Article pubs.acs.org/IECR
Larch Biorefinery: Technical and Economic Evaluation Hanna S. Hörhammer,*,† Trevor H. Treasure,‡ Ronalds W. Gonzalez,‡ and Adriaan R. P. van Heiningen†,§ †
School of Chemical Technology, Department of Forest Products Technology, Aalto University, Vuorimiehentie 1, Espoo, FI-00076 Aalto, Finland ‡ College of Natural Resources, Department of Forest Biomaterials, North Carolina State University, 1022F Biltmore Hall, Raleigh, North Carolina 27695-8005, United States § Department of Chemical and Biological Engineering, University of Maine, 5737 Jenness Hall, Orono, Maine 04469-5737, United States S Supporting Information *
ABSTRACT: In this study a forest biorefinery concept based on larch wood was technically and economically evaluated. Two slightly different cases of a larch-based biorefinery were compared to conventional kraft pulping. The wood chips of Larix sibirica (Lebed.) were pre-extracted (PE) and washed with water prior to pulping, in order to generate an additional sugar side-stream. The sugars were hydrolyzed into monosugars, which were then fermented by Bacillus coagulans into lactic acid. The lactic acid needs to be purified before sold to the market. By pulping the pre-extracted wood chips with anthraquinone (AQ) and polysulfide (PS), the pulp yield loss was reduced. The pulp was then bleached (O-D0-Ep-D1-P). The products of this larch biorefinery are bleached softwood pulp and lactic acid. Three process cases were simulated: conventional kraft pulping, PE-PSAQ with 0.5% PS, and PE-PSAQ with 2% PS, in terms of mass and energy balances. Considering the availability of larch resources, this kind of a biorefinery could suitably be located in Siberia, Russia. Market prices were collected, and based on the simulation results, cash flows were determined. Sensitivity analysis was carried out, and investment costs were estimated. Based on the simulation with the addition of a lactic acid production line to an existing pulp mill, the payback time for the investment costs would be about 16 months.
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INTRODUCTION
hydrolysis, but this usually requires higher temperatures.17,19,21,23−29 In the case of larch wood, which has a significantly higher amount of water-soluble hemicelluloses, i.e., arabinogalactan, compared to other wood species,30 the pre-extraction with water can be performed at significantly lower temperatures. This is advantageous from an energy requirement point of view, but also the lower temperature would reduce the potential of forming reactive lignin precipitates during autohydrolysis that cause severe plugging problems.19,31 During the present experimental work on extraction of Siberian larch,11,32,33 no lignin precipitates were seen in the autohydrolysate. Thus it may be that lignin repolymerization at the present optimum extraction condition of 90 min at 150 °C (equivalent to a Pfactor of 20034) was not significant.35 There are larch resources mainly in the northern and central parts of Russia and in the northern parts of North America.36 The removal of hemicelluloses prior to pulping may affect the final paper product. Polysulfide (PS) and anthraquinone (AQ) can be used as pulping additives in order to maintain the pulp yield. PS and AQ increase pulp yield by oxidizing the reducing end groups of polysaccharides to aldonic acid groups, thus stabilizing the polysaccharides against peeling reactions.37,38 Besides the yield increase, AQ accelerates the
The pulp and paper industry in temperate zones is facing challenges to remain competitive in the global market. A solution for this problem and an opportunity for the future could be to convert these traditional mills into forest biorefineries.1,2 In the forest biorefinery considered in the present work the mill continues to produce pulp but, in addition, creates new business opportunities for other products. There is a wide range of possible additional products which could increase the revenue of a mill. Hemicellulose extract may be used as feedstock for the production of xylitol,3 barrier films,4 ethanol,5,6 jet and diesel fuel,7 gasoline,8 furfural, formic and acetic acids,9 butanol,10 and lactic acid.11,12 Pulp and paper mills already have highly developed processes and well-working infrastructures which could relatively easy be adapted for a forest biorefinery. Other positive aspects for a forest biorefinery are year around availability of raw material and no competition with food or feed markets. The new products for a forest biorefinery, biofuels and biochemicals, can be produced from the extract of preextraction or prehydrolysis,13,14 gasification of black liquor can provide new byproducts,15,16 and products could be created by precipitation of lignin or separation of tall oil from black liquor.16 Different forms of pre-extraction or prehydrolysis of wood have been reported; the pre-extraction can for example be performed in the presence of acid17−20 or in alkaline conditions.17,20−22 Pre-extraction can also be done at neutral conditions with water, i.e., autohydrolysis or hydrothermal © 2013 American Chemical Society
Received: Revised: Accepted: Published: 1206
October 29, 2013 December 28, 2013 December 30, 2013 December 30, 2013 dx.doi.org/10.1021/ie403653j | Ind. Eng. Chem. Res. 2014, 53, 1206−1213
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Figure 1. Process diagram of the larch kraft process.
