two scenarios (i.e. with-ut energy integration, full energy integration) were considered inrder to analyze the influence of energy integration on the overallerformance of each technology. Each technological scheme wasimulated using Aspen Plus and Aspen Economic Analyzer soft-

are, in order to determine its production cost. Also, the waste

eduction algorithm and the carbon footprint were used as indica-ors to measured the environmental impact. In this sense, the aimf this paper is to evaluate and compare from the techno-economic

d Products 54 (2014) 175–184

and environmental point of view the extraction of essential oilsfrom Citronella and Lemongrass at the Colombian conditions. Inorder to compare extraction yields and determine the essential oilcomposition, an experimental procedure using water distillationwas considered.

2. Materials and methods

2.1. Raw materials

Citronella (C. winteriana) and Lemongrass (C. citrus), wereobtained from a farm placed in Chinchiná town, located in thedepartment of Caldas (west center of Colombia), which altitude is1368 m over sea level with an average temperature of 21 ◦C.

2.2. Experimental extraction of Citronella and Lemongrassessential oil

In order to analyze the technical feasibility of the extractionof essential oil from Citronella and Lemongrass, an experimentalanalysis was proposed using the water distillation as technology.Additionally, the objective of this experimental analysis was todetermine the chemical characterization of the essential oil and usethis information as a starting point to feed a simulation procedureto assess different extraction technologies from the economic andenvironmental point of view. The steps considered in the experi-mental analysis were: (i) reception and cutting of the raw material,(ii) drying at 30 ◦C until reaching a 10% of moisture, (iii) materialgrinding to particle size below 500 �m, (iv) extraction by waterdistillation (2 h), (v) condensation and separation, (vi) storage andsample preparation.

After the extraction procedure, 10 �l of the extracted oil werediluted in 1.5 ml of chromatographic grade hexane and addedto a test tube and injected in the gas chromatograph–massspectrometer. An Agilent Technologies 6850 series II gas chro-matographer was used. The gas chromatographer was equippedwith a HP-INNOWAX capillary column (30 m length, 0.25 mm inter-nal diameter). Helium (split ratio 30:1) was used as the carrier gas.The injector and detector were operated at 260 ◦C, respectively.A temperature program was used for efficient separation as fol-lows: 50 ◦C for 2 min, temperature ramp of 7 ◦C/min to 85 ◦C for5 min, temperature ramp of 10 ◦C/min to 130 ◦C for 5 min, temper-ature ramp of 10 ◦C/min to 200 ◦C for 3 min, temperature ramp of10 ◦C/min to 250 ◦C for 3 min. An Agilent Technologies 5975B massspectrometer was used for identification and quantification of theessential oil.

2.3. Process description

Technologies included in the techno-economic and environ-mental assessment of the extraction of essential oil from Citronellaand Lemongrass are: supercritical fluid extraction with carbondioxide, solvent extraction with n-hexane, and extraction by waterdistillation. A brief description of each technology is presented inthe following subsections.

2.3.1. Supercritical fluid extraction (SFE)The process to extract essential oil using supercritical fluids

begins with the reception of the raw material. After this the mate-rial is cut to a particle size 5 cm in average, and subsequently driedat 30 ◦C in order to reach a moisture content of 10% in weight. Afterthis, the solid is grinded to particle size below 500 �m in order

to expose the oily fraction allowing a proper extraction condition.Subsequently, the reduced size solid is directed to the extractionvessel to pack it. Once the last procedure is done, the carbon diox-ide must be prepared to the supercritical conditions, which begins

J. Moncada et al. / Industrial Crops and Products 54 (2014) 175–184 177

F rcritice r, (9)

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ig. 1. Simplified flowsheet diagram for the extraction of essential oils using supextraction vessel, (6) heat exchanger, (7) depressurization vessel, (8) heat exchange

ith a cooling process to approximately −30 ◦C in order to avoidump cavitation in the compression stage. The cooling fluid usedor this stage is ethylene glycol–water mixture (70:30). After this,he CO2 is compressed to 200 bar and its temperature is increasedo 35 ◦C reaching the supercritical conditions (Berna et al., 2000;hajeh et al., 2012). Later, the supercritical fluid is passed through

he extraction vessel previously packed with the solid material. It isery important to take into account that temperature and pressurehould be kept constant during the extraction stage, because a littleerturbation on these variables will affect notoriously the carbonioxide density and viscosity and therefore the extraction yield.fter the extraction process, two streams are obtained: one includ-

ng the exhausted solid, and a second one including the essential oililuted in supercritical CO2. Considering that the extract is obtainedt high pressure it is necessary to depressurize the stream and sep-rate the CO2 from the essential oil. The depressurization is donen two stages reducing the pressure to 50 bar and gasifying the car-on dioxide at 25 and 35 ◦C, respectively. This procedure is also very

