Supercritical ﬂuid extraction of spent coffee grounds - Measurement of extraction curves and economic analysis

J. of Supercritical Fluids 86 (2014) 150 159

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Superc ouextract no

Marcelo s, CDepartment of

a r t i c l

Article history:Received 10 JuReceived in re14 December Accepted 16 D

Keywords:Economic anaExtraction curModelingOilSpent coffee groundsSupercritical uid extraction

no-ender

bar anost ccids sion, ere cclud

at all

An economic analysis involving cost of manufacturing (COM) and net income calculations were per-formed for distinct operating conditions and unit arrangements. The optima results were obtained foran arrangement of 3 beds of 1 m3, extraction time of 2.0 h, 300 bar, 50 C and 30 kgCO2 kg

1SCG h

1. Underthese conditions production can reach 454 ton year1, a cost of manufacturing (COM) around 2.4 MD ,and process net income of 56.6 MD . A sensitivity analysis varying the unit capacity, extraction time and

1. Introdu

Accordinan annual crepresents a large volconsequencconsideringare generatture conten

Whethematerial thposal despicontent. In residue andbeen study[2,46]. Furtent up to 2pyrolysis isextractable

CorresponE-mail add

0896-8446/$ http://dx.doi.oprecipitation pressure (extract vessel), showed the process economics to remain viable. 2013 Elsevier B.V. All rights reserved.

ction

g to data from 2011, coffee market in Portugal involvesonsumption of around 50 kton [1]. Considering what itfor nal consumer drinking habits, this value impliesume of waste being generated by food industry ine of processing this raw material. For instance, when

soluble coffee, 24.5 tons of spent coffee grounds (SCG)ed per ton of soluble coffee produced [2,3], with a mois-t around 80% [3].r in domestic or industrial contexts, SCG are a wasteat typically undergoes incineration and landll dis-te its toxicity due to caffeine, tannins and polyphenolsview of minimizing the environmental impact of this

to increase its market protability, researchers haveing SCG features and identifying potential applicationsthermore it has been shown that SCG have an oil con-3.9% [4], and generates a biocrude oil up to 55% if fast

employed [7]. The SCG material comprising the non- residue can be further used as a fuel source through

ding author. Tel.: +351 234401549; fax: +351 234370084.ress: [email protected] (C.M. Silva).

pelletizing, as a fertilizer or even as a feedstock for bioethanolproduction [2,8]. In what concerns the composition of this oil,works may be found in literature aiming at phenolic [9] and diter-penic [10,11] compounds enrichment on its constitution. A veryrecent publication from Ribeiro et al. communicated the promisingpotential of SCG for cosmetic industry after a cream formulationcontaining SCG lipids has conrmed hydration features [6].

The employment of supercritical carbon dioxide (SC-CO2) forthe extraction of vegetable matrices has been widely studied asa green extraction solution aiming at the replacement of conven-tional organic solvents. For instance, in recent publications on thisextraction technology, different raw materials have been studied,like eucalypt [1216] and grape seed [1719], with attention toaspects such as optimization of working conditions [11,14], extractproperties [17] and modeling [12,13,20,21].

In addition, within the last years several works on economicassessments of SFE have been published employing cost of manu-facturing (COM) calculations, following a methodology proposed byTurton et al. [22]. It is the case of SFE of jabuticaba skins [23], Ama-zonian trees [24] and Tabernaemontana catharinensis [25], grapeseed [19], Anacardium occidentale L. [26] and rosemary [27].

Coffee was one the rst raw materials to be processed bysupercritical uid extraction, mainly for decaffeination purposes.It is thus likely that also SCG become matter of this technology,

see front matter 2013 Elsevier B.V. All rights reserved.rg/10.1016/j.supu.2013.12.016ritical uid extraction of spent coffee grion curves, oil characterization and eco

M.R. de Melo, Hugo M.A. Barbosa, Cludia P. Passo Chemistry, CICECO, University of Aveiro, Aveiro 3810-193, Portugal

e i n f o

ly 2013vised form2013ecember 2013

lysisve

a b s t r a c t

This work addresses scientic and techcoffee grounds which are of interest uand SFE curves were measured at 190the triacylglycerides proles were almSoxhlet results: linoleic and palmitic a

The oil solubility, intraparticle diffuone estimated for innite dilution) wconditions under analysis. It was concumulative extraction curves, and thtances./ locate /supf lu

nds: Measurement ofmic analysis

arlos M. Silva

conomic aspects of supercritical uid extraction (SFE) of spentthe biorenery context. Soxhlet experiments were carried outd 40 C/55 C. The extracts were characterized by GC-FID, and

onstant along an extraction curve, and similar to the n-hexanecontent in both extracts are 44.5 and 37.5% (wt.), respectively.convective mass transfer coefcient, and oil removal ux (thisalculated and discussed in detail in the ranges of operatinged that solubility is the chief parameter behind the distinctexperiments are subjected to equivalent mass transfer resis-

M.M.R. de Melo et al. / J. of Supercritical Fluids 86 (2014) 150 159 151

particularly if one takes into account that SFE is already applied toproduce decaffeinated coffee.

