An engineering and economic evaluation of wet and dry pre-fractionation processes for dry-grind ethanol facilities Tao Lin a,1 , Luis F. Rodríguez b,⇑ , Changying Li c,2 , Steven R. Eckhoff d,3 a University of Illinois at Urbana-Champaign, Department of Agricultural and Biological Engineering, 374 Agricultural Engineering Sciences Building, MC-644, 1304 W. Pennsylvania Avenue, Urbana, IL 61801, United States b University of Illinois at Urbana-Champaign, Department of Agricultural and Biological Engineering, 376C Agricultural Engineering Sciences Building, MC-644, 1304 W. Pennsylvania Avenue, Urbana, IL 61801, United States c University of Georgia, Department of Biological and Agricultural Engineering, 2329 Rainwater Road, P.O. Box 748, Tifton, GA 31793, United States d University of Illinois at Urbana-Champaign, Department of Agricultural and Biological Engineering, 360C Agricultural Engineering Sciences Building, MC-644, 1304 W. Pennsylvania Avenue, Urbana, IL 61801, United States article info Article history: Received 11 February 2011 Received in revised form 2 June 2011 Accepted 3 June 2011 Available online 16 June 2011 Keywords: Engineering–economic model Dry grind process Fractionation Ethanol Biofuel abstract An engineering–economic model was developed to compare the profitability of the wet fractionation pro- cess, a generic dry fractionation process, and the conventional dry grind process. Under market condi- tions as of January 2011, only fractionation processes generated a positive cash flow. Reduced unit manufacturing costs and increased ethanol production capacity were two major contributions. Corn and ethanol price sensitivity analysis showed that the wet fractionation process always outperformed a generic dry fractionation process at any scenario considered in this research. A generic dry fractionation process would provide better economic performance than the conventional dry grind process if corn price was low and ethanol price was high. All three processes would perform more resiliently if the DDGS price was determined by its composition. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The production of ethanol has increased rapidly from 60 million gallons in the mid 1970s to 10.6 billion gallons in 2009 (Renewable Fuels Association, 2010). Corn-based ethanol remains the most via- ble biofuel available on the market today, and it will continue to be an important renewable fuel source in the near future. The US Environmental Protection Agency proposed that corn-based etha- nol should be targeted to produce 15 billion gallons by 2022 (EPA, 2009). Currently, the conventional dry grind process domi- nates corn-based ethanol production. As ethanol production soars, distiller’s dried grains with solubles (DDGS), the single marketable coproduct of the conventional dry grind process, will increase pro- portionately, and it is expected to far exceed the conventional means of utilization by ruminant animals (Srinivasan et al., 2006). One possible solution is to modify the conventional dry grind process and produce other value-added coproducts that are in greater demand in the market place. In response to this need, two types of modified dry grind pro- cesses, wet fractionation (Singh and Eckhoff, 1997; Singh et al., 2005; Wahjudi et al., 2000) and dry fractionation (Clark, 2006; Cereal Process Technologies, 2011; Foster, 2008; FWS Technologies, 2011; Giguere, 1993; ICM, 2011; Murthy et al., 2009; Poet, 2011), were developed. Essentially, these pre-fractionation technologies separate germ and fiber from the corn kernel before fermentation. The backend of both types of processes (i.e., after germ and fiber recovery from corn) are the same as the conventional dry grind process. Although both technologies work towards the same goal, they operate quite differently. The dry fractionation processes are based on a traditional dry milling front end. Designed for ethanol production, the dry fractionation process maintains the cleanliness of the germ and pericarp fractions and minimizes the loss of starch in the fractionation process. The dry milling process is designed for food production and maximizes the