mportant since essential oil losses are avoided and carbon dioxides not depressurized to ambient pressure making easier its recir-ulation and further re-compression. The consequence of this is anasier recovery of the essential oil extracted. It is also importanto note that this description applies for both feedstocks. The ratiof g essential oil per kg of CO2 is 29.03 and 27.55 for citronella andemongrass, respectively. Besides, up to 97.95% of CO2 can be recov-red and recycled. However, it is first cooled to −30 ◦C and thenressurized to 200 bar. For both feedstocks, the power required toompress the carbon dioxide is 21.71 MJ/t of CO2. On the other hand,o give an idea of the stages considered in the extraction of essen-ial oil using supercritical carbon dioxide, Fig. 1 shows its simplifiedowsheet.

.3.2. Solvent extraction (SE)

In the case of extraction using solvents, the process begins with

he reception of the raw material. Then, the material is cut to a par-icle size 5 cm in average, and subsequently dried at 30 ◦C in ordero reach a moisture content of 10% in weight. After this, the solid

al carbon dioxide. (1) Heat exchanger, (2) pump, (3) heat exchanger, (4) mill, (5)heat exchanger.

is grinded to particle size below 500 �m in order to expose theoily fraction allowing a proper extraction condition and then thesolid is sent to the extraction column. It is very important to takeinto account that important conditions should be met to conduct aproper extraction process such as particle size, solvent to feed ratio,and temperature. The solvent to feed ratio (dry basis) was kept at4:1, while the extraction temperature was kept at 50 ◦C, thereforethe extracting solvent is prepared to the extraction conditions. Hex-ane was selected as solvent because its selectivity to extract organiccompounds (Fakhr Hoseini et al., 2009; Mohsen-Nia and Paikar,2007), however, its selection criteria is presented and discussedon Section 3. This selection is based on thermodynamics, however,the parameters that most affect the extraction process were care-fully considered in order to simulate the extraction process as muchaccurate as possible. On the other hand, after the extraction process,two streams are obtained: One stream including the solid and theaqueous phase, and a second stream containing the organic phase,which is rich in hexane an essential oil.

After the essential oil extraction, the solvent is recovered in avacuum distillation column with a solvent-rich top stream and abottom stream rich in essential oil. It is very important to takeinto account that the process must be done at vacuum conditionsto avoid degradation of the essential oil compounds. However, alow concentration of hexane is still remaining in the essential oil(<50 ppm), which significantly affects the quality and safety of theproduct. This explains why the separation technology should beenough efficient to avoid high solvent concentration in the prod-uct. Fig. 2 shows the simplified flowsheet diagram of the extractionprocess using solvents.

2.3.3. Water distillation extraction (WDE)In the case of extraction by water distillation, the process

includes the reception, material cutting to a particle size 5 cm

in average, drying at 30 ◦C in order to reach a moisture contentof 10% in weight, and grinding to particle size below 500 �m inorder to expose the oily fraction allowing a proper extraction con-dition to pack the solid extraction column. After this, steam is

178 J. Moncada et al. / Industrial Crops and Products 54 (2014) 175–184

F ts. (1h pump

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ig. 2. Simplified flowsheet diagram for the extraction of essential oils using solveneat exchanger, (7) vacuum distillation column, (8) pump, (9) heat exchanger, (10)

enerated in a boiler to subsequently pass through the packedolumn. However, steam should not be too high in order tovoid degradation of essential oil compounds (approx. 90–100 ◦C)Masango, 2005). It is very important to take into account thatemperature may affect notoriously the extraction yield and theuality of the oil, and therefore it should not exceed the namedounds. The water to feed ratio is 5:1 (dry basis). In the case ofater distillation the energy required to generate steam is using

ow-pressure steam (3 bar) and cooling water for the other units.t is also important to note that there can be a bunch of possi-ilities to integrate the system in order to avoid its demandinguantity of energy consumption. This is explained in detail in Sec-ion 3. After the extraction process, steam containing essential oils rapidly cooled to form two liquid fractions: an oily rich one and

ater rich one which are separated in a decanter. Fig. 3 shows theimplified flowsheet for the extraction of essential oils by wateristillation.

ig. 3. Simplified flowsheet diagram for the extraction of essential oils using water distiump, (8) decanter.

) Heat exchanger, (2) pump, (3) heat exchanger, (4) mill, (5) extraction column, (6), (11) heat exchanger.

