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- Janssen, Mathias, 1973, et al.
(författare)
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Life cycle assessment of wood-based ethanol production at high gravity conditions
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The development of economically feasible and environmentally benign processes for the production of second generation biofuels is an ongoing effort. The production of bio-ethanol from wood (spruce) using high gravity (high solids content) fermentation is one process concept that is currently under development. Such a process will lead to lower water use in the process, and consequently to lower energy use. However, high gravity conditions have adverse effects on the micro-organisms and high yields are thus not guaranteed. All this will affect the environmental impact of the process. Life cycle assessment (LCA) is used to evaluate the environmental impact of the process along its development path. The main objective of the LCA is to help improve the process under development from an environmental point of view. The LCA is based on the results of lab experiments that were done for the high gravity fermentation process using pretreated spruce as the feedstock. These experiments focused on the process configuration and detoxification strategies in order to increase yields. A spreadsheet model was set up that used the experimental data in order to calculate the mass and energy balances of the system under study, from the harvesting of the wood until the produced ethanol leaves the plant (cradle-to-gate). The results of the mass and energy balances were subsequently used in the LCA model in order to calculate the environmental impact of the ethanol production. The outcomes of the LCA for all the process variants studied were compared in order to identify the weak and strong points of the process. This information can then be used for further development of the technology.This poster presents the results of the LCA based on the lab experiments for this wood-based high gravity process under development. Comparisons are made with wood-based ethanol production using a fermentation process at lower solids content, and with ethanol production using first-generation feedstocks and technology. LCA is thus used during the process development and may potentially have a significant influence on this development, and therefore on the sustainability of 2nd generation biofuels that are produced with a high gravity production process.
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| 2. |
- Johansson, Emma, 1979, et al.
(författare)
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Fermentation performance and physiology of two strains of Saccharomyces cerevisiae during growth in high gravity spruce hydrolysate and spent sulphite liquor
- 2014
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Ingår i: BMC Biotechnology. - : Springer Science and Business Media LLC. - 1472-6750. ; 14, s. Art. no. 47-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Lignocellulosic materials are a diverse group of substrates that are generally scarce in nutrients, which compromises the tolerance and fermentation performance of the fermenting organism. The problem is exacerbated by harsh pre-treatment, which introduces sugars and substances inhibitory to yeast metabolism. This study compares the fermentation behaviours of two yeast strains using different types of lignocellulosic substrates; high gravity dilute acid spruce hydrolysate (SH) and spent sulphite liquor (SSL), in the absence and presence of yeast extract. To this end, the fermentation performance, energy status and fermentation capacity of the strains were measured under different growth conditions. Results: Nutrient supplementation with yeast extract increased sugar uptake, cell growth and ethanol production in all tested fermentation conditions, but had little or no effect on the energy status, irrespective of media. Nutrient-supplemented medium enhanced the fermentation capacity of harvested cells, indicating that cell viability and reusability was increased by nutrient addition. Conclusions: Although both substrates belong to the lignocellulosic spruce hydrolysates, their differences offer specific challenges and the overall yields and productivities largely depend on choice of fermenting strain.
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| 3. |
- Koppram, Rakesh, 1986, et al.
(författare)
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Lignocellulosic ethanol production at high-gravity: Challenges and perspectives
- 2014
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Ingår i: Trends in Biotechnology. - : Elsevier BV. - 0167-7799 .- 1879-3096. ; 32:1, s. 46-53
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Forskningsöversikt (refereegranskat)abstract
- In brewing and ethanol-based biofuel industries, high-gravity fermentation produces 10-15% (v/v) ethanol, resulting in improved overall productivity, reduced capital cost, and reduced energy input compared to processing at normal gravity. High-gravity technology ensures a successful implementation of cellulose to ethanol conversion as a cost-competitive process. Implementation of such technologies is possible if all process steps can be performed at high biomass concentrations. This review focuses on challenges and technological efforts in processing at high-gravity conditions and how these conditions influence the physiology and metabolism of fermenting microorganisms, the action of enzymes, and other process-related factors. Lignocellulosic materials add challenges compared to implemented processes due to high inhibitors content and the physical properties of these materials at high gravity. © 2013 Elsevier Ltd.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- Xiros, Charilaos, 1973, et al.
