Environmental assessment of biorefinery processes for the valorization of lignocellulosic wastes into oligosaccharides

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 1 Environmental assessment of Biorefinery processes for the valorization of lignocellulosic 1 wastes into oligosaccharides 2 Sara Gonzalez-Garcia*, Beatriz Gullón, Maria Teresa Moreira 3 Department of Chemical Engineering, School of Engineering, University of Santiago de Compostela. 15782- 4 Santiago de Compostela, Spain. 5 * Corresponding author: Tel.: +34 881816806; E-mail address: sara.gon[email protected] 6 7 Abstract 8 The European Commission is adopting strategies in order to "closing the loop" of product life cycles in 9 industrial production systems through better recycling and re-use under the perspective of circular 10 economy. One of the most relevant goals in the application of this approach is to convert low-value 11 side streams into more valuable products. In this sense, the conversion of lignocellulosic biomass into 12 biofuels and chemicals is a major challenge not only from the technological but also from the 13 economic and environmental perspectives. 14 In this study, the production of pectin-derived oligosaccharides (POS) from sugar beet pulp (SBP) was 15 environmentally assessed by means of the Life Cycle Assessment methodology under a cradle-to-16 gate approach. Two different scenarios at pilot scale were considered: Scenario 1 based on 17 conventional autohydrolysis at high temperature and Scenario 2 based on enzymatic hydrolysis. 18 The outcomes of this environmental study are highly dependent on the production yield of the target 19 compounds (POS) and the valorisation strategy considered. In fact, the POS yield of the 20 autohydrolysis approach is around 20% higher than in the enzymatic one. According to the results, 21 Scenario 1 reports the worst results when a functional unit based on the amount of valorised material 22 (100 kg of oven-dried SBP) is considered. However, the profile entirely changes when a unit based on 23 the economic revenue (1 €) is managed. Therefore, attention should be paid on the selection of the 24 functional unit since decision making strategies should highly depend on it. 25 26 *Manuscript Click here to view linked References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 Without waiting for the opportunity to conduct LCA of already-developed processes of the biorefinery 27 system, the development of new alternatives must be carried out with sustainability in mind. 28 Accordingly, the proposal of valorisation strategies for secondary streams should include the analysis 29 of the environmental impacts associated to each alternative, even at the pilot plant stage. 30 Keywords: environmental profile; life cycle assessment; pectin-derived oligosaccharides; prebiotics; 31 sugar beet pulp 32 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 3 1. Introduction 34 Sugar beet pulp is an abundant co-product from the sugar industry (Al-Tamimi et al., 2006; Zheng et 35 al., 2013). Around 5 Mtons are produced in European countries (Ziemiński et al., 2014), of which 36 nearly 20% is produced in Spain mainly for animal feed (Martínez et al., 2009a; Concha Olmos and 37 Zúñiga Hansen, 2012). 38 The sustainable development of bio-processes in the short and medium-term is receiving special 39 attention due to the fast depletion of fossil fuels, their fluctuating price as well as the increasing 40 concerns on greenhouse gases (GHG) emission (Huisingh et al., 2015; Montazeri and Eckelman, 41 2015; Philp, 2015). Therefore, the current industry must then face the challenge to transform industrial 42 low-value side products into more value-added materials (Pin et al., 2014; González-García et al., 43 2016; Van Uytvanck et al., 2014). In this sense, the implementation of the biorefinery scheme in the 44 framework of the sugar beet industry must promote the innovation technologies that increase not only 45 the yield and profitability of the processes but also that improve the environmental profile (Huisingh et 46 al., 2015; González-García et al., 2016; Russell and Shiang, 2013). 