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Techno-economic and life-cycle assessment of volatile oil extracted from Aquilaria sinensis using supercritical carbon dioxide
Journal of CO₂ Utilization 38 (2020) 158–167
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Techno-economic and life-cycle assessment of volatile oil extracted from Aquilaria sinensis using supercritical carbon dioxide
T
Yong Ling Gweea,b, Suzana Yusupa,b,*, Raymond R. Tanc, Chung Loong Yiind a
HiCoE, Biomass Processing Cluster, Centre for Biofuel and Biochemical Research, Institute of Sustainable Building, Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak, Malaysia b Chemical Engineering Department, Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak, Malaysia c Chemical Engineering Department, De La Salle University, 2401 Taft Avenue, 0922 Manila, Philippines d Chemical Engineering Department, Faculty of Engineering, Computing and Science, Swinburne University of Technology, Jalan Simpang Tiga, 93350, Kuching, Sarawak, Malaysia
A R T I C LE I N FO
A B S T R A C T
Keywords: Total capital investment Operating cost Profits Environmental impact Technology readiness level
Extracts of Aquilaria sinensis possess pharmacological activity that has been widely used in traditional medicines since ancient times. In this study, techno-economic assessment was conducted for extraction of volatile oil from abundant biomass (lignified ring) and resin of A. sinensis to evaluate their respective economic feasibility using supercritical carbon dioxide (SC-CO2) extraction in Malaysia. The assessment revealed that for a production capacity of 5280 kg/y volatile oil, the total capital investment (TCI) was $ 7.11 million from summation of fixed capital cost and working capital. In terms of operating expenditure (OPEX), the volatile oil extracted from resin and lignified ring of A. sinensis required $ 81.96 million and $ 52.39 million, respectively. The selling price of volatile oil from resin and lignified ring were estimated to be $ 0.025 million/kg and $ 0.0125 million/kg, respectively. Both volatile oil extracted from resin and lignified ring showed a positive net profit which indicated their profitability. In addition, a cradle-to-gate analysis of life-cycle assessment (LCA) was performed, whereby the extraction process contributed the highest impact towards the environment due to its high energy consumption. Nevertheless, this study estimated that the process might reduce the environmental impacts by approximately 90% when the technology readiness levels (TRLs) reach the level of 9–10. These findings are beneficial in providing preliminary insights in terms of economic and environmental aspects for volatile oil extraction using SC-CO2 technology.
1. Introduction The genus of Aquilaria species which is classified under plant family of Thymelaeaceae consists of resinous heartwood known as agarwood or gaharu. The term gaharu refers to the dark, dense and fragrant resinous wood located at the inner part of stem and branch of Aquilaria trees. It possesses pharmacological function and biological activity which has been used widely for medicines, perfumes and incenses. The stem of Aquilaria trees consists of resin that has unique balsamic notes and comprises of useful ingredients for perfumery which can be extracted as volatile oil [1]. For instance, many literatures have reported on pharmaceutical benefits of resin such as anti-inflammatory, anti-toxic, sedative, laxative and treatment in digestive, respiratory and nervous systems characteristics [2,3]. The lignified ring which is the outer layer of the resin comprises of a major portion from Aquilaria trees is
scrapped off in order to obtain resin that located at the inner part of the stem bark. It is usually disposed by the agriculturists after obtained the resin which indirectly contributed to the amount of wood waste. About 4.5 million t/y of wood waste is generated globally [4]. Thus, utilization of the lignified ring for the extraction of volatile oil with potential beneficial compounds has high novelty in generating wealth from biomass. Owning to high market value of volatile oil, the selection of extraction method and well-designed process are necessary to obtain maximum yield of the volatile oil. The most common extraction techniques comprise of Soxhlet extraction and hydrodistillation. Soxhlet extraction requires organic solvent leading to disadvantages, such as cost of high purity, toxicity, and residue in the extracts which could potentially affect the environment and human health. At industrial scale, hydrodistillation extraction is usually applied to extract volatile
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Corresponding author at: Chemical Engineering Department, Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak, Malaysia. E-mail addresses: [email protected] (Y.L. Gwee), [email protected] (S. Yusup), [email protected] (R.R. Tan), [email protected] (C.L. Yiin). https://doi.org/10.1016/j.jcou.2020.01.002 Received 27 February 2019; Received in revised form 23 December 2019; Accepted 3 January 2020 2212-9820/ © 2020 Elsevier Ltd. All rights reserved.
Journal of CO₂ Utilization 38 (2020) 158–167
Y.L. Gwee, et al.
oil from Aquilaria species. This method requires pre-treatment process whereby the sample is soaked in distilled water for approximately 7–14 days before extraction for maximum oil yield [5]. Besides, high temperature is involved during the extraction. There is a potential for a loss or degradation of some specific compounds, especially heat-sensitive compounds by thermal or hydrolysis effects which consequently impaired the quality of extracted volatile oil [6]. Sulaiman et al. [7] reported that the maximum extraction yield obtained was 0.18% at 72 h of extraction time using hydrodistillation method which showed low extraction efficiency and high energy consumption. With their respective shortcomings, the development of new separation technique for the chemical industries has gained a great attention due to the environment restriction and lower energy costs [8]. SC-CO2 extraction is one of the most promising methods due to its numerous advantages compared with conventional methods [9]. For example, hydrodistillation requires 72 h of extraction time and process temperature of 85 °C, with only 0.075% w/w of oil yield. In contrast, SC-CO2 extraction requires lower operating temperature (40–50 °C) and shorter extraction time (30–60 min) with higher oil yield of 3.66% w/w [10,11]. Besides, SC-CO2 extraction does not require extra steps of separation as CO2 is in gaseous state at room temperature and atmospheric pressure. The lower operating temperature is another advantage of SC-CO2 extraction whereby the degradation of bioactive compounds in the extracts can be avoided. In addition, the density of the CO2 can also be easily varied along with the pressure or temperature which is closely related to the solubility and solvent power. This feature is useful to obtain the specific yield and compounds. As discussed herein, this work aims to investigate the extraction of volatile oil from A. sinensis at industrial scale. Moncada et al. [12] had studied on the economic and environment point of view for extraction methods such as supercritical fluid, water and solvent distillation by using Rosemary and Oregano as raw materials. It was reported that supercritical fluid extraction (SFE) is the most profitable technology for Oregano oil extraction at $ 6.71/kg with full energy interaction. Besides, Aguiar et al. [13] had conducted economic analysis of oleoresin production from malagueta peppers through SCCO2 extraction and discovered this technology is economically feasible with estimated commercialization price of $ 223/kg. The SC-CO2 provides a higher oil yield with shorter extraction time and no separation of solvent and extracts is needed. From the aspects of life-cycle assessment (LCA), CO2 is categorized as a generally recognized as safe (GRAS) solvent. This could potentially aid the SC-CO2 extraction process to be a more environmental benign appealing option. Meizoso et al. [14] had studied on the green pilot-scale extraction processes such as pressurized hot water extraction and SFE. The result revealed that SFE process has lower environmental impacts of 23.64 kg CO2 eq. compared to pressurized hot water extraction with 63.89 kg CO2 eq. Moreover, De Marco et al. [15] reported that agricultural stage has contributed to higher environmental impact than SC-CO2 extraction process in extracting caffeine from coffee bean in terms of ozone depletion with a value of 2.94 × 10−7 and 1.59 × 10−7, respectively. However, to the extent of authors’ knowledge, this is the first attempt to evaluate the economic feasibility and LCA of SC-CO2 extraction of volatile oil from A. sinensis. Thus, the goal of this study was to produce a techno-economic analysis on the feasibility of SC-CO2 extraction in estimating the capital cost, operating cost, profits and revenue. In addition, LCA of volatile oil extraction was also performed to gauge its environmental impact. This study is vital in providing new insights on the economic potential of volatile oil extracted from lignified ring for scale up process.
Fig. 1. Response surface plots for the effects of (a) pressure and temperature; (b) CO2 flow rate and temperature; (c) CO2 flow rate and pressure.
years of plant operation. The optimum operating condition was obtained by using Response Surface Methodology (RSM) approach. Fig. 1 shows the response surface plots for the effect of temperature, pressure and CO2 flow rate towards the volatile oil yield. Based on the numerical optimization tool, the ideal condition to achieve maximum volatile oil yield was at 60 °C, 35 MPa and 8.5 mL/min of CO2 flow rate under 60 min of extraction time.The characterization of extracted volatile oil indicated that 2-(phenethyl-4H) chromones and 10-methylanthracene9-carboxaldehyde with composition of 52.74% and 29.67% are the main compounds responsible for the quality of oil from resin and lignified ring, respectively. Based on the laboratory scaled tests, 0.005 g of volatile oil was extracted from 1.4 g of feedstock. For scale up purposes, the amount of feedstock and CO2 required to extract 1 kg of volatile oil were scaled up evenly due to scarcity of available industrial data. According to the calculation, a total of 280 kg of feedstock and 476 L/min of CO2 flow rate were required to extract 1 kg of volatile oil per cycle. Aspen Plus (version 10.0) was used to simulate the extraction process at larger scale and GaBi LCA software (version 8.1.0.29) was used to evaluate the environmental impacts for each breakdown stages of the extraction process based on the inputs of energy consumption at respective stages.
2. Materials and methods In this section, techno-economic assessment and LCA were performed to evaluate the economic and environmental feasibility of SCCO2 extraction plant in extracting volatile oil from A. sinensis over 15 159
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Fig. 2. Process flow diagram of SC-CO2 extraction process.