operates production plants in the USA, The Netherlands, Spain, Brazil, and Thailand.49 NatureWorks LLC is located in Blair, NE, in the United States, and uses corn starch as raw material for the lactic acid.50 Starch can also be extracted from sugar beet, rice, wheat, or sweet potato.51 In the future a variety of biomass could be used as raw material for carbohydrate fermentation, for example, carbohydrates from woody biomass which would not compete with food or feed. The global market for lactic acid is forecast to reach about 330 thousand metric tons by the year 2015.47 The conversion of an existing mill into a biorefinery must be carefully evaluated on a case by case basis. Raw-material resources, processes, investments, markets, and logistics, etc., have to be considered. The choice of which biorefinery concept an existing mill should implement is a very critical decision.52 The mill has to weigh the estimated investment cost against the predicted additional revenues. The market prices of the raw material and products are most relevant when evaluating the profitability of a process. The aim of this study was to build a model of a realistic and practical larch biorefinery process and then to economically evaluate the process. In this larch biorefinery concept hemicelluloses are removed with water in a pre-extraction (PE) step before kraft pulping with polysulfide (PS) and anthraquinone (AQ). The wood fibers become bleached softwood pulp for, i.e., packaging paper, and the hemicellulose-rich extract is fermented to lactic acid. A conventional kraft process was used as a reference to the present PE-PSAQ process.
delignification rate of pulping by fragmenting and dissolving lignin.37 In softwood PS pulps the higher retention of glucomannans and in AQ pulps the preservation of mainly cellulose enhance the yield respectively.39 A synergism exists when PS and AQ are used together in alkaline pulping37,39−44 Lactic acid (C 3H6O 3, 2-hydroxypropionic acid) is a commodity chemical used in food, chemical, and pharmaceutical applications.45 Lactic acid can be produced through chemical synthesis or fermentation. In fermentation, lactic acid is produced from sugars, in this case derived from the carbohydrates in biomass. The biomass is first extracted and hydrolyzed in order to make the sugars accessible for fermentation. During the fermentation, microorganisms convert the carbohydrates into lactic acid. Successful lactic acid fermentation needs the right combination of microorganism, sugars, nutrients, and neutralizing agents in order to economically produce lactic acid of sufficient purity.45,46 Bacillus coagulans (B. coagulans) MXL-9 was found to be capable of consuming both pentoses and hexoses efficiently, being resistant against inhibitors, and producing lactic acid at high yields.12 B. coagulans MXL-9 produces lactic acid from all lignocellulosic monosugars, although it has a clear preference for glucose and mannose. However, after a 12 h lag phase when these two preferred sugars are consumed, the organism produces lactic acid at about equal efficiency from arabinose, xylose, and galactose. The largest lactic acid market is the United States, while Western Europe and Asia-Pacific make up the other major lactic acid producers and consumers on a global scale. The intensive production growth in China will significantly increase the share of the Asian region.47 Traditionally, lactic acid is primary used in the food industry, but now lactic acid is also used for production of different polymer applications. Lactic acid is the building block chemical for poly(lactic acid) (PLA), which is a biodegradable thermoplastic.48 In the future biodegradable plastics are expected to become the most promising end-use products for lactic acid.47 The lactic acid production was earlier limited to a small number of companies, for example, Purac and NatureWorks LLC, but now there are also several Asian companies producing lactic acid. Purac
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MATERIALS AND METHODS Scenarios Definition. In this study two slightly different larch biorefinery processes are compared to a larch kraft process. Three cases were studied: (1) a larch kraft process, (2) a PE-PSAQ process with PS charge 0.5% on wood, and 3) a PE-PSAQ process with a PS charge of 2.0% on wood. Siberian larch (Larix sibirica (L. sibirica) Lebed.) mill chips from Russia are used as raw material. The assumed capacity for all processes is 400,000 tons of bleached pulp/year. Schematic diagrams of
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Figure 2. Process diagram of the larch PE-PSAQ process.
