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Production of ethanol from carbohydrates from loblolly pine:A technical and economic assessment

W.J. Frederick Jr. a,*, S.J. Lien b, C.E. Courchene b, N.A. DeMartini b,A.J. Ragauskas c, K. Iisa a

a School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, IPST Building, 500, 10th Street NW,

Atlanta, GA 303320620, United Statesb Institute of Paper Science and Technology (IPST), Georgia Institute of Technology, Atlanta, GA, United States

c School of Chemistry and Biochemistry, Georgia Institute of Technology, United States

Received 5 February 2007; received in revised form 24 August 2007; accepted 28 August 2007Available online 21 February 2008

Abstract

Ethanol from lignocellulosic biomass has the potential to contribute substantially to bioethanol for transportation. We have evaluatedthe technical and economic feasibility of producing ethanol from the carbohydrates in loblolly pine. In the process evaluated, prehydro-lysis with dilute sulfuric acid was employed to hydrolyze hemicellulose and make the cellulose more accessible to hydrolysis by enzymes.Residual biomass from hydrolysis and extraction of carbohydrates was burned in a CHP plant to generate power and process steam.

Our analysis indicates that ethanol can be produced at a cost of $1.53/gal, based on a delivered wood cost of $63.80/dry metric tonand 75% conversion of the carbohydrates in wood to sugars for ethanol production. Improving the conversion of wood carbohydrates tosugars to 95% would reduce the production cost to $1.29/gal. These values are for a plant producing 74 million gal/yr and 93 million gal/

yr, respectively. At current feedstock prices, ethanol produced from loblolly pine would be competitive with ethanol produced from cornor other lignocellulosic biomass. Based on our analysis, discounted cash flow rates of return would be 18% and 25%, respectively forplants of this capacity. 2007 Published by Elsevier Ltd.

Keywords: Biomass; Economics; Ethanol; Fermentation; Pine

1. Introduction

The need for energy security in non oil-producing coun-tries and climate change imperatives world-wide are driving

the effort to replace petroleum-derived fuels with biofuels.Ethanol from lignocellulosic biomass has the potential tocontribute substantially to bioethanol for transportation(Ragauskas et al., 2006).

Cellulosic ethanol has the potential to contribute sub-stantially to bioethanol for transportation. Current esti-mates of biomass available in the US as bioenergy

feedstock on a sustainable basis are 368 million t/a for-est-derived biomass and 194 million t/a agricultural residue(Perlack et al., 2005). One projection is that, nationwide,the amount of lignocellulosic biomass available from

agriculture could increase to between 540 million and 998million dry metric tons/yr by 2050, while the amount offorest-derived biomass available would remain nearly con-stant (Perlack et al., 2005). This amount of biomass couldyield more than 25 billion gal/yr (78 GWth) of ethanol viafermentation, and another 15 billion gal/yr (46 GWth) ofmixed alcohols by catalytic production from synthesis gasderived from the fermentation residues (see Table 1).

Southern pine species, comprised mainly of loblolly andslash pine, are the predominant wood species grown in for-ests in the southeastern US, where forest productivity is

0960-8524/$ - see front matter 2007 Published by Elsevier Ltd.

doi:10.1016/j.biortech.2007.08.086

* Corresponding author. Tel.: +1 4048942082; fax: +1 4043850522.E-mail address: [email protected] (W.J. Frederick Jr.).

Available online at www.sciencedirect.com

Bioresource Technology 99 (2008) 50515057
mailto:[email protected]:[email protected]


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high. Pine is currently used primarily for solid wood prod-ucts and pulpwood; turpentine, pine oil, and other chemi-cals are also extracted from it, and power is generated incombined heat and power (CHP) plants fueled by wastepulping liquors.

There is considerable interest in utilizing pine as a feed-stock for production of transportation fuels. In the presentstudy, we have evaluated the technical and economicaspects of producing ethanol from the carbohydrates inloblolly pine. In subsequent papers we will evaluate optionsfor co-producing ethanol, fiber and power from southernpine in integrated biorefineries.

