| 1. |
- Albers, Eva, 1966, et al.
(författare)
-
Comparison of industrial xylose fermentation with yeast performed at different process scale
- 2012
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Ingår i: 13th International Congress on Yeasts, ICY 2012, August 26-30, Madison, USA.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Second generation of bioethanol production with yeast from lignocellulosic material may contribute to a sustainable production of energy. However, the commercialization of cellulose-to-ethanol remains challenging due to various limitations in process technology and microbial physiology. Despite that the technical progress lately has come far, lignocellulose bioethanol production is still not well established in full production scale. Production scale demands large financial investments and to minimize the risk knowledge about cellular performance of the yeast as response to conditions of large scale is needed. Large scale may impose specific conditions that normally are not present in smaller scale. Such conditions are then needed to be identified and mimicked in smaller scale to obtain crucial scaling-up data. In this project, we wanted to establish scalable cultivation processes and compare the performance at different scales. Experiments were performed at three process scales: lab (1.5 l), process development unit (15 l) and demonstration (10 m3) scales, with an industrial recombinant xylose fermenting Saccharomyces cerevisiae strain and corn cob, bagasse, and spruce lignocellulosic material. It was found that separate fermentation and SSF experiments could be reproducible at all scales. An ethanol level could be obtained above 4 % which is the threshold for feasible down-stream processing. Demonstration scale experiments on xylose-rich liquid of pre-treated corn cobs resulted in a 90% conversion of xylose to ethanol and on the slurry in SSF cultivation an ethanol yield of 0.44 g/g xylose was obtained.
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| 2. |
- Albers, Eva, 1966, et al.
(författare)
-
Development and large scale performance of efficient xylose fermenting yeast strains
- 2011
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Ingår i: Seventh International Conference on Renewable Resources and Biorefineries, Belgium.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Fermentation at large industrial scale poses several challenges for the fermenting microorganism to handle. Thus, for an efficient production it is desirable to have robust and efficient strains which can cope with the specific conditions in the process. For bioethanol production by yeast from lignocellulosic material the substrate for growth constitutes one of the largest challenges due to its mixture of sugars and content of inhibitory compounds. Wild-type strains of Saccharomyces cerevisiae can only convert hexose sugars but not the pentoses, xylose and arabinose, which may be present in lignocellulosic material. However, strains have been genetically modified to allow for xylose conversion, but their performance is needed to be improved in terms of rate and efficiency. During the pre-treatment of lignocellulosic material inhibitory compounds are formed; furans, phenolics and organic acids. In an industrial setting, a robust strain back ground (industrial yeast strains) is a prerequisite, in which earlier pentose fermenting traits should be incorporated and further adaptation to the inhibitory compounds need to follow. In the present project, we have used directed evolution to simultaneously improve the inhibitor tolerance and xylose conversion capability of recombinant yeast strains with an industrial background. Improved yeast strains resulting from several strategies were evaluated and one of the best strains with high ethanol production, good xylose utilization capacity, and low xylitol formation was selected for evaluation in larger scale. Fermentations on pre-treated corn cobs were performed with good results regarding ethanol production and xylose utilization both in process development unit scale (15 l) and demonstration scale (10 m3).
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| 3. |
- Alvfors, Per, 1954-, et al.
