| 1. |
- Ferreira-Leitão, Viridiana, et al.
(författare)
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An approach to the utilisation of CO2 as impregnating agent in steam pretreatment of sugar cane bagasse and leaves for ethanol production.
- 2010
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Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: BACKGROUND: The conditions for steam pretreatment of sugar cane bagasse and leaves were studied using CO2 as an impregnating agent. The following conditions were investigated: time (5 to 15 min) and temperature (190 to 220 degrees C). The pretreatment was assessed in terms of glucose and xylose yields after enzymatic hydrolysis and inhibitor formation (furfural and hydroxymethylfurfural) in the pretreatment. Results from pretreatment using SO2 as impregnating agent was used as reference. RESULTS: For sugar cane bagasse, the highest glucose yield (86.6% of theoretical) was obtained after pretreatment at 205 degrees C for 15 min. For sugar cane leaves the highest glucose yield (97.2% of theoretical) was obtained after pretreatment at 220 degrees C for 5 min. The reference pretreatment, using impregnation with SO2 and performed at 190 degrees C for 5 min, resulted in an overall glucose yield of 79.7% and 91.9% for bagasse and leaves, respectively. CONCLUSIONS: Comparable pretreatment performance was obtained with CO2 as compared to when SO2 is used, although higher temperature and pressure were needed. The results are encouraging as some characteristics of CO2 are very attractive, such as high availability, low cost, low toxicity, low corrosivity and low occupational risk.
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| 2. |
- Kovacs, Krisztina, et al.
(författare)
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Enzymatic hydrolysis of steam-pretreated lignocellulosic materials with Trichoderma atroviride enzymes produced in-house
- 2009
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Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- Background: Improvement of the process of cellulase production and development of more efficient lignocellulose-degrading enzymes are necessary in order to reduce the cost of enzymes required in the biomass-to-bioethanol process. Results: Lignocellulolytic enzyme complexes were produced by the mutant Trichoderma atroviride TUB F-1663 on three different steam-pretreated lignocellulosic substrates, namely spruce, wheat straw and sugarcane bagasse. Filter paper activities of the enzymes produced on the three materials were very similar, while beta-glucosidase and hemicellulase activities were more dependent on the nature of the substrate. Hydrolysis of the enzyme preparations investigated produced similar glucose yields. However, the enzymes produced in-house proved to degrade the xylan and the xylose oligomers less efficiently than a commercial mixture of cellulase and beta-glucosidase. Furthermore, accumulation of xylose oligomers was observed when the TUB F-1663 supernatants were applied to xylan-containing substrates, probably due to the low beta-xylosidase activity of the enzymes. The efficiency of the enzymes produced in-house was enhanced by supplementation with extra commercial beta-glucosidase and beta-xylosidase. When the hydrolytic capacities of various mixtures of a commercial cellulase and a T. atroviride supernatant produced in the lab were investigated at the same enzyme loading, the glucose yield appeared to be correlated with the beta-glucosidase activity, while the xylose yield seemed to be correlated with the beta-xylosidase level in the mixtures. Conclusion: Enzyme supernatants produced by the mutant T. atroviride TUB F-1663 on various pretreated lignocellulosic substrates have good filter paper activity values combined with high levels of beta-glucosidase activities, leading to cellulose conversion in the enzymatic hydrolysis that is as efficient as with a commercial cellulase mixture. On the other hand, in order to achieve good xylan conversion, the supernatants produced by the mutant have to be supplemented with additional beta-xylosidase activity.
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| 3. |
- Macrelli, Stefano, et al.
(författare)
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Effects of production and market factors on ethanol profitability for an integrated first and second generation ethanol plant using the whole sugarcane as feedstock
- 2014
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Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Background: Sugarcane is an attractive feedstock for ethanol production, especially if the lignocellulosic fraction can also be treated in second generation (2G) ethanol plants. However, the profitability of 2G ethanol is affected by the processing conditions, operating costs and market prices. This study focuses on the minimum ethanol selling price (MESP) and maximum profitability of ethanol production in an integrated first and second generation (1G + 2G) sugarcane-to-ethanol plant. The feedstock used was sugarcane juice, bagasse and leaves. The lignocellulosic fraction was hydrolysed with enzymes. Yields were assumed to be 95% of the theoretical for each of the critical steps in the process (steam pretreatment, enzymatic hydrolysis (EH), fermentation, solid/liquid separation, anaerobic digestion) in order to obtain the best conditions possible for ethanol production, to assess the lowest production costs. Techno-economic analysis was performed for various combinations of process options (for example use of pentoses, addition of leaves), EH conditions (water-insoluble solids (WIS) and residence time), operating cost (enzymes) and market factors (wholesale prices of electricity and ethanol, cost of the feedstock). Results: The greatest reduction in 2G MESP was achieved when using the pentoses for the production of ethanol rather than biogas. This was followed, in decreasing order, by higher enzymatic hydrolysis efficiency (EHE), by increasing the WIS to 30% and by a short residence time (48 hours) in the EH. The addition of leaves was found to have a slightly negative impact on 1G + 2G MESP, but the effect on 2G MESP was negligible. Sugarcane price significantly affected 1G + 2G MESP, while the price of leaves had a much lower impact. Net present value (NPV) analysis of the most interesting case showed that integrated 1G + 2G ethanol production including leaves could be more profitable than 1G ethanol, despite the fact that the MESP was higher than in 1G ethanol production. Conclusions: A combined 1G + 2G ethanol plant could potentially outperform a 1G plant in terms of NPV, depending on market wholesale prices of ethanol and electricity. Therefore, although it is more expensive than 1G ethanol production, 2G ethanol production can make the integrated 1G + 2G process more profitable.
