| 1. |
- Bondesson, Pia-Maria, et al.
(författare)
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Comparison of energy potentials from combined ethanol and methane production using steam-pretreated corn stover impregnated with acetic acid
- 2014
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Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 67, s. 413-424
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Tidskriftsartikel (refereegranskat)abstract
- Acetic acid was investigated as a catalyst in steam pretreatment of corn stover. The purpose was to study ethanol production using either baker's yeast or a genetically modified pentose-fermenting version of Saccharomyces cerevisiae, KE6-12. Biogas production was investigated as an alternative for utilization of xylose. The high levels of acetic acid was found to be toxic using KE6-12. Some pentose fermentation was achieved, but the ethanol end concentration was almost the same as using baker's yeast (28 g L1 compared to 27 g L1). Using xylose for biogas production resulted in a high total energy recovery. The highest total energy recovery in the products, i.e. ethanol, methane and solids, obtained was 88% compared with the energy in ingoing raw material. This result was achieved when the solids and the liquid was separated after pretreatment.
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| 2. |
- Erdei, Borbala, et al.
(författare)
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Simultaneous saccharification and co-fermentation of whole wheat in integrated ethanol production
- 2013
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Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 56, s. 506-514
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Tidskriftsartikel (refereegranskat)abstract
- Two of the most important ways of reducing the production cost of lignocellulosic ethanol are to increase the ethanol yield and the concentration in the fermentation broth. This can be facilitated by co-fermentation of glucose and xylose from agricultural residues such as wheat straw, due to the high amount of xylose in the hemicelluloses in these materials. Simultaneous saccharification and co-fermentation (SSCF) of steam-pretreated wheat straw (SPWS) with and without the addition of liquefied wheat meal (LWM) was performed using the pentose-fermenting yeast, TMB3400. The highest overall ethanol yield in batch operation, of around 70%, equivalent to an ethanol concentration of 43.7 g L-1, was achieved using SPWS with 7.5% water-insoluble solids (WIS) and addition of LWM with 1% WIS. Using SPWS with a higher WIS (10%) resulted in a decreased yield, 60%, although the concentration of ethanol increased to 53.0 g L-1. SSCF of 7.5% straw was also performed with a single (after 20 h) or fed-batch addition of 1% WIS LWM (after 20, 24 and 28 h) resulting in an increase in both ethanol yield and concentration compared to the reference, without wheat meal addition, but no significant difference compared to the batch experiments. The addition of wheat meal to SSCF did not improve xylose utilization significantly, probably due to the instant release of glucose from the liquefied meal, which hampers the uptake of xylose. The instant release of glucose was shown to be caused by the high amylase activity of the beta-glucosidase enzyme preparation. (C) 2013 Elsevier Ltd. All rights reserved.
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| 3. |
- Galbe, Mats, et al.
(författare)
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Pretreatment: The key to efficient utilization of lignocellulosic materials
- 2012
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Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 46, s. 70-78
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Tidskriftsartikel (refereegranskat)abstract
- Second-generation ethanol production from various lignocellulosic materials based on enzymatic hydrolysis of cellulose has moved from research in lab scale to pilot- and demo scale but has not yet reached commercial scale. One of the crucial process steps is the pretreatment of the biomass, which has as primary aim to make the biomass accessible to enzymatic attack, as it has a large impact on all the other steps in the process. Several pretreatment methods have been developed, comprising methods working at low pH, i.e., acid based, at medium pH (without addition of catalysts), or at high pH, i.e., with a base as catalyst. Many methods result in high sugar yields, above 90% of theoretical for agricultural residues while more recalcitrant materials like hardwood, and especially softwood, require dilute-acid pretreatment to reach high sugar yields. However, most studies on pretreatment have been assessed by enzymatic hydrolysis at low solids content and high enzyme dosages. The various pretreatment methods need in the future to be reassessed at more industrial-like conditions considering the whole integrated process taking into consideration the influence on all process steps. In this review, various pretreatment methods are discussed and how assessment should be performed to reach optimal conditions. (C) 2012 Elsevier Ltd. All rights reserved.
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| 4. |
- Linde, Marie, et al.