(författare)
-
Research and development challenges for Swedish biofuel actors – three illustrative examples : Improvement potential discussed in the context of Well-to-Tank analyses
- 2010
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Currently biofuels have strong political support, both in the EU and Sweden. The EU has, for example, set a target for the use of renewable fuels in the transportation sector stating that all EU member states should use 10% renewable fuels for transport by 2020. Fulfilling this ambition will lead to an enormous market for biofuels during the coming decade. To avoid increasing production of biofuels based on agriculture crops that require considerable use of arable area, focus is now to move towards more advanced second generation (2G) biofuels that can be produced from biomass feedstocks associated with a more efficient land use. Climate benefits and greenhouse gas (GHG) balances are aspects often discussed in conjunction with sustainability and biofuels. The total GHG emissions associated with production and usage of biofuels depend on the entire fuel production chain, mainly the agriculture or forestry feedstock systems and the manufacturing process. To compare different biofuel production pathways it is essential to conduct an environmental assessment using the well-to-tank (WTT) analysis methodology. In Sweden the conditions for biomass production are favourable and we have promising second generation biofuels technologies that are currently in the demonstration phase. In this study we have chosen to focus on cellulose based ethanol, methane from gasification of solid wood as well as DME from gasification of black liquor, with the purpose of identifying research and development potentials that may result in improvements in the WTT emission values. The main objective of this study is thus to identify research and development challenges for Swedish biofuel actors based on literature studies as well as discussions with the the researchers themselves. We have also discussed improvement potentials for the agriculture and forestry part of the WTT chain. The aim of this study is to, in the context of WTT analyses, (i) increase knowledge about the complexity of biofuel production, (ii) identify and discuss improvement potentials, regarding energy efficiency and GHG emissions, for three biofuel production cases, as well as (iii) identify and discuss improvement potentials regarding biomass supply, including agriculture/forestry. The scope of the study is limited to discussing the technologies, system aspects and climate impacts associated with the production stage. Aspects such as the influence on biodiversity and other environmental and social parameters fall beyond the scope of this study. We find that improvement potentials for emissions reductions within the agriculture/forestry part of the WTT chain include changing the use of diesel to low-CO2-emitting fuels, changing to more fuel-efficient tractors, more efficient cultivation and manufacture of fertilizers (commercial nitrogen fertilizer can be produced in plants which have nitrous oxide gas cleaning) as well as improved fertilization strategies (more precise nitrogen application during the cropping season). Furthermore, the cultivation of annual feedstock crops could be avoided on land rich in carbon, such as peat soils and new agriculture systems could be introduced that lower the demand for ploughing and harrowing. Other options for improving the WTT emission values includes introducing new types of crops, such as wheat with higher content of starch or willow with a higher content of cellulose. From the case study on lignocellulosic ethanol we find that 2G ethanol, with co-production of biogas, electricity, heat and/or wood pellet, has a promising role to play in the development of sustainable biofuel production systems. Depending on available raw materials, heat sinks, demand for biogas as vehicle fuel and existing 1G ethanol plants suitable for integration, 2G ethanol production systems may be designed differently to optimize the economic conditions and maximize profitability. However, the complexity connected to the development of the most optimal production systems require improved knowledge and involvement of several actors from different competence areas, such as chemical and biochemical engineering, process design and integration and energy and environmental systems analysis, which may be a potential barrier.
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| 4. |
- Alvfors, Per, et al.
(författare)
-
Research and development challenges for Swedish biofuel actors – three illustrative examples
- 2010
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Currently biofuels have strong political support, both in the EU and Sweden. The EU has, for example, set a target for the use of renewable fuels in the transportation sector stating that all EU member states should use 10% renewable fuels for transport by 2020. Fulfilling this ambition will lead to an enormous market for biofuels during the coming decade. To avoid increasing production of biofuels based on agriculture crops that require considerable use of arable area, focus is now to move towards more advanced second generation (2G) biofuels that can be produced from biomass feedstocks associated with a more efficient land use.Climate benefits and greenhouse gas (GHG) balances are aspects often discussed in conjunction with sustainability and biofuels. The total GHG emissions associated with production and usage of biofuels depend on the entire fuel production chain, mainly the agriculture or forestry feedstock systems and the manufacturing process. To compare different biofuel production pathways it is essential to conduct an environmental assessment using the well-to-tank (WTT) analysis methodology. In Sweden the conditions for biomass production are favourable and we have promising second generation biofuels technologies that are currently in the demonstration phase. In this study we have chosen to focus on cellulose based ethanol, methane from gasification of solid wood as well as DME from gasification of black liquor, with the purpose of identifying research and development potentials that may result in improvements in the WTT emission values. The main objective of this study is thus to identify research and development challenges for Swedish biofuel actors based on literature studies as well as discussions with the the researchers themselves. We have also discussed improvement potentials for the agriculture and forestry part of the WTT chain. The aim of this study