| 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. |
- Bondesson, Pia-Maria, et al.
(författare)
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Ethanol and biogas production after steam pretreatment of corn stover with or without the addition of sulphuric acid
- 2013
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Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Background: Lignocellulosic biomass, such as corn stover, is a potential raw material for ethanol production. One step in the process of producing ethanol from lignocellulose is enzymatic hydrolysis, which produces fermentable sugars from carbohydrates present in the corn stover in the form of cellulose and hemicellulose. A pretreatment step is crucial to achieve efficient conversion of lignocellulosic biomass to soluble sugars, and later ethanol. This study has investigated steam pretreatment of corn stover, with and without sulphuric acid as catalyst, and examined the effect of residence time (5-10 min) and temperature (190-210 degrees C) on glucose and xylose recovery. The pretreatment conditions with and without dilute acid that gave the highest glucose yield were then used in subsequent experiments. Materials pretreated at the optimal conditions were subjected to simultaneous saccharification and fermentation (SSF) to produce ethanol, and remaining organic compounds were used to produce biogas by anaerobic digestion (AD). Results: The highest glucose yield achieved was 86%, obtained after pretreatment at 210 degrees C for 10 minutes in the absence of catalyst, followed by enzymatic hydrolysis. The highest yield using sulphuric acid, 78%, was achieved using pretreatment at 200 degrees C for 10 minutes. These two pretreatment conditions were investigated using two different process configurations. The highest ethanol and methane yields were obtained from the material pretreated in the presence of sulphuric acid. The slurry in this case was split into a solid fraction and a liquid fraction, where the solid fraction was used to produce ethanol and the liquid fraction to produce biogas. The total energy recovery in this case was 86% of the enthalpy of combustion energy in corn stover. Conclusions: The highest yield, comprising ethanol, methane and solids, was achieved using pretreatment in the presence of sulphuric acid followed by a process configuration in which the slurry from the pretreatment was divided into a solid fraction and a liquid fraction. The solid fraction was subjected to SSF, while the liquid fraction, together with the filtered residual from SSF, was used in AD. Using sulphuric acid in AD did not inhibit the reaction, which may be due to the low concentration of sulphuric acid used. In contrast, a pretreatment step without sulphuric acid resulted not only in higher concentrations of inhibitors, which affected the ethanol yield, but also in lower methane production.
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| 3. |
- Bondesson, Pia-Maria
(författare)
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Evaluation of Pretreatment and Process Configurations for Combined Ethanol and Biogas Production from Lignocellulosic Biomass
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In view of global climate change and the increasing energy demand there is a need for renewable energy resources. This thesis discusses an energy-driven biorefinery concept based on the agricultural residues corn stover and wheat straw. The work is divided into two main parts. The first part is concerned with the effects of steam pretreatment and choice of acid catalyst on ethanol and biogas production, as well as the overall energy yield. The second part focuses on the combination of acetic-acid-catalysed steam pretreatment and simultaneous saccharification and co-fermentation (SSCF) and the role of process configuration on SSCF.Steam pretreatment was found to be a useful instrument to improve access of the main components of corn stover. This pretreatment resulted in high energy recovery. The choice of catalyst during steam pretreatment affected the overall energy recovery and product yield. Steam pretreatment with acetic acid or sulphuric acid improved the energy recovery compared with steam pretreatment with no catalyst or phosphoric acid. Phosphoric acid had toxic effects on ethanol and biogas production, while acetic acid was toxic only to ethanol production. The toxic effects on ethanol production were overcome by increasing the pH from 5.0 to 5.5. Process configuration also influenced the total energy recovery and product yield. This showed that not only the type of pretreatment, but also the process configuration, is important in an energy-driven biorefinery.Acetic acid is a known inhibitor during ethanol production. Using the S. cerevisiae strain KE6-12b resulted in ethanol production from both glucose and xylose, despite the fact that acetic-acid-catalysed steam pretreatment was used. Fed-batch improved SSCF in terms of ethanol yield and final ethanol concentration. Increasing the water insoluble solids (WIS) concentration from 10% to 11.7% improved the ethanol concentration, but the higher amount of inhibitors had a negative effect on the ethanol yield. Increasing the yeast concentration improved the results with higher WIS, but improvements are still required to increase the ethanol yield and concentration.
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| 4. |
- Bondesson, Pia-Maria, et al.
(författare)
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Optimizing Ethanol and Methane Production from Steam-pretreated, Phosphoric Acid-impregnated Corn Stover.