47 Thus, sugar beet pulp (from now SBP) - a lignocellulosic source, could be considered a promising by-48 product with potential valorisation in a biorefinery scheme due to its composition and abundance. In 49 the sugar beet processing system, the main product is sucrose, which accounts for 10-12% of the total 50 biomass processed. However, the analysis of the SBP composition also comprises 20-25% cellulose, 51 25-36% hemicelluloses (mainly arabinans), 20-25% pectin, 10-15% protein and 1-2% lignin (Concha 52 Olmos and Zúñiga Hansen, 2012; Ziemiński et al., 2014). 53 Although feed formulation is the main use of SBP (Concha Olmos and Zúñiga Hansen, 2012), other 54 applications are also possible (Ziemiński et al., 2014), such as in the production of composites (Liu et 55 al., 2005), galacturonic acid and arabinose (Leijdekkers et al., 2013) or biogas (Ziemiński et al., 2014) 56 as well as in the papermaking industry due its low lignin content (Bellido et al., 2015). In recent 57 studies, SBP has been evaluated as a potential source for the production of functional carbohydrates, 58 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 4 paying attention to neutral and acidic oligosaccharides by means of a direct enzymatic saccharification 59 treatment (Concha Olmos and Zúñiga Hansen, 2012; Martínez et al., 2009a). 60 Oligosaccharides are attracting increasing interest as prebiotic functional food ingredients (Rastall, 61 2010; Patel and Goyal, 2011) as they may confer health benefits on the host associated with the 62 modulation of microbiota (Martínez et al., 2009b), especially pectin-derived oligosaccharides (POS) 63 (Rastall, 2010; Patel and Goyal, 2011). POS can be produced from waste biomass or low-cost 64 byproducts by applying a selective fractionation based on physical, chemical and enzymatic methods 65 (Sun and Hughes, 1998; Patel and Goyal, 2011). 66 To the best of our knowledge, only one environmental study has been published with special focus on 67 the environmental footprints of different production schemes of soluble saccharides of polymeric and 68 oligomeric nature from woody residual streams (González-García et al., 2016). In this work, the 69 assessment of the environmental impacts associated to the valorisation of SBP from the sugar refining 70 industry for the production of POS was performed. To do this, a Life Cycle Assessment (LCA) was 71 undertaken to analyse two valorisation scenarios based on different extraction routes considering SBP 72 as raw material. On the basis of experimental results carried out at semi-pilot scale, the environmental 73 hotspots responsible of the largest environmental impacts were identified. This environmental 74 methodology considers all the resources (mass and energy balances) required to make a product, the 75 wastes generated as well as the environmental burdens associated with the product (Goedkoop et al., 76 2008). In addition, this methodology can provide useful information to stakeholders and policy makers 77 on decision making of processes under development. The principles established by ISO standards 78 (ISO 14040, 2006) were followed in this research study. 79 2. Materials and methods 80 2.1 Goal and scope definition 81 This study aims to assess the environmental performance of different extraction routes of SBP from 82 the sugar industry to obtain a POS extract with high content in arabino-oligosaccharides and 83 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 5 oligogalacturonides. Side-streams are also derived from the system which could be used for further 84 applications such as a solid stream rich on cellulose for bioethanol production and a liquid stream rich 85 on monosaccharides. The description of both valorisation scenarios is included below. 86  Scenario 1 based on the autohydrolysis of SBP (hydrothermal processing under non-87 isothermal conditions) performed in a stirred and pressurised stainless steel reactor at 163ºC 88 (Martínez et al., 2009b). 89  Scenario 2 based on the enzymatic hydrolysis of SBP performed by a combined enzyme 90 concentrate of Cellulast and Viscozyme at 37ºC (Martínez et al., 2009a). 