cleanliness of the grit, meal and flour; for more details refer to Eckhoff (2004). The wet fractionation processes (Quick-germ/Quick-fiber process (QQ) and E-milling for dry grind) are based on a wet milling front end. E-milling for the dry grind process extends the QQ process to recover endosperm fiber from the corn prior to ethanol fermenta- tion (Singh et al., 2005). To provide decision support for ethanol producers, an engineer- ing–economic model was developed to evaluate the QQ process technology (Li et al., 2010; Rodríguez et al., 2010). The work 0960-8524/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2011.06.013 ⇑ Corresponding author. Tel.: +1 217 333 2694; fax: +1 217 244 0323. E-mail addresses: [email protected](T. Lin), [email protected](L.F. Rodríguez), [email protected](C. Li), [email protected](S.R. Eckhoff). 1 Fax: +1 217 244 0323. 2 Tel.: +1 229 386 3915; fax: +1 229 386 3958. 3 Tel.: +1 217 244 4022; fax: +1 217 244 0323. Bioresource Technology 102 (2011) 9013–9019 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech
An engineering and economic evaluation of wet and dry pre-fractionationprocesses for dry-grind ethanol facilities
Tao Lin a,1, Luis F. Rodríguez b,⇑, Changying Li c,2, Steven R. Eckhoff d,3
a University of Illinois at Urbana-Champaign, Department of Agricultural and Biological Engineering, 374 Agricultural Engineering Sciences Building,MC-644, 1304 W. Pennsylvania Avenue, Urbana, IL 61801, United Statesb University of Illinois at Urbana-Champaign, Department of Agricultural and Biological Engineering, 376C Agricultural Engineering Sciences Building, MC-644,1304 W. Pennsylvania Avenue, Urbana, IL 61801, United Statesc University of Georgia, Department of Biological and Agricultural Engineering, 2329 Rainwater Road, P.O. Box 748, Tifton, GA 31793, United Statesd University of Illinois at Urbana-Champaign, Department of Agricultural and Biological Engineering, 360C Agricultural Engineering Sciences Building,MC-644, 1304 W. Pennsylvania Avenue, Urbana, IL 61801, United States
a r t i c l e i n f o
Article history:Received 11 February 2011Received in revised form 2 June 2011Accepted 3 June 2011Available online 16 June 2011
An engineering–economic model was developed to compare the profitability of the wet fractionation pro-cess, a generic dry fractionation process, and the conventional dry grind process. Under market condi-tions as of January 2011, only fractionation processes generated a positive cash flow. Reduced unitmanufacturing costs and increased ethanol production capacity were two major contributions. Cornand ethanol price sensitivity analysis showed that the wet fractionation process always outperformeda generic dry fractionation process at any scenario considered in this research. A generic dry fractionationprocess would provide better economic performance than the conventional dry grind process if corn pricewas low and ethanol price was high. All three processes would perform more resiliently if the DDGS pricewas determined by its composition.
� 2011 Elsevier Ltd. All rights reserved.
1. Introduction In response to this need, two types of modified dry grind pro-
The production of ethanol has increased rapidly from 60 milliongallons in the mid 1970s to 10.6 billion gallons in 2009 (RenewableFuels Association, 2010). Corn-based ethanol remains the most via-ble biofuel available on the market today, and it will continue to bean important renewable fuel source in the near future. The USEnvironmental Protection Agency proposed that corn-based etha-nol should be targeted to produce 15 billion gallons by 2022(EPA, 2009). Currently, the conventional dry grind process domi-nates corn-based ethanol production. As ethanol production soars,distiller’s dried grains with solubles (DDGS), the single marketablecoproduct of the conventional dry grind process, will increase pro-portionately, and it is expected to far exceed the conventionalmeans of utilization by ruminant animals (Srinivasan et al.,2006). One possible solution is to modify the conventional drygrind process and produce other value-added coproducts that arein greater demand in the market place.
ll rights reserved.