is to, in the context of WTT analyses, (i) increase knowledge about the complexity of biofuel production, (ii) identify and discuss improvement potentials, regarding energy efficiency and GHG emissions, for three biofuel production cases, as well as (iii) identify and discuss improvement potentials regarding biomass supply, including agriculture/forestry. The scope of the study is limited to discussing the technologies, system aspects and climate impacts associated with the production stage. Aspects such as the influence on biodiversity and other environmental and social parameters fall beyond the scope of this study. We find that improvement potentials for emissions reductions within the agriculture/forestry part of the WTT chain include changing the use of diesel to low-CO2-emitting fuels, changing to more fuel-efficient tractors, more efficient cultivation and manufacture of fertilizers (commercial nitrogen fertilizer can be produced in plants which have nitrous oxide gas cleaning) as well as improved fertilization strategies (more precise nitrogen application during the cropping season). Furthermore, the cultivation of annual feedstock crops could be avoided on land rich in carbon, such as peat soils and new agriculture systems could be introduced that lower the demand for ploughing and harrowing. Other options for improving the WTT emission values includes introducing new types of crops, such as wheat with higher content of starch or willow with a higher content of cellulose. From the case study on lignocellulosic ethanol we find that 2G ethanol, with co-production of biogas, electricity, heat and/or wood pellet, has a promising role to play in the development of sustainable biofuel production systems. Depending on available raw materials, heat sinks, demand for biogas as vehicle fuel and existing 1G ethanol plants suitable for integration, 2G ethanol production systems may be designed differently to optimize the economic conditions and maximize profitability. However, the complexity connected to the development of the most optimal production systems require improved knowledge and involvement of several actors from different competence areas, such as chemical and biochemical engineering, process design and integration and energy and environmental systems analysis, which may be a potential barrier. Three important results from the lignocellulosic ethanol study are: (i) the production systems could be far more complex and intelligently designed than previous studies show, (ii) the potential improvements consist of a large number of combinations of process integration options wich partly depends on specific local conditions, (iii) the environmental performance of individual systems may vary significantly due to systems design and local conditons.From the case study on gasification of solid biomass for the production of biomethane we find that one of the main advantages of this technology is its high efficiency in respect to converting biomass into fuels for transport. For future research we see a need for improvements within the gas up-grading section, including gas cleaning and gas conditioning, to obtain a more efficient process. A major challenge is to remove the tar before the methanation reaction. Three important results from the biomethane study are: (i) it is important not to crack the methane already produced in the syngas, which indicates a need for improved catalysts for selective tar cracking, (ii) there is a need for new gas separation techniques to facilitate the use of air oxidation agent instead of oxygen in the gasifier, and (iii) there is a need for testing the integrated process under realistic conditions, both at atmospheric and pressurized conditions. From the case study on black liquor gasification for the production of DME we find that the process has many advantages compared to other biofuel production options, such as the fact that black liquor is already partially processed and exists in a pumpable, liquid form, and that the process is pressurised and tightly integrated with the pulp mill, which enhances fuel production efficiency. However, to achieve commercial status, some challenges still remain, such as demonstrating that materials and plant equipment meet the high availability required when scaling up to industrial size in the pulp mill, and also proving that the plant can operate according to calculated heat and material balances. Three important results from the DME study are: (i) that modern chemical pulp mills, having a potential surplus of energy, could become important suppliers of renewable fuels for transport, (ii) there is a need to demonstrate that renewable DME/methanol will be proven to function in large scale, and (iii) there is still potential for technology improvements and enhanced energy integration. Although quantitative improvement potentials are given in the three biofuel production cases, it is not obvious how these potentials would affect WTT values, since the biofuel production processes are complex and changing one parameter impacts other parameters. The improvement potentials are therefore discussed qualitatively. From the entire study we have come to agree on the following common conclusions: (i) research and development in Sweden within the three studied 2G biofuel production technologies is extensive, (ii) in general, the processes, within the three cases, work well at pilot and demonstration scale and are now in a phase to be proven in large scale, (iii) there is still room for improvement although some processes have been known for decades, (iv) the biofuel production processes are complex and site specific and process improvements need to be seen and judged from a broad systems perspective (both within the production plant as well as in the entire well-to-tank perspective), and (v) the three studied biofuel production systems are complementary technologies. Futher, the process of conducting this study is worth mentioning as a result itself, i.e. that many different actors within the field have proven their ability and willingness to contribute to a common report, and that the cooperation climate was very positive and bodes well for possible future collaboration within the framework of the f3 center. Finally, judging from the political ambitions it is clear that the demand for renewable fuels will significantly increase during the coming decade. This will most likely result in opportunities for a range of biofuel options. The studied biofuel options all represent 2G biofuels and they can all be part of the solution to meet the increased renewable fuel demand.