2. Basis

In the study reported here, we have evaluated the poten-tial for producing ethanol by (a) hydrolyzing the carbohy-drates (cellulose and hemicellulose) in loblolly pine tofermentable sugars, and (b) fermenting those sugars to eth-anol. The basis for this study is an ethanol plant that pro-cesses 3000 dry short tons/day (2727 t/day) of loblolly pineon a dry, bark-free basis.

Loblolly pine consists of nearly 65% cellulose and hemi-cellulose that can be converted to sugars, lignin as a thirdmajor component, and other constituents Table 2.

Residue from conversion of biomass feedstock, fromhydrolysis of the carbohydrates, and fermentation of theresulting sugars, represents a significant energy stream.We estimate that the energy value of the combined residueis greater than the energy value of the ethanol product. In

the plant considered here, waste is dewatered and burned in

a CHP plant to generate power and process steam. Processsteam is extracted from the turbine at two pressures. Pro-cess steam is produced corresponding to steam demandand excess biomass is exported for fuel. The power demand

for the plant is balanced by purchasing additional powerfrom the grid.The conceptual process evaluated here follows qualita-

tively the process schemes outlined by Wooley et al. (1999)for ethanol production from yellow poplar, and Hamelincket al. (2003) for ethanol production from lignocellulosic bio-mass. Fig. 1 shows the components of the ethanol plant andintegrated CHP plant. Mass and energy flows between theethanol plant and CHP plant are indicated.

3. Acid prehydrolysis

Pretreatment with dilute sulfuric acid was selected as themeans of increasing the permeability of comminuted lob-lolly pine bole wood to enzymes and to the sugars and oli-gimers produced from hemicellulose and cellulose. Thistechnology is well established (Rydholm, 1965; Casebieret al., 1969; Elmore, 1984). It converts most of the hemicel-lulose to sugars (xylose, mannose, arabinose, and galact-ose), and produces acetic acid by cleavage of acetylgroups from the hemicellulose. Dilute acid hydrolysisdegrades less of the sugars to fermentation inhibitors (fur-fural, and hydroxymethyl furfural) than do other methods(Nguyen et al., 1998).

Although it may be desirable to completely hydrolyze all

of the cellulose in loblolly pine to glucose, there may betechnical and economic limitations to doing so. In thisstudy, we considered a range of 7595% conversion ofwood carbohydrates to sugars. Seventy-five percentage rep-resents an achievable conversion with current technology(Hamelinck et al., 2003), while 95% represents an optimis-tic target as the technologies for prehydrolysis and enzy-matic hydrolysis of cellulose are improved.

3.1. Hydrolyzate conditioning

Degradation products of pentose and hexose sugars

(primarily furfural and hydroxymethyl furfural), acetic

Table 1Potential for ethanol from cellulosic biomass (annual basis)

Fromwood

Fromagriculturalresidues

Total

Available from biomass via fermentation of sugars from carbohydrate

Woody biomass

available

368 998 1366 Million

tonsPotentially available

carbohydrate matter(includeshemicellulose)

258 699 957 Milliontons

Ethanol/carbohydratematter

40% 40% 40% t/t

Maximum ethanol fromcellulosic matter

103 279 382 Milliontons

2.58 106 6.99 106 9.56 106 gal/yr78,800 213,600 292,300 MWth

% of USDOE 2012 target 42% 115% 158%

Ethanol from residual woody biomass via thermochemical processing

Residual available 2.63 2.63 2.63 t/t

EtOHYield of mixed alcohols 75 75 75 gal/t

SludgeSelectivity for ethanol 75% 75% 75%Ethanol from residual

biomass1.52E+10 4.13E+10 5.65E+10 gal/yr

46,600 126,200 173,000 MWth

Table 2Chemical constituents of loblolly pine

Cellulose 43.6%Hemicellulose convertible to sugars

Mannan 10.8%Galactan 2.2%Xylan 6.6%

Arabinan 1.6%Acetal 1.1%Uronic anhydride 3.7%Lignin 26.8%Extractives 3.2%Ash 0.4%Total 100.0%