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| 4. |
- Macrelli, Stefano
(författare)
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Ethanol from Sugarcane Lignocellulosic Residues - Opportunities for Process Improvement and Production Cost Reduction
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bioethanol from sugarcane is a sustainable alternative to fossil fuels, and the increasing demand for fuel ethanol has prompted studies on the use of the lignocellulosic residues of sugarcane, namely bagasse and leaves, as new feedstock. This thesis describes various process designs and the economic feasibility of producing second generation (2G) ethanol from bagasse and leaves via the enzymatic route in an integrated sugarcane biorefinery, where first-generation (1G) ethanol is produced from sugarcane sugar. Techno-economic analysis have been performed for the Brazilian context to evaluate the influence of several process designs and the main production factors on the 2G ethanol process, in terms of energy efficiency, 2G ethanol production cost(2G MESP) and profitability. The study of process design focused on ways to integrate the 1G and 2G ethanol processes, and on configurations to hydrolyse and ferment bagasse. The existing 1G ethanol process and the proposed 2G ethanol process were combined in a single plant by integration of thermal and material streams. The resulting synergies could improve the use of feedstock and reduce the 2G ethanol production cost. Simultaneous saccharification and fermentation (SSF)and time-separated hydrolysis and fermentation (tSHF) were the configurations investigated experimentally for the production of 2G ethanol from bagasse. In an attempt to increase the ethanol concentration before distillation, the fermented liquid of tSHF was also recirculated back to tSHF. The tSHF configurations showed a lower 2G MESP than SSF. Process options were also investigated considering the pentose use and the addition of leaves to the 1G+2G process. Pentoses can either be fermented to ethanol or anaerobically digested to produce electricity from biogas combustion, and in the former case the highest potential reduction in 2G MESP could be achieved. The addition of leaves could improve the overall profitability of the 1G+2G process. Residence time and water-insoluble solids (WIS) loading in hydrolysis were the main process conditions considered together with costing factors, such as enzyme, sugarcane and leaves costs. The selling price of electricity and ethanol were found to have relevant impacts on the profitability of the 1G+2G ethanol process. Among the numerous operating conditions studied for the 2G ethanol process, the cases showing the best trade-off between technical and economic feasibility were also tested experimentally on laboratory scale obtaining promising results. In fact, it was possible to achieve high concentrations of 2G ethanol (47 g/L) in short time (60 hours), overcoming the mixing problems by feeding repeatedly the pretreated bagasse up to 20% WIS.
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| 5. |
- Macrelli, Stefano, et al.
(författare)
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Techno-economic evaluation of 2nd generation bioethanol production from sugar cane bagasse and leaves integrated with the sugar-based ethanol process
- 2012
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Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Background: Bioethanol produced from the lignocellulosic fractions of sugar cane (bagasse and leaves), i.e. second generation (2G) bioethanol, has a promising market potential as an automotive fuel; however, the process is still under investigation on pilot/demonstration scale. From a process perspective, improvements in plant design can lower the production cost, providing better profitability and competitiveness if the conversion of the whole sugar cane is considered. Simulations have been performed with AspenPlus to investigate how process integration can affect the minimum ethanol selling price of this 2G process (MESP-2G), as well as improve the plant energy efficiency. This is achieved by integrating the well-established sucrose-to-bioethanol process with the enzymatic process for lignocellulosic materials. Bagasse and leaves were steam pretreated using H3PO4 as catalyst and separately hydrolysed and fermented. Results: The addition of a steam dryer, doubling of the enzyme dosage in enzymatic hydrolysis, including leaves as raw material in the 2G process, heat integration and the use of more energy-efficient equipment led to a 37 % reduction in MESP-2G compared to the Base case. Modelling showed that the MESP for 2G ethanol was 0.97 US $/L, while in the future it could be reduced to 0.78 US$/L. In this case the overall production cost of 1G + 2G ethanol would be about 0.40 US$/L with an output of 102 L/ton dry sugar cane including 50 % leaves. Sensitivity analysis of the future scenario showed that a 50 % decrease in the cost of enzymes, electricity or leaves would lower the MESP-2G by about 20%, 10% and 4.5%, respectively. Conclusions: According to the simulations, the production of 2G bioethanol from sugar cane bagasse and leaves in Brazil is already competitive (without subsidies) with 1G starch-based bioethanol production in Europe. Moreover 2G bioethanol could be produced at a lower cost if subsidies were used to compensate for the opportunity cost from the sale of excess electricity and if the cost of enzymes continues to fall.
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