(författare)
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Comparison of strategies to overcome the inhibitory effects in high-gravity fermentation of lignocellulosic hydrolysates
- 2014
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 65, s. 79-90
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Tidskriftsartikel (refereegranskat)abstract
- High-gravity (HG) technology aims at generating final ethanol concentrations above 50 kg m(-3) in order to reduce the cost of the distillation step. The generation of higher amounts of inhibitors during the pretreatment step is one of the challenges that accompany the increase in initial dry matter. Detoxification of spruce hydrolysate, adaptation of the cells before fermentation, supplementation with nutrients, and washing of solids were the strategies compared in this study. They represent different approaches to cope with the inhibitory effects, and we compared their efficiencies using a thermotolerant strain of Saccharomyces cereuisiae at temperatures from 30 degrees C up to 40 degrees C. The dilute acid-pretreated spruce used as substrate in this study was not fermentable under HG conditions (200 g kg(-1) water-insoluble solids) when no improvement method was applied. In HG simultaneous saccharification and fermentation at 30 degrees C combined with a 24 h pre-hydrolysis step, the detoxification of pretreated spruce with reducing agent (Na2S2O4) gave the best result with an ethanol yield of 57% (on total sugars) of the maximum theoretical and a volumetric productivity of 1.58 g dm(-3) h(-1). In HG separate hydrolysis and fermentation, nutrients supplementation gave better final ethanol yields than detoxification of the material, reaching an ethanol yield of about 60% of the theoretical (on total sugars). The results obtained, showed an increase in severity of inhibitory effects with temperature increase. Improved cell viability was observed when detoxified material was used and also when yeast extract addition was coupled with adaptation of the cells to the hydrolysate. (C) 2014 Published by Elsevier Ltd.
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| 8. |
- Xiros, Charilaos, 1973, et al.
(författare)
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Evaluation of different strategies to overcome the inhibitory effects at high gravity processes using multivariate data analysis (MVDA)
- 2014
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Ingår i: Lignobiotech III, October 26-29, 2014, Concepcion, Chile.
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Konferensbidrag (refereegranskat)abstract
- High-gravity (HG) technology aims at generating final ethanol concentrations above 50 kg m3 in order to reduce the cost of the distillation step. The generation of higher amounts of inhibitors during the pretreatment step is one of the challenges that accom-pany the increase in initial dry matter. Detoxification of spruce hydrolysate, adaptation of the cells before fermentation, supplementation with nutrients, and washing of solids were the strategies compared in this study. They represent different approaches tocope with the inhibitory effects, and we compared their efficiencies using a thermotolerant strain of Saccharomyces cerevisiae at temperatures from 30oC up to 40oC.The dilute acid-pretreated spruce used as substrate in this study was not fermentable under HG conditions (200 g kg-1water-insoluble solids) when no improvement method was applied. In HG simultaneous saccharification and fermentationat 30oC combined with a 24 h pre-hydrolysis step, the detoxification of pretreated spruce with reducing agent (Na2S2O4) gave the best result with an ethanol yield of 57% (on total sugars) of the maximum theoretical and a volumetric productivity of1.58 g dm3 h−1. In HG separate hydrolysis and fermentation, nutrients supplementation gave better final ethanol yields than detoxification of the material, reaching an ethanol yield of about 60% of the theoretical (on total sugars). The results obtained, showed an increase in severity of inhibitory effects with temperature increase. Improved cell viability was observed when detoxified material was used and also when yeast extract addition was coupled with adaptation of the cells to the hydrolysate. The different fractions of hydrolysates after the application of different treatments were characterised and analysed using MVDA in order to evaluate the differences observed.
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