91 A cradle-to-gate approach was considered in the scenarios under assessment that is, considering the 92 extraction of raw materials to produce the required inputs and the production of POS but not the 93 phases of use and/or final disposal of POS. This perspective was assumed since the production 94 systems are at semi-pilot scale and the products are not available in the markets yet. Among the 95 processes considered throughout the production life cycle of both valorising schemes, centrifugation, 96 membrane concentration and freeze-drying are performed after the extraction phase. 97 Considering that SBP is a co-product of the sugar refining process, the background process of SBP 98 production (activities directly linked to the sugar production) was excluded from the assessment. Thus, 99 derived environmental impacts were entirely allocated to the sugar. 100 The LCA functional unit must be selected carefully to allow comparisons between the valorising 101 systems under study. Thus, the functional unit is defined as the valorisation of 100 kg of dry SBP at 102 the factory gate, provided by a local pulp factory (Martínez et al., 2009b). 103 2.2 Description of the SBP valorisation scenarios 104 Each valorisation scenario destined to the production of POS was divided in five different subsystems 105 which are depicted in Figure 1: hydrolysis (autohydrolysis - SS1.1 or enzymatic hydrolysis - SS1.2), 106 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 6 centrifugation (SS2), concentration (SS3), diafiltration (SS4), freeze-drying (SS5) and wastewater 107 treatment (SS6). The subsystems were assessed from the production of raw materials (resources) up 108 to the final product at the pilot plant gate. The analysis of a pilot scale process located in the Faculty of 109 Sciences from the University of Vigo (Orense, NW Spain) was performed. As indicated above, further 110 processing and transport activities were excluded from the system boundaries as well as the activities 111 related with the production of the SBP used as raw material. In both scenarios, SBP (70-72% 112 moisture) was provided by a local pulp factory, homogenised in a single lot to avoid compositional 113 differences, and stored in polyethylene bags at -18°C until use. 114 <Figure 1 around here> 115 Scenario 1 – Autohydrolysis treatment 116 SBP is subjected an aqueous processing (autohydrolysis treatment – SS1.1) with tap water in a ratio 117 of 12 g water per g dry pulp. In this work, the reactor was heated up to achieve a maximum 118 temperature of 163ºC, the optimum conditions reported for the production of pectic-oligomers from 119 SBP (Martínez et al. 2009a). The autohydrolysis treatment permits the selective breakdown of pectic 120 polymers to give valuable soluble hydrolysis products such as pectin-oligomers (POS) and a solid 121 fraction rich in cellulose and lignin. At the end of treatment, the reactor was rapidly cooled to 60ºC for 122 12 min, and the liquors were separated from the spent solids by centrifugation (SS2). Table 1 shows 123 the composition of the autohydrolysis liquors. 124 <Table 1 around here> 125 Scenario 2 – Enzymatic Hydrolysis treatment 126 Based on previous studies (Martínez, 2009b), POS mixtures were obtained by enzymatic processing 127 of SBP (SS1.2) using commercial enzymes (Celluclast 1.5L cellulases from Trichoderma reesei and 128 Viscozyme 1.5L endopolygalacturonases from Aspergillus aculeatus). The experimental conditions 129 considered were the following: water/solid ratio of 12 g/ g dry pulp, endopolygalacturonase/solid ratio 130 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 7 of 10 U1/g, cellulase/endopolygalacturonase ratio of 0.725 FPU2/U and reaction time of 12.8 h. Sodium 131 acetate buffer was used to maintain the medium at pH~5. At the end of process, liquors were 132 separated by centrifugation (SS2). The experiments were carried out at 37ºC in Erlenmeyer flasks with 133 orbital agitation (150 rpm). Table 2 shows the composition of the hydrolysates obtained by enzymatic 134 treatment. 