30 days are scheduled for plant maintenance [19]. The CAPEX includes all the required cost for the plant facilities such as fixed capital investment (FCI) and working capital. FCI is the cost required for the installation of the unit operation. It is divided into two sections which are direct costs and indirect costs. Direct costs include the cost of purchased equipment, installation of the equipment, cost of piping, cost of electrical system, instrumentation and building and service facilities. Indirect costs comprise of cost of engineering and supervision, legal expenses, construction expenses, contractor’s fees and contingency. In this study, the direct and indirect costs of the plant are calculated based on the solid fluid processing plant. A ratio factors of 3.15 was applied across the purchased cost equipment for physical plant cost, while the fixed capital investment was obtained using a factor of 1.40 across the physical plant cost [20]. Any additional investment required to start up the plant that excluded FCI is classified under working capital. The working capital cost is typically around 10–20% of the FCI [20,21]. Total capital investment (TCI) was calculated through the summation of the total cost for FCI and working capital. For the estimation of OPEX for the process plant, it can be divided into variable and fixed costs as tabulated in Table 1. Variable costs varied according to the production rate. It increased with higher production rate and decreased when production rate was lower [22]. The variable costs include the cost of raw materials, utilities, waste treatment and shipping. In this case study, resin and lignified ring of A. sinensis were utilized for comparison study with CO2 gases as extracting solvent and ethylene glycerol as refrigerant in cooling the CO2. The electricity consumption for each individual equipment was obtained through the simulation data from Aspen Plus. Steam was utilized as the heating medium in the heat exchanger. The cost of waste treatment was neglected for SC-CO2 extraction process because the residue is a dry solid wood that may be incorporated into the soil as it does not contain any residue of toxic solvents [23] and can be reused for paper production or as fuel. In addition, the CO2 was recycled and used in the next cycle of extraction. As shown in Table 1, the fixed cost covers the maintenance, laboratory cost, supervision, operating labor, plant
2.1. Supercritical CO2 (SC-CO2) extraction Supercritical extraction was modelled using CO2 (SC) as solvent under supercritical condition of 60 °C and 35 MPa. As a design basis, the oil yield obtained for one cycle of extraction process was set as 1 kg of volatile oil. The duration of the extraction was designed at 60 min, with additional 30 min for preparation, loading and unloading of the feedstock [16,17]. This enabled a total of 16 extraction cycles per day and 5280 cycles annually with 330 days of plant operation. Fig. 2 shows the process flow diagram of the SC-CO2 extraction process. The CO2 (g) was supplied from a gas tank at compressed pressure of 6 MPa and liquefied by cooling to 5 °C using a cooler before being pumped at desired pressure. The process was designed in pumping the CO2 (SC) at 20 MPa and further pressurized to 35 MPa in two separated pumps, respectively. Two pumps connected in serial were used due to lower power consumption compared to one large pump operating at the same condition point, thus enabling higher efficiency to be achieved. The CO2 (SC) was heated at 60 °C using a heat exchanger before the extraction process starts in the extractors. A hammer mill was used to crush the feedstock into smaller particle size of 151–250 μm before being loaded into the extractors. The extractors were designed to be operated in two trains in order to reduce the load of the extractors and to improve the extraction efficiency. After the SC-CO2 entered the extractors, the extraction process was initiated which further led to extraction of volatile oil. The volatile oil was flowed into a separator for the separation of CO2. The solvent was assumed to undergo a loss of 2% of the total solvent per extraction cycle [18]. Thereafter, the separated CO2 was recycled back into the process line by using a recycle pump. 2.2. Process economics The feasibility of the extraction technology was evaluated based on the estimated cost in terms of both capital expenditure (CAPEX) and annual operating cost (OPEX) over 15 years of plant life. The process plant was assumed to operate 24 h/day for 330 days per year in which 160
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Cb = 3.00 exp[8.833 − 0.6019(ln Q H ) + 0.0519(ln Q H )2 ]
Table 1 Estimated value of operating cost.
2
Components of operating cost
FT = exp[b1 + b2 (ln Q H ) + b3 (ln Q H ]
Estimated value
Variable costs 1. Raw materials
3. Waste treatment Fixed costs [20] 1. Maintenance 2. Labor cost 3. Laboratory cost 4. Supervision 5. Plant overheads 6. Capital charges 7. Insurance 8. Local taxes 9. Royalties 10. Transportation
2.2.1.3. Extractor and separator. The correlated expression as shown in Eq. (8) was used to calculate the cost of equipment in the year of 2009 with Chemical Engineering Plant Cost Index (CEPCI) value of 521.9 [30].
7% of FCI $ 30/h 20% of operating labor 20% of operating labor 50% of operating labor 10% of FCI 1% of FCI 2% of FCI 1% of FCI Fuel usage: 0.034 L tonne-km−1 [25] Variable cost + fixed cost 25% of direct production cost
Direct production cost General expenses including sales expense, general overhead, R & D
Cost =
(10)
2.2.1.4. Tank. The storage tank purchased cost was computed according to the designed volume [29].
C = 1.218FM exp[2.631 + 1.3673(ln V )0.06309(ln V )2 ]
(11)
where the cost factor, FM for stainless steel 316 material is 2.7 and V is the volume of the designed tank. 2.2.1.5. Grinder. The price of hammer mill was calculated using Eq. (12) as shown below [29]: (12)
C = 2.97W 0.78 where W is in the range of 2 < W < 200 tons/h
(1) 2.2.2. Revenues The revenues were generated based on the selling price of the extracted volatile oil, in which the value of product depends on the quality of resin. The revenues also varied with the operating costs, market value and current economics. The gross profit, net profit of the plant, and return on investment (ROI) were calculated using Eqs. (13)–(15) [31]. A straight line depreciation method was used with a depreciable life of 15 years whereas the federal income tax for Malaysia is at 24% of annual profit based on standard corporate tax rate [32].
where P represents the number of processing steps in handling particulate; Nnp is the number of non-particulate processing steps of total units of equipment for non-particulate processing steps in the plant such as pump and heat exchanger. The factors applied across each components of operating costs were taken from Sinnott [20] for estimation of the production cost. In terms of transportation, it was suggested that a 5-axle truck that has a payload of 24.5 tonnes to be used for transportation of feedstock to the extraction plant. Abbas and Handler [25] reported that a normalized fuel usage value of 0.034 L tonne-km-1 was utilized for truck transportation. 2.2.1. Estimation of purchased equipment cost Each individual equipment purchased cost was estimated using the basis of the factorial method as follows:
C = 1.218fd fm fp Cb
(2)
Cb = exp[8.821 − 0.30863(ln A) + 0.0681(ln A)2 ]
(3)
fd = exp[−0.9816 + 0.0830(ln A)]
(4)
fp = 1.1400 + 0.12088(ln A)
(5)
fm = g1 + g2 (ln A)
Gross profit = Total revenue – operating cost
(13)
Net profit = Gross profit − taxes − depreciation
(14)
Return on investment (ROI ) =
2.2.1.1. Heat exchanger. The purchased cost of the heat exchanger was dependent on the heat transfer area. For the shell-and-tube heat exchanger, the purchased cost was computed using the following equations [29].
Net profit × 100% Total investment
(15)
2.3. Life-cycle assessment (LCA) The environmental impact assessment of SC-CO2 extraction process was performed using GaBi LCA software (version 8.1.0.29) equipped with Professional Database. LCA is a technique to evaluate the potential environmental burdens related to a product or process throughout their entire life cycle for environmental sustainability and product development [33]. The International Organization ISO 14040 specifies principles and general framework in conducting and reporting LCA studies which includes certain minimal requirements as a guideline to assess LCA systematically [34]. There are four phases in the structured LCA technique: (1) goal and scope definition, (2) life cycle inventory analysis, (3) life cycle impact assessment and (4) interpretation. In this study, the environmental impacts of the SC-CO2 extraction process based on optimized conditions were investigated through the standard LCA approach.
(6) 2
where A is the heat transfer area in ft ; g1 and g2 for stainless steel 316 material are 0.860 and 0.233 respectively. 2.2.1.2. Pump. The purchased cost of the pump was estimated using the following equations [29]:
C = FM FT Cb
I2 × [31, 901 × V 0.6909] I2009
where I2 is the CEPCI value in the current year and V is the volume of the equipment.
overheads, insurance, local taxes, royalties, and sales expenses. The operating labor cost was estimated to be $ 30/h and the number of workers needed was estimated using the Eq. (1) [24].
NOL = (6.29 + 31.7P 2 + 0.23Nnp )0.5
(9)
where the cost factor, FM is 2.00 for stainless steel 316 or 304 material; Q is the volumetric flow rate of the pump in gpm; H in ft head; b1, b2 and b3 are 9.8849, −1.6164, 0.0834, respectively for multistage pump.
∼$ 40/kg for A. sinensis $ 0.94/kg for CO2 [26] $ 336/ton for ethylene glycerol [27] $ 0.11/kWh [28] $ 1.8/ton for steam Negligible
2. Utilities
(8)
2.3.1. Goal and scope definition The goal of this LCA study was to estimate the environmental impacts of volatile oil extraction using SC-CO2 for extraction of 1 kg of
(7) 161
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Table 2 Life-cycle inputs for extraction of 1 kg of volatile oil from A. sinensis. Parameter/item
Value
Unit
Reference
Harvesting activity Transportationa Milling of feedstock Cooling of CO2 Pumping of CO2 Heating of CO2 SC-CO2 extraction Separation of CO2 and volatile oil
5.60 5.72 145.00 163.27 100.44 151.47 14.34 4.67
kg CO2 eq. kg CO2 eq. kWh kWh kWh kWh kWh kWh
[25] [25] [16] – – – – –
a
200 km is assumed in this case study as baseline scenario.