collect all the removed sugars. The excess water used in the prehydrolysis is sent to the mill’s effluent treatment plant. The pre-extracted and washed chips are cooked with PS liquor, to which also AQ is added, in order to maintain the pulp yield. A smaller amount of additional NaOH is needed to compensate for the consumption of alkali by PS. A PS charge of 2% on wood and an AQ charge of 0.1% of wood is enough to maintain the yield at the same level as kraft pulping.32 The pulp is washed and bleached (O-D0-Ep-D1-P). Less bleaching chemicals are needed for the bleaching of the PE-PSAQ pulp, and the PE-PSAQ pulp quality is comparable with other softwood kraft pulp.33 The black liquor, with dry solids content somewhat lower than but with heating value similar to those in kraft pulping,32 is burnt and recovered. A MOXY reactor is used for regenerating the PS liquor.53,54 Otherwise, the recovery process is the same as in the kraft case. The combined sugar stream of extract and wash water is hydrolyzed, neutralized, and then fermented.11 The polymeric sugars are hydrolyzed with sulfuric acid into monosugars, in order to be available for the bacteria in the fermentation unit. The solution is neutralized with Ca(OH)2 before fermentation. The neutralization results in formation of gypsum as byproduct. During fermentation the bacteria (B. coagulans MXL-9) convert the sugars into lactic acid at a high yield. The lactic acid has to be purified in order to sell it on the market. A two-stage membrane technology was chosen for lactic acid purification in this larch biorefinery.56,57 The purification process contains a desalting electrodialysis, a water-splitting electrodialysis, and an ion exchange stage. The lactate salt-containing broth from the fermentation is fed to the first electrodialysis step (desalting). There the lactate salt, i.e., sodium lactate, is recovered and concentrated. Viable bacteria cells are fed back to the fermentation unit. Then the concentrated lactate is fed to the second electrodialysis step (water-splitting). An aqueous lactic acid solution is formed and also a base. The base is recycled back to the fermentation unit. The lactic acid solution is then fed to an ion exchanger unit. First it is treated by a strongly acidic cationic exchange resin and then a weakly basic anionic exchange resin to remove
the kraft and PE-PSAQ processes are presented in Figure 1 and Figure 2, respectively. The larch kraft process (Figure 1) is a conventional kraft pulping process. The larch wood chips are conventionally cooked with white liquor, washed, and bleached (O-D0-Ep-D1P). The black liquor from the cook is burnt and recovered. The process inputs are larch wood, water, and cooking and bleaching chemicals. The product is bleached softwood pulp. The aim of the larch biorefinery process (Figure 2) is to get additional revenue from the lactic acid production. The combined pulp mill and lactic acid unit could be a green field mill, or a pre-extraction stage and lactic acid production operation could be added to an existing pulp mill. The PEPSAQ process was modeled using practical conditions and equipment available on the market. This version of the PEPSAQ process is mainly based on earlier described experiments by the present author.11,32,33 In the biorefinery processes described here, the PS liquor is prepared in a MOXY reactor53,54 and not by dissolving elemental sulfur as was done in the laboratory experiments. Information about lactic acid purification was