In this work, SFE curves of SCG oil are measured, and its compo-sition is analyzed. SFE and Soxhlet extraction results are comparedwith data tpreliminaryperformed operating c(COM) are investigatedupon a sensunit capacitremarks are

2. Experim

2.1. Materi

A fatty aheptadecanUSA). All otavailable p99.95% fromwere of ana

2.2. Sample

Espressovending ma(Portugal). 11294-1993[28].

2.3. Soxhlet

For comwere rstlygrounds wa300 mL of avent was evanalyzed by

2.4. Superc

The SFEunder semiat the Univemay be condrawn fromthen pressuvessel. Themeans of asure is xedseed bed, thThe valves adue to oil ain a separat

In each ethe extractoture varied fconditions aliterature tobelow. It went sources

comparable. Nevertheless they are distinguished as blocks A1, A2(this work) and B1 and B2 (data from [29]).

2.5. Triacylglycerides prole

triam oobtaing tundsose

onom

rdercess

on crvernevai1SCG

inante to

econ2] w]. It ent

ent c rela

0.30

peciices ) calure r

list are btainn 7.3

ults

s sectxhletom lred cre; f thevity a

xhlet

le 3 pion ore fo

ther ome4% tot al. ion yt, usfee bwt.)

extruns,orkaken from the literature in Sections 3.1 and 3.2 and a economic evaluation of the supercritical the process isin Section 3.3 in order to determine the most promisingonditions. Here values for the costs of manufacturingestimated as well as net income and production are. Still in Section 2.3, economic results are also assesseditivity analysis regarding the impact of extraction time,y, and separator pressure on the process viability. Final

presented in Section 4.

ental

als and methods

cids methyl esters (FAME) mix (C8C24) and methyloate ester were purchased from Supelco (Bellefonte, PA,her reagents used were of analytical grade or higherurity. Carbon dioxide was supplied with a purity of

Praxair (Porto, Portugal) and all the other reagentslytical grade or higher available purity.

s and general procedures

spent coffee grounds (SCG) were obtained in a coffeechine from a commercial batch of Delta Cafs PlatinaThe SCG samples were dried according to the ISO/DIS, by the method of oven drying at 105 C during 8 h

extraction

parison purposes an extract of spent coffee grounds obtained by Soxhlet. An amount of 30.4 g of spent coffees placed inside the Soxhlet apparatus and treated withnalytical grade n-hexane for 4 h. At the end the sol-aporated to dryness and the extract was weighed and

GC-FID. The extraction was performed in triplicate.

ritical uid extraction

experiments were carried out with carbon dioxide-continuous operation in an apparatus built/assembledrsity of Aveiro. A detailed description of this equipmentsulted in a previous work [17]. Briey the CO2 with-

a container is rstly liqueed in a refrigerated bath andrized by an air driven liquid pump to a high-pressure

solvent is brought to the extraction temperature by long tubing coil placed inside the oven and the pres-

in a forward pressure regulator. After percolating thee extract stream passes through micrometering valves.nd the adjoining line are heated to prevent blocking upnd CO2 freezing, enabling the safe collection of extractor. At the end extract samples were dried and weighed.xperiment, 60 g of dried raw material was placed insider, the ow rate used was 12 gCO2 min

1, the tempera-rom 40 to 55 C, and a pressure of 190 bar. The operatingre shown in Table 1, along with two runs taken from the

enrich the preliminary economic analysis performedas considered acceptable to combine data from differ-

because the contents of lipids and fatty acid proles are

Thethe suesters accordcompowith th

2.6. Ec

In othe probased that gotion pr(wCO2 wis domow ra

Theet al. [2[3133investmtreatmlowing

COM =By s

rent pr COMdisclos

Theresultswere o(versio

3. Res

Thiour Sodata frmeasuliteratument osensiti

3.1. So

Tabextractliteratuwith osuffer sfrom 1Cruz eextractSoxhlethe cof23.9% (

Thethree rvious wcylglycerides content was determined by GC-FID byf the amounts of the individual fatty acids methylined after transesterication with sodium methoxideo the methodology described by Passos et al. [17]. The

were identied by comparing their retention timesof a commercial FAME mixture (C8C24).