3. Results and discussion 3.1. Economic assessment 3.1.1. Total capital investment CAPEX is the amount used to purchase the major facilities and equipment when starting up a process plant. Based on the factorial factor for estimation of purchased cost equipment, the total cost of equipment was $ 1.40 million. The cost for each individual equipment is shown in Table 3. The largest share of the total equipment cost was pumps followed by grinder and extractors. Pumps which were the prime capital cost contributor have attributed to the high pressure outlet to achieve the supercritical state of CO2 before entering to the extractors. FCI was calculated according to the total cost of process equipment by applying the typical factors. The breakdown of each item in estimating the FCI for a fluids-solids plant is shown in Table 4 as stated by Sinnott [20] with total FCI of $ 6.18 million for SC-CO2 extraction process plant. The working capital was calculated based on 15% of FCI which was equivalent to $ 0.92 million. A total cost investment (TCI) of $ 7.11 million was obtained through summation of the FCI and working capital for the production capacity of 5280 kg/y essential oil. 3.1.2. Operating costs (OPEX) OPEX is the expenses utilized in maintaining and operating a business based on a day-to-day basis. It reflects the income generated for the company and changes annually depending on the economic and market conditions [31]. Fig. 4 shows the breakdown of each item in operating cost of the extraction plant which includes material cost, utilities, maintenance, local taxes, plant overheads, supervision and so forth. The cost of raw material, general expenses and operating labor were the major contributors in the operating costs. Approximately 280 kg of feedstock is required to extract 1 kg of volatile oil and this has attributed to raw material cost taken up the largest portion of total operating costs for production capacity of 5280 kg/y volatile oil. Electricity and steam were the main energy inputs for the extraction process. The cost of electricity was counted as $ 0.11/kWh based on pricing and tariffs under industrial category from Tenaga Nasional Berhad, Malaysia. General expenses include research and development, general overheads and sales expenses which have estimated to be 25% of direct production
Fig. 3. System boundary of LCA defined by dashed-line box for volatile oil extraction using SC-CO2 extraction.
crude volatile oil at the process plant gate as the functional unit (FU). Downstream usage of this crude volatile oil for various applications was excluded in this study. Fig. 3 shows the system boundary of this study (cradle-to-gate analysis) which evaluated the environmental impacts based on harvesting, transportation operations, milling of feedstock and SC-CO2 extraction process. 2.3.2. Life-cycle inventory (LCI) A life-cycle inventory analysis (LCI) involves the assembling of inputs and outputs as well as interpretation of the necessary data regarding the system boundary for the environmental assessment. In this section, the data collection for operations such as harvesting activity, transportation and milling were obtained from the literature, while the extraction process was acquired through experimental and simulation data of Aspen Plus version 10.0. The electricity utilization for each stages of SC-CO2 extraction was used as LCI as shown in Table 2.
Table 3 Individual equipment cost for SC-CO2 extraction process plant.
2.3.3. Life-cycle impact assessment (LCIA) An assessment of the inventory data was performed using GaBi software (version 8.1.0.29), corresponding to the CML 2001 for the determination of impact indicators based on the emissions from each single processing stage [35]. The impact categories considered in this study were Global Warming Potential (GWP), Acidification Potential (AP), Eutrophication Potential (EP), Human Toxicity Potential (HTP) and Photochemical Ozone Formation Potential (POFP). 162
Equipment
Cost
Tank for CO2 storage Tank for essential oil storage Grinder Chiller Pumps Heat exchanger Two extractors Separator
$ $ $ $ $ $ $ $
54,998 45,481 261,083 92,936 794,669 20,958 87,534 45,903
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Table 4 Factors for fluids-solid processing plant [20]. Item
1. Major equipment, total purchase cost f1 Equipment erection f2 Piping f3 Instrumentation f4 Electrical f5 Buildings, process f6 Utilities f7 Storages f8 Site development f9 Ancillary buildings 2. Total physical plant cost (PPC) PPC = PCE (1 + f1 + … + f9) = PCE x f10 Design and Engineering f11 Contractor’s fee f12 Contingency Fixed capital = PPC (1 + f10 + f11 + f12) = PPC x
Purchased cost equipment factor for fluids-solids process
0.45 0.45 0.15 0.10 0.10 0.45 0.20 0.05 0.20
Fig. 5. Operating cost, revenue, gross profits and net profits of volatile oil extracted from resin and lignified ring of A. sinensis using SC-CO2.
3.15 0.25 0.05 0.10 1.40
value of total net present worth for the plant life was $ 32.43 million at 15% of discount rate indicated that the extraction plant has high potential earning capacity.
cost [20]. The number of operators required to run the process was determined by solving Eq. (1) which showed the NOL to be 17. Besides, it was estimated that 5 labors and 2 truck drivers were required in collecting or harvesting of feedstock and transportation, respectively. The laborers’ wages were estimated to be $ 30/h which corresponded to approximately $ 5.26 million/y.
3.1.3.2. Lignified ring of A. sinensis as feedstock. Based on the experimental results, the extracted volatile oil from lignified ring and resin have the same amount of the oil yield. The item that varied in operating cost category was the cost of raw material. As shown in Fig. 5, the operating cost of lignified ring as the feedstock was lower due to lower raw material price compared to resin.Since there is no study reported on the price of lignified ring, it was assumed to be half of the resin price. In terms of revenues, the selling price of volatile oil was the influencing factor. The selling price of volatile oil extracted from lignified ring was predicted to be lower than the commercialized product which assumed to be sold at $ 0.0125 million/kg. Through this assumption, a revenue of $ 66 million/y was obtained in this case study with gross and net profit of $ 13.61 and $ 7.40 million, respectively. Besides, the ROI of 12.05% also gave a positive income. Based on the comparison of the net profit for volatile oil of resin and lignified ring, the oil extracted from resin was more profitable due to higher selling price.
3.1.3. Profits 3.1.3.1. Resin of A. sinensis as feedstock. The profit of an operation was estimated based on the operating costs and total revenue. In this study, the volatile oil extracted from A. sinensis was the main product of the whole production line. Fig. 5 shows the operating cost of the extraction plant by utilizing resin as feedstock which amounted to be $ 81.96 million/y. The main contribution of the operating cost originated from the raw material category as 280 kg of resin was used to extract 1 kg of volatile oil. Nevertheless, it was reported that distilled volatile oil from high grade Aquilaria species can cost up to $ 0.025 million/kg [36]. This gave a total revenue of $ 105.60 million/y for the production capacity of 5280 kg/y of volatile oil. The gross profit was estimated based on the revenues and operating cost as shown in Eq. (13). Net profit was obtained after deducted 24% of income tax and 10% of straight line depreciation from gross profit as shown in Eq. (14). By using Eqs. (13) and (14), the gross profit and net profit were calculated to be $ 23.64 million and $ 17.42 million, respectively. Besides, the calculation for ROI showed 19.16% which implied that this extraction plant was economically feasible at larger scale. In addition, the postive
3.1.4. Sensitivity analysis The yield of volatile oil at industrial scale was estimated using laboratory experimental data as part of the techno-economic analysis to determine the profitability of the SC-CO2 extraction process. The extraction efficiency might differ from the laboratory scale after the extraction process was being scaled up. Nevertheless, it is expected that a higher performance of the process can be achieved at industrial scale with proper equipment design, process optimization and integration.
Fig. 4. Breakdown of the operating cost for SC-CO2 extraction process. 163
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Fig. 6. Sensitivity analysis of economic assessment to percentage of volatile oil yield against changes of OPEX, gross profit, net profit and ROI.