- 2015
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Ingår i: Applied Biochemistry and Biotechnology. - : Springer Science and Business Media LLC. - 1559-0291 .- 0273-2289. ; 175:3, s. 1371-1388
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Tidskriftsartikel (refereegranskat)abstract
- Pretreatment is of vital importance in the production of ethanol and methane from agricultural residues. In this study, the effects of steam pretreatment with phosphoric acid on enzymatic hydrolysis (EH), simultaneous saccharification and fermentation (SSF), anaerobic digestion (AD) and the total energy output at three different temperatures were investigated. The effect of separating the solids for SSF and the liquid for AD was also studied and compared with using the whole slurry first in SSF and then in AD. Furthermore, the phosphoric acid was compared to previous studies using sulphuric acid or no catalyst. Using phosphoric acid resulted in higher yields than when no catalyst was used. However, compared with sulphuric acid, an improved yield was only seen with phosphoric acid in the case of EH. The higher pretreatment temperatures (200 and 210 °C) resulted in the highest yields after EH and SSF, while the highest methane yield was obtained with the lower pretreatment temperature (190 °C). The highest yield in terms of total energy recovery (78 %) was obtained after pretreatment at 190 °C, but a pretreatment temperature of 200 °C is, however, the best alternative since fewer steps are required (whole slurry in SSF and then in AD) and high product yields were obtained (76 %).
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| 5. |
- Bondesson, Pia-Maria, et al.
(författare)
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Process design of SSCF for ethanol production from steam-pretreated, acetic-acid-impregnated wheat straw
- 2016
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Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundPretreatment is an important step in the production of ethanol from lignocellulosic material. Using acetic acid together with steam pretreatment allows the positive effects of an acid catalyst to be retained, while avoiding the negative environmental effects associated with sulphuric acid. Acetic acid is also formed during the pretreatment and hydrolysis of hemicellulose, and is a known inhibitor that may impair fermentation at high concentrations. The purpose of this study was to improve ethanol production from glucose and xylose in steam-pretreated, acetic-acid-impregnated wheat straw by process design of simultaneous saccharification and co-fermentation (SSCF), using a genetically modified pentose fermenting yeast strain Saccharomyces cerevisiae.ResultsEthanol was produced from glucose and xylose using both the liquid fraction and the whole slurry from pretreated materials. The highest ethanol concentration achieved was 37.5 g/L, corresponding to an overall ethanol yield of 0.32 g/g based on the glucose and xylose available in the pretreated material. To obtain this concentration, a slurry with a water-insoluble solids (WIS) content of 11.7 % was used, using a fed-batch SSCF strategy. A higher overall ethanol yield (0.36 g/g) was obtained at 10 % WIS.ConclusionsEthanol production from steam-pretreated, acetic-acid-impregnated wheat straw through SSCF with a pentose fermenting S. cerevisiae strain was successfully demonstrated. However, the ethanol concentration was too low and the residence time too long to be suitable for large-scale applications. It is hoped that further process design focusing on the enzymatic conversion of cellulose to glucose will allow the combination of acetic acid pretreatment and co-fermentation of glucose and xylose.
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| 6. |
- Gladis, Arne, et al.
(författare)
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Influence of different SSF conditions on ethanol production from corn stover at high solids loadings
- 2015
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Ingår i: Energy Science & Engineering. - : Wiley. - 2050-0505. ; 3:5, s. 481-489
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Tidskriftsartikel (refereegranskat)abstract
- In this study, three different kinds of simultaneous saccharification and fermentation (SSF) of washed pretreated corn stover with water-insoluble solids (WIS) content of 20% were investigated to find which one resulted in highest ethanol yield at high-solids loadings. The different methods were batch SSF, prehydrolysis followed by batch SSF and fed-batch SSF. Batch-SSF resulted in an ethanol yield of 75–76% and an ethanol concentration of 53 g/L. Prehydrolysis prior to batch SSF did not improve the ethanol yield compared with batch SSF. Fed-batch SSF, on the other hand, increased the yield, independent of the feeding conditions used (79–81%, 57–60 g/L). If the initial amount of solids during fed-batch SSF was lowered, the yield could be improved to some extent. When decreasing the enzyme dosage, the greatest decrease in yield was seen in the fed-batch mode (75%), while lower or the same yield was seen in batch mode with and without prehydrolysis (73%). This resulted in similar ethanol yields in all methods. However, the residence time to achieve the final ethanol yield was shorter using fed-batch. This shows that fed-batch can be a better alternative also at a lower enzyme loading.
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