5052 W.J. Frederick Jr. et al. / Bioresource Technology 99 (2008) 50515057


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acid, and other contaminants (terpenes, resin acids, etc.)must be removed prior to fermentation. The contents ofthe pretreatment reactor are flashed to separate water,some of the acetic acid produced, most of the furfuraland hydroxymethyl furfural produced, and terpenes andother volatiles from the wood. The flashed vapor is con-densed to provide process heat. The organic matter in

the condensate is used as a process fuel. The remaininghydrolyzate solution is separated from the wood chipsby filtration. The remaining acetic and sulfuric acids areremoved by continuous ion exchange, using ammonia asa regenerant. The product stream is neutralized withexcess lime. This generates gypsum as a low value by-product. Acetic acid would have value as a co-productif recovered and purified; however this option was notevaluated.

3.2. Simultaneous saccharification and fermentation

After hydrolyzate conditioning, the remaining celluloseis converted by enzymatic hydrolysis (saccharification) toglucose using cellulase enzymes, and the glucose and xylosefrom hemicellulose are fermented. The enzymes were con-sidered to be produced on site, and the capital and produc-tion costs for enzymes were included in this analysis. In thiswork, we considered Z. mobilis bacterium as the ethanolo-gen because it will ferment both glucose and xylose to eth-anol (Zhang et al., 1995). Other sugars were assumed not tobe fermented by Z. mobilis bacterium.

The stoichiometric factors and conversion efficiencieswere used in calculating the yield of ethanol produced fromsugars from hydrolysis of wood carbohydrates are included

in Table 3.

3.3. Ethanol recovery

The products from fermentation are an ethanolwaterstream that contains unreacted sugars and suspended bio-mass, and carbon dioxide. Ethanol and water are steamstripped from the aqueous fermentation product to pro-duce a 35 wt% ethanol/65 wt% water overhead productwhich is then distilled to 92.5 wt% ethanol and dehydrated

with molecular sieves.The bottoms from the steam stripper are concentrated

by multiple-effect evaporation to 50 wt% solids and burnedto generate steam.

3.4. Steam and power generation

Bark, wood residues from hydrolysis, and steam stripperbottoms are dewatered and burned in a biomass boiler togenerate high pressure, superheated steam (79 bar,482 C). Power is generated with an extraction turbine,from which process steam is extracted at 6 and 12 bar. Pro-

duction of process steam is balanced with demand by

Table 3Conversion factors and yields for carbohydrates to ethanol

Sugars and ethanol from carbohydrates

C5 carbohydrates to pentoses 1.136C6 carbohydrates to hexoses 1.110Pentoses to ethanol 0.511Hexoses to ethanol 0.511