natural gas and hydropower with a proportion of 51%, 45% and 4%, respectively [43]. According to this weightage of electricity generation contribution, the electricity consumption for each single stage of extraction process was calculated based on this ratio and applied in the GaBi LCA software (version 8.1.0.29) equipped with professional data. The results showed that the cradle-to-gate of volatile oil extraction contributed certain impacts towards the environmental. This outcome was due to immaturity of technology and product stage since the data used was scaled up linearly based on lab-scale which potentially caused the results to be overestimated. In general, laboratory scale experiments exclude the energy recovery, heat insulation, recycling of materials and process integration which could affect the overall process efficiency. However, when the technology matured and developed into larger scale, these aspects of the process can be achieved and further improved the productivity of process and environmental performance. The most effective solution is to reduce the CO2 solvent for the extraction process, as most of the equipment is used to covert the phase of CO2 into supercritical state before entering into the extractor. By reducing the amount of CO2 solvent, the usage of electricity could be minimized which eventually contributed less severe impact towards the environment. Meanwhile, other potential improvements such as process modelling, heat integration, adopting energy conserving process and on-site power supply using waste biomass should also taken into consideration when designing an extraction plant. As such, it is predicted that the environmental impacts could be further reduced with higher technology maturity and production scale [38]. Thus, in this context, each single stage of volatile oil extraction and the assumption of solvent loss during the process were estimated to contribute approximately 90% of reduction towards environmental impact when TRL reached 9-10, as shown in Table 5. Based on the system boundary, the first stage of volatile oil extraction was the harvesting activity of A. sinensis. Since there is no data reported for the environmental impact on the harvesting activity of the specific species, the impact contributed to the environment was taken from the study done by Abbas and Handler [25] with a total emission of 20.0 kg CO2 eq. for one tonne of harvested wood. As a baseline scenario, the distance from the plantation to the process plant was assumed to be 200 km per round trip. The work from Abbas and Handler [25] was referred for the emissions, whereby 1 kg of diesel used for transportation contributed 3.62 kg CO2 eq. in GWP. As seen from Table 5, the significant impacts were electricity consumption at the milling and extraction process. The electricity consumption contributed around 90% of the total GWP might be due to consumption of high percentage of non-renewable sources such as hard coal and natural gas for electricity generation. The emissions resulted from CO2 released
The sensitivity of the economic analysis such as OPEX, gross profit, net profit gained and ROI based on variation in percentage of volatile oil yield are shown in Fig. 6. A +5% variation in volatile oil yield resulted in deduction of OPEX to 3.43% due to smaller amount of feedstock was required. This led to increase in gross and net profit of 11.91% and 16.16%, respectively. The ROI also increased from 19.16% to 19.83%. On the other hand, when the volatile oil yield was reduced by 5%, it caused the net profit loss up to 17.87% due to the increment of the total cost of OPEX by 3.80%. 3.2. Environmental impact analysis This study attempted to evaluate the LCA of extracting volatile oil from A. Sinensis using SC-CO2 extraction at industrial scale. Data gaps are still remain as fundamental problems in performing ex-ante LCA of technologies because there are yet to exist at commercial scale [37]. Nevertheless, assessments need to be performed, and it is essential that any uncertainties arising from data gaps and parametric uncertainties are properly documented [38]. In this work, the environmental impact for harvesting activity and transportation were retrieved from the established literature [25]. Simulation of the scaled-up extraction process was performed using Aspen Plus version 10. The simulation data was then applied in GaBi LCA software for the evaluation of environmental impacts. Nonetheless, the process itself remained technologically immature, and rated at a Technology Readiness Level (TRL) of 3. The TRL is a widely used nine-point scale for rating technology maturity [39]. Straub [40] has proposed the addition of a tenth level to indicate an extended history of commercial scale use. Previous research has reported that the process of scaling up with an elevated TRL could reduce the environmental impacts significantly due to higher gains in efficiency through factors such as optimum surface area-to-volume ratios and process integration which involved the energy and heat recovery, and recycling of resources. For instance, the environmental assessment for recycling of waste and anaerobic digestion of organic waste with energy recovery in cogeneration plant have the minimum environmental impact as compared to the current situation with landfilling of waste without energy recovery [41]. It was also reported that in the case of carbon nanotubes (CNT) manufacturing, environment impacts were reduced significantly by up to 84–94% when commercial production volume was achieved [42]. In general, the environmental assessment varied based on the level of technology maturity. As the maturity of TRL increased, it was estimated that the environmental impact would be reduced proportionally after upscaled the extraction process from laboratory to industrial scale. In Malaysia, the main resources for energy mix comprised of coal, 164
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Table 5 Cradle-to-gate analysis of extraction of 1 kg of volatile oil from A. sinensis. Supercritical carbon dioxide extraction of volatile oil from A. sinensis Impact category GWPb APc EPd
Unit
Harvesting of the plant
kg CO2 eq. 5.60 kg SO2 eq. NA kg PO43− NA eq. e kg DCB eq. NA HTP POFPf kg C2H4 eq. NA Estimated emissions when TRLs = 9–10 kg CO2 eq. 5.60 GWPb APc kg SO2 eq. NA EPd kg PO43− NA eq. e HTP kg DCB eq. NA POFPf kg C2H4 eq. NA
Transportation
Electricity for milling
Electricity for SC-CO2 extraction
Assumption of CO2 loss during extraction process
Total
5.72 NA NA
118.13 1.14 3.51 × 10−2
352.56 3.39 0.10
1.05 NA NA
513.84 4.53 0.14
NA NA
20.73 6.27 × 10−2
61.88 0.19
NA NA
82.61 0.25
5.72 NA NA
11.81a 0.11a 3.51 × 10−3a
35.26a 0.34a 0.01a
0.11a NA NA
58.50 0.45 1.40 × 10−2
NA NA
2.07a 6.27 × 10−3a
6.19a 1.90 × 10−2a
NA NA
8.26 2.60 × 10−2
a Estimation of 90% of reduction in the cradle-to-gate environmental impacts when SC-CO2 extraction process is ramped up from small to large scale (TRL 9–10) production [42]. b Global warming potential. c Acidification potential. d Eutrophication potential. e Human toxicity potential. f Photochemical ozone formation potential.
on the variation in percentage of extraction efficiency. As the extraction efficiency improved, the environment impacts were reduced as observed in the negative bar. A +20% variation in extraction efficiency resulted in deduction of 11.70 kg CO2 eq. and 1.65 kg DCB eq. Besides, sensitivity analysis with variation of 10% electricity consumption was also conducted. The results showed that 10% of reduction in electricity usage decreased the GWP and HTP by 5.14 kg CO2 eq. and 0.83 kg DCB eq., respectively. These results indicated that an improvement in the oil yield extraction and reduction of electricity consumption were relatively vital as these affect the sustainability of the environment during mass production.
during combustion and upstream emissions of CO2 and CH4 in the fuel supply chains [44]. Besides, coal combustion during electricity generation emitted gases such as SOx, NOx, CO2 and PM which contributed towards the environmental impacts [45]. The second highest contributor for the volatile oil extraction was HTP that mainly related to health and safety issues. Brizmohun et al. [46] pointed out that the emissions of heavy metals to air, water and soil during coal mining are the reason which attributed to high amount of DCB. Thus, renewable energy or low carbon energy sources such as solar power and hydropower should be considered and developed for emissions reduction [47]. Another potential solution is the on-site use of residual biomass as fuel for heat and electricity generation to meet process heat requirements [48]. Somehow, these modifications would shift the process techno-economics due to higher capital costs and lower electricity purchases.
3.2.2. Limitations of this LCA study The system boundary which investigated the extraction of volatile oil from A. sinensis at industrial scale was defined as “cradle-to-gate” that started from harvesting activity and ended with the extracted volatile oil. Biomass cultivation and further processing of extracted volatile oil that beyond the LCA system boundary are not investigated in this work. As there is limited information on the data input for the scale-up of the extraction process, the applied data in LCA simulation
3.2.1. Sensitivity analysis Sensitivity analysis was performed to examine the most impactful category of environmental burden related to the extraction process. Fig. 7 shows the sensitivity analysis of the environmental impacts based
Fig. 7. Sensitivity analysis of environmental impacts against percentage of volatile oil yield and electricity consumption. 165
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were obtained through laboratory scale experiments that was evenly scaled up for extraction of 1 kg of volatile oil. This LCA study which was based on the available laboratory experiments data only provided limited indication on the potential environmental impacts of the same materials or process operating condition at industrial scale. Besides, the environmental impacts for harvesting activity and transportation retrieved from the established literature were based on the forest biomass grown in Tennessee which might vary based on the countries.
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4. Conclusions A techno-economic and LCA of SC-CO2 extraction for volatile oil extracted from A. sinensis were evaluated. The abundant lignified biomass was used as the feedstock to evaluate its economic feasibility towards commercialization. Based on the calculation of CAPEX, the FCI and TCI of the process plant were estimated to be $ 6.18 million and $ 7.11 million, respectively for the production capacity of 5280 kg/y volatile oil. In terms of operating cost, the cost of raw materials contributed the main portion. With respect to the estimated selling price and cost of raw material for resin and lignified ring, both economic studies revealed a positive net profit. This indicated that the volatile oil extracted from lignified ring was economically competitive to the volatile oil extracted from resin. The cradle-to-gate LCA analysis showed that SC-CO2 extraction process was the major contributor towards the environmental burden due to its high energy consumption. Nonetheless, the study estimated that at higher TRLs, the process could greatly reduce the impacts at industrial scale as the technology matured. In particular, the prospect of recovering residual biomass from the process for on-site use as fuel is able to reduce life cycle GHG emissions. This study leads to further research on the biomass utilization in extracting volatile oil by using SC-CO2 extraction method from economic perspective and environmental point of view. Conflict of interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. CRediT authorship contribution statement Yong Ling Gwee: Writing - original draft, Formal analysis, Conceptualization, Methodology, Investigation. Suzana Yusup: Writing - review & editing, Supervision, Funding acquisition, Project administration. Raymond R. Tan: Writing - review & editing, Formal analysis, Resources. Chung Loong Yiin: Writing - review & editing. Acknowledgement The authors express gratitude to Biomass Processing Cluster, Center for Biofuel and Biochemical Research, Chemical Engineering Department, Universiti Teknologi PETRONAS for the support and Eco Midori Sdn Bhd for supplying Aquilaria Species as the feedstock for this study. Lastly, support from Ministry of High Education Malaysia through HiCoE award to CBBR is duly acknowledged. References [1] S.P. Chong, M.F. Osman, N. Bahari, E.A. Nuri, R. Zakaria, K. Abdul-Rahim, Agarwood inducement technology: a method for producing oil grade Agarwood in cultivated Aquilaria malaccensis Lamk, J. Agrobiotechnol. 6 (2015). [2] H.I.M. Kakino, T. Ito, K. Tsuruma, Y. Araki, M. Shimazawa, M. Oyama, M. Iinuma, H. Hara, Agarwood induced laxative effects via acetylcholine receptors on loperamide-induced constipation in mice, Biosci. Biotechnol. Biochem. 74 (2010) 1550–1555. [3] S. Akter, Md.T. Islam, M. Zulkefeli, M. Khan, Agarwood production—a multidisciplinary field to be explored in Bangladesh, Int. J. Pharm. Life Sci. 2 (2013) 22–32.
