| 1. |
- 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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| 2. |
- 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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| 3. |
- Koppram, Rakesh, 1986, et al.
(författare)
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Simultaneous saccharification and co-fermentation for bioethanol production using corncobs at lab, PDU and demo scales
- 2015
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Ingår i: Fuel production from non-food biomass: Corn stover. - : Apple Academic Press. - 9781498728430 - 9781771881234 ; , s. 155-179
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The global CO2 emissions in 2010 from fossil energy use grew at the fastest rate since 1969. The year 2010 also witnessed that the global oil production did not match the rapid growth in consumption [1]. These recent data further intensify worldwide concerns about greenhouse gas emissions and energy security for a sustained economic development. For a reduced dependence on oil from fossil reserves, use of biofuels such as bioethanol from abundantly available lignocellulosic biomass is of great interest nowadays because they will count towards meeting the mandate of 10% binding target for biofuels from renewable sources in the transport for all European member states by 2020 [2]. Along with this interest comes increased interest in commercializing ethanol production technology from inexpensive lignocellulosic feedstocks which includes wood biomass, agricultural and forestry residues, biodegradable fraction of industrial and municipal wastes. Irrespective of type, the basic structural composition of lignocellulosic biomass consists of cellulose, hemicellulose and lignin. The cellulose and hemicellulose that form the polysaccharide fraction are embedded in a recalcitrant and inaccessible arrangement [3] and therefore requires a pretreatment step to disrupt the structure and make it accessible for subsequent steps. Since lignocellulosic materials are very complex, not one pretreatment method can apply for all the materials. Several methods that are classified in to physical, physico-chemical, chemical and biological pretreatment have been investigated and an elaborate review on each of these methods has been presented by Taherzadeh and Karimi [4]. One of the most commonly used pretreatment methods is steam explosion, with the addition of H2SO4 or SO2, which removes most of the hemicellulose, followed by enzymatic hydrolysis to convert cellulose to glucose [5,6].
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| 4. |
- Nielsen, Fredrik, et al.
(författare)
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Prefermentation improves ethanol yield in separate hydrolysis and cofermentation of steam-pretreated wheat straw
- 2016
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Ingår i: Sustainable Chemical Processes. - : Springer Science and Business Media LLC. - 2043-7129. ; 4:10
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural residues, such as wheat straw, are feasible substrates for ethanol fermentation provided that pentoses and hexoses can be converted efficiently. Separate hydrolysis and cofermentation (SHCF) constitute a framework for improvement of conversion efficiency, because it permits independent optimization of the enzymatic hydrolysis and cofermentation steps. A drawback is that the high glucose concentrations present in SHCF repress xylose utilization and constrain ethanol yields. To improve xylose utilization the xylose-rich hydrolyzate liquor was separated from glucose-rich solids and the phases were cofermented sequentially. Prefermentation of the xylose-rich hydrolyzate liquor followed by fed-batch cofermentation of glucose-rich prehydrolyzed solids enabled sequential targeting of xylose and glucose conversion. The aim was to improve the xylose conversion by lowering the glucose repression of the xylose uptake. Various prefermentation configurations and feed patterns for prehydrolyzed solids were examined. Prefermentation increased ethanol yields overall, and fed-batch prefermentation reduced xylitol production. The best results were obtained by balancing promotion of efficient xylose conversion with maintained yeast viability. Fed-batch prefermentation and a single addition of prehydrolyzed solids, elicited an ethanol yield of 0.423 g·g−1 and a xylitol yield of 0.036 g·g−1.
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| 5. |
- Nielsen, Fredrik, et al.
(författare)
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Sequential Targeting of Xylose and Glucose Conversion in Fed-Batch Simultaneous Saccharification and Co-fermentation of Steam-Pretreated Wheat Straw for Improved Xylose Conversion to Ethanol
- 2017
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Ingår i: Bioenergy Research. - : Springer Science and Business Media LLC. - 1939-1234 .- 1939-1242. ; 10:3, s. 800-810
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Tidskriftsartikel (refereegranskat)abstract
- Efficient conversion of both glucose and xylose in lignocellulosic biomass is necessary to make second-generation bioethanol from agricultural residues competitive with first-generation bioethanol and gasoline. Simultaneous saccharification and co-fermentation (SSCF) is a promising strategy for obtaining high ethanol yields. However, with this method, the xylose-fermenting capacity and viability of yeast tend to decline over time and restrict the xylose utilization. In this study, we examined the ethanol production from steam-pretreated wheat straw using an established SSCF strategy with substrate and enzyme feeding that was previously applied to steam-pretreated corn cobs. Based on our findings, we propose an alternative SSCF strategy to sustain the xylose-fermenting capacity and improve the ethanol yield. The xylose-rich hydrolyzate liquor was separated from the glucose-rich solids, and phases were co-fermented sequentially. By prefermentation of the hydrolyzate liquor followed fed-batch SSCF, xylose, and glucose conversion could be targeted in succession. Because the xylose-fermenting capacity declines over time, while glucose is still converted, it was advantageous to target xylose conversion upfront. With our strategy, an overall ethanol yield of 84% of the theoretical maximum based on both xylose and glucose was reached for a slurry with higher inhibitor concentrations, versus 92% for a slurry with lower inhibitor concentrations. Xylose utilization exceeded 90% after SSCF for both slurries. Sequential targeting of xylose and glucose conversion sustained xylose fermentation and improved xylose utilization and ethanol yield compared with fed-batch SSCF of whole slurry.
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| 6. |
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