taken from the literature.55−57 For the PEPSAQ process the additional processing units needed are: extraction, washing, hydrolysis, neutralization, fermentation, a MOXY reactor, and a natural gas fired boiler. The additional inputs are steam for pre-extraction of wood, AQ and NaOH for PSAQ pulping, H2SO4 for hydrolysis, Ca(OH)2 for neutralization, nutrition for bacteria, and KOH for pH adjustment. The bacteria in the process reproduce themselves and except during start-up do not need to be purchased. The product in addition to bleached pulp is lactic acid. Gypsum is formed as a byproduct from the neutralization step. In the PE-PSAQ process the larch wood chips are treated with water in a pre-extraction unit. The ideal temperature is about 150 °C, whereby mostly the arabinogalactan dissolves which otherwise would be fully removed during regular kraft pulping, while xylan is mostly retained.11 The pre-extracted chips are mildly washed, in order to remove the dissolved sugars from the extracted wood chips.32 The extract and the wash water from washing the extracted chips are combined, to 1208
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positively and negatively charged impurities producing a highly purified form of lactic acid solution (purity 90−100%). It is assumed that the losses of lactic acid by ion exchange are negligible.58 The byproduct gypsum may for example be used as fertilizer or to produce wallboard for building.59,60 The chemical formula of gypsum is CaSO4·2H2O. Gypsum is mined from gypsum mines, or synthetic gypsum is formed in industrial neutralization processes. However, the market price of crude gypsum is very low, i.e., 5 €/ton.60 With logistics included the gypsum revenue would be negative. Therefore, the gypsum is landfilled near the site in this study. If the biorefinery process appears to be very profitable, the gypsum could be transported away from the site and sold. This would slightly decrease the profit of the larch biorefinery. Mass and Energy Balances from Modeling. Steady-state material and energy balance process models for the base case and proposed biorefinery case were produced using WinGEMS V.5.3.61 This process simulation software was originally developed for the pulp and paper industry and has specialty blocks and unit operations (i.e., solid/liquid handling, washing, and separation) critical for modeling of biomass-based processing technologies. Once the WinGEMS model converged on a steady-state solution, data related to pulp/lactic acid production, chemical usage, and electricity balance are written into the financial spreadsheet. Input data for the simulation was mainly taken from experimental results described in previous papers.32,33 The fermentation experiments were performed by Walton at Maine University, USA.11 Some parts of the process model were constructed on the basis of information taken from literature54−57 and equipment producers.53 Economic Evaluation. Information about cost and prices was collected from the literature, market reports, equipment producers, and discussions with experts. General assumptions were made, operating costs estimated, and revenues calculated. The PE-PSAQ processes were compared to a conventional kraft process. The cash flow was determined in order to analyze the different cases; also sensitivity analyses were performed. Investment costs were estimated. By comparing the cash flow with the estimated investment costs, the profitability of a larch biorefinery could be determined.