Yields

Ethanol from hexose 92%Ethanol from xylan 85%Ethanol from other pentoses 0%

CHP PLANT

HYDROLYSIS OFHEMICELLULOSE

CHP PLANT

DISTILLATION/

DEHYDRATION/

EVAPORATION

Enzyme

ofuel

WOOD

HANDLINGACID PRETREATMENT

CELLULASEPLANT

HYDROLYZATE

CLEANUP

HYDROLYZATE

CLEANUP

HYDROLYZATE

CLEANUP

CHP PLANT

Gypsum

CHP PLANT

HYDROLYSIS OFHEMICELLULOSE

ProcessBiofuelSteamPower

CHP PLANT

DISTILLATION/

DEHYDRATION/

EVAPORATION

DISTILLATION/

DEHYDRATION/

EVAPORATION

Wood

Lime

EnzymeNutrientsCO2

Acetic Acid

SIMULTANEOUS

SACCHARIFICATION& FERMENTATION

Ethanol

Power

ExcessBi

WOOD

HANDLINGACID PRETREATMENT

CELLULASEPLANT

CELLULASEPLANT

H2SO4

HYDROLYZATE

CLEANUP

HYDROLYZATE

CLEANUP

HYDROLYZATE

CLEANUP

HYDROLYZATE

CLEANUP

HYDROLYZATE

CLEANUP

HYDROLYZATE

CLEANUP

CHP PLANTCHP PLANT

Fig. 1. Conceptual diagram of an ethanol plant with an integrated CHP plant.

W.J. Frederick Jr. et al. / Bioresource Technology 99 (2008) 50515057 5053


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adjusting the amount of biomass fuel burned. Additionalbiomass residue generated is exported as biomass fuel.

4. Process and cost analysis

Material and energy balances, equipment sizing, andcapital and operating costs were estimated using an ethanolplant version of BioRefinOptTM, a proprietary softwarepackage developed by three of the authors of this paper.BioRefinOptTM is spreadsheet based with worksheets foreach unit operation in the plant including detailed modelsfor a biomass boiler and extraction turbine, a capital costestimation worksheet, and a production cost worksheet.It can be adapted for any biomass feedstock. Processparameters for the ethanol plant were taken primarily fromWooley et al. (1999) and Hamelinck et al. (2003).

Estimation of capital costs for the plant was based onthe results of Wooley et al. (1999). The size and cost of

the various unit operations were scaled from their cost esti-mates, using the scaling parameters given in Tables 4 and 5.The impact of inflation on process equipment costs wasaccounted for via the Chemical Engineering cost index.

The cost of producing ethanol from loblolly pine wasestimated based on the various raw material, costs shownin Table 6.

5. Results

The wood consumed and the products resulting fromethanol production when 75% and 95% of the carbohy-drates in the feedstock are converted to sugars are shownin Table 7. The distribution of energy between the main

products from the ethanol plant are shown in Table 8.

Table 4Total installed cost and total capital investment for an ethanol plant based

on 75% conversion of carbohydrates to fermentable sugarsOperation Scale basis Actual size Total

installedcost (2006)

Feedstock storageand handling

Dry woodflow rate

2700 ODt/d $6,857,008

Pretreat andhydrolyzateconditioning

Dry woodflow rate

2700 ODt/d $37,928,843

Simultaneoussaccharificationand co-fermentation

Hydrolyzatesolution flowrate

6534 m3/day $12,807,108

Enzyme production Cellulose flowrate to SSCF

33,264 kg/hr $22,223,533

Distillation,dehydration,and evaporation

Flow ratefromprehydrolysis

259,710 kg/hr $11,386,318

Wastewater treatment Dry woodflow rate

2700 ODt/d $14,517,402

Product and feedchemical storage

Stored ethanolvolume

5810 m3 $2,465,924

Burner, boiler andturbogenerator

Superheatedsteamto turbine

69,230 dry kg/hr $50,804,311

Utilities Dry woodflow rate

2700 ODt/d $7,728,579

Total installedequipment cost

$166,719,027

Total capital investment $285,089,537

Table 5Total installed cost and total capital investment for an ethanol plant basedon 95% conversion of carbohydrates to fermentable sugars

Operation Scale basis Actual size Totalinstalled cost(2006)