135 <Table 2 around here> 136 The autohydrolysis and enzymatic liquors (from SS1.1 and SS1.2 respectively) were treated for 137 purification and concentration using a membrane processing unit (SS3 and SS4) in order to get a 138 stream rich on POS. The experiments were carried out using a polymeric spiral membrane with 139 molecular weight cut-off of 1 kDa and pressure of 8 bar. The processing was carried out at room 140 temperature. 141 The processing started with the concentration of both streams to achieve a volume/concentration 142 (VCR) ratio of 5 (SS3). For additional refining, water was added to the retentate to reach initial volume, 143 and the resulting solution was concentrated again (discontinuous diafiltration – SS4) to achieve the 144 same VCR. At the end of processing, two streams were obtained, a retentate rich on POS and a 145 permeate rich on monosaccharides and other non-saccharide compounds. Finally, the retentate 146 stream was freeze-dried (SS5) and permeates from SS4 and SS5 in both scenarios were sent to a 147 wastewater treatment plant (SS6) for further treatment. 148 2.3 Inventory data collection and allocation approach 149 A reliable environmental assessment requires the collection of Life Cycle Inventory (LCI) data. In this 150 study, inventory data for the foreground system (direct inputs and outputs for each stage) such as 151 electricity requirements (estimated with power and operational data from the different units: reactors, 152 centrifuges, membranes, orbital shakers and freeze-dryers) as well as the use of chemicals, enzymes 153 1 U: unit of enzymatic activity. It is defined as the amount of enzyme catalyzing the formation of 1 μmol of D- galacturonic acid per minute at 37ºC and pH 5. 2 FPU: Filter Paper Activity 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 8 and water were average data of the pilot plant (primary data). A summary of the primary data is 154 displayed in Table 3 for the different valorisation scenarios. According to this table, the POS 155 production yield (the main desired product) is around 20% higher in the autohydrolysis based scenario 156 than in the enzymatic one. This result could be expected due to the enzymatic treatment commonly 157 produces low weight POS which should derive on largest losses ratios in the purification units 158 (membranes). 159 <Table 3 around here> 160 Concerning the background system, the inventory data corresponding to the production of the different 161 inputs to the systems (electricity, sodium acetate and tap water) and the wastewater treatment 162 process were taken from Ecoinvent database® v3.1. Regarding sodium acetate, the specific 163 production process is not included in the database and therefore, a representative process 164 corresponding to the production of inorganic chemicals was considered instead of excluding it from the 165 system boundaries. Regarding the production of enzymes (Viscozyme and Celluclast),information 166 concerning the environmental burdens has been directly supplied by Novozymes3 under confidential 167 issues. Detailed information with regard to the background processes is summarised in Table 4. 168 <Table 4 around here> 169 All the scenarios under assessment are multi-outputs systems with more than one product. Allocation 170 of the environmental impacts is required for multi-functional processes and the selection of an 171 allocation approach can have a strong effect on the results. According to the functional unit chosen 172 based on the amount of waste valorized per batch (100 kg of dry SBP), no allocation procedure was 173 required. The economic value of all the bioproducts differs significantly, which should motivate the use 174 of an economic based approach. Therefore, an alternative functional unit in terms of economic value 175 was considered based on the expected economic revenues of the bioproducts obtained in each 176 scenario. Table 5 reports the market prices considered for the different co-products and the expected 177 net revenue. 178 3 http://www.novozymes.com . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 9 <Table 5 around here> 179 2.4 Impact assessment methodology 180 LCA evaluates the environmental burdens by identifying resource and energy consumption as well as 181 emissions to different environmental compartments associated to the life cycle of the process under 182 assessment, including the identification of priority areas to apply improvement actions (ISO 14040, 183 2006). The characterisation factors reported by the Centre of Environmental Science of Leiden 184 University - CML 2001 method (Guinée et al. 2001) v2.05 were considered in this study for the 185 analysis. The following impact categories were evaluated: abiotic depletion potential (ADP), 186 acidification potential (AP), eutrophication potential (EP), global warming potential (GWP), 187 photochemical oxidation potential (POFP), ozone layer depletion potential (ODP), human toxicity 188 potential (HTP), terrestrial ecotoxicity potential (TEP), freshwater aquatic ecotoxicity potential (FEP) 189 and marine aquatic ecotoxicity potential (MEP). Moreover, SimaPro 8.02 was the software used for 190 the computational implementation of the LCI (PRé Consultants, 2016). 191 3. Results and discussion 192 The environmental assessment in terms of characterisation results obtained for both schemes is 193 displayed in Table 6. As previously indicated, the production of SBP, the main raw material, was 194 excluded from the study because it was managed as a waste stream from sugar factories. Thus, 195 environmental burdens derived from sugar processing are totally allocated to the main product of the 196 production systems, i.e. sugar. 197 <Table 6 around here> 198 According to the environmental results presented in Table 6, remarkable differences can be identified 199 between both valorising schemes of SBP for the production of POS, which should be directly related 200 with differences on the production systems. Although they share a number of stages in common 201 (centrifugation – SS2, concentration – SS3, diafiltration – SS4, freeze-drying – SS5 and wastewater 202 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 16 References 347 Al-Tamimi, M. A. H. M., Palframan, R. J., Cooper, J. M., Gibson, G. R., Rastall, R. A. (2006). 348 In vitro Fermentation of Sugar Beet Arabinan and Arabino-oligosaccharides by the Human Gut 349 Microflora. J. Appl. Microbiol. 100, 407-414. 350 Bellido, C., Infante, C., Coca, M., González-Benito, G., Lucas, S., García-Cubero, M.T. (2015). 351 Efficient acetone–butanol–ethanol production by Clostridium beijerinckii from sugar beet pulp. 352 Bioresour. Technol. 190, 332-338. 353 Concha Olmos, J., Zúñiga Hansen, M.E. (2012). Enzymatic depolymerization of sugar beet 354 pulp: Production and characterization of pectin and pectic-oligosaccharides as a potential source for 355 functional carbohydrates. Chem. Eng. J. 192, 29-36. 356 Ecoinvent database ® (2016). http://www.ecoinvent.org/database (accessed October 2015). 357 Goedkoop M., Heijungs, R., Huijbregts, M., de Schryver, A., Struijs, J., Van Zelm, R. (2009). 358 ReCiPe 2008, A Life Cycle Impact Assessment Method Which Comprises Harmonised Category 359 Indicators at the Midpoint and the Endpoint Level. Report: Characterisation, first ed.; May 2013. 360 http://www.lcia-recipe.net (accessed October 2015). 361 Gómez, B., Gullón, B., Yáñez, R., Schold, H., Alonso, J.L., 2016, Prebiotic potential of pectins 362 and pectic oligosaccharides derived from lemon peel wastes and sugar beet pulp: A comparative 363 evaluation. J. Funct. Foods. 20, 108-121. 364 Gonzalez-Garcia, S., Gullón, B., Rivas, S., Feijoo, G., Moreira, M.T. (2016). Environmental 365 performance of Biomass refining into High-added value compounds. J. Clean. Prod. 120,170-180. 366 Guinée JB, Gorrée M, Heijungs R, Huppes G, Kleijn R, de Koning A, van Oers L, Wegener A, 367 Suh S, Udo de Haes HA., 2001. Life Cycle Assessment. An operational guide to the ISO standards. 368 Centre of Environmental Science, Leiden, The Netherlands. 369 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 17 Huisingh, D., Zhang, Z., Moore, J.C., Qiao, Q., Lif, Q. (2015). Recent advances in carbon 370 emissions reduction: policies, technologies, monitoring, assessment and modeling. J. Clean. Prod. 371 103, 1-12. 