Table 1. Assumptions for the Evaluation general planned location: Siberia in Russia, in the area of the Yenisei river wood raw material: Larix sibirica Lebed. general grid is close to the mill other labor needed: 50 persons operating time: 350 days/year (8400 h) currency: € (1 € ∼ 1.30 US$) pulp mill production capacity: 400,000 t (tons) pulp/year (about 1000 tons/ day) consistency of produced bleached pulp: 90% no external energy is needed for pulp mill labor needed for pulp mill: 400 persons pre-extraction and lactic acid (LA) production addition of lactic acid production to a greenfield or existing pulp mill additional process units: pre-extraction, washing, hydrolysis, neutralization, fermentation, purification, MOXY reactor, natural gas boiler external energy in form of natural gas is needed for the lactic acid production bacteria reproducing in fermentation costs for fermentation chemicals: 100 €/ton consumption and cost for LA purification chemicals have not been considered produced byproduct gypsum left on site labor needed for lactic acid production: 50 persons extra costs for wastewater treatment of effluent from lactic acid recovery process not included
Table 2. Process Information from Experiments and Simulation Results process information
case I: kraft
case II: PEPS(0.5)AQ
capacity of bleached pulp (dry), 400,000 400,000 tons/year Pre-extraction (PE) and Washing wood demand (dry), tons/year 1,108,499 1,221,960 sugar yield, % on wood 10.2 dissolved sugars (100%), 124,640 tons/year Pulp Production effective alkali, % on wood as 23 20 NaOH polysulfide charge, % on wood 0.5 anthraquinone charge, 0.1 % on wood pulp yield, % on wood 40.4 36.3 unbleached pulp production 448,029 443,593 (dry), tons/year bleached pulp production (dry), 403,226 403,226 tons/year dried bleached pulp production 400,000 400,000 (dry), tons/year Lactic Acid Production lactic acid production, 93,480 tons/year lactic acid production, purity 86,002 99% (100%), tons/year Power Plant energy from recovery boiler, 315,168 308,101 Mcal/h energy from natural gas boiler, 0 78,125 Mcal/h
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RESULTS AND DISCUSSION Assumptions for the Evaluation. The assumptions used in the economic evaluation are summarized in Table 1. Technical Evaluation. Technical characteristics of the three process cases are presented in Table 2. Basic information, i.e., capacity, charges, and yields, are mentioned in order to describe the different processes. Values for chemical and energy consumption have been taken from the simulation and are relevant for the economic evaluation. Case II has the highest wood demand, due to lowest pulp yield. As a result of pre-extraction a lower amount of carbohydrates is going into the pulping step with the extracted wood chips in cases II and III. Therefore, less alkali and a lower H factor can be used in the PE processes.32 The PE pulps are easier to bleach,33 which results in lower consumption of bleaching chemicals in cases II and III. Somewhat more lactic acid is produced in case II compared to case III, because the wood demand in case II is larger. Therefore, the chemical consumption of the lactic acid production is also somewhat larger for case II. Based on earlier experiments, the amount of gypsum formed was estimated to be about 75% of the lactic
case III: PEPS(2.0)AQ 400,000
1,183,548 10.2 120,722
20 2 0.1 37.5 443,593 403,226 400,000
90,541 83,298
291,420 89,833
acid production. Process alternatives without gypsum formation have not been investigated in the present study. 1209
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based on the simulation results and the unit prices (Table 5). The calculated cash flow values show that the kraft process has a positive cash flow of about 77 million €/year, but that for both cases of lactic acid production the cash flow increases remarkably to about 150 million €/year. This means that the larch biorefinery process increases revenue by about 73 million €/year. Sensitivity Analysis. The key parameters influencing the cash flow of these processes are wood price, pulp price, and price for lactic acid. A sensitivity analysis of ±25% was determined for the PE-PS(2.0)AQ process (case III). The minimum (−25%) and the maximum (+25%) prices for wood, pulp, and lactic acid were calculated. Table 6 presents the ±25% values for wood, pulp, and lactic acid. The cash flows were then determined for the different prices. For example, when determining the cash flow for pulp price of −25%, the pulp price of 405 € was used, while the other prices were kept unchanged. Figure 3 presents the sensitivity analyses, which show that the pulp price influences the cash flow most, but the wood price is also an important parameter when looking at the economy of this process. The sensitivity analysis for the PEPS(0.5)AQ process (case II) would be similar. Investment Costs. The investment costs for the preextraction and hydrolysis units, MOXY reactor, and natural gas boiler were available at similar scales in the literature and could therefore be directly used in the evaluation. The costs for the fermentation and purification units were rescaled to the exact present size according to eq 1, where n is an equipment specific index (0.8 for electrodialysis).69