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| 5. |
- Alvors, Per, et al.
(författare)
-
Research and development challenges for Swedish biofuel actors – three illustrative examples : Improvement potential discussed in the context of Well-to-Tank analyses
- 2010
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Currently biofuels have strong political support, both in the EU and Sweden. The EU has, for example, set a target for the use of renewable fuels in the transportation sector stating that all EU member states should use 10% renewable fuels for transport by 2020. Fulfilling this ambition will lead to an enormous market for biofuels during the coming decade. To avoid increasing production of biofuels based on agriculture crops that require considerable use of arable area, focus is now to move towards more advanced second generation (2G) biofuels that can be produced from biomass feedstocks associated with a more efficient land use.Climate benefits and greenhouse gas (GHG) balances are aspects often discussed in conjunction with sustainability and biofuels. The total GHG emissions associated with production and usage of biofuels depend on the entire fuel production chain, mainly the agriculture or forestry feedstock systems and the manufacturing process. To compare different biofuel production pathways it is essential to conduct an environmental assessment using the well-to-tank (WTT) analysis methodology.In Sweden the conditions for biomass production are favourable and we have promising second generation biofuels technologies that are currently in the demonstration phase. In this study we have chosen to focus on cellulose based ethanol, methane from gasification of solid wood as well as DME from gasification of black liquor, with the purpose of identifying research and development potentials that may result in improvements in the WTT emission values. The main objective of this study is thus to identify research and development challenges for Swedish biofuel actors based on literature studies as well as discussions with the the researchers themselves. We have also discussed improvement potentials for the agriculture and forestry part of the WTT chain. The aim of this study is to, in the context of WTT analyses, (i) increase knowledge about the complexity of biofuel production, (ii) identify and discuss improvement potentials, regarding energy efficiency and GHG emissions, for three biofuel production cases, as well as (iii) identify and discuss improvement potentials regarding biomass supply, including agriculture/forestry. The scope of the study is limited to discussing the technologies, system aspects and climate impacts associated with the production stage. Aspects such as the influence on biodiversity and other environmental and social parameters fall beyond the scope of this study.We find that improvement potentials for emissions reductions within the agriculture/forestry part of the WTT chain include changing the use of diesel to low-CO2-emitting fuels, changing to more fuel-efficient tractors, more efficient cultivation and manufacture of fertilizers (commercial nitrogen fertilizer can be produced in plants which have nitrous oxide gas cleaning) as well as improved fertilization strategies (more precise nitrogen application during the cropping season). Furthermore, the cultivation of annual feedstock crops could be avoided on land rich in carbon, such as peat soils and new agriculture systems could be introduced that lower the demand for ploughing and harrowing. Other options for improving the WTT emission values includes introducing new types of crops, such as wheat with higher content of starch or willow with a higher content of cellulose.From the case study on lignocellulosic ethanol we find that 2G ethanol, with co-production of biogas, electricity, heat and/or wood pellet, has a promising role to play in the development of sustainable biofuel production systems. Depending on available raw materials, heat sinks, demand for biogas as vehicle fuel and existing 1G ethanol plants suitable for integration, 2G ethanol production systems may be designed differently to optimize the economic conditions and maximize profitability. However, the complexity connected to the development of the most optimal production systems require improved knowledge and involvement of several actors from different competence areas, such as chemical and biochemical engineering, process design and integration and energy and environmental systems analysis, which may be a potential barrier.Three important results from the lignocellulosic ethanol study are: (i) the production systems could be far more complex and intelligently designed than previous studies show, (ii) the potential improvements consist of a large number of combinations of process integration options wich partly depends on specific local conditions, (iii) the environmental performance of individual systems may vary significantly due to systems design and local conditons.From the case study on gasification of solid biomass for the production of biomethane we find that one of the main advantages of this technology is its high efficiency in respect to converting