372 ISO 14040, (2006). Environmental Management - Life Cycle Assessment - Principles and 373 Framework. Second ed. Geneva, Switzerland. 374 Leijdekkers, A.G.M., Bink, J.P.M., Geutjes, S., Schols, H.A., Gruppen, H. (2013). Enzymatic 375 saccharification of sugar beet pulp for the production of galacturonic acid and arabinose; a study on 376 the impact of the formation of recalcitrant oligosaccharides. Bioresour. Technol. 128, 518–525. 377 Liu, L.C., Fishman, M.L., Hicks, K.B., Liu, C.-K. (2005). Biodegradable composites from sugar 378 beet pulp and poly(lactic acid). J. Agr. Food Chem. 53, 9017–9022. 379 Marketing study (2009). Marketing Study for Biomass Treatment Technology (October 2009). 380 Techical Appendix 3- Products and Markets. 381 Martínez, M., Gullón, B., Yáñez, R., Alonso, J.L., Parajó, J.C. (2009a). Direct Enzymatic 382 Production of Oligosaccharide Mixtures from Sugar Beet Pulp: Experimental Evaluation and 383 Mathematical Modeling. J. Agric. Food. Chem. 57, 5510-5517. 384 Martínez, M., Gullón, B., Schols, H.A., Alonso, J.L., Parajó, J.C. (2009b). Assessment of the 385 production of Oligomeric compounds from Sugar beet pulp. Ind. Eng. Chem. Res. 48, 4681-4687. 386 Megazyme (2016). https://www.megazyme.com/. Accessed September 2016 387 Moniz, P., Ling Ho, Ai, Duarte, L.C., Kolida, S., Rastall, R.A., Pereira, H., Carvalheiro, F., 388 2016. Assessment of the bifidogenic effect of substituted xylo-oligosaccharides obtained from corn 389 straw. Carbohyd. Polym. 136, 466-473. 390 Montazeri, M., Eckelman, M.J. (2015). Life Cycle Assessment of Catechols from Lignin 391 Depolymerization. ACS Sustainable Chem. Eng. DOI: 10.1021/acssuschemeng.5b00550. 392 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 18 Patel, S., Goyal, A. (2011). Functional oligosaccharides: production, properties and 393 applications. World. J. Microbiol. Biotechnol. 27, 1119-1128. 394 Pérez-López, P., Balboa, E.M., González-García, E.M., Domínguez, H., Feijoo, G., Moreira, 395 M.T. (2014). Comparative environmental assessment of valorization strategies of the invasive 396 macroalgae Sargassum muticum. Bioresource Technology 161: 137–148 397 Philp, J. (2015). Balancing the bioeconomy: supporting biofuels and bio-based materials in 398 public policy. Energy Environ. Sci. 8, 3063-3068. 399 Pin, J.M., Guigo, N., Mija, A., Vincent, L., Sbirrazzuoli, N., van der Waal, J.C., de Jond, E. 400 (2014). Valorization of Biorefinery Side-Stream Products: Combination of Humins with Polyfurfuryl 401 Alcohol for Composite Elaboration. ACS Sustainable Chem. 2, 2182-2190. 402 PRé Consultants (2016). http://www.pre.nl 403 Rastall, R.A. (2010). Functional oligosaccharides: application and manufacture, Annu. Rev. 404 Food Sci. Technol. 1 (2010) 305–339 405 Russell, D.A.M., Shiang, D.L. (2013). Thinking about More Sustainable Products: Using an 406 Efficient Tool for Sustainability Education, Innovation, and Project Management To Encourage 407 Sustainability Thinking in a Multinational Corporation. ACS Sustainable Chem. 1, 2-7. 408 Sigmaaldrich (2016). www.sigmaaldrich.com. Accessed June 2016. 409 Sun, R., Hughes, S. (1998). Fractional extraction and physico-chemical characterization of 410 hemicelluloses and cellulose from sugar beet pulp. Carbohydr. Polym. 36, 293–299. 411 Van Uytvanck, P.P., Hallmark, B., Haire, G., Marshall, P.J., Dennis, J.S. (2014). Impact of 412 Biomass on Industry: Using Ethylene Derived from Bioethanol within the Polyester Value Chain. ACS 413 Sustainable Chem. 2, 1098-1105. 414 Zheng, Y., Lee, C., Yu, C., Cheng, Y., Zhang, R., Jenkins, B.M., VanderGheynst, J.S. (2013). 415 Dilute acid pretreatment and fermentation of sugar beet pulp to ethanol. Appl. Energy 105, 1–7. 416 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 19 Ziemiński, K., Romanowska, I., Kowalska-Wentel, M., Cyran, M. (2014). Effects of 417 hydrothermal pretreatment of sugar beet pulp for methane production. Bioresour. Technol. 166, 187-418 193. 