: +1 217 244 0323.illinois.edu (L.F. Rodríguez),
ff).
cesses, wet fractionation (Singh and Eckhoff, 1997; Singh et al.,2005; Wahjudi et al., 2000) and dry fractionation (Clark, 2006;Cereal Process Technologies, 2011; Foster, 2008; FWS Technologies,2011; Giguere, 1993; ICM, 2011; Murthy et al., 2009; Poet, 2011),were developed. Essentially, these pre-fractionation technologiesseparate germ and fiber from the corn kernel before fermentation.The backend of both types of processes (i.e., after germ and fiberrecovery from corn) are the same as the conventional dry grindprocess. Although both technologies work towards the same goal,they operate quite differently. The dry fractionation processes arebased on a traditional dry milling front end. Designed for ethanolproduction, the dry fractionation process maintains the cleanlinessof the germ and pericarp fractions and minimizes the loss of starchin the fractionation process. The dry milling process is designedfor food production and maximizes the cleanliness of the grit,meal and flour; for more details refer to Eckhoff (2004). The wetfractionation processes (Quick-germ/Quick-fiber process (QQ)and E-milling for dry grind) are based on a wet milling front end.E-milling for the dry grind process extends the QQ process torecover endosperm fiber from the corn prior to ethanol fermenta-tion (Singh et al., 2005).
To provide decision support for ethanol producers, an engineer-ing–economic model was developed to evaluate the QQ processtechnology (Li et al., 2010; Rodríguez et al., 2010). The work
Table 1aDry basis product yield and composition comparison among the conventional drygrind process, the QQ process, and a generic dry fractionation processes.
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described in this study extends the analysis to consider a genericdry fractionation process technology and compares it to the QQand the conventional dry grind processes. The wet fractionationprocess, E-milling for dry grind, was not considered in this studybecause the dry fractionation process and QQ process are morecomparable, as both processes recover germ and coarse fiber.
The objectives of this study are: (1) to evaluate the economicperformance of a generic dry fractionation process, the QQ process,and the conventional dry grind process; (2) to perform a sensitivityanalysis with corn and ethanol price changes, corn oil pricechanges, and retrofitting cost changes. All sensitivity analyses areperformed given current DDGS market prices; the sensitivity ofcorn and ethanol prices are also considered utilizing an optimisticprice for modified DDGS, which varies with DDGS quality.
Table 1bThe product yield by a generic dry fractionation process used in this manuscript ascompared to the yield information from the industrial companies. No data is availabledescribing two processes previously mentioned in the text: Dry Corn Fractionationtechnology by ICM and BFrac™ by Poet.
Thisstudy
MarketFLEX™ bycereal processtechnologies
FWS fractionationby FWStechnologies
Percent of availablestarch in corn forfermentation
94.5% >91%a >95%b
Oil yield as percent ofoil in corn
69.3% >65%a <50%c
Percent of endospermin corn
85.2% >80%a >80%b
a Cereal Process Technologies, 2011.b Estimated from the product literature from FWS Technologies.c Murthy et al., 2009.
Table 2Market price of raw materials, utilities, and products as of January 2011.
Market price
Raw materialCorn $6.21 per bushela
UtilitiesElectricity $0.075 per kWhb
Natural gas $4.59 per million Btuc
ProductsEthanol $2.35 per gallond
DDGS $175 per tone
Corn oil $0.585 per lbf
a http://www.ams.usda.gov/mnreports/gx_gr115.txt (accessed on Jan. 13, 2011).b http://www.eia.doe.gov/electricity/epm/table 5_6_a.html (accessed on Jan. 13,
2011).c http://www.eia.doe.gov/oog/info/ngw/ngupdate.asp (accessed on Jan. 13,
sed on Jan. 13, 2011).e http://www.ams.usda.gov/mnreports/sj_gr225.txt (accessed on Jan. 13, 2011).f http://www.ams.usda.gov/mnreports/gx_gr115.txt (accessed on Jan. 13, 2011).
2. Methods
2.1. Economic model overview and baseline assumptions
The model is based on a conventional dry grind plant with acapacity of 36 million annual gallon ethanol production (136 mil-lion l). The plant runs 350 days each year and leaves 15 days formaintenance.
The capital costs of the dry grind plant are determined to be $80million by Rodríguez et al. (2010). Based on a ±5% engineering de-sign for retrofitting a conventional dry grind plant with this capac-ity, the cost of the QQ process retrofitting is 70¢ per annual gallonof ethanol production capacity (Danforth, 2011). For this analysis,we refer to the schematics of the conventional dry grind and theQQ processes put forth by Rodríguez et al. (2010); please see Fig-ure 1 in Rodríguez et al. (2010).