External energy (about 20%) is needed for the pre-extraction step in cases II and III, while the kraft process is self-sufficient regarding energy. Steam is produced in the process. A part of the produced steam is also consumed by the process, and the remaining steam is converted to power. The power is used in the process, and the net power of the three integrated cases is very close to zero. Market Prices. Market and mill gate prices for the products are presented in Table 3. During the past 10 years the market Table 3. Prices for Pulp and Lactic Acid64−66 product prices
price
pulp 650 €/ton64 110 €/ton65 540 €/ton
market price logistic costs price at mill gate lactic acid market price logistic costs price at mill gate
1100 €/ton66 110 €/ton65 990 €/ton
price for pulp has fluctuated between 500 and 700 €/(ton of pulp).62 In 2009 the price dropped to about 400 €/(ton of pulp), but then immediately increased again. In April 2013 the market price for northern soft wood bleached kraft (NSWBK) pulp was 650 €/ton.63 Market pulp on the market is generally sold as air-dried pulp, which has a moisture content of 10%. When also considering the logistic costs of the product from the mill to the market, the product price is somewhat lower at the mill gate compared to the market price. Unit prices at the mill gate for wood, chemicals, products, energy, labor, and maintenance are presented in Table 4. Costs, Revenues, and Cash Flow. The variable costs, fixed costs, and revenues were determined for the processes
new cost = original cost × (new size/original size)n
The scaled investment costs for the biorefinery processes are estimated to be totally 105,000,000 € (Table 7). Smaller investment costs should also be reserved for the handling of the byproduct gypsum. The cash flow determines the size of the investment which can be implemented. As a rule, the investment costs should certainly be less than five times the annual cash flow. Comparing the investment costs to the cash flow values in cases II and III shows that the payback time for the investment costs would be about 16 months.
Table 4. Unit Prices at Mill Gate64,65,67,68 unit prices at mill gate wood chips (wet) cooking chemicals NaOH (100%) CaCO3 (100%, 30 kg of CaCO3/ton pulp (dry) pulp) AQ (100%) bleaching chemicals MgSO4 consumption (100%) H2SO4 consumption (100%) NaOH consumption (100%) H2O2 consumption (50%) NaCl consumption (100%) NaClO3 consumption (100%) LA production chemicals H2SO4 (100%) Ca(OH)2 (100%) fermentation (nutrition, KOH, etc.) products pulp lactic acid natural gas for LA production electricity labor (including taxes) maintenance material
(1)
price
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50 €/ton65
CONCLUSION A process flowchart for a larch biorefinery process is presented. The process is based on water pre-extraction of the larch wood chips before pulping with polysulfide (PS) and anthraquinone (AQ). About 10.2% sugar on wood is recovered through preextraction. The recovered sugars are fermented into lactic acid. An existing kraft pulp mill could relatively easy be converted into a larch biorefinery. For the pre-extraction and the lactic acid production the following additional process units are needed: extraction, hydrolysis and neutralization, fermentation, purification, and a natural gas boiler. For the preparation of the PS liquor a MOXY unit is needed. Two slightly different larch biorefinery processes were compared with a conventional kraft process. Mass and energy balances were obtained through simulation. The cash flows were determined for each process case, and it showed that an additional lactic acid production for a kraft pulp mill would be profitable. The sensitivity analysis shows that the pulp price has the biggest effect on the economy of the PEPS(2.0)AQ process. The investment costs could be paid back within 16 months, when adding a lactic acid production part to an existing pulp mill.