Feedstock storage and

handling

Dry wood

flow rate

2700 ODt/d $6,857,008

Pretreat & Hydrolyzateconditioning

Dry woodflow rate

2700 ODt/d $37,928,843

Simultaneoussaccharification andco-fermentation

Hydrolyzatesolution flowrate

7480 m3/day $14,079,302

Enzyme production Cellulose flowrate to SSCF

42,134 kg/hr $26,849,919

Distillation,dehydration, andevaporation

Flow ratefromprehydrolysis

298,099 kg/hr $12,626,626

Wastewater treatment Dry woodflow rate

2700 ODt/d $14,517,402

Product and feedchemical storage

Stored ethanolvolume

7360 m3 $2,841,693

Burner, boiler andturbogenerator

Superheatedsteam toturbine

85,542 dry kg/hr $55,983,092

Utilities Dry woodflow rate

2700 ODt/d $7,728,579

Total installed equipment cost $179,412,465

Total capital investment $306,795,315

Table 6Raw material waste treatment, and disposal costs

Pine chips $63.80/OD metric tonPower $60.00/MW hrBiomass fuel $29.70/OD metric ton

Process chemicals

Sulfuric acid $0.026/kgLime $0.074/kgAmmonia $0.184/kgCorn steep liquor $0.158/kgNutrients $0.290/kgAmmonium sulfate $0.044/kgAntifoam (corn oil) $0.531/kgDiesel $0.129/kg

Chemicals for utilities

Boiler feedwater treatment $2.27/kg

Cooling tower water treatment $2.20/kgWastewater treatment nutrients $0.24/kgWastewater treatment chemicals $5.26/kgAsh disposal cost $0.022/kgMake-up water cost $130/million gal



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The rate of biomass fuel consumption and power gener-ation by the integral CHP plant within the wood-to-etha-nol plant are shown in Table 9. The residual biomassincludes bark, lignin, extractives, and unconverted carbo-hydrates and sugars. 240 MWth or 64% of the residual bio-mass is consumed as fuel by the CHP plant when 75% ofthe carbohydrates in wood are recovered as sugars for eth-anol production, 35 MWe of power is generated, and137 MWth of residual biomass is available for export asfuel. If 95% of the carbohydrates in wood were recoveredas sugars for ethanol production, the biomass fuel require-ment for the plant would increase to 261 MWth while thetotal biomass residue available for steam and power gener-ation or export would decrease from 377 MWth to 310MWth. Power generation would increase to 41 MWe andresidual biomass available for export would decrease to34 MWth.

6. Cost of ethanol production

The revenues and costs for each scenario and the pro-duction cost for ethanol determined under these assump-

tions are shown in Table 10.

Fig. 2 shows the sensitivity of the production cost forethanol to four variables: the cost of wood, the cost ofpower, the selling price of excess biofuel, and the annualcapital recovery factor. The results are for the case where75% of the carbohydrates in loblolly pine are convertedto sugars. These results show that the production cost ofethanol depends strongly on the price of wood and on

the annual capital recovery rate, but not so for power costs.The breakeven cost of ethanol decreases with an increasingvalue of biofuel since ethanol production is a net producerof biofuel.

The estimated production cost of producing fuel-gradeethanol by fermentation of sugars from various feedstockand the capital investment required have been reported

Table 7Wood consumed and products generated at two levels of conversion ofwood carbohydrates to sugars

Carbohydrates converted to sugars, wt% 75% 95%Wood mass extracted for ethanol production, dry,

bark-free basis57.3% 71.2%

Wood purchased (bark-free basis), t/a 915,818 915,818

Ethanol produced, t/a 219,918 278,563Gypsum produced, t/a 38,621 38,621Purchased power, MWe 5.0 0.6Exportable biomass fuel, t/a 183,608 45,244

Table 8Distribution of energy value among products

Carbohydrates converted to sugars, wt% 75% 95%

Energy input

Wood purchased (undebarked), MWth 629.9 629.9Power purchased, MWe 5.0 0.6

Energy output

Ethanol, MWth 203.8 258.2

Exportable biomass fuel, MWth 136.9 33.7Conversion efficiency of energy input to ethanol, % 32.10% 41.0%

Table 9Biomass fuel consumption, export, and power generation

Carbohydrates converted to sugars, wt% 75% 95%Bark input rate, kg/s 3.12 3.12Higher heating value of bark, MJ/kg 21.7 21.7Residual biomass generation rate, kg/s 18.2 14.7Higher heating value of residual biomass, MJ/kg 17.0 16.6Total biomass fuel rate, MWth 377 310Internal biomass fuel consumption rate, MWth 240 261Exported biomass, MWth 137 49