The cost of a generic dry fractionation process retrofitting is dif-ficult to estimate because the designs of each dry fractionation pro-cesses (e.g., BFrac™ by Poet; MarketFLEX™ by Cereal ProcessTechnologies; Dry Corn Fractionation by ICM; FWS fractionationby FWS Technologies) are held as proprietary by each companywe consulted. Industrial contacts estimated the cost at 50¢ per an-nual gallon. For this analysis, we refer to an example of the FWSdry fractionation process diagram put forth previously by Murthyet al. (2009); please see Figure 1 in Murthy et al. (2009).
Corn germ oil production is planned in the baseline analysis.The cost of an oil-expelling system is estimated at $5.7 millionand $8.5 million for the QQ and the generic dry fractionation pro-cesses, respectively. The higher cost of an oil-expelling system bythe generic dry fractionation process is due to its lower expellingefficiency.
A mass-balance composition table is provided to compare prod-uct composition assumed in this study of the conventional drygrind, the QQ process, and a generic dry fractionation process(Table 1a). The product yield of a generic dry fractionation processused in this study is compared to the available data provided bytwo companies (Table 1b). The yield used in this study met allrequirements guaranteed by Cereal Process Technologies (2011).
As a further verification of our input data, the compositions ofthe coproducts were compared to data provided by Poet (2011).The DDGS from Poet’s facilities using BFracTM contains 40% protein,27.9% NDF, 4% oil, and 2.4% ash based on 43 samples, on a dry massbasis (Poet, 2011). The non-fermentable component fractions ofDDGS are comparable to the values used in this study (Table 1a).
The baseline analysis considers the market price of raw materi-als, utilities, and coproducts prices as of January 2011 (Table 2),and these economic assumptions are held for all three processes.The profit before tax is calculated by subtracting total ethanolmanufacturing costs from ethanol sale revenues. The depreciationand amortization costs are included in the total ethanol
manufacturing costs. The plant is assumed to have a 15 year lifespan and straight-line depreciation method, with zero salvage va-lue at the end. An interest rate of 4% with a 15-year payback period
T. Lin et al. / Bioresource Technology 102 (2011) 9013–9019 9015
is assumed to determine the annual amortization costs for thebaseline analysis. The coproduct values (DDGS, germ meal, oil,and coarse fiber) are taken into account by offsetting the total eth-anol manufacturing costs. The payback period for the retrofit of aconventional dry grind facility is determined as a ratio of retrofitcapital expenditures to annual cash flow. The net present value(NPV) was calculated by Eq. (1) where A is the annual cash flowgenerated by the plant; i is the interest rate; n is the number ofyears; 15 years in this case.
NPV ¼ AX15
n¼0ð1þ iÞn ð1Þ
2.2. Sensitivity analysis
2.2.1. Corn and ethanol price changes under existing DDGS marketconditions
Based on historical data, current prices, and the future trend ofcorn and ethanol prices, six levels of the ethanol price have beenselected from $1.25 to $3.75/gal with a step of $0.50/gal, and sevenlevels of the feedstock price are chosen from $2.00 to $8.00/bu witha step of $1/bu. A fixed price of $175/ton for DDGS, as observed inJanuary 2011, is used in this analysis.
2.2.2. Corn and ethanol price change given a preferred DDGS marketGiven the improved quality of DDGS produced by the pre-frac-
tionation technologies, the modified DDGS should command ahigher price as compared to the conventional DDGS. A regressionmodel (Li et al., 2010) has been used to predict the improved DDGSprice. The economic sensitivity analysis of the three process tech-nologies is conducted with the DDGS price varying with corn priceand the composition of DDGS. The results are compared to the sen-sitivity analysis given the fixed price of DDGS.
2.2.3. Corn oil price change under the existing DDGS marketSimilarly, corn oil price is expected to have significant impact
on plant profitability. Over the past decade corn oil prices variedfrom 13.54¢ to 69.40¢ per lb (USDA-ERS, 2010). Four levels of cornoil price have been selected, 23.5¢ to 67.5¢ per lb at increments of15¢ per lb, to estimate the impact on profit among the threetechnologies.