biomass into fuels for transport. For future research we see a need for improvements within the gas up-grading section, including gas cleaning and gas conditioning, to obtain a more efficient process. A major challenge is to remove the tar before the methanation reaction.Three important results from the biomethane study are: (i) it is important not to crack the methane already produced in the syngas, which indicates a need for improved catalysts for selective tar cracking, (ii) there is a need for new gas separation techniques to facilitate the use of air oxidation agent instead of oxygen in the gasifier, and (iii) there is a need for testing the integrated process under realistic conditions, both at atmospheric and pressurized conditions.From the case study on black liquor gasification for the production of DME we find that the process has many advantages compared to other biofuel production options, such as the fact that black liquor is already partially processed and exists in a pumpable, liquid form, and that the process is pressurised and tightly integrated with the pulp mill, which enhances fuel production efficiency. However, to achieve commercial status, some challenges still remain, such as demonstrating that materials and plant equipment meet the high availability required when scaling up to industrial size in the pulp mill, and also proving that the plant can operate according to calculated heat and material balances. Three important results from the DME study are: (i) that modern chemical pulp mills, having a potential surplus of energy, could become important suppliers of renewable fuels for transport, (ii) there is a need to demonstrate that renewable DME/methanol will be proven to function in large scale, and (iii) there is still potential for technology improvements and enhanced energy integration.Although quantitative improvement potentials are given in the three biofuel production cases, it is not obvious how these potentials would affect WTT values, since the biofuel production processes are complex and changing one parameter impacts other parameters. The improvement potentials are therefore discussed qualitatively. From the entire study we have come to agree on the following common conclusions: (i) research and development in Sweden within the three studied 2G biofuel production technologies is extensive, (ii) in general, the processes, within the three cases, work well at pilot and demonstration scale and are now in a phase to be proven in large scale, (iii) there is still room for improvement although some processes have been known for decades, (iv) the biofuel production processes are complex and site specific and process improvements need to be seen and judged from a broad systems perspective (both within the production plant as well as in the entire well-to-tank perspective), and (v) the three studied biofuel production systems are complementary technologies. Futher, the process of conducting this study is worth mentioning as a result itself, i.e. that many different actors within the field have proven their ability and willingness to contribute to a common report, and that the cooperation climate was very positive and bodes well for possible future collaboration within the framework of the f3 center.Finally, judging from the political ambitions it is clear that the demand for renewable fuels will significantly increase during the coming decade. This will most likely result in opportunities for a range of biofuel options. The studied biofuel options all represent 2G biofuels and they can all be part of the solution to meet the increased renewable fuel demand.
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| 6. |
- Barta, Zsolt, et al.
(författare)
-
Process design and economics of on-site cellulase production on various carbon sources in a softwood-based ethanol plant.
- 2010
-
Ingår i: Enzyme Research. - : Hindawi Limited. - 2090-0414.
-
Tidskriftsartikel (refereegranskat)abstract
- On-site cellulase enzyme fermentation in a softwood-to-ethanol process, based on S -catalysed steam pretreatment followed by simultaneous saccharification and fermentation, was investigated from a techno-economic aspect using Aspen Plus and Aspen Icarus Process Evaluator softwares. The effect of varying the carbon source of enzyme fermentation, at constant protein and mycelium yields, was monitored through the whole process. Enzyme production step decreased the overall ethanol yield (270 L/dry tonne of raw material in the case of purchased enzymes) by 5–16 L/tonne. Capital cost was found to be the main cost contributor to enzyme fermentation, constituting to 60–78% of the enzyme production cost, which was in the range of 0.42–0.53 SEK/L ethanol. The lowest minimum ethanol selling prices (4.71 and 4.82 SEK/L) were obtained in those scenarios, where pretreated liquid fraction supplemented with molasses was used as carbon source. In some scenarios, on-site enzyme fermentation was found to be a feasible alternative.
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| 7. |
- Barta, Zsolt, et al.
(författare)
-
Techno-economic evaluation of stillage treatment with anaerobic digestion in a softwood-to-ethanol process.