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Techno-economic and life-cycle assessment of volatile oil extracted from Aquilaria sinensis using supercritical carbon dioxide
T
Yong Ling Gweea,b, Suzana Yusupa,b,*, Raymond R. Tanc, Chung Loong Yiind a
HiCoE, Biomass Processing Cluster, Centre for Biofuel and Biochemical Research, Institute of Sustainable Building, Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak, Malaysia b Chemical Engineering Department, Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak, Malaysia c Chemical Engineering Department, De La Salle University, 2401 Taft Avenue, 0922 Manila, Philippines d Chemical Engineering Department, Faculty of Engineering, Computing and Science, Swinburne University of Technology, Jalan Simpang Tiga, 93350, Kuching, Sarawak, Malaysia
A R T I C LE I N FO
A B S T R A C T
Keywords: Total capital investment Operating cost Profits Environmental impact Technology readiness level
Extracts of Aquilaria sinensis possess pharmacological activity that has been widely used in traditional medicines since ancient times. In this study, techno-economic assessment was conducted for extraction of volatile oil from abundant biomass (lignified ring) and resin of A. sinensis to evaluate their respective economic feasibility using supercritical carbon dioxide (SC-CO2) extraction in Malaysia. The assessment revealed that for a production capacity of 5280 kg/y volatile oil, the total capital investment (TCI) was $ 7.11 million from summation of fixed capital cost and working capital. In terms of operating expenditure (OPEX), the volatile oil extracted from resin and lignified ring of A. sinensis required $ 81.96 million and $ 52.39 million, respectively. The selling price of volatile oil from resin and lignified ring were estimated to be $ 0.025 million/kg and $ 0.0125 million/kg, respectively. Both volatile oil extracted from resin and lignified ring showed a positive net profit which indicated their profitability. In addition, a cradle-to-gate analysis of life-cycle assessment (LCA) was performed, whereby the extraction process contributed the highest impact towards the environment due to its high energy consumption. Nevertheless, this study estimated that the process might reduce the environmental impacts by approximately 90% when the technology readiness levels (TRLs) reach the level of 9–10. These findings are beneficial in providing preliminary insights in terms of economic and environmental aspects for volatile oil extraction using SC-CO2 technology.
1. Introduction The genus of Aquilaria species which is classified under plant family of Thymelaeaceae consists of resinous heartwood known as agarwood or gaharu. The term gaharu refers to the dark, dense and fragrant resinous wood located at the inner part of stem and branch of Aquilaria trees. It possesses pharmacological function and biological activity which has been used widely for medicines, perfumes and incenses. The stem of Aquilaria trees consists of resin that has unique balsamic notes and comprises of useful ingredients for perfumery which can be extracted as volatile oil [1]. For instance, many literatures have reported on pharmaceutical benefits of resin such as anti-inflammatory, anti-toxic, sedative, laxative and treatment in digestive, respiratory and nervous systems characteristics [2,3]. The lignified ring which is the outer layer of the resin comprises of a major portion from Aquilaria trees is
scrapped off in order to obtain resin that located at the inner part of the stem bark. It is usually disposed by the agriculturists after obtained the resin which indirectly contributed to the amount of wood waste. About 4.5 million t/y of wood waste is generated globally [4]. Thus, utilization of the lignified ring for the extraction of volatile oil with potential beneficial compounds has high novelty in generating wealth from biomass. Owning to high market value of volatile oil, the selection of extraction method and well-designed process are necessary to obtain maximum yield of the volatile oil. The most common extraction techniques comprise of Soxhlet extraction and hydrodistillation. Soxhlet extraction requires organic solvent leading to disadvantages, such as cost of high purity, toxicity, and residue in the extracts which could potentially affect the environment and human health. At industrial scale, hydrodistillation extraction is usually applied to extract volatile
⁎
Corresponding author at: Chemical Engineering Department, Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak, Malaysia. E-mail addresses: [email protected] (Y.L. Gwee), [email protected] (S. Yusup), [email protected] (R.R. Tan), [email protected] (C.L. Yiin). https://doi.org/10.1016/j.jcou.2020.01.002 Received 27 February 2019; Received in revised form 23 December 2019; Accepted 3 January 2020 2212-9820/ © 2020 Elsevier Ltd. All rights reserved.
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oil from Aquilaria species. This method requires pre-treatment process whereby the sample is soaked in distilled water for approximately 7–14 days before extraction for maximum oil yield [5]. Besides, high temperature is involved during the extraction. There is a potential for a loss or degradation of some specific compounds, especially heat-sensitive compounds by thermal or hydrolysis effects which consequently impaired the quality of extracted volatile oil [6]. Sulaiman et al. [7] reported that the maximum extraction yield obtained was 0.18% at 72 h of extraction time using hydrodistillation method which showed low extraction efficiency and high energy consumption. With their respective shortcomings, the development of new separation technique for the chemical industries has gained a great attention due to the environment restriction and lower energy costs [8]. SC-CO2 extraction is one of the most promising methods due to its numerous advantages compared with conventional methods [9]. For example, hydrodistillation requires 72 h of extraction time and process temperature of 85 °C, with only 0.075% w/w of oil yield. In contrast, SC-CO2 extraction requires lower operating temperature (40–50 °C) and shorter extraction time (30–60 min) with higher oil yield of 3.66% w/w [10,11]. Besides, SC-CO2 extraction does not require extra steps of separation as CO2 is in gaseous state at room temperature and atmospheric pressure. The lower operating temperature is another advantage of SC-CO2 extraction whereby the degradation of bioactive compounds in the extracts can be avoided. In addition, the density of the CO2 can also be easily varied along with the pressure or temperature which is closely related to the solubility and solvent power. This feature is useful to obtain the specific yield and compounds. As discussed herein, this work aims to investigate the extraction of volatile oil from A. sinensis at industrial scale. Moncada et al. [12] had studied on the economic and environment point of view for extraction methods such as supercritical fluid, water and solvent distillation by using Rosemary and Oregano as raw materials. It was reported that supercritical fluid extraction (SFE) is the most profitable technology for Oregano oil extraction at $ 6.71/kg with full energy interaction. Besides, Aguiar et al. [13] had conducted economic analysis of oleoresin production from malagueta peppers through SCCO2 extraction and discovered this technology is economically feasible with estimated commercialization price of $ 223/kg. The SC-CO2 provides a higher oil yield with shorter extraction time and no separation of solvent and extracts is needed. From the aspects of life-cycle assessment (LCA), CO2 is categorized as a generally recognized as safe (GRAS) solvent. This could potentially aid the SC-CO2 extraction process to be a more environmental benign appealing option. Meizoso et al. [14] had studied on the green pilot-scale extraction processes such as pressurized hot water extraction and SFE. The result revealed that SFE process has lower environmental impacts of 23.64 kg CO2 eq. compared to pressurized hot water extraction with 63.89 kg CO2 eq. Moreover, De Marco et al. [15] reported that agricultural stage has contributed to higher environmental impact than SC-CO2 extraction process in extracting caffeine from coffee bean in terms of ozone depletion with a value of 2.94 × 10−7 and 1.59 × 10−7, respectively. However, to the extent of authors’ knowledge, this is the first attempt to evaluate the economic feasibility and LCA of SC-CO2 extraction of volatile oil from A. sinensis. Thus, the goal of this study was to produce a techno-economic analysis on the feasibility of SC-CO2 extraction in estimating the capital cost, operating cost, profits and revenue. In addition, LCA of volatile oil extraction was also performed to gauge its environmental impact. This study is vital in providing new insights on the economic potential of volatile oil extracted from lignified ring for scale up process.
Fig. 1. Response surface plots for the effects of (a) pressure and temperature; (b) CO2 flow rate and temperature; (c) CO2 flow rate and pressure.
years of plant operation. The optimum operating condition was obtained by using Response Surface Methodology (RSM) approach. Fig. 1 shows the response surface plots for the effect of temperature, pressure and CO2 flow rate towards the volatile oil yield. Based on the numerical optimization tool, the ideal condition to achieve maximum volatile oil yield was at 60 °C, 35 MPa and 8.5 mL/min of CO2 flow rate under 60 min of extraction time.The characterization of extracted volatile oil indicated that 2-(phenethyl-4H) chromones and 10-methylanthracene9-carboxaldehyde with composition of 52.74% and 29.67% are the main compounds responsible for the quality of oil from resin and lignified ring, respectively. Based on the laboratory scaled tests, 0.005 g of volatile oil was extracted from 1.4 g of feedstock. For scale up purposes, the amount of feedstock and CO2 required to extract 1 kg of volatile oil were scaled up evenly due to scarcity of available industrial data. According to the calculation, a total of 280 kg of feedstock and 476 L/min of CO2 flow rate were required to extract 1 kg of volatile oil per cycle. Aspen Plus (version 10.0) was used to simulate the extraction process at larger scale and GaBi LCA software (version 8.1.0.29) was used to evaluate the environmental impacts for each breakdown stages of the extraction process based on the inputs of energy consumption at respective stages.
2. Materials and methods In this section, techno-economic assessment and LCA were performed to evaluate the economic and environmental feasibility of SCCO2 extraction plant in extracting volatile oil from A. sinensis over 15 159
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Fig. 2. Process flow diagram of SC-CO2 extraction process.