2.4. Simulation procedure

Simulations of the extraction of essential oil from Citronellaand Lemongrass were carried out using Aspen plus v8.0 (AspenTechnology Inc., USA). Simulations considered a plant capacity toprocess 200 kg/h of fresh feedstock. The physical-property data forcomponents missing in the Aspen Plus databases, and requiredin the simulations were estimated by correlating data availablefrom the National Institute of Standards and Technology (NIST)to the Aspen properties correlation and missing properties wereestimated using the method reported byMarrero and Gani (2001)which is suitable for complex molecules. Additional data wereobtained from the work of Wooley and Putsche (1996) (i.e. Hemicel-lulose, Lignin). The Unifac-Dortmund thermodynamic model was

used to calculate the activity coefficients in the liquid phase and theHayden–O’Conell equation of state was used to model the vaporphase.

llation. (1) Pump, (2) boiler, (3) mill, (4) extraction column, (5) heat exchanger, (7)

J. Moncada et al. / Industrial Crops an

Table 1Prices used in the economic evaluation.

Item Value Unit

Citronellaa 18 USD/tLemongrassa 22 USD/tCitronella oilb 10 USD/kgLemongrass oilb 20 USD/kgCO2

b 1.55 USD/kgHexaneb 0.31 USD/LWaterc 1.252 USD/m3Electricityc 0.1 USD/kWhMid P. steamc 9.86 USD/tLow P. steamc 1.57 USD/tOperatorc 2.14 USD/hSupervisorc 4.29 USD/h

a Price due to transport charges and average market. Average travelled radio:100 km. Type of truck: 10 t truck. Diesel price: 4.11 USD/gal.

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b Prices based on ICIS pricing indicatives (ICISpricing, 2013).c Colombian national average Anastas and Eghbali (2010).

.5. Estimation of energy consumption and total costs

Estimation of the energy consumption was performed based onhe results of the mass and energy balances generated by simula-ions. For this, energy required by heat exchangers and reboilers,s well as electric energy needs of the pumps, mills, and otherquipment were considered. To evaluate the influence of energyntegration on the overall performance of the processes describedn Section 2.1, two scenarios were proposed. Scenario 1 includeshe extraction process without any le energy integration (Sc. 1),hile Scenario 2 includes full level of energy integration (Sc. 2)

Sánchez et al., 2011). The energy integration approach consideredhe pinch method, which includes the construction of compositeurves based on the enthalpy of each stream. After this, the heatingnd cooling targets can be easily calculating by minimizing the tem-erature difference between heating and cooling streams (Linnhoffnd Hindmarsh, 1983; Rev and Fonyo, 1991). Furthermore, it isery important to mention that in all cases, solvents (i.e. CO2, hex-ne, water) were recovered as much as possible following a massntegration approach.

In the economic assessment, the capital and operating costsere calculated using the software Aspen Economic Analyzer

Aspen Technologies, Inc., USA). However, specific parametersegarding some Colombian conditions such as raw material costs,ncome tax (33%), labor salaries, and interest rate (16.02%), amongthers, were incorporated in order to calculate the production costser unit of essential oil at the Colombian conditions. The above-entioned software estimates the capital costs of process units asell as the operating costs, among other valuable data. This soft-are uses the design information provided by Aspen Plus and data

ntroduced by the user for specific conditions, for instance projectocation. Equipment calculations were performed following thespen Economic Analyzer V8.0 user guide (Aspen Technologies,

nc., USA), which also uses correlations reported by Peters et al.Peters et al., 2003). Utilities, civil works, pipelines, man-hours,nd many different parameters were estimated using the sameoftware. Table 1 shows prices used in the economic evaluation.

.6. Environmental assessment

The Waste Reduction Algorithm (WAR), developed by theational Risk Management Research Laboratory from the U.S. Envi-

onmental Protection Agency (EPA) was used as the method for

he calculation of the Potential Environmental Impact (PEI). This

ethod proposes to add a conservation reaction over the PEI, basedn the impact of input and output flow rates from the process. TheEI for a given mass or energy quantity could be defined as the

d Products 54 (2014) 175–184 179

effect that those (energy and mass) would have on the environ-ment if they were arbitrarily discharged. The environmental impactis a quantity that cannot be directly measured. However, it canbe calculated from different measurable indicators (Cabezas et al.,1999; Cardona et al., 2004; Ramzan et al., 2008). The WAR Algo-rithm includes eight categories: human toxicity by ingestion (HTPI),human toxicity by dermal exposition or inhalation (HTPE), terres-trial toxicity potential (TTP), aquatic toxicity potential (ATP), globalwarming (GWP), ozone depletion potential (ODP), photochemicaloxidation potential (PCOP), and acidification potential (AP). Theweighted sum of all impacts ends in the final impact per massof products. It is very important to clarify that this environmen-tal assessment only corresponds to the possible impact generatedin processing stage. In other words, the limits of the system corre-spond to the processing facility. In this way a LCA is not considered,and a simpler evaluation is carried out considering the mass andenergy balances from the technical evaluation. This also serves asa basis to compare different processing configurations.