2.2.4. Retrofitting cost change under the existing DDGS marketBecause the designs of the dry fractionation processes are pro-
prietary, the retrofitting cost is varied from 30¢ to 70¢ per annualgallon. The cost of the QQ process ranges from 50¢ to 90¢ perannual gallon. A step of 10¢ per annual gallon for both fraction-
Table 3Plant capacity and capital investment comparison. Total capital investment for the convecapital. For the QQ and dry fractionation processes, total capital investment includes both tcosts.
Conventional dry grind
Grind rate 934 tons/day(36,749 Bu/day)
Production 37,532,311 gal/year denatured
Capital investmentTotal purchased equip. $20,400,000Total installed equip. $27,988,800Total fixed capital invest. $61,720,902Working capital $11,981,116Start-up capital $6,172,090
Add-on capital costsPrefractionation front end –Oil expelling system –License fee for technology –
Total capital investment $79,874,108
ation processes is selected to quantify the impact of retrofittingcosts.
3. Results and discussion
3.1. Baseline profitability analysis
Given a 36 MGY conventional dry grind ethanol facility, the fi-nal engineering and economic performance of the conventionaldry grind, the QQ, and a generic dry fractionation plant are listedin Table 3. The total capital investment for a generic dry fraction-ation plant includes $80 million for the capital costs of a conven-tional dry grind plant, $27.3 million for the retrofitting, and $2million license fee for the technology.
Both pre-fractionation technologies have higher variable costsmainly because of the increased corn processing demand as wellas the additional electricity demand to run the pre-fractionationequipment (Table 4). The unit production cost difference is primar-ily due to difference in energy consumption (Fig. 1). Compared tothe QQ process, the dry fractionation process requires moreequipment in the front-end separation process and the equipmentis required to deal with drier materials (Murthy et al., 2009;Rodríguez et al., 2010). Further, the oil content of the germ streamis lower for the dry fractionation process, requiring more equipmentand energy for oil expelling. Therefore, electricity cost for the dryfractionation process is 12.2 ¢/gal as compared to 9.1¢/gal for theQQ process (Table 4). Other variable costs, such as enzyme, yeast,and other chemicals, used by the retrofit plants increases propor-tionally with the increased process capacity; however, relative tothe conventional dry grind plant, both the dry fractionation andthe QQ plant reduce their unit natural gas costs by $2.78 and$3.29/gal, respectively. This significant cost reduction is mainlyderived from the increased ethanol concentration generated bythe pre-fractionation processes.
Both pre-fractionation technologies have increased fixed costsdue to the increased process capacity. The total fixed costs are$4.5 million for the dry fractionation plant, as compared to $4.8million and $3.5 million for the QQ and the conventional dry grindplant, respectively (Table 4). This result also corresponds to theprocess capacity of these three plants, where the QQ plant hasthe largest corn process capacity, followed by the dry fractionationand the conventional dry grind plant.
The total revenue of a corn-to-ethanol facility comes from twosources: sale of ethanol and coproducts. Due to the pre-fraction-ation, i.e., removal of the germ and fiber before fermentation, eth-anol production of the dry fractionation and the QQ plants is
ntional dry grind process includes the equipment, installation, and other necessaryhe capital required for the conventional dry grind process and also the add-on capital
Profit analysisTotal cash costs (Variable + Fixed) 80,449 214.35 81,524 192.41 80,832 200.09Depreciation 5325 14.19 7588 17.91 7276 18.01Amortized payment (P&I) 4310 11.48 6250 14.75 5998 14.85Total manufacturing Cost 90,084 233.93 95,361 192.41 94,106 214.94Change in manufacturing cost with retrofit (A) �5277 �12.45 �4022 �9.96Sales value of ethanol 88,200 235 99,570 235 94,935 235Increased revenue/year with retrofit (B) 11,370 26.83 6734 16.67Total offset in cost of ethanol production (A + B) 6093 14.38 2713 6.71Profit before tax �1883 �5.02 4210 9.93 829 2.05
Fig. 1. Energy consumption comparison of the conventional dry grind, dryfractionation, and the QQ process.