30 days are scheduled for plant maintenance [19]. The CAPEX includes all the required cost for the plant facilities such as fixed capital investment (FCI) and working capital. FCI is the cost required for the installation of the unit operation. It is divided into two sections which are direct costs and indirect costs. Direct costs include the cost of purchased equipment, installation of the equipment, cost of piping, cost of electrical system, instrumentation and building and service facilities. Indirect costs comprise of cost of engineering and supervision, legal expenses, construction expenses, contractor’s fees and contingency. In this study, the direct and indirect costs of the plant are calculated based on the solid fluid processing plant. A ratio factors of 3.15 was applied across the purchased cost equipment for physical plant cost, while the fixed capital investment was obtained using a factor of 1.40 across the physical plant cost [20]. Any additional investment required to start up the plant that excluded FCI is classified under working capital. The working capital cost is typically around 10–20% of the FCI [20,21]. Total capital investment (TCI) was calculated through the summation of the total cost for FCI and working capital. For the estimation of OPEX for the process plant, it can be divided into variable and fixed costs as tabulated in Table 1. Variable costs varied according to the production rate. It increased with higher production rate and decreased when production rate was lower [22]. The variable costs include the cost of raw materials, utilities, waste treatment and shipping. In this case study, resin and lignified ring of A. sinensis were utilized for comparison study with CO2 gases as extracting solvent and ethylene glycerol as refrigerant in cooling the CO2. The electricity consumption for each individual equipment was obtained through the simulation data from Aspen Plus. Steam was utilized as the heating medium in the heat exchanger. The cost of waste treatment was neglected for SC-CO2 extraction process because the residue is a dry solid wood that may be incorporated into the soil as it does not contain any residue of toxic solvents [23] and can be reused for paper production or as fuel. In addition, the CO2 was recycled and used in the next cycle of extraction. As shown in Table 1, the fixed cost covers the maintenance, laboratory cost, supervision, operating labor, plant
2.1. Supercritical CO2 (SC-CO2) extraction Supercritical extraction was modelled using CO2 (SC) as solvent under supercritical condition of 60 °C and 35 MPa. As a design basis, the oil yield obtained for one cycle of extraction process was set as 1 kg of volatile oil. The duration of the extraction was designed at 60 min, with additional 30 min for preparation, loading and unloading of the feedstock [16,17]. This enabled a total of 16 extraction cycles per day and 5280 cycles annually with 330 days of plant operation. Fig. 2 shows the process flow diagram of the SC-CO2 extraction process. The CO2 (g) was supplied from a gas tank at compressed pressure of 6 MPa and liquefied by cooling to 5 °C using a cooler before being pumped at desired pressure. The process was designed in pumping the CO2 (SC) at 20 MPa and further pressurized to 35 MPa in two separated pumps, respectively. Two pumps connected in serial were used due to lower power consumption compared to one large pump operating at the same condition point, thus enabling higher efficiency to be achieved. The CO2 (SC) was heated at 60 °C using a heat exchanger before the extraction process starts in the extractors. A hammer mill was used to crush the feedstock into smaller particle size of 151–250 μm before being loaded into the extractors. The extractors were designed to be operated in two trains in order to reduce the load of the extractors and to improve the extraction efficiency. After the SC-CO2 entered the extractors, the extraction process was initiated which further led to extraction of volatile oil. The volatile oil was flowed into a separator for the separation of CO2. The solvent was assumed to undergo a loss of 2% of the total solvent per extraction cycle [18]. Thereafter, the separated CO2 was recycled back into the process line by using a recycle pump. 2.2. Process economics The feasibility of the extraction technology was evaluated based on the estimated cost in terms of both capital expenditure (CAPEX) and annual operating cost (OPEX) over 15 years of plant life. The process plant was assumed to operate 24 h/day for 330 days per year in which 160
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Cb = 3.00 exp[8.833 − 0.6019(ln Q H ) + 0.0519(ln Q H )2 ]
Table 1 Estimated value of operating cost.
2
Components of operating cost
FT = exp[b1 + b2 (ln Q H ) + b3 (ln Q H ]
Estimated value
Variable costs 1. Raw materials
3. Waste treatment Fixed costs [20] 1. Maintenance 2. Labor cost 3. Laboratory cost 4. Supervision 5. Plant overheads 6. Capital charges 7. Insurance 8. Local taxes 9. Royalties 10. Transportation
2.2.1.3. Extractor and separator. The correlated expression as shown in Eq. (8) was used to calculate the cost of equipment in the year of 2009 with Chemical Engineering Plant Cost Index (CEPCI) value of 521.9 [30].
7% of FCI $ 30/h 20% of operating labor 20% of operating labor 50% of operating labor 10% of FCI 1% of FCI 2% of FCI 1% of FCI Fuel usage: 0.034 L tonne-km−1 [25] Variable cost + fixed cost 25% of direct production cost
Direct production cost General expenses including sales expense, general overhead, R & D
Cost =
(10)
2.2.1.4. Tank. The storage tank purchased cost was computed according to the designed volume [29].
C = 1.218FM exp[2.631 + 1.3673(ln V )0.06309(ln V )2 ]
(11)
where the cost factor, FM for stainless steel 316 material is 2.7 and V is the volume of the designed tank. 2.2.1.5. Grinder. The price of hammer mill was calculated using Eq. (12) as shown below [29]: (12)
C = 2.97W 0.78 where W is in the range of 2 < W < 200 tons/h
(1) 2.2.2. Revenues The revenues were generated based on the selling price of the extracted volatile oil, in which the value of product depends on the quality of resin. The revenues also varied with the operating costs, market value and current economics. The gross profit, net profit of the plant, and return on investment (ROI) were calculated using Eqs. (13)–(15) [31]. A straight line depreciation method was used with a depreciable life of 15 years whereas the federal income tax for Malaysia is at 24% of annual profit based on standard corporate tax rate [32].
where P represents the number of processing steps in handling particulate; Nnp is the number of non-particulate processing steps of total units of equipment for non-particulate processing steps in the plant such as pump and heat exchanger. The factors applied across each components of operating costs were taken from Sinnott [20] for estimation of the production cost. In terms of transportation, it was suggested that a 5-axle truck that has a payload of 24.5 tonnes to be used for transportation of feedstock to the extraction plant. Abbas and Handler [25] reported that a normalized fuel usage value of 0.034 L tonne-km-1 was utilized for truck transportation. 2.2.1. Estimation of purchased equipment cost Each individual equipment purchased cost was estimated using the basis of the factorial method as follows:
C = 1.218fd fm fp Cb
(2)
Cb = exp[8.821 − 0.30863(ln A) + 0.0681(ln A)2 ]
(3)
fd = exp[−0.9816 + 0.0830(ln A)]
(4)
fp = 1.1400 + 0.12088(ln A)
(5)
fm = g1 + g2 (ln A)
Gross profit = Total revenue – operating cost
(13)
Net profit = Gross profit − taxes − depreciation
(14)
Return on investment (ROI ) =
2.2.1.1. Heat exchanger. The purchased cost of the heat exchanger was dependent on the heat transfer area. For the shell-and-tube heat exchanger, the purchased cost was computed using the following equations [29].
Net profit × 100% Total investment
(15)
2.3. Life-cycle assessment (LCA) The environmental impact assessment of SC-CO2 extraction process was performed using GaBi LCA software (version 8.1.0.29) equipped with Professional Database. LCA is a technique to evaluate the potential environmental burdens related to a product or process throughout their entire life cycle for environmental sustainability and product development [33]. The International Organization ISO 14040 specifies principles and general framework in conducting and reporting LCA studies which includes certain minimal requirements as a guideline to assess LCA systematically [34]. There are four phases in the structured LCA technique: (1) goal and scope definition, (2) life cycle inventory analysis, (3) life cycle impact assessment and (4) interpretation. In this study, the environmental impacts of the SC-CO2 extraction process based on optimized conditions were investigated through the standard LCA approach.
(6) 2
where A is the heat transfer area in ft ; g1 and g2 for stainless steel 316 material are 0.860 and 0.233 respectively. 2.2.1.2. Pump. The purchased cost of the pump was estimated using the following equations [29]:
C = FM FT Cb
I2 × [31, 901 × V 0.6909] I2009
where I2 is the CEPCI value in the current year and V is the volume of the equipment.
overheads, insurance, local taxes, royalties, and sales expenses. The operating labor cost was estimated to be $ 30/h and the number of workers needed was estimated using the Eq. (1) [24].
NOL = (6.29 + 31.7P 2 + 0.23Nnp )0.5
(9)
where the cost factor, FM is 2.00 for stainless steel 316 or 304 material; Q is the volumetric flow rate of the pump in gpm; H in ft head; b1, b2 and b3 are 9.8849, −1.6164, 0.0834, respectively for multistage pump.
∼$ 40/kg for A. sinensis $ 0.94/kg for CO2 [26] $ 336/ton for ethylene glycerol [27] $ 0.11/kWh [28] $ 1.8/ton for steam Negligible
2. Utilities
(8)
2.3.1. Goal and scope definition The goal of this LCA study was to estimate the environmental impacts of volatile oil extraction using SC-CO2 for extraction of 1 kg of
(7) 161
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Table 2 Life-cycle inputs for extraction of 1 kg of volatile oil from A. sinensis. Parameter/item
Value
Unit
Reference
Harvesting activity Transportationa Milling of feedstock Cooling of CO2 Pumping of CO2 Heating of CO2 SC-CO2 extraction Separation of CO2 and volatile oil
5.60 5.72 145.00 163.27 100.44 151.47 14.34 4.67
kg CO2 eq. kg CO2 eq. kWh kWh kWh kWh kWh kWh
[25] [25] [16] – – – – –
a
200 km is assumed in this case study as baseline scenario.