480 €/ton65 20 €/ton65 3,400 €/ton67 80 €/ton67 230 €/ton67 380 €/ton67 300 €/ton67 60 €/ton67 460 €/ton67 35 €/ton65 120 €/ton67 100 €/ton (assumption) 540 €/ton (calculated) 990 €/ton (calculated) 150 €/(1000 m3)65 40 €/MWh64 15,000 (€/year)/person64 6,000,000 €/year68 1210
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Table 5. Cash Flow for the Three Processes Studied case I: kraft cash flow
case II: PE-PS(0.5)AQ €/year
tons/year
variable costs wood chips (wet) cooking chemicals bleaching chemicals LA production chemicals energy fixed costs labor maintenance material revenues bleached pulp (90%) lactic acid (85%)
tons/year
150,232,684 110,880,000 10,320,000 28,558,033 0 474,650 12,750,000 6,750,000 6,000,000 240,000,000 240,000,000 0
2,217,600
444,444 0
cash flow
2,444,400
444,444 101,178
77,017,316
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Table 6. Prices Used in the Sensitivity Analysis prices
at mill gate
−25%
+25%
wood pulp lactic acid
50.00 540.00 990.00
37.50 405.00 742.50
62.50 675.00 1237.50
€/year 175,034,139 122,220,000 12,299,040 25,450,855 3,331,599 11,732,646 13,500,000 7,500,000 6,000,000 340,166,520 240,000,000 100,166,520 151,632,381
case III: PE-PS(2.0)AQ tons/year 2,368,800
444,444 97,998
€/year 171,219,652 118,440,000 10,763,520 25,451,205 3,226,871 13,338,056 13,500,000 7,500,000 6,000,000 337,017,831 240,000,000 97,017,831 152,298,179
ASSOCIATED CONTENT
S Supporting Information *
Extended versions of Table 2 (Table S1) and Table 5 (Table S2). This material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*Tel.: +358 9 47001. Fax: +358 9 470 24259. E-mail: hanna. horhammer@aalto.fi. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The financial support of TEKES through the FiDiPro program is greatly appreciated.
(1) Thorp, B. Biorefinery offers industry leaders business model for major change. Pulp Pap. 2005, 79 (11), 35−39. (2) van Heiningen, A. Converting a kraft mill into an integrated forest biorefinery. Pulp Pap. Can. 2006, 107 (6), 38−43. (3) Werpy, T.; Petersen, G. Top Value Added Chemicals from Biomass, Volume IResults of Screening for Potential Candidates from Sugars and Synthesis Gas (Online); Report by PNNL, NREL, EERE, August 2004. http://www.eere.energy.gov/biomass/pdfs/35523.pdf (accessed May 13, 2013). (4) Edlund, U.; Ryberg, Y. Z.; Albertsson, A.-C. Barrier films from renewable forestry waste. Biomacromolecules 2010, 11, 2532−2538. (5) Liu, T.; Lin, L.; Sun, Z.; Hu, R.; Liu, S. Bioethanol fermentation by recombinant E. coli FBR5 and its robust mutant FBHW using hotwater wood extract hydrolyzate as substrate. Biotechnol. Adv. 2010, 28, 602−608. (6) Walton, S. L.; van Heiningen, A. R. P.; van Walsum, G. P. Inhibition effects on fermentation of hardwood extracted hemicelluloses by acetic acid and sodium. Bioresour. Technol. 2010c, 101 (6), 1935−1940. (7) Xing, R.; Subrahmanyam, A. V.; Olcay, H.; Qi, W.; van Walsum, G. P.; Pendse, H.; Huber, G. W. Production of jet and diesel fuel range alkanes from waste hemicellulose-derived aqueous solutions. Green Chem. 2010, 12, 1933−1946. (8) Li, N.; Tompsett, G. A.; Zhang, T.; Shi, J.; Wyman, C. E.; Huber, G. W. Renewable gasoline from aqueous phase hydrodeoxygenation of aqueous sugar solutions prepared by hydrolysis of maple wood. Green Chem. 2011, 13, 91−101.
Figure 3. Sensitivity analysis of ±25% of wood, pulp, and lactic acid prices for the PE-PS(2.0)AQ process (case III).
Table 7. Estimated Investment Costs for Additional Units in a Larch Biorefinery55,65,70,71 investment costs
price, €
pre-extraction and hydrolysis fermentation and purification MOXY unit natural gas boiler
25,000,00070 50,000,00055 15,000,00065 15,000,00071
total
REFERENCES
105,000,000
A combined pulp and lactic acid production using larch wood as raw material would have potential, both technically and economically. 1211
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