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increased by 7.6% and 12.9%, respectively (Table 3). The dry frac-tionation process produces ethanol at the rate of 2.61 gal/bu,which was lower than 2.72 and 2.78 gal/bu for the QQ and conven-tional dry grind process, respectively. The relatively lower ethanolyield per bushel of corn input by the dry fractionation is due tostarch loss using dry fractionation technology.
In the baseline analysis, the improved quality of the DDGS inboth pre-fractionation processes does not command a premiumprice. Corn oil sale provides a significant revenue boost for thedry fractionation and the QQ process at $9.7 million and $12.9million, respectively. The lower purity of germ recovery in thedry fractionation process reduces corn oil yield. However, the dryfractionation process produces higher quantities of corn germ mealand DDGS. The total coproduct sale from the dry fractionation pro-cess provides $34.1 million total offset for ethanol productioncosts, outperforms both the QQ and the conventional dry grindprocesses, which are $33.5 million and $19.5 million, respectively(Table 4).
Considering the market conditions observed in January of 2011,both the dry fractionation and the QQ process achieve a positivecash flow at approximately $2.5 million and $4.8 million, respec-tively (Table 5). Only the conventional dry grind process suffers anegative cash flow of $0.4 million (Table 5). The improved profit-ability of both fractionation processes mainly results from the sig-nificantly reduced unit manufacturing costs, attributed to thehigher coproduct sales, and the increased ethanol productioncapacity.
After 15 years, NPV for new ethanol plant construction isstrongly negative for all three technologies (Table 5). This is largelydue to high capital investment costs and relatively low profit mar-gins given in the market condition as of January 2011. The NPV of
Table 5Cash flow analysis, payback period, and net present value for the baseline case considering January 2011 prices. A tax rate on profits of 35% is assumed. Dividends in the amount of12% of equity are is assumed.
Retrofit capital costs – $33,939,567 $29,266,155Total capital investment (new construction) $79,874,108 $113,813,676 $109,140,263Payback period (retrofit) – 7.1 years 11.8 yearsPayback period (new construction) – 23.9 years 44.0 yearsNet present value (new construction) ($84,235,321) ($60,837,896) ($81,563,167)
Fig. 2. Comparison of the profit before tax generated by the conventional dry grind process, the QQ process, and a generic dry fractionation process with corn and ethanolprice variation, given a fixed DDGS price at $175/ton.
T. Lin et al. / Bioresource Technology 102 (2011) 9013–9019 9017
the dry fractionation plant is lower than that of the QQ plant butslightly higher than the conventional dry grind plant.
3.2. Sensitivity analysis
3.2.1. Corn and ethanol price changes under the existing DDGSconditions
Fig. 2 compares the profit before tax of the conventional drygrind, the dry fractionation and the QQ process at different levelsof corn and ethanol prices. With the rise of ethanol price and thefall of corn price, both the dry fractionation and the QQ processesimprove their profit before tax more rapidly relative to theconventional dry grind process. This is because of the increasedethanol production capacity for both fractionation plants. Whencorn prices remain the same, for every $0.5/gal increase ofethanol price, the QQ and the Dry fractionation process wouldimprove its profit before tax by $20.1 million and $19.2 million,respectively, compared to $17.8 million for the conventional drygrind process.
The QQ process always outperforms the dry fractionation pro-cess at all ethanol and corn price combinations considered. In addi-tion, the QQ process generates higher profit than the conventional
dry grind in most scenarios – the only exception being if corn pricereaches $8/bu when ethanol price is at $1.25/gal. The QQ processachieves more significant advantages with higher ethanol prices.
The dry fractionation process outperforms the conventional drygrind process at all seven corn price scenarios when ethanol is at orabove $2.25/gal, but it generates lower profits if corn is over $6/buand ethanol is $1.25/gal.