(författare)
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Steam inretreatment of dilute H2SO4-impregnated wheat straw and SSF with low yeast and enzyme loadings for bioethanol production
- 2008
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Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 32:4, s. 326-332
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Tidskriftsartikel (refereegranskat)abstract
- Conversion of lignocellulosic material to monomeric sugars and finally ethanol must be performed at low cost, i.e, with limited consumption of chemicals, yeast and enzymes while still reaching high yields, if it is to compete with other fuel conversion processes. The objective of this study was thus to investigate ethanol production from steam-pretreated wheat straw by simultaneous saccharification and fermentation (SSF). The concentration of sulphuric acid in the impregnation liquid prior to pretreatment was kept low, 0.2%, and SSF was performed at low enzyme loadings, 3-14 FPU g(-1) water-insoluble solids (WIS), and a low yeast concentration, 2 g L-1. The pretreatment conditions were optimised to give the highest overall glucose and xylose recovery after enzymatic hydrolysis of the residual WIS. The highest recovery of glucose (102%) and xylose (96%) was obtained after pretreatment at 190 degrees C for 10 min. Achieving high yields of glucose and xylose with the same pretreatment conditions is unusual and makes wheat straw a highly suitable raw material for bioethanol production. SSF was performed on whole slurry from straw pretreated under the optimal conditions. A high overall ethanol yield, 67% of the theoretical based on glucose in the raw material, was obtained.
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| 5. |
- Monauari, Sanarn, et al.
(författare)
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Influence of impregnation with lactic acid on sugar yields from steam pretreatment of sugarcane bagasse and spruce, for bioethanol production
- 2011
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Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 35:7, s. 3115-3122
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Tidskriftsartikel (refereegranskat)abstract
- Lignocellulosic biomass can be utilized to produce ethanol, a promising alternative energy source produced through fermentation of sugars. However, in order to achieve high sugar and ethanol yields, the lignocellulosic material must be pretreated before the enzymatic hydrolysis and fermentation. Dilute acid pretreatment, using SO2, is one of the most promising methods of pretreatment for softwood and agricultural residues. However, handling the high acidity of the slurry obtained from pretreatment and difficulty in recycling/degradation of the impregnating agent are some of the drawbacks of the dilute acid processes. In the present study the influence of utilization of a weak organic acid (lactic acid), as impregnating agent, on the sugar yield from pretreatment, with and without addition of SO2, was investigated. The efficiency of pretreatment was assessed by enzymatic hydrolysis of the slurry obtained by pretreatment, using sugarcane bagasse and spruce, stored for one and two months in the presence of lactic acid separately, as feedstocks. Pretreatment of bagasse after storage with 0.5% lactic acid resulted in an overall glucose yield, i.e. after enzymatic hydrolysis, of 79% of theoretical based on the amount available in the raw material. This was as good as pretreatment using SO2 as impregnating agent. However, storage of spruce with lactic acid before pretreatment, with and without addition of SO2, was not efficient and resulted in lower sugar yields than pretreatment using SO2 only. (C) 2011 Elsevier Ltd. All rights reserved.
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| 6. |
- Sassner, Per, et al.
(författare)
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Techno-Economic Evaluation of Bioethanol Production from Three Different Lignocellulosic Materials
- 2008
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Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 32:5, s. 422-430
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Tidskriftsartikel (refereegranskat)abstract
- The lignocellulosic materials spruce (softwood), Salix (hardwood) and corn stover (agricultural residue) are all potential feedstock for ethanol production. In this study the utilization of these materials for bioethanol production was compared in terms of production cost and energy demand using a process concept based on SO2-catalysed steam pretreatment followed by simultaneous saccharification and fermentation (SSF). A model including all major process steps was implemented in the commercial flowsheeting program Aspen Plus, and the model input was based on data recently obtained on lab scale or in a process development unit. The main focus of the study was on the pretreatment and the SSF steps. Sensitivity analyses of important process parameters showed their relative effects on the production cost and on the potential for cost reduction for each raw material. The study clearly demonstrates the importance of a high ethanol yield and the necessity of utilizing the pentose fraction for ethanol production to obtain good process economy, especially when using Salix or corn stover. Furthermore, a less energy-demanding process, here mainly achieved by increasing the dry matter content in SSF, reduces the capital cost and results in higher co-product credit, and therefore has a significant effect on the overall process economy.
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| 7. |
- Öhgren, Karin, et al.