419 420 Figure 1. System boundaries and process chain under study corresponding to the Scenario 1 - Autohydrolysis treatment and Scenario 2 – Enzymatic hydrolysis treatment. Processes marked in black were excluded from the system boundaries. Processes and lines marked in grey correspond exclusively to Scenario 2. FOREGROUNDSYSTEM Agricultural activities Sugar factory Sugar SS1.1 AUTOHYDROLYSIS / SS1.2 ENZYMATIC HYDROLYSIS SS3 CONCENTRATION Tap water SBP Cellulose Hemicellulose Lignin Uronic acids Solid fraction Electricity SS5 FREEZE DRYING POS powder Liquid fraction ELECTRICITY PRODUCTION TAP WATER PRODUCTION CHEMICALS PRODUCTION BACKGROUND SYSTEM SYSTEM BOUNDARIES Electricity RAW MATERIALS AIR, WATER & SOIL EMISSIONS Electricity SS2 CENTRIFUGATION SS4 DIAFILTRATION Concentrate Concentrate Electricity Tap water Permeate SS6 WASTEWATER TREATMENT Vizcozyme Cellulast Acetate ENZYMES PRODUCTION Figure Figure 2. a) Distribution of environmental impacts per subsystems involved in Scenario 1; b) Distribution of environmental impacts per subsystems involved in Scenario 2. Acronyms: abiotic depletion potential (ADP), acidification potential (AP), eutrophication potential (EP), global warming potential (GWP), ozone layer depletion potential (ODP), human toxicity potential (HTP), freshwater aquatic ecotoxicity potential (FEP), marine aquatic ecotoxicity potential (MEP), terrestrial ecotoxicity potential (TEP) and photochemical oxidation potential (POFP). a b 0% 20% 40% 60% 80% 100% ADP AP EP GWP ODP HTP FEP MEP TEP POFP Relative contributions SS6 SS5 SS4 SS3 SS2 SS1.1 0% 20% 40% 60% 80% 100% ADP AP EP GWP ODP HTP FEP MEP TEP POFP Relative contributions SS6 SS5 SS4 SS3 SS2 SS1.2 Figure 3. Distribution of impact burdens derived from SS1.2 between the different processes involved. Acronyms: abiotic depletion potential (ADP), acidification potential (AP), eutrophication potential (EP), global warming potential (GWP), ozone layer depletion potential (ODP), human toxicity potential (HTP), freshwater aquatic ecotoxicity potential (FEP), marine aquatic ecotoxicity potential (MEP), terrestrial ecotoxicity potential (TEP) and photochemical oxidation potential (POFP). 0% 20% 40% 60% 80% 100% ADP AP EP GWP ODP HTP FEP MEP TEP POFP Relative contributions Enzymes Acetate Tap water Electricity Figure 4. Comparative environmental profile considering 1 € of potential revenue as functional unit. Scenario 1 – Autohydrolysis treatment; Scenario 2 – Enzymatic hydrolysis treatment. Acronyms: abiotic depletion potential (ADP), global warming potential (GWP), ozone layer depletion potential (ODP), human toxicity potential (HTP), freshwater aquatic ecotoxicity potential (FEP), marine aquatic ecotoxicity potential (MEP), terrestrial ecotoxicity potential (TEP), photochemical oxidation potential (POFP), acidification potential (AP) and eutrophication potential (EP). 0 20 40 60 80 100 ADP GWP ODP HTP FEP MEP TEP POFP AP EP Comparative profile (%) Scenario 1 Scenario 2 1 Table 1. Composition of liquid fraction (rich on pectic oligosaccharides) obtained by autohydrolysis treatment. 2 3 4 Component Composition Monosaccharides Glucose 2.36 g L-1 Galactose 2.43 g L-1 Arabinose 0.39 g L-1 Pectin-derived oligosaccharides (POS) GlcOS 1.61 g L-1 GalOS 2.96 g L-1 AraOS 14.44 g L-1 AcO 2.06 g L-1 OGalA 11.86 g L-1 Volatile compounds Acetic acid 0.38 g L-1 Other non-volatile compounds 8.21 g L-1 GlcOS = glucooligosaccharides; GalOS = galactooligosaccharides; AraOS = arabinooligosaccharides; AcO = acetyl substituents in oligomers; OGalA = oligogalacturonides 5 6 7 8 Table Table 2. Composition of hydrolysates (rich on pectic oligosaccharides) obtained by enzymatic processing. 9 Component Composition Monosaccharides Glucose 4.89 g L-1 Galactose 2.90 g L-1 Galacturonic acid 3.50 g L-1 Arabinose 0.31 g L-1 Pectin-derived oligosaccharides (POS) GlcOS 6.59 g L-1 GalOS 3.02 g L-1 AraOS 11.21 g L-1 AcO 1.62 g L-1 OGalA 10.29 g L-1 Volatile compounds Acetic acid 0.55 g L-1 Other non-volatile compounds 13.87 g L-1 GlcOS = glucooligosaccharides; GalOS = galactooligosaccharides; AraOS = arabinooligosaccharides; AcO = acetyl substituents in oligomers; OGalA = oligogalacturonides 10 11