- 2010
-
Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 3
-
Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: BACKGROUND: Replacing the energy-intensive evaporation of stillage by anaerobic digestion is one way of decreasing the energy demand of the lignocellulosic biomass to the ethanol process. The biogas can be upgraded and sold as transportation fuel, injected directly into the gas grid or be incinerated on-site for combined heat and power generation. A techno-economic evaluation of the spruce-to-ethanol process, based on SO2-catalysed steam pretreatment followed by simultaneous saccharification and fermentation, has been performed using the commercial flow-sheeting program Aspen Plus™. Various process configurations of anaerobic digestion of the stillage, with different combinations of co-products, have been evaluated in terms of energy efficiency and ethanol production cost versus the reference case of evaporation. RESULTS: Anaerobic digestion of the stillage showed a significantly higher overall energy efficiency (87-92%), based on the lower heating values, than the reference case (81%). Although the amount of ethanol produced was the same in all scenarios, the production cost varied between 4.00 and 5.27 Swedish kronor per litre (0.38-0.50 euro/L), including the reference case. CONCLUSIONS: Higher energy efficiency options did not necessarily result in lower ethanol production costs. Anaerobic digestion of the stillage with biogas upgrading was demonstrated to be a favourable option for both energy efficiency and ethanol production cost. The difference in the production cost of ethanol between using the whole stillage or only the liquid fraction in anaerobic digestion was negligible for the combination of co-products including upgraded biogas, electricity and district heat.
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| 8. |
- Björnsson, Lovisa
(creator_code:cre_t)
-
Pretreating non-wood lignocellulosic material (e.g. bagasse) to produce ethanol, comprises adding organic acid or organic acid-producing bacteria to lignocellulosic material, and storing and heating the organic acid-impregnated material
- 2012
-
Patent (övrigt vetenskapligt/konstnärligt)abstract
- NOVELTY - Pretreating non-wood lignocellulosic material containing less than 5 wt.% starch or sugar for producing ethanol from lignocellulose, comprises: (a) adding organic acid or organic acid-producing bacteria to the lignocellulosic material; (b) storing the lignocellulosic material in presence of organic acid for at least 2 weeks in an atmosphere of less than 5% oxygen to obtain organic acid-impregnated material; and (c) heating the organic acid-impregnated material at a temperature of at least 190 degrees C for at least 5 minutes to obtain pretreated lignocellulosic material. USE - The method is useful for pretreating non-wood lignocellulosic material to produce ethanol, where the non-wood lignocellulosic material is bagasse (preferably sugar cane bagasse or sweet Sorghum bagasse), sugar cane trash, wheat straw, rice straw, Sorghum species, Arundo, Miscanthus or agricultural residues (all claimed). ADVANTAGE - The method: avoids the need of inorganic acid or base (sulfur dioxide), and utilizes containers which are less corrosion resistant, hence economical; has higher net energy gain; utilizes organic acid which is biodegradable, and produces degradation products (e.g. 5-hydroxymethylfurfural and furfural which acts as inhibitory substances in the subsequent fermentation process), thus environmentally friendly. DETAILED DESCRIPTION - Pretreating non-wood lignocellulosic material containing less than 5 wt.% starch or sugar for producing ethanol from lignocellulose, comprises: (a) adding organic acid or organic acid-producing bacteria to the lignocellulosic material; (b) storing the lignocellulosic material in the presence of organic acid for at least 2 weeks in an atmosphere of less than 5% oxygen to obtain organic acid-impregnated material; and (c) heating the organic acid-impregnated material at a temperature of at least 190 degrees C for a period of at least 5 minutes to obtain pretreated lignocellulosic material, where no inorganic acid or base including sulfur dioxide is added in the method.
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| 9. |
- Bondesson, Pia-Maria, et al.
(författare)
-
Comparison of energy potentials from combined ethanol and methane production using steam-pretreated corn stover impregnated with acetic acid
- 2014
-
Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 67, s. 413-424
-
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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| 10. |
- Bondesson, Pia-Maria, et al.
(författare)
-
Ethanol and biogas production after steam pretreatment of corn stover with or without the addition of sulphuric acid
- 2013
-
Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 6
-
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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