Other important environmental parameter is the greenhousegas (GHG) emissions associated to a chemical process. This pro-cedure was completed following the IPPC Guidelines of 2007represented as the carbon footprint (Eggleston, 2007). The GHGemissions are calculated using an equivalence factor of 94,600 kgCO2-eq per TJ, using charcoal as fuel for external energy supply. Itis very important to note that this evaluation corresponds to thepotential emissions related to processing stage including only theenergy balance.

3. Results and discussion

3.1. Experimental analysis, essential oil composition and propertyestimation

Water distillation technology led to an experimental yield of7.50 and 8.27 kg/t for Lemongrass and Citronella, respectively. Therelative density of the Citronella extract was 0.898 at 25 ◦C, therefraction index of 1.466 at 20 ◦C, and the solubility in ethanol at80% and 20 ◦C of 1:2 (v/v). In the case of Lemongrass, relative den-sity of the extract was 0.869 at 25 ◦C, the refraction index of 1.483at 25 ◦C, and the solubility in ethanol at 80% and 20 ◦C is insoluble. Itis very important to highlight that this technology was used to con-duct the extraction due to its potential availability and accessibilityin zones where the materials are harvested.

The main compounds identified in the Citronella essentialoil were (mass percentage): citronellal (54.16%), d-limonene(6.49%), citronellyl acetate (3.29%), �-bourbonene (5.60%), �-cubebene (4.54%), �-elemene (2.41%), �-bergamotene (2.19%),�-caryophyllene (2.34%), �-gurjunene (2.85%) and �-selinene(2.02%). The main compounds identified in the Lemongrass essen-tial oil were: citral (72.32%), myrcene (14.28%), farsenol (10.37%),and linalool, terpineol, citronellal, geraniol, and nerol (3.03%). Thesedata was used as starting point to feed simulations. However, giventhe complex composition of each essential oil, it was necessary toestimate some physicochemical properties of the compounds andinclude them in the database of Aspen Plus. To do this, experimen-tal reported by the National Institute of Standards and Technology(NIST) was fitted to the Aspen Properties correlations. The missingproperties were estimated using the method reported by Marrero& Gani (Marrero and Gani, 2001) which is suitable for complexmolecules. In this sense, it can be noted the interaction betweenthe experimental setup with simulations.

3.2. Process simulation

The analysis of process simulation for the extraction of essen-tial oil from Citronella and Lemongrass is focused on the processingyield, which is defined as kg of essential oil per tonne of fresh raw

180 J. Moncada et al. / Industrial Crops an

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respectively. As a result, the values are very similar to those shownfor Citronella, because the extraction conditions are the same. Fur-thermore, the analysis on energy consumption is very important

ig. 4. Citronella essential oil quaternary liquid–liquid equilibria for the system (A):-limonene, (B): solvent, (C): water, (D): citronellal at 50 ◦C. (a) Solvent: ethanol;b) solvent: n-hexane.

aterial. In this sense, the extraction yield depends on the tech-ology and also in the characteristics of the raw material. For both

eedstocks (citronella and lemongrass), the moisture content wasround 60–70%. Yields for Citronella correspond to 10.16, 9.97, and.75 kg/t for SFE, SE, and WDE, respectively. SFE technology led to

high processing yield, which can affect the energy consumptionnd the total production cost. However, there is not a big differenceetween SFE and SE. SFE yield is only 1.92% higher than SE, whileFE is 13.88% higher than WDE. In the case of Lemongrass, yieldsorrespond to 9.64, 9.57, and 8.14 for SFE, SE and WDE, respectively.he behavior is very similar for those presented for Citronella withFE 0.79% higher than SE, and 15.61% higher than WDE. In the casef Lemongrass, the processing yields for all technologies (SFE, SE,nd WDE) are lower than those presented for Citronella. For SFE, thextraction yield shown for Citronella is 5% higher than Lemongrass.he yields obtained in simulations are in good agreement with typ-cal values reported in literature (Berna et al., 2000; Cannon et al.,013; Jiménez-Carmona et al., 1999; Khajeh et al., 2012; Masango,005; Mira et al., 1996, 1999; Monsálvez et al., 2010; Papamichailt al., 2000; Verma et al., 2013; Zhang et al., 2012).