Power generated, MWe 34 41

Table 10The costs and income by item for the two cases in Table 5

Carbohydrates converted tosugars, wt%

75% 95%

Wood mass extracted 57.3% 71.2%Production price for ethanol,

$/gal$1.66 $1.41

Costs Million$/yr

$/gal Million$/yr

$/gal

Wood ($63.80/ODt) $63.69 $0.86 $63.69 $0.68Purchased power ($60.00/

MW hr)$2.43 $0.03

Chemicals for ethanol plant $11.78 $0.16 $14.92 $0.16Waste treatment chemicals and

disposal$1.18 $0.02 $1.49 $0.02

Fixed operating costs $10.60 $0.14 $11.18 $0.12Capital recovery (10%/a) $28.51 $0.39 $30.68 $0.33Total cost ($/a) $118.18 $1.61 $121.96 $1.31

Revenue from co-products

Excess biomass fuel($29.70/OD t)

$5.45 $0.07 $1.34 $0.01

Exported power($60.00/MW hr)

$0.31 $0.003

Net cost of ethanol production $112.73 $1.53 $120.30 $1.29

These results are for a 10% annual capital return factor.

Biomass Fuel Value

$1.00

$1.50

$2.00

$2.50

$3.00

-50% 0% 50% 100%

Change in price or value

Break-even

costofeth

anol,$/gal

Wood Cost

Power Cost

Biomass Fuel Value

Cost of Capital

Fig. 2. Sensitivity of the production cost for ethanol to the cost of wood,the cost of power, the selling price of excess biofuel, and the cost of capital.

Results are for 75% conversion of wood carbohydrates to sugars.



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by a number of investigators. Our results for loblolly

pine as feedstock are compared in Table 11 with recentresults from other studies in which the feedstock wascorn, corn stover, or yellow poplar. Because each of thesestudies used a different base year for cost and revenueestimates, they were not directly comparable. Weadjusted the costs of producing ethanol in each of thestudies to account for changes in feedstock, capital, andoperating costs between the year in which the variousstudies were performed and the costs or values in late2006. The adjustments used are included in Tables 12and 13. We also scaled the total capital investment ofeach ethanol plant to 50 million gal/yr capacity using a

power law relationship with an exponent of 0.6 (Seider

et al., 2004).The results in Table 11 indicate that ethanol produced

from carbohydrates from loblolly pine is comparable withethanol from other feedstock including corn when com-pared on a basis of production costs. The capital invest-ment required per unit of ethanol produced is higher forany of the lignocellulosic ethanol plants than for corn eth-anol. Part of the reason for this is that the utilities requiredby the corn ethanol plant were estimated as purchasedfrom a co-located industrial facility, so that neither CHPplant nor cooling tower were included in the capital costfor that plant. They were included in all of the other three

ethanol plants. The CHP plant was the most expensive cap-ital cost in each of those other plants, accounting forbetween 28% and 42% of the total capital cost.

7. Profitability of ethanol from loblolly pine

Net present value for a plant producing ethanol fromloblolly pine was estimated using an ethanol sales priceof $2.00/gal, the production cost and sales revenueresults in Table 10, a federal income tax rate of 35%,and a rate of return of 10%. The project life was takenas 11 yr, with the plant constructed in year 1 and oper-ating at full capacity by the beginning of year 2. Totalcapital investments for the two cases, including 15%working capital were $328 million for the case where75% of the carbohydrate mass in wood is converted tosugars, and $353 million for the 95% conversion case.For these conditions, the net present value is $114 mil-lion for the case where 75% of the carbohydrate massin wood is converted to sugars and $228 million forthe 95% conversion case.