ic analysis

to accomplish a preliminary economic evaluation of viability at industrial scale, lab results were scaled-upiteria that take into account the nature of the limitations the extraction process [30]: when solubility limita-ls, the ratio of mass of solvent to mass of raw material) shall be kept constant, but if a diffusional mechanismt the ratio to be held constant is the quotient of solvent

mass of feed.omic analysis was based on the methodology of Turtonhich has been used by other authors for SFE processessets the cost of manufacturing (COM) as a function of

cost (FCI), labor cost (COL), utility cost (CUT), wasteost (CWT) and raw material cost (CRM), using the fol-tion:

4 FCI + 2.73 COL + 1.23 (CUT + CWT + CRM) (1)fying a market value for the extracted oil based on cur-of coffee oil, revenue and a net income (annual revenueculations were also accomplished, which lead to a trueegarding the economy of the SFE process.of assumptions that support our economic assessmentpresented in Table 2. All data regarding utilities costsed from simulations of the SFE process in Aspen Plus

).

and discussion

ion is divided in three subsections: Section 3.1 presents extraction results and establishes a comparison withiterature; Section 3.2 is devoted to the SFE, where theurves are also analyzed and compared with results fromthe third subsection comprises the economic assess-

most promising results from Section 3.2, followed by analysis.

extraction

resents the Soxhlet results obtained in this assay for thef SCG with n-hexane, along with others reported in ther the same system. By comparing the obtained valuesequivalent works it is noticeable that the oil yields can

variation depending on the samples employed, ranging 18% (wt.). This observation has been also reported by

[4] who analyzed and compared the composition andield of SCG oil obtained from 13 coffee brands through

ing petroleum ether. They showed that, depending onrand, the total soluble solids could range from 18.2% to.action yield determined in this essay, as an average of

is 15.0% (wt.) and lies within the values found in pre-s for this raw material (see Table 3) [29,39,40]. In what

152 M.M.R. de Melo et al. / J. of Supercritical Fluids 86 (2014) 150 159

Table 1Operating conditions of the experiments performed in this work and taken from literature for comparison purposes.

wSCG (g) QCO2 (g min1) QCO2 w

1SCG (h

1) P (bar) T (C) Ref.

Run A1 60 12 12 190 40 This workRun A2 60 12 12 190 55 This workRun B1 20 10 30 200 50 [29]Run B2 20 10 30 300 50 [29]

Table 2List of assumptions of the economic analysis of the SFE of spent coffee grounds (SCG).

General - Unit working period: 24 h per day, 330 days per year.- Number of workers per extractor = 1.- Scale-up criterion: solvent ow rate per mass of SCG in theextractor (QCO2 w

1SCG)

- Minimum pressure in the separator (extract collectionv--(-o----vc--

FCI --(b(c(c

COL -

CUT --

CWT -

CRM --

concerns faues publish37.37% agaabundant faa share of 4palmitic aci

3.2. Superc

Fig. 1 pr190 bar/55

the Soxhlet

cumulative curves from Couto et al. [29] are also represented forcomparison. In general all curves exhibit the typical trend found inthe SFE of edible oils, i.e. a constant period of extraction followed bya second diffusional period. In this work, the registered curvaturesevidence kinetic limitations to mass transfer, particularly in RunsA1, A2, B1.

Considering that pressure, ow rate, and mass of SCG beded cperfoC). Itses oundsoppore anvity elm resulyzed

oil s

Table 3Fatty acids pro

Fatty acid

Palmitic Stearic Oleic Linoleic -Linoleic Arachidic

Total extractessel) = 45 bar. Required time to unload, load and pressurize 1 extractor (tprep): 1 h Whenever the extraction time is inferior to the preparation timet < tprep = 1 h), the unit is switched off.

The CO2 losses in each full decompression correspond to the massf CO2 inside the extractor at 45 bar and 40 C.

SCG bed density = 400 kg m3. SCG bed porosity = 0.8. Exchange ratio D /$US (on May 2013) = 0.766 Market price of coffee oil = 130 D kg1 [34] (in ref. [35], a largealue of 194 D kg1 is reported. We adopted the lower one for aonservative analysis of the process.)