The processing yields are directly related to the extractionechnology and its thermodynamic behaviors, which restrict thextraction process. Therefore, different thermodynamic aspects areiscussed in order to support the selection of technologies. In thease of WDE, the extraction process considers the volatility of theompounds that are dragged in the vapor phase considering a vaporiquid equilibrium. Another advantage in WDE is the ability to formwo liquid phases after a cooling process, then a decanter is used toeparate both liquid streams. Considering this, to show that theres an insolubility region between the compounds of the essentialil with water and solvent, a quaternary liquid–liquid diagram isresented for Citronella and Lemongrass. In the case of Citronella,he selected compounds to represent the essential oil are Citronel-al and d-limonene, which are the compounds in higher proportions presented in the oil composition. Given this, Fig. 4 shows theernary diagram for the liquid–liquid equilibria system Citronel-al, d-Limonene, and Water and solvent at 50 ◦C. In the case ofemongrass, the selected compounds to describe the essential oilre Myrcene and Citral. Fig. 5, shows the liquid–liquid equilibriaor the system myrcene, citral, solvent and water at 50 ◦C. For botheedstocks, the liquid–liquid equilibria represent a large portion onhe quaternary diagrams (see Figs. 4 and 5). In this sense, two liq-ids can be obtained if the composition of the stream leaving theop of the column is inside of the shadowed region of the ternaryiagram. However, the liquid is split in two regions: water richne, and other corresponding to any point on the left line of thehadowed region (organic rich).

In the case of SFE the extraction conditions were selected basedn previous works (Fakhr Hoseini et al., 2009; Mohsen-Nia andaikar, 2007). However, the quality to recover the carbon dioxide inhe depressurization process at 50 bar and 25 ◦C it is easy to obtain

d Products 54 (2014) 175–184

the liquid fraction rich in essential oil, and the vapor fraction richin CO2, for almost all compositions between 0 and 1.

In the case of SE, the thermodynamic analysis is focused onselecting the extracting solvent. Therefore, a comparison betweenn-hexane and ethanol is represented in quaternary liquid–liquiddiagrams (see Figs. 4 and 5). For both feedstocks (i.e. Citronella andLemongrass), the behavior of the quaternary liquid–liquid equi-libriums is very similar, however, there are significant differencesamong each solvent. In the case of Citronella with ethanol as sol-vent (see Fig, 4a), the liquid–liquid equilibria region is smaller thanthat presented for n-hexane (see Fig. 4b). This is due to the misci-bility between ethanol and water, and also the miscibility betweenethanol and each of the compounds. Furthermore, when hexane isused as solvent the liquid–liquid region is bigger due to the immis-cibility between hexane and water. Therefore, the extraction oforganic compounds is in advantage, and the selectivity using hex-ane is higher. However, there are different parameters that affectthe liquid–liquid equilibria. In this sense, the miscibility is stronglyaffected by temperature and in most cases the insolubility regioncan be decreased or increased. Considering this, it can be expectedthat extraction temperature allow the system to extend the equilib-rium conditions and a high selectivity could be reached. Conversely,a low temperature may be considered, but it is very important toremark that the essential oil is contained within a solid matrix andimportant mass transfer restrictions appears at low temperatures.Given this, the most important is to find a temperature to increasethe mass transfer rate (high viscosity and density at low tempera-tures), and also allow the extraction process based on equilibriumconditions. As a consequence, the selected temperature was 50 ◦C.On the other hand, the selection criteria for this type of solventsshould not be seen only from the thermodynamics point of view,but also from the impact of using the solvents from an economicsand environmental points of view.

The energy consumption required by each technology for theextraction of the essential oil is considered in the analysis. Asmentioned in Section 2.3, two scenarios were analyzed for eachtechnology and each raw material. In this sense, the energy con-sumption for Citronella in Sc. 1 (Sc. 1, standalone process withoutenergy integration) correspond to 280.33, 244.76, and 303.76 MJ/tof fresh citronella, for SFE, SE and WDE, respectively. On the otherhand, when full energy integrated scenario is considered (Sc. 2),savings on energy can be achieved in contrast to Sc. 1. These savingscorrespond to 57.46%, 5.13%, and 71.49% for the case of SFE, SE, andWDE, respectively. In the case of Lemongrass, the energy consump-tion for Sc. 1 correspond to 268.18, 243.34, and 298.76 MJ/t of freshlemongrass, for SFE, SE and WDE, respectively. In the case of Sc. 2these correspond to 58.23%, 5.05% and 70.08% for SFE, SE, and WDE,

Fig. 5. Lemongrass essential oil quaternary liquid–liquid equilibria for the system(A): citral, (B): solvent, (C): water, (D): myrcene at 50 ◦C. (a) Solvent: ethanol; (b)solvent: n-hexane.