(författare)
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Fuel ethanol production from steam-pretreated corn stover using SSF at higher dry matter content
- 2006
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Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 30:10, s. 863-869
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Tidskriftsartikel (refereegranskat)abstract
- Replacing fossil fuels by bio-fuels has many advantages, such as the reduction of CO2-emission to the atmosphere, the possibility for non-oil-producing countries to be self-sufficient in fuel, and increased local job opportunities. Bio-ethanol is such a promising renewable fuel. However, today it is produced from sugar or starch-raw materials that are relatively expensive. To lower the production cost of bio-ethanol the cost of the raw material must be reduced and the production process made more efficient. The production of bio-ethanol from corn stover using simultaneous saccharification and fermentation (SSF) at high dry matter content addresses both issues. Corn stover is an agricultural by-product and thus has a low economic value. SSF at high dry matter content results in a high ethanol concentration in the fermented slurry, thereby decreasing the energy demand in the subsequent distillation step. In this study, SSF was performed on steam-pretreated corn stover at 5, 7.5 and 10% water-insoluble solids (WIS) with 2g/L hexosefermenting Saccharomyces cerevisiae (ordinary compressed baker's yeast). SSF at 10% WIS resulted in an ethanol yield of 74% based on the glucose content in the raw material and an ethanol concentration of 25 g/L. Neither higher yeast concentration (5 g/L) nor yeast cultivated on the liquid after the pretreatment resulted, under these conditions, in a higher overall ethanol yield. (c) 2006 Elsevier Ltd. All rights reserved.
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| 8. |
- Capecchi, Lorenzo, et al.
(författare)
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Combined ethanol and methane production from switchgrass (Panicum virgatum L.) impregnated with lime prior to steam explosion
- 2016
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Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 0961-9534. ; 90, s. 22-31
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Tidskriftsartikel (refereegranskat)abstract
- Pretreatments are crucial to achieve efficient conversion of lignocellulosic biomass to soluble sugars. In this light, switchgrass was subjected to 13 pretreatments including steam explosion alone (195 °C for 5, 10 and 15 min) and after impregnation with the following catalysts: Ca(OH)2 at low (0.4%) and high (0.7%) concentration; Ca(OH)2 at high concentration and higher temperature (205 °C for 5, 10 and 15 min); H2SO4 (0.2% at 195 °C for 10 min) as reference acid catalyst before steam explosion. Enzymatic hydrolysis was carried out to assess pretreatment efficiency in both solid and liquid fraction. Thereafter, in selected pretreatments the solid fraction was subjected to simultaneous saccharification and fermentation (SSF), while the liquid fraction underwent anaerobic digestion (AD). Lignin removal was lowest (12%) and highest (35%) with steam alone and 0.7% lime, respectively. In general, higher cellulose degradation and lower hemicellulose hydrolysis were observed in this study compared to others, depending on lower biomass hydration during steam explosion. Mild lime addition (0.4% at 195 °C) enhanced ethanol in SSF (+28% than steam alone), while H2SO4 boosted methane in AD (+110%). However, methane represented a lesser component in combined energy yield (ethanol, methane and energy content of residual solid). Mild lime addition was also shown less aggressive and secured more residual solid after SSF, resulting in higher energy yield per unit raw biomass. Decreased water consumption, avoidance of toxic compounds in downstream effluents, and post process recovery of Ca(OH)2 as CaCO3 represent further advantages of pretreatments involving mild lime addition before steam explosion.
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| 9. |
- Söderström, Johanna, et al.
(författare)
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Two-step steam pretreatment of softwood by dilute H2SO4 impregnation for ethanol production
- 2003
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Ingår i: Biomass & Bioenergy. - 1873-2909. ; 24:6, s. 475-486
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Tidskriftsartikel (refereegranskat)abstract
- Fuel ethanol can be produced from softwood through hydrolysis in an enzymatic process. Prior to enzymatic hydrolysis of the softwood, pretreatment is necessary. In this study two-step steam pretreatment by dilute H2SO4 impregnation to improve the overall sugar and ethanol yield has been investigated. The first pretreatment step was performed under conditions of low severity (180°C, 10 min, 0.5% H2SO4) to optimise the amount of hydrolysed hemicellulose. In the second step the washed solid material from the first pretreatment step was impregnated again with H2SO4 and pretreated under conditions of higher severity to hydrolyse a portion of the cellulose, and to make the cellulose more accessible to enzymatic attack. A wide range of conditions was used to determine the most favourable combination. The temperatures investigated were between 180°C and 220°C, the residence times were 2, 5 and 10 min and the concentrations of H2SO4 were 1% and 2%. The effects of pretreatment were assessed by both enzymatic hydrolysis of the solids and with simultaneous saccharification and fermentation (SSF) of the whole slurry, after the second pretreatment step. For each set of pretreatment conditions the liquid fraction was fermented to determine any inhibiting effects. The ethanol yield using the SSF configuration reached 65% of the theoretical value while the sugar yield using the SHF configuration reached 77%. Maximum yields were obtained when the second pretreatment step was performed at 200°C for 2 min with 2% H2SO4. This form of two-step steam pretreatment is a promising method of increasing the overall yield in the wood-to-ethanol process.
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