SCG initial moisture = 60.7% (wt) [36] Dried SCG heat capacity = 1.434 kJ kg1 C1 [37]

remainferent vs. 55

procescomponamic pressudiffusiin the uxes is anal

The

Annual depreciation rate = 10% SFE units prices:i) 1.5 MD for a unit comprising two 0.4 m3 extractors as presentedy Rosa et al. [32];ii) 2.3 MD for a three-extractors unit each with 0.4 m3 of capacity,alculated by the expression proposed by Lack et al. [38];iii) 3.2 MD for a three-extractors unit each with 1.0 m3 of capacity,alculated by the expression proposed by Lack et al. [38].

Labor cost = 10 D h1 worker1

Cost of electricity = 50 D MWh1 Cost of steam = 1.53 D ton1

Cost of waste treatment = 0 D

Cost of spent coffee grounds drying = 0.016 D kg1SCG Cost of CO2 = 800 D ton1

tty acids proles, the obtained results fall below the val-ed by Couto et al. [29], particularly for palmitic acid,inst 46.22% (wt.) (Table 3). For this reason, the mosttty acid found in our SCG samples is linoleic acid, with4.67% (wt.), while in the case of the referred authorsd was the most representative.

ritical uid extraction

esents the SFE curves measured at 190 bar/40 C andC plotted against time. The results are normalized by

extraction yield and graphed as function of time. The

of del ValleSC-CO2 den

ys = 10.724

where densand Schreibconvective correlation

Sh = 2.0 + 1

Here the vAltunin an(cm2 s1) othe very sim

D12 = t(

a

1

where T ia = 6.34288ties inside account thFinally, thepredicted ai.e.:

Noil = kf CO

le of the extracted oil obtained by Soxhlet with n-hexane.

This work Couto et

C16:0 (wt. %) 37.37 46.22 C18:0 (wt. %) 7.07 6.87 C18:1 (wt. %) 8.31 8.63 C18:2 (wt. %) 44.67 34.36 C18:3 (wt. %) 1.42 1.39C20:0 (wt. %) 1.16 2.53

ion yield (kgSCG oil 100 kg1SCG) 15.0 18.3 onstant in our experiments (Runs A1 and A2), the dif-rmances are due to the inuence of temperature (40 C

is known that this variable is usually important in SFEwing to its impact on the solubility and diffusivity of. Any increase in temperature generates two thermody-sing effects the positive inuence upon solute vapord negative impact on CO2 density and also an effectivenhancement inside the particle. The external diffusionmay evidence a more complex dependence. The solutet obviously from the combination of these factors as it

in detail in the following.olubility (kg m3) can be estimated by the correlation

and Aguilera [41] as function of temperature (K) andsity (kg m3) by:

exp(

18708T

+ 2186840T2

+ 40.361)

(2)

ity can be computed by the accurate equation of Pitzerer [42]. The increment (over the same reference) of themass transfer coefcient (kf) can be estimated by the

of Wakao and Funazkri [43]:

.1Re0.6Sc1/3 (3)

iscosity of SC-CO2 was obtained by the equation ofd Sakhabetdinov [44], and the diffusion coefcientf triolein (taken as model molecule) was estimated byple and accurate model of Magalhes et al. [45]:

+ b)

(4)

s in K, viscosity in cP, and triolein constants are 109 and b = 4.89262 108. The effective diffusivi-the biomass particles may be estimated taking intoeir porosity () and tortuosity () by Deff = D12 /.

oil ux from the matrix to the supercritical bulk can bes a rst approximation by its value at innite dilution,

2 (ys 0) (5)

al. [29] Calixto et al. [39] Al-Hamamre et al. [40]

14.0 15.3


Fig. 1. SFE curves of spent coffee grounds (SCG) oil at different pressu

Fig. 2. Normalized (a) oil solubility computed by the expression proposed by delValle and Aguilera [41], and (b) intraparticle effective diffusivities calculated by thecorrelation of Magalhes et al. [45], as functions of temperature and pressure.

In Figs. 2tive intrapaand oil uxthe inuenvariable, th190 bar/55the enhancequantities cin this essa

From FiB2 in compof pressureA1 Run Bics inside tinternal limexperimentvariation = 0Deff is: Runmalized confollowing bglobal variaplotted in Fsince Run AAs a result,is the solubthe uxes. Mexternal limFig. 1 will b

Coming A1) to 55

the processcomparisonprogressiveof the extraattained weffect of temgreat agreeshown in Fsates the ne(confront F

The nato the valueOn the othehigher (medisagrees winto accounfarther fromres and temperatures (see Table 1).