3.2.2. Corn and ethanol price change given a preferred DDGS priceFrom the mass balance analysis (Table 1a), it is clear that both
the QQ and the dry fractionation processes produce a differentquality of coproducts (namely DDGS, germ meal, oil, and coarse fi-ber) and a slightly different ethanol yield. Based on the DDGS priceprediction model in Li et al. (2010), the nutritional improvement ofthe DDGS could potentially affect its price. When the corn price is$6.21/bushel, the price of the DDGS from conventional dry grindis $259/ton, dry fractionation is $293/ton, and the QQ process is$342/ton.
Fig. 3 shows that both the dry fractionation and the QQ processoutperform the conventional dry grind process with higher ethanolprice and lower corn price. Comparing Figs. 2 and 3, the resultsindicate that, given a preferred DDGS market, all three processes
Fig. 3. Comparison of the profit before tax generated by the conventional dry grind process, the QQ process, and a generic dry fractionation process with corn and ethanolprice variation, given an optimistic DDGS price varying with its composition and corn price.
Fig. 4. Sensitivity analysis of corn oil price changes.
9018 T. Lin et al. / Bioresource Technology 102 (2011) 9013–9019
would perform more resiliently with corn price changes becausethe DDGS prices tend to follow corn price trends.
3.2.3. Corn oil price changeSince no corn oil is produced in the conventional dry grind
plant, corn oil price changes only affect the profit before tax ofthe dry fractionation and the QQ plants. Fig. 4 shows that profit be-fore tax of both pre-fractionation plants is sensitive to corn oilprice changes. For every penny change in corn oil price, profit be-fore tax increases by $0.17 million and $0.22 million for dry frac-tionation and the QQ process, respectively.
3.2.4. Retrofitting cost changeConsidering market conditions as of January 2011, the QQ
process always generates positive profit before tax at anyretrofitting cost level, while the dry fractionation process suffersa negative cash flow given a retrofitting cost of 70¢/gal (Table 6).Despite the higher initial capital costs, the QQ process providesbetter NPV performance as compared to the conventional drygrind process at any retrofitting cost level, while the dryfractionation process outperforms the conventional dry grindprocess only when the retrofitting costs are below $0.5/gal(Table 6).
3.3. Life cycle impacts of prefractionation processes
The energy demand at the biorefinery site is the majorcontributor to the corn-to-ethanol life cycle analysis of energy
Table 6Sensitivity analysis retrofit cost changes on the economic performance of two fractionatio
consumption (Hill et al., 2006). Both the QQ and the dry fraction-ation processes reduce energy consumption as compared to theconventional dry grind process (Fig. 1) and this directly improvesthe life cycle energy balance of the corn-to-ethanol process. Fur-ther, displacement and allocation energy credits derived from thenutritional value and market value of these coproducts can be usedto offset life cycle impacts of processes with multiple product
n processes for the baseline case considering January 2011 prices.
T. Lin et al. / Bioresource Technology 102 (2011) 9013–9019 9019
streams (Wang et al., 2010). The improved coproduct quality fromboth fractionation processes will improve the displacement ratio ofthe ingredients used for animal feeds given the adoption of theimproved DDGS produced by these processes, which will furtherimprove the life cycle energy balance. The same is true for othercoproducts. A detailed life cycle analysis of various corn-to-ethanolprocesses is under development.
4. Conclusions
An engineering–economic model, which is mass balanced andcompositionally driven, was used to compare the performance ofthe conventional dry grind process, the wet fractionation process(QQ) and a generic dry fractionation process. Given market condi-tions as of January 2011, only the two fractionation processesachieve a positive annual cash flow. Because of its higher ethanolproduction and corn oil yields, the QQ process outperforms thedry fractionation process at all scenarios in this analysis. Consider-ing a preferred DDGS market, all three processes perform moreresiliently with the corn price fluctuation.
Acknowledgements
This work was partially funded by the Illinois Council on Foodand Agricultural Research (C-FAR) and USDA CSREES through hatchproject #ILLU-741-342 (NC Regional Project 1016).
Cereal Process Technologies, 2011. Available at <http://www.cerealprocess.com/index.html>. Accessed on January 17, 2011.