J. Moncada et al. / Industrial Crops and Products 54 (2014) 175–184 181

Table 2Citronella essential oil production cost using SFE, SE, and WDE as technologies for each scenario.

Item Cost (USD/kg) and share (%) SFE SE WDE

Sc. 1 Sc. 2 Sc. 1 Sc. 2 Sc. 1 Sc. 2

Raw materials Cost 2.54 2.54 2.23 2.23 2.06 2.06Share 32.09 36.91 25.54 26.04 25.08 31.73

Operating labor Cost 0.95 0.95 1.27 1.27 1.10 1.10Share 12.02 13.82 14.50 14.78 13.44 17.00

Utilities Cost 2.60 1.53 2.72 2.55 3.30 1.52Share 32.89 22.19 31.10 29.76 40.25 23.44

Operating charges, plantoverhead, maintenance

Cost 0.65 0.65 0.95 0.95 0.64 0.64Share 8.26 9.50 10.84 11.05 7.85 9.93

General and administrativecost

Cost 0.31 0.31 0.37 0.37 0.34 0.34Share 3.87 4.45 4.25 4.33 4.15 5.25

Depreciation of capitala Cost 0.86 0.90 1.20 1.20 0.76 0.82Share 10.87 13.12 13.77 14.04 9.23 12.65

Total Cost 7.91 6.88 8.74 8.57 8.20 6.48Share 100.00 100.00 100.00 100.00 100.00 100.00

1.26

boecdoedoditpot

3

slte(cc

TL

Sale price/total production cost

a Calculated using the straight line method.

ecause it has a direct effect on the process economics and alson the environmental impact. This is basically due to the externalnergy requirements that most of the times are covered by fossilharcoal, natural gas and/or oil. In this sense, if external energy isecreased the impact by emissions will be lower and a decreasen fuel is expected. Additionally, the technology with the highestnergy consumption is WDE, because of the energy required to pro-uce the steam needed in the extraction (see Fig. 3). In the casef SFE the energy required is mainly due to the compression andepressurization process to adequate and separate de carbon diox-

de, respectively. In the case of SE most of the energy required is dueo the recovery process of the solvent. It can be inferred that eachrocess has any specific unit that consumes most of the energy. Inrder to evaluate the effect of technologies and integration levels,he economic evaluation is presented in the following section.

.3. Economic evaluation

As mentioned in Section 2.3, the economic evaluation is pre-ented for each technology (i.e. SFE, SE, and WDE) at two differentevels: without energy integration (Sc. 1) and full energy integra-ion (Sc. 2). Considering this, the production cost is presented for

ach feedstock (i.e. Citronella and Lemongrass), for each technologyi.e. SFE, SE, WDE), and each scenario. Table 2 shows the productionost for Citronella essential Oil, while Table 3 shows the productionost for Lemongrass essential Oil.

able 3emongrass essential oil production cost using SFE, SE, and WDE as technologies for each

Item Cost (USD/kg) and share (%) SFE

Sc. 1

Raw materials Cost 3.09Share 35.31

Operating labor Cost 1.00Share 11.45

Utilities Cost 2.74Share 31.33

Operating charges, plantoverhead, maintenance

Cost 0.69Share 7.87

General and administrativecost

Cost 0.32Share 3.69

Depreciation of capitala Cost 0.90Share 10.35

Total Cost 8.74Share 100.00

Sale price/total production cost 2.29

a Calculated using the straight line method.

1.45 1.14 1.17 1.22 1.54

In the case of Citronella essential oil (See Table 2), the productioncost fluctuates from 6.48 to 8.74 USD/kg. The highest productioncost corresponds to SE technology without any level of integration,and the lowest cost corresponds to WDE with full energy integra-tion. On the other hand, it is shown that for a standalone technology(Sc. 1) the lowest cost is obtained for SFE. Nevertheless it is alsoshown (SFE, Sc. 1) that raw material costs and utilities contributein the majority of the total costs. Furthermore, for a fully integratedscenario (SFE, Sc. 2), the share of utilities is significantly reduced dueto the saving potentials (57.46% savings on utility supply). Never-theless, it is very important to take into account that depreciation ofcapital increases when an energy-integrated scenario is proposed.In this sense, it is strongly recommended to evaluate the influenceof energy integration on the capital costs, because a non-feasiblescenario to decrease total production costs may appear.

In the case of SE (Citronella), the analysis is very similar tothat discussed for SFE. It can be seen that the production cost isdecreased when full energy integration is considered (Sc. 2) butnot as high as SFE. This is mainly because the saving potential ofenergy after the integration is significantly lower (only 5%) thanthose shown for SFE and WDE. In the case of WDE, the effect ofenergy integration on production cost is similar to SFE and SE. How-

ever, because of the high saving potential on energy (representedin utilities) the effect on production cost is more notorious (around70% of savings). It is very important to note that the integration onWDE is done mainly in the boiler section to produce the enough

scenario.