and 3 the calculated results for the oil solubility, effec-rticle diffusivity, convective mass transfer coefcient,

at innite dilution are plotted. In order to evaluatece of the operating conditions upon each dependentey are represented normalized by the same quantity atC (Run A2), giving readers the opportunity to capturements over the reference values. In the case of Fig. 2, theorresponding to the experimental runs under analysisy are superimposed.g. 2a it is evident that solubility favors largely Runarison to Runs A1, A2 and B1, due to the chief effect; the ys values increase like Run A2 < Run B1 < Run2 (global variation = 3.43). On the other hand, the kinet-he particles disclosed in Fig. 2b emphasize that theitations to mass transfer are equally important in alls, since there is not any major diffusivity jump (global.08); however the increasing sequence of normalized

A1 < Run B2 < Run B1 < Run A2. In terms of the nor-vective mass transfer coefcient, Fig. 3a points out the

ehavior: Run A1 < Run A2 Run B2 < Run B1, though thetion is 0.25. Finally, the oil uxes at innite dilutionig. 3b detach once again the importance of the pressure,2 < Run A1 Run B1 Run B2 (global variation = 2.96).

the distinguishing factor behind the four experimentsility enhancement observed which affects signicantlyoreover all runs are equally affected by internal and/oritations to mass transfer. The experimental results of

e now analyzed on the light of these principles.back to Fig. 1, a temperature increase from 40 C (RunC (Run A2) at 190 bar penalized the performance of, since the rate of extraction at 55 C was delayed in

to the results at 40 C. While Run A1 yields increasedly until reaching 73% of Soxhlet value, within the 7.2 h

ction curve at 190 bar/55 C (Run A2), the highest yieldas 61%. These two assays denote a counterproductive

perature for the process at this pressure, which is inment with the indicative N

iresults for the two runs

ig. 3b. In this case, the solubility increment compen-gative effects of the internal and external mass transferig. 2a with Figs. 2b and 3a).l yield achieved on Run A1 (190 bar/40 C) is comparable

obtained by Couto et al. [29] on Run B1, at 200 bar/50 C.r hand the extraction velocity from these authors is 60%asured by the slopes at short times), which apparentlyith the N

itrend suggested in Fig. 3b. However taking

t that the space time of Run B1 is 40% of Run A1, we are the innite dilute conditions, which means that the


Fig. 3. (a) Nordilute solution

real ux in A1 and B1 i

When copressure co3, the oil re1 h of extracin the yieldinuence ofthe higher oOnce againthe transpo

3.3. Triacyl

The fattsupercriticamined and ithe sampleslowed by oacids prese(C20:0) acidation betweand that of Sis also in gmalized convective mass transfer coefcient calculated by the correlation of Puiggen ets.

our case is inferior. This fact justies the slit of curvesn Fig. 1.nsidering the extraction curve 4 obtained at a harderndition (300 bar) but same temperature (50 C) of Runmoval rate is visibly increased (3.6 times). In fact aftertion the curve has already achieved a nearly at region

ratios range of 7882%. Such evidence unveils the great pressure upon this SFE process, which is conrmed byil uxes estimated by N

i(see Fig. 3b): 1.62 versus 3.96.

the milestone effect is the solubility (see Fig. 2a) sincert limitations are similar (see Figs. 2b and 3a).

glycerides prole

y acids prole along time of the SCG oil obtained byl extraction in Run A2 (190 bar/55 C) has been deter-s represented in Fig. 4. The main fatty acids present in all

are linoleic acid (C18:2) and palmitic acid (C16:0), fol-leic acid (C18:1) and stearic acid (C18:0). Other minornt in the extracts are linolenic (C18:3), and arachidics. Furthermore, Fig. 4 shows that there is a small vari-en the composition of individual supercritical extractsoxhlet. The global oil obtained by joining all SC extractsood agreement with our Soxhlet and those reported

in the literSoxhlet andsame amouthe data. Inprole is inroasted), mextraction

Fig. 4. Fatty acritical extract al. [46], and (b) normalized oil removal uxes in the limit of innite

ature for SCG [4,29] (see Table 4). In this work, both supercritical experiments were performed using thent of SCG, which explains the high correlation between

general, literature results show that the fatty acidsdependent of the raw material treatment (green vs.

ethod of preparation (coffee brew vs. ltration), and alsomethod (Soxhlet vs. supercritical CO2). The maximum

cids prole of Soxhlet extracted SCG oil, and of the individual super-s E1E5 obtained at 190 bar/55 C (Run A2 of Table 1 and Fig. 1).


Table 4Extraction yields and fatty acids proles obtained in this work and taken from literature. Data for SFE and Soxhlet extraction.