A discounted cash flow rate of return (DCFRR) analysiswas also performed for the same two cases. The DCFRR is18% for the case where 75% of the carbohydrate mass inwood is converted to sugars, and 25% for the 95% conver-

sion case.

Table 11Comparison of results this and other studies for production of ethanol by fermentation using various feedstocks

Feedstock Dry milled corn Corn stover Yellow poplar Loblolly pine 75% Loblolly pine 95%

Source McAloon et al. (2000) McAloon et al. (2000) Wooley et al. (1999) This study This studyEthanol yield, gal/t dry biomass 114 72 68 80 102

Production costs

Feedstock $1.33 $0.65 $0.55 $0.86 $0.68Variable costs 0.33 0.33 0.26 0.21 0.18Labor, supplies, overhead 0.16 0.47 0.20 0.14 0.12Capital recovery (10%/yr) 0.08 0.40 0.53 0.49 0.33Co-products 0.38 0.12 0.07 0.07 0.01Total production costs, $/gal $1.52 $1.74 $1.48 $1.53 $1.30

Total capital investment, millions $48a $232 $327 $285 $307Capital intensity, $/(gal/yr) $0.96 $4.64 $6.53 $3.87 $3.29

The results shown have been scaled to plants operating in late 2006 and producing 50 gal/yr of ethanol.a The cost of utilities required by the corn ethanol plant were estimated as purchased from a co-located industrial facility; a CHP plant and cooling tower

were not included in the capital cost.

Table 12Cost of feedstock in the year in which the various studies were performedand in 2006

Feedstock Cost in yearof study

2006 Cost Reference

Corn $1.94/bu $3.80/bu CBOT CornMonthly PriceChart, NovemberDecember, 2006

Corn stover $35.00/ODT $47.35/ODT Perlack andTurhollow (2003)

Yellow poplar $28.00/ODT $41.68/ODT Siry et al. (2006)Loblolly pine $58.00/ODT

Table 13Other adjustments to ethanol production costs between the year in whichthe various studies were performed and 2006

Fixed costs 4%/year increaseVariable costs 4%/year increaseDistillers dried grains and solubles (DDGS)

from dry milling of cornIncreased from $86/ODTto $125/ODT

Capital recovery rate Changed to 10%/year

where different



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8. Co-product recovery

Recovery of co-products from ethanol production,except for power and residual biomass for fuel, has notbeen considered with respect to the economics of ethanolproduction. Two co-products that could be recovered forsale are acetic acid and tall oil. The amounts each thatare potentially recoverable during processing of loblollypine for ethanol production are shown in Table 14. Thecombined gross value of these co-products is $16.5 million,or about $0.22/gal of ethanol produced at 75% carbohy-drate conversion, and $0.12/gal of ethanol produced at75% carbohydrate conversion. This value is based onpotential sales revenues and does not include capital andoperating costs for recovery of these co-products.

9. Conclusions

Ethanol from loblolly pine will be competitive with eth-anol from both corn and other lignocellulosic biomass. Theeconomic calculations in this paper indicate that the avail-able technology can produce ethanol profitably at current

feedstock and ethanol prices. The economics will furtherimprove with higher conversion of cellulose to sugars viaenzymatic hydrolysis and when the other pentose sugarsin addition to xylan can be converted rapidly and efficientlyto ethanol. Combined biomass processing to produce mul-tiple products could decrease the cost of ethanol produc-tion further by utilizing more effectively biomass andenergy via process integration. Recovery of wood-derivedco-products, if economically justified, could make produc-tion of ethanol from loblolly pine even more attractive.

References

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Table 14Amounts and value of acetic acid and tall oil potentially recoverableduring processing of loblolly pine for ethanol production

Acetic acid Crude tall oil

Yield, wt% of dry, debarked wood 0.72% 4.3%Production rate, t/yr 6569 43520Bulk price, $/t 1452 160

Potential annual sales revenue, millions $9.54 $6.96

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