Danforth, S., 2011. Personal communication. AP Innovations, Stuttgart, Arkansas.Eckhoff, S.R., 2004. Maize dry milling. In: Wrigley, C. (Ed.), Encyclopedia of Grain
Science. Academic Press Inc., Orlando, FL, pp. 215–225.EPA, 2009. New Regulations for the National Renewable Fuel Standard Program for
2010 and Beyond. Available at <http://www.epa.gov/OMS/renewablefuels/420f09023.htm>. Accessed on December 2, 2009.
FWS Technologies, 2011. Available at <http://www.fwstl.com/pdfs/fwst_presenta-tion.pdf>. Accessed on January 17, 2011.
Foster, G., 2008. Corn fractionation process. US Patent No. 7419,108.Giguere, R.J., 1993. Grain milling and degermination process. US Patent No.
5250,313.Hill, J., Nelson, E., Tilman, D., Polasky, S., Tiffany, D., 2006. Environmental, economic,
and energetic costs and benefits of biodiesel and ethanol biofuels. Proc. Natl.Acad. Sci. USA 103 (30), 11206–11210.
ICM, 2011. Available at <http://www.icminc.com/pdf/ProductLines/Dry_Corn_Frac-tionation.pdf>. Accessed on January 17, 2011.
Li, C., Rodriguez, L.F., Khanna, M., Spaulding, A.D., Lin, T., Eckhoff, S.R., 2010. Anengineering and economic evaluation of quick germ–quick fiber process for dry-grind ethanol facilities: model description and documentation. Bioresour.Technol. 101 (14), 5275–5281.
Murthy, G.S., Sall, E.D., Metz, S.F., Foster, G., Singh, V., 2009. Evaluation of a dry cornfractionation process for ethanol production with different hybrids. Ind. CropProd. 29 (1), 67–72.
Poet, 2011. Available at <http://www.dakotagold.com/about/bfrac.asp>. Accessed atJanuary 15, 2011.
Renewable Fuels Association, 2010. Climate of opportunity: Ethanol IndustryOutlook 2009. Available at <http://ethanolrfa.org/page/-/objects/pdf/outlook/RFAoutlook2010_fin.pdf?nocdn=1>. Accessed on January 13, 2011.
Rodríguez, L.F., Li, C., Khanna, M., Spaulding, A.D., Lin, T., Eckhoff, S.R., 2010. Anengineering and economic evaluation of quick germ–quick fiber process for dry-grind ethanol facilities: analysis. Bioresour. Technol. 101 (14),5282–5289.
Singh, V., Eckhoff, S.R., 1997. Economics of germ pre-separation for dry-grindethanol facilities. Cereal Chem. 74 (4), 462–466.
Singh, V., Tumbleson, M.E., Belyea, R.L., Rausch, K.D., Johnston, D.B., Naidu, K., 2005.Comparison of modified dry-grind corn processes for fermentationcharacteristics and DDGS composition. Cereal Chem. 82 (2),187–190.
Srinivasan, R., Singh, V., Belyea, R.L., Rausch, K.D., Moreau, R.A., Tumbleson, M.E.,2006. Economics of fiber separation from distillers dried grains with solubles(DDGS) using sieving and elutriation. Cereal Chem. 83 (4), 324–330.
USDA-ERS, 2010. Oil crops outlook monthly tables. Available at: <http://www.ers.usda.gov/Briefing/soybeansOilCrops/data.htm>. Accessed 7 January2010.
Wahjudi, J., Xu, L., Wang, P., Singh, V., Buriak, P., Rausch, K.D., McAloon, A.J.,Tumbleson, M.E., Eckhoff, S.R., 2000. Quick fiber process: effect of mashtemperature, dry solids, and residual germ on fiber yield and purity. CerealChem. 77 (5), 640–644.
Wang, M., Huo, H., Arora, S., 2010. Methods of dealing with coproducts of biofuels inlife-cycle analysis and consequent results within the U.S. context. Energ. Policy.doi:10.1016/j.enpol.2010.03.052.
