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Pilot-scale conversion of lime-treated wheat straw into bioethanol: quality assessment of bioethanol and valorization of side streams by anaerobic digestion and combustion.

Maas RH, Bakker RR, Boersma AR, Bisschops I, Pels JR, de Jong E, Weusthuis RA, Reith H - Biotechnol Biofuels (2008)

Bottom Line: One approach to meeting the increasing energy demands and reduction of greenhouse gas emissions is by large-scale substitution of petrochemically derived transport fuels by the use of carbon dioxide-neutral biofuels, such as ethanol derived from lignocellulosic material.Based on the achieved experimental values, 16.7 kg of pretreated wheat straw could be converted to 1.7 kg of ethanol, 1.1 kg of methane, 4.1 kg of carbon dioxide, around 3.4 kg of compost and 6.6 kg of lignin-rich residue.The higher heating value of the lignin-rich residue was 13.4 MJ thermal energy per kilogram (dry basis).

View Article: PubMed Central - HTML - PubMed

Affiliation: Agrotechnology and Food Sciences Group, Wageningen University and Research Centre, PO Box 17, 6700 AA Wageningen, The Netherlands.

ABSTRACT

Introduction: The limited availability of fossil fuel sources, worldwide rising energy demands and anticipated climate changes attributed to an increase of greenhouse gasses are important driving forces for finding alternative energy sources. One approach to meeting the increasing energy demands and reduction of greenhouse gas emissions is by large-scale substitution of petrochemically derived transport fuels by the use of carbon dioxide-neutral biofuels, such as ethanol derived from lignocellulosic material.

Results: This paper describes an integrated pilot-scale process where lime-treated wheat straw with a high dry-matter content (around 35% by weight) is converted to ethanol via simultaneous saccharification and fermentation by commercial hydrolytic enzymes and bakers' yeast (Saccharomyces cerevisiae). After 53 hours of incubation, an ethanol concentration of 21.4 g/liter was detected, corresponding to a 48% glucan-to-ethanol conversion of the theoretical maximum. The xylan fraction remained mostly in the soluble oligomeric form (52%) in the fermentation broth, probably due to the inability of this yeast to convert pentoses. A preliminary assessment of the distilled ethanol quality showed that it meets transportation ethanol fuel specifications. The distillation residue, which contained non-hydrolysable and non-fermentable (in)organic compounds, was divided into a liquid and solid fraction. The liquid fraction served as substrate for the production of biogas (methane), whereas the solid fraction functioned as fuel for thermal conversion (combustion), yielding thermal energy, which can be used for heat and power generation.

Conclusion: Based on the achieved experimental values, 16.7 kg of pretreated wheat straw could be converted to 1.7 kg of ethanol, 1.1 kg of methane, 4.1 kg of carbon dioxide, around 3.4 kg of compost and 6.6 kg of lignin-rich residue. The higher heating value of the lignin-rich residue was 13.4 MJ thermal energy per kilogram (dry basis).

No MeSH data available.


Related in: MedlinePlus

Changes in dissolved chemical oxygen demand, volatile fatty acids (VFAs) and methane production during the anaerobic fermentation, and methane production during the accumulation test. (A) Dissolved chemical oxygen demand, dissolved volatile fatty acids and methane production during the anaerobic biodegradability test with a ten times diluted liquid fraction (20 ml in a total of 200 ml). Data were corrected for the blank. (B) Methane production during the accumulation test where the ratio of the liquid fraction to sludge was increased. All data are represented as averages of duplicate experiments.
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Figure 2: Changes in dissolved chemical oxygen demand, volatile fatty acids (VFAs) and methane production during the anaerobic fermentation, and methane production during the accumulation test. (A) Dissolved chemical oxygen demand, dissolved volatile fatty acids and methane production during the anaerobic biodegradability test with a ten times diluted liquid fraction (20 ml in a total of 200 ml). Data were corrected for the blank. (B) Methane production during the accumulation test where the ratio of the liquid fraction to sludge was increased. All data are represented as averages of duplicate experiments.