SE WDE

Sc. 2 Sc. 1 Sc. 2 Sc. 1 Sc. 2

3.09 2.79 2.79 2.70 2.70 40.19 28.76 29.37 29.04 35.99

1.00 1.35 1.35 1.18 1.18 13.03 13.87 14.17 12.73 15.78 1.61 2.89 2.69 3.54 1.67 20.91 29.75 28.26 38.12 22.27 0.69 1.01 1.01 0.69 0.69 8.96 10.38 10.60 7.44 9.22 0.32 0.39 0.39 0.37 0.37 4.20 4.07 4.15 3.93 4.87

0.98 1.28 1.28 0.81 0.89 12.72 13.17 13.46 8.74 11.87 7.68 9.70 9.50 9.30 7.50

100.00 100.00 100.00 100.00 100.00 2.60 2.06 2.10 2.15 2.67

182 J. Moncada et al. / Industrial Crops and Products 54 (2014) 175–184

on tec

siWtetba

ictcTtctf(sgT

ctosibma

3

iftatfliea

Fig. 6. Potential environmental impact of extracti

team to perform the extraction process. Therefore, when a fully-ntegrated scenario is considered, the lowest cost is obtained for

DE, instead of its lower yield (see Section 3.1). Table 2 also showshe sale price to production cost ratio to give an idea of the grossconomic income at the processing level (Posada et al., 2012). Inhis sense if this indicator is above the unity, profit can be expectedy selling the product at its market price (see Table 1). For citronelland all technologies, it can be seen that all are above the unity.

In the case of Lemongrass essential oil (see Table 3), the analysiss very similar to the one shown for Citronella oil. The productionosts fluctuates from 7.50 to 9.70 USD/kg, which are higher thanhose shown for Citronella. This effect is mainly because the pur-hasing price of raw material is higher for Lemongrass (see Table 1).he fully integrated scenario, the production cost is lower becausehe saving potentials on utilities as discussed for the Citronella oilase. Nonetheless, the analysis should be focused on the sale priceo total production cost ratio (Posada et al., 2012) to compare botheedstocks. Despite of a higher production cost for Lemongrass oilall technologies), its sale price/total cost ratio is higher than thosehown for Citronella. In this sense, it can be inferred that the Lemon-rass essential Oil has a higher added value than Citronella oil (seeable 1).

At this point it is also very important to note that all technologiesan be feasible, even when no integration is included. In this sense,his could serve a basis to draw recommendations on the selectionf technologies to extract essential oils. Furthermore, this selectionhould take into account different aspects such as environmentalmpact. This is significantly relevant since all technologies shoulde seen not only from the economics, but also from the environ-ental point of view. The environmental assessment is presented

s follows.

.4. Environmental assessment

The environmental assessment is based on the criteria of thempacts named in the methodology item including the analysisor different technologies and feedstocks. The results of the poten-ial environmental impact per kilogram of product (essential oil)re presented in Fig. 6 for Citronella and Fig. 7 for Lemongrass. Inhe case of Citronella oil (see Fig. 6), the results showed that theriendliest configuration is WDE fully integrated (WDE, Sc. 2), fol-

owed by SFE. Sc. 2. The analysis is very similar to the one presentedn the economic evaluation. In this sense it can be inferred thatnergy consumption affects the environmental impact as it directlyffects the economics. On the other hand, it is shown that the SE

hnologies at different scenarios for Citronella oil.

technologies without and within energy integration, showed thehighest impact. This is due to the solvent selected for the extrac-tion, because the hexane purge affects impacts such as ATP, andPCOP in a most dramatic way than technologies using CO2, andwater. The toxicity of hexane, and its harmful effects significantlyincrease the impact if it is not properly handle at the processinglevel. Therefore, it can be inferred that the potentials affected byenergy are the GWP and the AP. At this point it is very importantto take into account that total environmental impact is the resultof the weighted sum of all categories, and as mentioned in Section2.4 the WAR algorithm is used to compare different process config-urations. Considering this, it can be also seen that SFE can also beconsidered a promising technology due to the similarity to WDE.

Other important aspect to consider in the selection of technolo-gies is the possible impact of traces on the final product. In thecase of SFE, the essential oil can be completely separated from theCO2 at normal conditions. The WDE leads to a very little amount ofwater in the final product because of the insolubility of the Oil in anaqueous phase. Also the water is not considered a substance withhigh environmental potential impact at normal conditions. Againstthis, a technology using solvents would lead to traces in the finalcomposition of the essential oil, which can certainly affect the qual-ity of product. In this way, greener solvents should be proposedor newer technologies following the green engineering and greenchemistry rules (Anastas and Eghbali, 2010; Anastas and Kirchhoff,2002; Lankey and Anastas, 2002), for instance, the use of ionicliquids as green solvents (Arce et al., 2007; Lee, 2011; Yang et al.,2012).