3. Results and discussion 3.1. Economic assessment 3.1.1. Total capital investment CAPEX is the amount used to purchase the major facilities and equipment when starting up a process plant. Based on the factorial factor for estimation of purchased cost equipment, the total cost of equipment was $ 1.40 million. The cost for each individual equipment is shown in Table 3. The largest share of the total equipment cost was pumps followed by grinder and extractors. Pumps which were the prime capital cost contributor have attributed to the high pressure outlet to achieve the supercritical state of CO2 before entering to the extractors. FCI was calculated according to the total cost of process equipment by applying the typical factors. The breakdown of each item in estimating the FCI for a fluids-solids plant is shown in Table 4 as stated by Sinnott [20] with total FCI of $ 6.18 million for SC-CO2 extraction process plant. The working capital was calculated based on 15% of FCI which was equivalent to $ 0.92 million. A total cost investment (TCI) of $ 7.11 million was obtained through summation of the FCI and working capital for the production capacity of 5280 kg/y essential oil. 3.1.2. Operating costs (OPEX) OPEX is the expenses utilized in maintaining and operating a business based on a day-to-day basis. It reflects the income generated for the company and changes annually depending on the economic and market conditions [31]. Fig. 4 shows the breakdown of each item in operating cost of the extraction plant which includes material cost, utilities, maintenance, local taxes, plant overheads, supervision and so forth. The cost of raw material, general expenses and operating labor were the major contributors in the operating costs. Approximately 280 kg of feedstock is required to extract 1 kg of volatile oil and this has attributed to raw material cost taken up the largest portion of total operating costs for production capacity of 5280 kg/y volatile oil. Electricity and steam were the main energy inputs for the extraction process. The cost of electricity was counted as $ 0.11/kWh based on pricing and tariffs under industrial category from Tenaga Nasional Berhad, Malaysia. General expenses include research and development, general overheads and sales expenses which have estimated to be 25% of direct production
Fig. 3. System boundary of LCA defined by dashed-line box for volatile oil extraction using SC-CO2 extraction.
crude volatile oil at the process plant gate as the functional unit (FU). Downstream usage of this crude volatile oil for various applications was excluded in this study. Fig. 3 shows the system boundary of this study (cradle-to-gate analysis) which evaluated the environmental impacts based on harvesting, transportation operations, milling of feedstock and SC-CO2 extraction process. 2.3.2. Life-cycle inventory (LCI) A life-cycle inventory analysis (LCI) involves the assembling of inputs and outputs as well as interpretation of the necessary data regarding the system boundary for the environmental assessment. In this section, the data collection for operations such as harvesting activity, transportation and milling were obtained from the literature, while the extraction process was acquired through experimental and simulation data of Aspen Plus version 10.0. The electricity utilization for each stages of SC-CO2 extraction was used as LCI as shown in Table 2.
Table 3 Individual equipment cost for SC-CO2 extraction process plant.
2.3.3. Life-cycle impact assessment (LCIA) An assessment of the inventory data was performed using GaBi software (version 8.1.0.29), corresponding to the CML 2001 for the determination of impact indicators based on the emissions from each single processing stage [35]. The impact categories considered in this study were Global Warming Potential (GWP), Acidification Potential (AP), Eutrophication Potential (EP), Human Toxicity Potential (HTP) and Photochemical Ozone Formation Potential (POFP). 162
Equipment
Cost
Tank for CO2 storage Tank for essential oil storage Grinder Chiller Pumps Heat exchanger Two extractors Separator
$ $ $ $ $ $ $ $
54,998 45,481 261,083 92,936 794,669 20,958 87,534 45,903
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Table 4 Factors for fluids-solid processing plant [20]. Item
1. Major equipment, total purchase cost f1 Equipment erection f2 Piping f3 Instrumentation f4 Electrical f5 Buildings, process f6 Utilities f7 Storages f8 Site development f9 Ancillary buildings 2. Total physical plant cost (PPC) PPC = PCE (1 + f1 + … + f9) = PCE x f10 Design and Engineering f11 Contractor’s fee f12 Contingency Fixed capital = PPC (1 + f10 + f11 + f12) = PPC x
Purchased cost equipment factor for fluids-solids process
0.45 0.45 0.15 0.10 0.10 0.45 0.20 0.05 0.20
Fig. 5. Operating cost, revenue, gross profits and net profits of volatile oil extracted from resin and lignified ring of A. sinensis using SC-CO2.
3.15 0.25 0.05 0.10 1.40
value of total net present worth for the plant life was $ 32.43 million at 15% of discount rate indicated that the extraction plant has high potential earning capacity.
cost [20]. The number of operators required to run the process was determined by solving Eq. (1) which showed the NOL to be 17. Besides, it was estimated that 5 labors and 2 truck drivers were required in collecting or harvesting of feedstock and transportation, respectively. The laborers’ wages were estimated to be $ 30/h which corresponded to approximately $ 5.26 million/y.
3.1.3.2. Lignified ring of A. sinensis as feedstock. Based on the experimental results, the extracted volatile oil from lignified ring and resin have the same amount of the oil yield. The item that varied in operating cost category was the cost of raw material. As shown in Fig. 5, the operating cost of lignified ring as the feedstock was lower due to lower raw material price compared to resin.Since there is no study reported on the price of lignified ring, it was assumed to be half of the resin price. In terms of revenues, the selling price of volatile oil was the influencing factor. The selling price of volatile oil extracted from lignified ring was predicted to be lower than the commercialized product which assumed to be sold at $ 0.0125 million/kg. Through this assumption, a revenue of $ 66 million/y was obtained in this case study with gross and net profit of $ 13.61 and $ 7.40 million, respectively. Besides, the ROI of 12.05% also gave a positive income. Based on the comparison of the net profit for volatile oil of resin and lignified ring, the oil extracted from resin was more profitable due to higher selling price.
3.1.3. Profits 3.1.3.1. Resin of A. sinensis as feedstock. The profit of an operation was estimated based on the operating costs and total revenue. In this study, the volatile oil extracted from A. sinensis was the main product of the whole production line. Fig. 5 shows the operating cost of the extraction plant by utilizing resin as feedstock which amounted to be $ 81.96 million/y. The main contribution of the operating cost originated from the raw material category as 280 kg of resin was used to extract 1 kg of volatile oil. Nevertheless, it was reported that distilled volatile oil from high grade Aquilaria species can cost up to $ 0.025 million/kg [36]. This gave a total revenue of $ 105.60 million/y for the production capacity of 5280 kg/y of volatile oil. The gross profit was estimated based on the revenues and operating cost as shown in Eq. (13). Net profit was obtained after deducted 24% of income tax and 10% of straight line depreciation from gross profit as shown in Eq. (14). By using Eqs. (13) and (14), the gross profit and net profit were calculated to be $ 23.64 million and $ 17.42 million, respectively. Besides, the calculation for ROI showed 19.16% which implied that this extraction plant was economically feasible at larger scale. In addition, the postive
3.1.4. Sensitivity analysis The yield of volatile oil at industrial scale was estimated using laboratory experimental data as part of the techno-economic analysis to determine the profitability of the SC-CO2 extraction process. The extraction efficiency might differ from the laboratory scale after the extraction process was being scaled up. Nevertheless, it is expected that a higher performance of the process can be achieved at industrial scale with proper equipment design, process optimization and integration.
Fig. 4. Breakdown of the operating cost for SC-CO2 extraction process. 163
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Fig. 6. Sensitivity analysis of economic assessment to percentage of volatile oil yield against changes of OPEX, gross profit, net profit and ROI.
