Tag Archives: steam explosion

928-939 N. Sjulander, V. Rooni, L. Rocha-Meneses and T. Kikas
Comparison of different chemical-free pretreatment methods for the production of sugars, ethanol and methane from lignocellulosic biomass
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Comparison of different chemical-free pretreatment methods for the production of sugars, ethanol and methane from lignocellulosic biomass

N. Sjulander¹*, V. Rooni¹, L. Rocha-Meneses² and T. Kikas¹*

¹Estonian University of Life Sciences, Institute of Forestry and Engineering, Chair of Biosystems Engineering, EE51014 Tartu, Estonia
²Renewable and Sustainable Energy Research Center, Technology Innovation Institute, P.O.Box: 9639, Masdar City, Abu Dhabi, United Arab Emirates
*Correspondence: nikki.sjulander@emu.ee; timo.kikas@emu.ee

Abstract:

Most pretreatment methods for lignocellulosic biomass use strong chemicals, such as sulphuric acid and ammonia, to open up the cellular structure of plant biomass. However, those chemicals are not environmentally friendly and their use leads to safety risks. As a result, different chemical-free pretreatment methods have been developed, which focus on the usage of pressure, high or low temperatures and mild chemicals. Freezing pretreatment and explosive decompression pretreatments, using different operating gases, such as nitrogen and steam, are compared in the context of glucose, ethanol and methane yield in this review. For the methane production, the stillage from bioethanol production is used. The usage of this waste improves the overall valorisation of lignocellulosic biomass. The review also investigates, whether the nitrogen explosive decompression pretreatment is suitable for the treatment of softwoods, hardwoods and herbaceous materials. In the comparison of different chemical-free pretreatment methods, it is concluded that heat and water are the most influential parameters for opening up the lignocellulosic biomass structure. The operating gas and pressure in the pretreatment reactor are less relevant. Steam explosion, nitrogen explosive decompression pretreatment and autohydrolysis pretreatment are the most suitable chemical-free pretreatment methods for lignocellulosic biomass.

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391-396 M. Pointner, P. Kuttner, T. Obrlik, A. Jäger and H. Kahr
Composition of corncobs as a substrate for fermentation of biofuels
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Composition of corncobs as a substrate for fermentation of biofuels

M. Pointner*, P. Kuttner, T. Obrlik, A. Jäger and H. Kahr

University of Applied Sciences Upper Austria, Wels Campus, Stelzhamerstr. 23, 4600 Wels, Austria; *Correspondence: manuel.pointner@fh-wels.at

Abstract:

Lignocellulosic residues as for instance corncobs can be used as substrates for the production of biofuels. The corncobs are usually pre-treated in a thermal-physical step (steam explosion) before enzymatic hydrolysis. The pre-treatment process increases the accessibility of the raw material for the hydrolysis. The products of the hydrolyses are used as substrates for the fermentation of bio-ethanol. As an alternative, the hydrolysates could be used for the fermentation of oleaginous yeasts. These yeasts produce and accumulate lipids from glucose during growth. For the energetic use in the form of bio-diesel, the lipids can be converted into fatty acid methyl esters (FAME) in the same way as vegetable oils. The fibre composition of the raw material was determined in regard to the proportions of cellulose, hemicellulose und lignin. It was investigated whether different corn varieties show varying compositions. The fibre compositions before the pre-treatment of ten different varieties of corncobs (from locations in Upper Austria) were determined. No significant differences were observed (cellulose: 38.8% ± 2.5%, hemicellulose: 44.4% ± 5.2%, lignin: 11.9% ± 2.3% in the dry matter).

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417-424 M. Tutt, T. Kikas, H. Kahr, M. Pointner, P. Kuttner and J. Olt
Using steam explosion pretreatment method for bioethanol production from floodplain meadow hay
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Using steam explosion pretreatment method for bioethanol production from floodplain meadow hay

M. Tutt¹*, T. Kikas¹, H. Kahr², M. Pointner², P. Kuttner² and J. Olt¹

¹Institute of Technology, Estonian University of Life Sciences, Kreutzwaldi 56, EE51014 Tartu, Estonia; *Correspondence: marti.tutt@emu.ee 2Upper Austria University of Applied Sciences, Wels Campus, Stelzhamerstraße 23, 4600 Wels, Austria

Abstract:

This article investigates influence of the steam explosion pretreatment method at different temperatures on sugar conversion rates and bioethanol production efficiencies from floodplain meadow hay. Floodplain meadow hay is used as a raw material, because these semi-natural grasslands need regular maintenance to preserve their high biodiversity. So far, this biomass has been largely unused, but it could provide a good feedstock for bioethanol production. In this work, steam explosion pretreatment is used in combination with enzymatic hydrolysis. Effects of steam explosion pretreatment on the fibre content and cell wall structure are also studied. Results from fibre analysis show, that the floodplain meadow hay has very high lignin content of 24.16%, but relatively low cellulose content of 27.19%. Highest cellulose to glucose conversion rate of 234.6 g kg-1 and ethanol yield of 115.7 g kg-1 of biomass were achieved with the steam explosion pretreatment at 200°C. Scanning electron microscope (SEM) images show that pretreatment at 150°C does very little damage to plant cells, while steam explosion at 200°C disintegrates most of the plant cell walls and exposes cellulose fibres.

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173-182 K. Eisenhuber, A. Jäger, J. Wimberger and H. Kahr
Comparison of different pretreatment methods for straw for lignocellulosic bioethanol production
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Comparison of different pretreatment methods for straw for lignocellulosic bioethanol production

K. Eisenhuber, A. Jäger*, J. Wimberger and H. Kahr

University of Applied Sciences Upper Austria, Stelzhamerstr 23, A 4600 Wels, Austria;
*Correspondence: Alexander.Jaeger@fh-wels.at

Abstract:

In order to reduce carbon dioxide emissions from the combustion of fossil fuels, the production  of  biofuels  from  lignocellulosic  agricultural  residues  is  the  focus  of  industrial  and scientific  interest.  The  feedstocks  of  the  second  generation  used  for  bioethanol  production  are lignocellulose-containing  raw  materials  like  different  types  of  straw,  or  other  plants  like miscanthus x giganteus. In all these plants, the cellulose in the lignocellulose is not accessible to enzymes. Therefore, lignin and/or hemicelluloses have to be removed by a specific pretreatment in order to make enzymatic degradation of cellulose possible. We examined and compared the pretreatment of wheat straw by means of steam treatment and steam explosion treatment. After  hydrolysis,  glucose  concentrations  up  to  ³00 g kg-¹  were  reached  both  for  steam- pretreated straw and steam-exploded straw. After fermentation, ethanol concentrations ranging from  ¹²0–¹⁴0 g kg-¹  were  achieved.  Results  suggest  that  the  explosion  process  slightly  favors the  solubilisation  of  sugars  and,  therefore,  enhances  ethanol  production.  Only  at  higher temperature and longer incubation time does the explosion process not seem to be necessary. In  addition  to  this,  we  examined  most  of  the  lignocellulosic  residuals  in  Austria  available  for bioethanol  production.  As  a  result,  we  can  show  that  even  in  a  country  not  focused  on agricultural production all the bioethanol needed for E¹0 can easily be provided.

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