Composition This work Couto et al. [29] Cruz et al. [4]

Soxhlet (n-hexane) SFE (Run A2) Soxhlet (n-hexane) SFE (Run B1) Soxhlet (petroleum ether)

C16:0 37.37 37.48 46.22 36.19 32.8C18:0 7.07 6.02 6.87 7.59 7.1C18:1 8.31 9.53 8.63 11.24 10.3C18:2 44.67 44.52 34.36 41.45 44.2C18:3 1.42 0.99 1.39 0.86 1.5C20:0 1.16 1.46 2.53 2.68 2.6

(%) 15.0 18.3 12.5

yield of SCG oil obtained was 15.0% of the SCG (dry weight) whichis slightly lower when compared to Couto et al. [29] but higherwhen compared to Cruz et al. [4], all within an acceptable range.

3.4. Economic analysis

3.4.1. Selection of extraction curves and extraction timesIn view of the objective to perform an economic evaluation of

this SFE proon the normwere choseTable 1 and

To perfotion time sof this variawhen an exthrough thicosts are asition fromby externalparticle diffby the inteFig. 5). The 190 bar/40

3.4.2. EconoThe econ

data of Fig.extraction t

A SFE unchosen to cconsidered facturing (Ceach circumthere are si

Fig. 5. SFE curand determina

lower pressure case (190 bar/40 C, Run A1) leads to a COM of642 kD year1, at 300 bar and 50 C it reaches 951 kD year1. Tobetter understand the nature of these very distinct COM values,Fig. 7 provides the partition of COM values in their respective frac-tions, namely, investment (FCI), labor (COL), utility (CUT), wastetreatment (CWT), and raw material (CRM) costs see Eq. (1).

While FCI + COL absolute costs are exactly the same in both cases,(the SFE unit and the work load is the same), the CUT + CRM parcelsincrease signicantly, passing from 25% of COM in Run A1 to 50% of

Run B2. Such increase is a direct consequence of the severerions of pressure (300 bar) and temperature (50 C), and ofher number of batches being processed annually in view ofrterher eps wr extUT) aal (Che ecould procas sins. Ach caanc

alues300 br, it areebser

bar, 5nd t cess, the selection of the operating conditions was basedalized cumulative curves of Fig. 1. Runs A1 and B2

n for this purpose: 190 bar/40 C and 300 bar/50 C (see Fig. 1).rm the comparative economic evaluation, the extrac-hould be held constant in each case. The specicationble is very important because it denes the momenttracted bed should be replaced by a virgin one, and

s denition aspect like utilities, SCG processed or energylso affected. In this essay it corresponds to the tran-

the period when process is being mostly controlled mass transfer limitations and the period when intra-usion starts to be dominant, which can be determinedrsection of the straight lines tting both regimes (seetimes obtained are 0.7 h and 3.8 h for 300 bar/50 C andC runs, respectively.

mic evaluationomic assessment of the SFE of the SCG oil based on the

5, Tables 1 and 2 was accomplished after tting theime.it comprising two 0.4 m3 extractors (see Table 2) wasompare the performances of the two SFE conditions(Runs A1 and B2). Fig. 6 presents the cost of manu-OM) and the annual SCG oil production expected instance. In what concerns COM, it may be observed

gnicant differences between the two cases. While the

COM inconditthe higthe shothe higsion stshortetion (Cmateri

If tone wlower ology procesfor eacperformCOM vtions (greatewhich tages oat 30040 C aves of spent coffee grounds (SCG) for experiments A1 and B2 of Table 1,tion of their extraction times.

Fig. 6. Cost ofparallel, at 190

t = 0.7 h, QCO2 w extraction time (0.7 h). The more the batches processedthe amount of CO2 that is lost due to full decompres-hich increases of the make-up costs of CO2. Moreover,

raction cycles also imply higher costs of repressuriza-nd, also, a higher cost regarding the drying of the raw

UT).onomic assessment was based only on COM values,be tempted to opt toward the situation that leads toess costs. This is the drawback of using this method-gle tool to evaluate the economic attractiveness of a

cordingly, if productivities are also taken into accountse, one may disclose that the differences between thees of the two cases are even greater than those of the, as shown in Fig. 6. While SFE case with severer condi-ar/50 C/30 kgCO2 kg

1SCG h

1) lead to a COM 1.5 timeslso leads to an annual production 4.1 times greater,

cts the great impact of the higher extraction rate advan-ved in Fig. 5. As a result, the expected annual production0 C and t = 0.7 h is 176 ton of SCG oil, while at 190 bar,

= 3.8 h, it is set on 43 ton. Furthermore if the COM and manufacturing (COM) and oil production for two 0.4 m3 extractors in bar, 40 C, t = 3.8 h, QCO2 w

1SCG = 12 kgCO2 kg

1SCG h

1, and 300 bar, 50 C,1SCG = 30 kgCO2 kg

1SCG h

1, respectively.