natural gas and hydropower with a proportion of 51%, 45% and 4%, respectively [43]. According to this weightage of electricity generation contribution, the electricity consumption for each single stage of extraction process was calculated based on this ratio and applied in the GaBi LCA software (version 8.1.0.29) equipped with professional data. The results showed that the cradle-to-gate of volatile oil extraction contributed certain impacts towards the environmental. This outcome was due to immaturity of technology and product stage since the data used was scaled up linearly based on lab-scale which potentially caused the results to be overestimated. In general, laboratory scale experiments exclude the energy recovery, heat insulation, recycling of materials and process integration which could affect the overall process efficiency. However, when the technology matured and developed into larger scale, these aspects of the process can be achieved and further improved the productivity of process and environmental performance. The most effective solution is to reduce the CO2 solvent for the extraction process, as most of the equipment is used to covert the phase of CO2 into supercritical state before entering into the extractor. By reducing the amount of CO2 solvent, the usage of electricity could be minimized which eventually contributed less severe impact towards the environment. Meanwhile, other potential improvements such as process modelling, heat integration, adopting energy conserving process and on-site power supply using waste biomass should also taken into consideration when designing an extraction plant. As such, it is predicted that the environmental impacts could be further reduced with higher technology maturity and production scale [38]. Thus, in this context, each single stage of volatile oil extraction and the assumption of solvent loss during the process were estimated to contribute approximately 90% of reduction towards environmental impact when TRL reached 9-10, as shown in Table 5. Based on the system boundary, the first stage of volatile oil extraction was the harvesting activity of A. sinensis. Since there is no data reported for the environmental impact on the harvesting activity of the specific species, the impact contributed to the environment was taken from the study done by Abbas and Handler [25] with a total emission of 20.0 kg CO2 eq. for one tonne of harvested wood. As a baseline scenario, the distance from the plantation to the process plant was assumed to be 200 km per round trip. The work from Abbas and Handler [25] was referred for the emissions, whereby 1 kg of diesel used for transportation contributed 3.62 kg CO2 eq. in GWP. As seen from Table 5, the significant impacts were electricity consumption at the milling and extraction process. The electricity consumption contributed around 90% of the total GWP might be due to consumption of high percentage of non-renewable sources such as hard coal and natural gas for electricity generation. The emissions resulted from CO2 released
The sensitivity of the economic analysis such as OPEX, gross profit, net profit gained and ROI based on variation in percentage of volatile oil yield are shown in Fig. 6. A +5% variation in volatile oil yield resulted in deduction of OPEX to 3.43% due to smaller amount of feedstock was required. This led to increase in gross and net profit of 11.91% and 16.16%, respectively. The ROI also increased from 19.16% to 19.83%. On the other hand, when the volatile oil yield was reduced by 5%, it caused the net profit loss up to 17.87% due to the increment of the total cost of OPEX by 3.80%. 3.2. Environmental impact analysis This study attempted to evaluate the LCA of extracting volatile oil from A. Sinensis using SC-CO2 extraction at industrial scale. Data gaps are still remain as fundamental problems in performing ex-ante LCA of technologies because there are yet to exist at commercial scale [37]. Nevertheless, assessments need to be performed, and it is essential that any uncertainties arising from data gaps and parametric uncertainties are properly documented [38]. In this work, the environmental impact for harvesting activity and transportation were retrieved from the established literature [25]. Simulation of the scaled-up extraction process was performed using Aspen Plus version 10. The simulation data was then applied in GaBi LCA software for the evaluation of environmental impacts. Nonetheless, the process itself remained technologically immature, and rated at a Technology Readiness Level (TRL) of 3. The TRL is a widely used nine-point scale for rating technology maturity [39]. Straub [40] has proposed the addition of a tenth level to indicate an extended history of commercial scale use. Previous research has reported that the process of scaling up with an elevated TRL could reduce the environmental impacts significantly due to higher gains in efficiency through factors such as optimum surface area-to-volume ratios and process integration which involved the energy and heat recovery, and recycling of resources. For instance, the environmental assessment for recycling of waste and anaerobic digestion of organic waste with energy recovery in cogeneration plant have the minimum environmental impact as compared to the current situation with landfilling of waste without energy recovery [41]. It was also reported that in the case of carbon nanotubes (CNT) manufacturing, environment impacts were reduced significantly by up to 84–94% when commercial production volume was achieved [42]. In general, the environmental assessment varied based on the level of technology maturity. As the maturity of TRL increased, it was estimated that the environmental impact would be reduced proportionally after upscaled the extraction process from laboratory to industrial scale. In Malaysia, the main resources for energy mix comprised of coal, 164
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Table 5 Cradle-to-gate analysis of extraction of 1 kg of volatile oil from A. sinensis. Supercritical carbon dioxide extraction of volatile oil from A. sinensis Impact category GWPb APc EPd
Unit
Harvesting of the plant
kg CO2 eq. 5.60 kg SO2 eq. NA kg PO43− NA eq. e kg DCB eq. NA HTP POFPf kg C2H4 eq. NA Estimated emissions when TRLs = 9–10 kg CO2 eq. 5.60 GWPb APc kg SO2 eq. NA EPd kg PO43− NA eq. e HTP kg DCB eq. NA POFPf kg C2H4 eq. NA
Transportation
Electricity for milling
Electricity for SC-CO2 extraction
Assumption of CO2 loss during extraction process
Total
5.72 NA NA
118.13 1.14 3.51 × 10−2
352.56 3.39 0.10
1.05 NA NA
513.84 4.53 0.14
NA NA
20.73 6.27 × 10−2
61.88 0.19
NA NA
82.61 0.25
5.72 NA NA
11.81a 0.11a 3.51 × 10−3a
35.26a 0.34a 0.01a
0.11a NA NA
58.50 0.45 1.40 × 10−2
NA NA
2.07a 6.27 × 10−3a
6.19a 1.90 × 10−2a
NA NA
8.26 2.60 × 10−2
a Estimation of 90% of reduction in the cradle-to-gate environmental impacts when SC-CO2 extraction process is ramped up from small to large scale (TRL 9–10) production [42]. b Global warming potential. c Acidification potential. d Eutrophication potential. e Human toxicity potential. f Photochemical ozone formation potential.
on the variation in percentage of extraction efficiency. As the extraction efficiency improved, the environment impacts were reduced as observed in the negative bar. A +20% variation in extraction efficiency resulted in deduction of 11.70 kg CO2 eq. and 1.65 kg DCB eq. Besides, sensitivity analysis with variation of 10% electricity consumption was also conducted. The results showed that 10% of reduction in electricity usage decreased the GWP and HTP by 5.14 kg CO2 eq. and 0.83 kg DCB eq., respectively. These results indicated that an improvement in the oil yield extraction and reduction of electricity consumption were relatively vital as these affect the sustainability of the environment during mass production.
during combustion and upstream emissions of CO2 and CH4 in the fuel supply chains [44]. Besides, coal combustion during electricity generation emitted gases such as SOx, NOx, CO2 and PM which contributed towards the environmental impacts [45]. The second highest contributor for the volatile oil extraction was HTP that mainly related to health and safety issues. Brizmohun et al. [46] pointed out that the emissions of heavy metals to air, water and soil during coal mining are the reason which attributed to high amount of DCB. Thus, renewable energy or low carbon energy sources such as solar power and hydropower should be considered and developed for emissions reduction [47]. Another potential solution is the on-site use of residual biomass as fuel for heat and electricity generation to meet process heat requirements [48]. Somehow, these modifications would shift the process techno-economics due to higher capital costs and lower electricity purchases.
3.2.2. Limitations of this LCA study The system boundary which investigated the extraction of volatile oil from A. sinensis at industrial scale was defined as “cradle-to-gate” that started from harvesting activity and ended with the extracted volatile oil. Biomass cultivation and further processing of extracted volatile oil that beyond the LCA system boundary are not investigated in this work. As there is limited information on the data input for the scale-up of the extraction process, the applied data in LCA simulation
3.2.1. Sensitivity analysis Sensitivity analysis was performed to examine the most impactful category of environmental burden related to the extraction process. Fig. 7 shows the sensitivity analysis of the environmental impacts based
Fig. 7. Sensitivity analysis of environmental impacts against percentage of volatile oil yield and electricity consumption. 165
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were obtained through laboratory scale experiments that was evenly scaled up for extraction of 1 kg of volatile oil. This LCA study which was based on the available laboratory experiments data only provided limited indication on the potential environmental impacts of the same materials or process operating condition at industrial scale. Besides, the environmental impacts for harvesting activity and transportation retrieved from the established literature were based on the forest biomass grown in Tennessee which might vary based on the countries.
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4. Conclusions A techno-economic and LCA of SC-CO2 extraction for volatile oil extracted from A. sinensis were evaluated. The abundant lignified biomass was used as the feedstock to evaluate its economic feasibility towards commercialization. Based on the calculation of CAPEX, the FCI and TCI of the process plant were estimated to be $ 6.18 million and $ 7.11 million, respectively for the production capacity of 5280 kg/y volatile oil. In terms of operating cost, the cost of raw materials contributed the main portion. With respect to the estimated selling price and cost of raw material for resin and lignified ring, both economic studies revealed a positive net profit. This indicated that the volatile oil extracted from lignified ring was economically competitive to the volatile oil extracted from resin. The cradle-to-gate LCA analysis showed that SC-CO2 extraction process was the major contributor towards the environmental burden due to its high energy consumption. Nonetheless, the study estimated that at higher TRLs, the process could greatly reduce the impacts at industrial scale as the technology matured. In particular, the prospect of recovering residual biomass from the process for on-site use as fuel is able to reduce life cycle GHG emissions. This study leads to further research on the biomass utilization in extracting volatile oil by using SC-CO2 extraction method from economic perspective and environmental point of view. Conflict of interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. CRediT authorship contribution statement Yong Ling Gwee: Writing - original draft, Formal analysis, Conceptualization, Methodology, Investigation. Suzana Yusup: Writing - review & editing, Supervision, Funding acquisition, Project administration. Raymond R. Tan: Writing - review & editing, Formal analysis, Resources. Chung Loong Yiin: Writing - review & editing. Acknowledgement The authors express gratitude to Biomass Processing Cluster, Center for Biofuel and Biochemical Research, Chemical Engineering Department, Universiti Teknologi PETRONAS for the support and Eco Midori Sdn Bhd for supplying Aquilaria Species as the feedstock for this study. Lastly, support from Ministry of High Education Malaysia through HiCoE award to CBBR is duly acknowledged. References [1] S.P. Chong, M.F. Osman, N. Bahari, E.A. Nuri, R. Zakaria, K. Abdul-Rahim, Agarwood inducement technology: a method for producing oil grade Agarwood in cultivated Aquilaria malaccensis Lamk, J. Agrobiotechnol. 6 (2015). [2] H.I.M. Kakino, T. Ito, K. Tsuruma, Y. Araki, M. Shimazawa, M. Oyama, M. Iinuma, H. Hara, Agarwood induced laxative effects via acetylcholine receptors on loperamide-induced constipation in mice, Biosci. Biotechnol. Biochem. 74 (2010) 1550–1555. [3] S. Akter, Md.T. Islam, M. Zulkefeli, M. Khan, Agarwood production—a multidisciplinary field to be explored in Bangladesh, Int. J. Pharm. Life Sci. 2 (2013) 22–32.
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