For Lemongrass oil (see Fig. 7), the results are very similar tothose shown for Citronella oil. The friendliest configuration is WDEfor the second scenario (Sc. 2), followed by SFE fully integrated.In the case of SE, the tendency is very similar to the previouslydiscussed for Citronella oil. Nevertheless, it can be seen that theimpact categories are lower than those shown for Lemongrass. Forinstance, the configuration with the highest impact for Citronellaoil is SE without any level of integration (SE, Sc. 1) with an approx-imately value of 0.14 PEI/kg. In the case of Lemongrass oil, thesame technology shows an impact of approximately 0.11 PEI/kg,which difference is significant. At this point, Lemongrass oil can beobtained in a cleaner way than Citronella oil. This is mainly becauseits energy consumption for all technologies is lower and also the

possible saving on energy drives to a lower impact. Another rele-vant issue from the environmental point of view is the solid residueand its handling. For all technologies the solid fraction remainingis not currently used, however it can be sent to other productive

J. Moncada et al. / Industrial Crops and Products 54 (2014) 175–184 183

n technologies at different scenarios for Lemongrass oil.

ppbm(

arkecholavtmitetic

Fe

Fig. 7. Potential environmental impact of extractio

rocess to take advantage of its polysaccharide fraction and obtainlatform chemicals to drive biorefinery products, or a fraction cane used to feed cogeneration systems and cover the energy require-ents of the process and obtain electric power as a new product

Moncada et al., 2013).The analysis also included the equivalent carbon dioxide as

measure of GHG emissions due to external fossil fuel energyequirements. In this sense, this reports the carbon footprint inilograms of equivalent CO2 per kg of essential oil. After this, it isxpected that the carbon footprint will be higher for higher energyonsumption. Nevertheless, it must be considered that only theeating requirement contributes to the carbon footprint. In the casef Citronella (see Fig. 8), it can be seen that the technology with theowest carbon footprint is the WDE and Sc. 2, followed by the SFEnd Sc. 2. It is presented that savings on energy affects the emissionsalue. However, the tendency of each technology is not the same tohose presented in the WAR algorithm (see Fig. 6). For instance, the

ost harmful technology is the WDE without any level of energyntegration. This is because the energy needed to heat the watero its bubble point is higher compared to other processes. A similarffect occurs with the SFE, because the external energy required forhe compression of the CO leads to a higher footprint. Consider-

2ng all of this, it is shown that a heat integration strategy should beonsidered in the design of cleaner processes to avoid emissions.

ig. 8. Carbon footprint due to fossil energy requirements to obtain 1 kg of Citronellassential oil.

Fig. 9. Carbon footprint due to fossil energy requirements to obtain 1 kg of Lemon-grass essential oil.

In the specific case of Lemongrass oil, the tendency of the car-bon footprint is similar to the Citronella case. The highest value isobtained for WDE Sc. 1, while the lowest is obtained for the sametechnology (WDE) fully integrated. In this sense, the analysis iscompletely analogous to that discussed for Citronella. As can beseen in Fig. 9, the carbon footprint values for Lemongrass are lowerin all technologies than Citronella. Thus, it can be inferred that ingeneral the Lemongrass essential oil extraction shows lower envi-ronmental impact, both from the WAR algorithm and the carbonfootprint indicator.

4. Conclusions

The results showed that it is possible to extract essential oilfrom Citronella and Lemongrass as raw materials for different cost-effective technologies. Furthermore, the evaluated technologies arefeasible from the techno-economic point of view. Nonetheless, theeffect of energy integration decreases the production cost of alltechnologies. From the potential environmental point of view themost harmful technology is the solvent extraction using hexanebecause its toxicity. However from the carbon footprint point of

view the most harmful is the extraction by water distillation with-out any level of energy integration. Finally, the most promisingtechnology from the techno-economic and environmental pointsof view is the extraction by water distillation when a full energy

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ntegrated scenario is considered. In this way, energy integrations a promising strategy to add value and decrease the potentialnvironmental impact and GHG emissions on the processing stage.omparing both feedstocks, the Lemongrass is the most promisingne to extract essential oil, since its added value is higher and itsnvironmental impact is slightly lower than Citronella case.

cknowledgment

The authors want to express their gratitude to the National Uni-ersity of Colombia in Manizales for funding this work.

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