Fig. 7. Parcels (%) of the COM values (see Eq. (1)) for the SFE units working at 190 bar, 40 C, t = 3.8 h, QCO2 w1SCG = 12 kgCO2 kg

1SCG h

1 and 300 bar, 50 C, t = 0.7 h, QCO2 w1SCG =

30 kgCO2 kg1SCG h

1, respectively. In both cases there are two extractors of 0.4 m3 working in parallel.

production results are combined in terms of a net income calcu-lation, which is shown in Fig. 8, economic viability can be fullyunveiled. Nitive econom(300 bar, 50less producstress that ported by tvalue of SCGharder extr

3.4.3. SensiIt is wort

behave whemore, if theequipment,respondingmay be meawhich largeously discu

Fig. 8. Net Int = 3.8 h, QCO230 kgCO2 kg

1SCG

the best cas50 C and Q

9 prthreef extrstmee proases,easer anond

max)

tprepd, loa

the ibute

illusig. 1t is evr maotwithstanding the fact that the two cases lead to a pos-ic viability, the choice upon the fastest extraction case

C, t = 0.7 h) represents 4.4 times the net income of thetive case, reaching 21.9 MD year1. It is worthwhile toin this case the viability of the process is highly sup-he larger productivity in view of the high commercial

oil, which thus pay the higher costs resulting from theaction conditions implied.

tivity analysis: extraction time and SFE unit capacityhwhile to check how COM, productivity and net incomen some chief process parameters are changed. Further-

SFE unit layout is changed, the conjugation of different raw material, labor and utilities costs with the cor-

variations on productivity and thus product revenuesningfully different. The same is true for extraction time,ly inuences the overall process net income, as previ-ssed. The sensitivity analysis of this section is based on

Fig.of the time oof invesent thin all cto decrtors. Focorresp

t (COM

where(unloadue tois attriclearly

In Ftime. Ias theicome for two 0.4 m3 extractors in parallel at 190 bar, 40 C,w1SCG = 12 kgCO2 kg

1SCG h

1, and 300 bar, 50 C, t = 0.7 h, QCO2 w1SCG =

h1, respectively.

Fig. 9. Cost ofextraction timfor different Se studied before, namely SFE extraction curve at 300 bar,CO2 w

1SCG = 30 kgCO2 kg1SCG h

1 (Run B2).esents COM as a function of extraction time for each

SFE unit congurations referred in Table 2. Values foraction equal to zero are provided to disclose the impactnt (FCI) and operational labor (COL) costs, which repre-cess xed costs. The COM values exhibit a similar trend

namely, they increase up to a maximum and then start: the maxima are 2 h for 3 extractors and 1 h for 2 extrac-

arrangement of N extractors in parallel, such maxima to:

= (N 1) tprep (6)is the time required for the preparation of an extractord and pressurization). The growing sections of Fig. 9 arencrement of utilities cost (CUT) while their diminishingd to the fall of CRM. Without loss of generality, this istrated in Fig. 10 for the case of 3 extractors of 1 m3.1 the SCG oil production is plotted against extractionident the differences found for the three arrangements,xima lie between 177 and 454 ton year1. However, the manufacturing (COM) of spent coffee grounds (SCG) oil as function ofe per cycle, at 300 bar, 50 C, QCO2 w

1SCG = 30 kgCO2 kg

1SCG h

1 (Run B2),FE unit congurations.


Fig. 10. Utility (CUT) and raw material (CRM) costs against extraction time for theSFE of spent coffee grounds (SCG) oil at 300 bar, 50 C, QCO2 w

1SCG = 30 kgCO2 kg

1SCG h

1

(Run B2) for unit layout comprising 3 extractors of 1 m3 in parallel.

Fig. 11. Annuatime, at 300 bacongurations

most signi2 0.4 m3 ain this peritprep = 1 h.

The net extraction t

Fig. 12. Net itime, at 300 bacongurations

Fig. 13. Variapressure (refe

30 kgCO2 kg1SCG

149.4 and 171

assumptiontime and lais quite simthe expecte

risonum

2 h, xtrac

(timax), compamaximand t =for 2 et = 0.7 h(COMml production of spent coffee grounds (SCG) oil as function of extractionr, 50 C, QCO2 w

1SCG = 30 kgCO2 kg

1SCG h

1 (Run B2), for different SFE unit.

cant feature is the overlapping of the 3 0.4 m3 andrrangements for extraction times lower than 1 h, sinceod the process is controlled by the preparation time,

income values are presented in Fig. 12 as function ofime for the different SFE unit arrangement. Given all the

ncome of spent coffee grounds (SCG) oil as function of extractionr, 50 C, QCO2 w

1SCG = 30 kgCO2 kg

1SCG h

1 (Run B2), for different SFE unit.

it decreases

3.4.4. SensiBesides

parameter separator wCO2 that isheating andin Fig. 13 fot and QCO2 w

and 30 kgCOwas varied tant withnonlinear vthe pressurreduced 3.4relies in thfull decompto pressurizobservable CO2 penalizsavings redused in the18.2% higheoperates atvariable is i

4. Conclus

The supeoil was studferent condeconomic athe literatution of cost of manufacturing (COM) as function of the separatorrence =45 bar). Data for SFE at 300 bar, 50 C, t = 0.7 h, QCO2 w

1SCG =

h1 (Run B2). The corresponding densities are 83.9, 97.8, 113.2, 130.2,.6 kg m3.

s of Table 2, the net income is positive for any extractionyout considered. The shape of the net income prolesilar to the annual production proles (Fig. 11), becaused revenues from the produced oil are rather high in

to the respective costs of manufacturing (COM). Thevalues for each unit are 56 MD for 3 extractors of 1 m322 MD for 3 extractors of 0.4 m3 and t = 2 h, and 22 MDtors of 0.4 m3 and t = 1 h. Within the interval betweene established from extraction curve see Fig. 5) and t

the net income prole slightly increases, while outside sharply instead.

tivity analysis: minimum pressure of the systemtime and extractors arrangement, another workingthat also affects COM is the minimum pressure in thehere the extract precipitates, by means of the mass of

lost in each batch and through the energy needed for cooling. In this respect, a sensitivity analysis is providedr an arrangement of 2 extractors with 0.4 m3, where P, T,

1SCG conditions were held constant (300 bar, 50

C, 0.7 h

2kg1SCG h

1, respectively) while the separator pressurefrom 40 to 65 bar. The effect upon COM is very impor-

variations between 3.4 to +18.2% and it reects theariation of CO2 density with pressure. Furthermore, ife in the separator is decreased to 40 bar, COM value is%, a substantial saving. The implication of this resulte balance between the less CO2 that is lost in every

ression to atmospheric pressure, and utilities necessarye the unit to 300 bar. Considering the increasing trendin Fig. 13, results show that the impact of losing morees more the COM value than the corresponding energyuce its value. In addition, if 65 bar rather than 45 bar are

separator, the system will lead to a COM value that isr. If one takes into account that 25 bar in a process that

300 bar may seem inoffensive, results reveal that suchn fact quite inuential in the nal costs.

ions

rcritical uid extraction of spent coffee grounds (SCG)ied in this work by measuring extraction curves at dif-itions, followed by oil characterization, modeling andnalysis. Results were deeply compared with data fromre. Under the range of experimental conditions covered,


the nal extraction yields lie within 0.610.81 of n-hexane Soxhletvalues.

The obtained SFE oils are rich in linoleic and palmitic acids (44.5and 37.5%) with proles comparable to Soxhlet results (44.7 and37.4%) and ture. Moreothe supercr

A prelimfrom the 300 bar/50operating considered.like 0439If extraction2.4 MD yearwhich is a v

Throughdenition oon COM valead to a CO

Acknowled

AuthorsC/CTM/LA0

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Supercritical fluid extraction of spent coffee grounds: Measurement of extraction curves, oil characterization and economi...1 Introduction2 Experimental2.1 Materials and methods2.2 Samples and general procedures2.3 Soxhlet extraction2.4 Supercritical fluid extraction2.5 Triacylglycerides profile2.6 Economic analysis

3 Results and discussion3.1 Soxhlet extraction3.2 Supercritical fluid extraction3.3 Triacylglycerides profile3.4 Economic analysis3.4.1 Selection of extraction curves and extraction times3.4.2 Economic evaluation3.4.3 Sensitivity analysis: extraction time and SFE unit capacity3.4.4 Sensitivity analysis: minimum pressure of the system

4 ConclusionsAcknowledgementReferences

Documents

Supercritical ﬂuid extraction of spent coffee grounds - Measurement of extraction curves and economic analysis