Mentions: Directly after SSF and subsequent distillation, the distillation residue was collected and a solid/liquid separation was performed by centrifugation. Using this method, 71.6 kg distillation residue (17.3% dry matter and 9.7% insoluble solids) was divided into two fractions: 52.7 kg (10.9% dry matter) liquid fraction serving as a substrate for biogas production, and 18.6 kg (35.6% dry matter) of wet solid fraction functioning as a fuel for thermal conversion tests. The centrifugation step, however, was not optimized resulting in a liquid fraction containing a significant amount of solids present in the form of small particles such as fines and salts. The liquid fraction, including dissolved organic compounds (for example, xylose, arabinose, glycerol, acetic acid and lactic acid), was tested for potential anaerobic biodegradability to biogas (methane). Figure 2A shows the changes in dissolved chemical oxygen demand (COD), volatile fatty acids (VFAs) and methane production during the anaerobic fermentation. Throughout the fermentation, no VFA accumulation or acidification occurred (initial pH 6.7). The methane content of the biogas was 57% ± 5%. Furthermore, Table 3 shows an anaerobic biodegradability of 57% ± 1% on a COD basis. The remaining non-degraded fraction is most likely partly composed of non-biodegradable dissolved COD (Figure 2A) and partly of non- or very slowly biodegradable solid matter, as visual inspection after 8 days showed that the solid material present in the effluent had not disappeared. Table 3 shows a COD balance of the experiment. It can be concluded from the values that the dissolved fraction was almost completely degraded, whereas the non-dissolved organic matter was partially degraded.


Pilot-scale conversion of lime-treated wheat straw into bioethanol: quality assessment of bioethanol and valorization of side streams by anaerobic digestion and combustion.

Maas RH, Bakker RR, Boersma AR, Bisschops I, Pels JR, de Jong E, Weusthuis RA, Reith H - Biotechnol Biofuels (2008)

Changes in dissolved chemical oxygen demand, volatile fatty acids (VFAs) and methane production during the anaerobic fermentation, and methane production during the accumulation test. (A) Dissolved chemical oxygen demand, dissolved volatile fatty acids and methane production during the anaerobic biodegradability test with a ten times diluted liquid fraction (20 ml in a total of 200 ml). Data were corrected for the blank. (B) Methane production during the accumulation test where the ratio of the liquid fraction to sludge was increased. All data are represented as averages of duplicate experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2572599&req=5

Figure 2: Changes in dissolved chemical oxygen demand, volatile fatty acids (VFAs) and methane production during the anaerobic fermentation, and methane production during the accumulation test. (A) Dissolved chemical oxygen demand, dissolved volatile fatty acids and methane production during the anaerobic biodegradability test with a ten times diluted liquid fraction (20 ml in a total of 200 ml). Data were corrected for the blank. (B) Methane production during the accumulation test where the ratio of the liquid fraction to sludge was increased. All data are represented as averages of duplicate experiments.
Mentions: Directly after SSF and subsequent distillation, the distillation residue was collected and a solid/liquid separation was performed by centrifugation. Using this method, 71.6 kg distillation residue (17.3% dry matter and 9.7% insoluble solids) was divided into two fractions: 52.7 kg (10.9% dry matter) liquid fraction serving as a substrate for biogas production, and 18.6 kg (35.6% dry matter) of wet solid fraction functioning as a fuel for thermal conversion tests. The centrifugation step, however, was not optimized resulting in a liquid fraction containing a significant amount of solids present in the form of small particles such as fines and salts. The liquid fraction, including dissolved organic compounds (for example, xylose, arabinose, glycerol, acetic acid and lactic acid), was tested for potential anaerobic biodegradability to biogas (methane). Figure 2A shows the changes in dissolved chemical oxygen demand (COD), volatile fatty acids (VFAs) and methane production during the anaerobic fermentation. Throughout the fermentation, no VFA accumulation or acidification occurred (initial pH 6.7). The methane content of the biogas was 57% ± 5%. Furthermore, Table 3 shows an anaerobic biodegradability of 57% ± 1% on a COD basis. The remaining non-degraded fraction is most likely partly composed of non-biodegradable dissolved COD (Figure 2A) and partly of non- or very slowly biodegradable solid matter, as visual inspection after 8 days showed that the solid material present in the effluent had not disappeared. Table 3 shows a COD balance of the experiment. It can be concluded from the values that the dissolved fraction was almost completely degraded, whereas the non-dissolved organic matter was partially degraded.

Bottom Line: One approach to meeting the increasing energy demands and reduction of greenhouse gas emissions is by large-scale substitution of petrochemically derived transport fuels by the use of carbon dioxide-neutral biofuels, such as ethanol derived from lignocellulosic material.Based on the achieved experimental values, 16.7 kg of pretreated wheat straw could be converted to 1.7 kg of ethanol, 1.1 kg of methane, 4.1 kg of carbon dioxide, around 3.4 kg of compost and 6.6 kg of lignin-rich residue.The higher heating value of the lignin-rich residue was 13.4 MJ thermal energy per kilogram (dry basis).

View Article: PubMed Central - HTML - PubMed

Affiliation: Agrotechnology and Food Sciences Group, Wageningen University and Research Centre, PO Box 17, 6700 AA Wageningen, The Netherlands.

ABSTRACT

Introduction: The limited availability of fossil fuel sources, worldwide rising energy demands and anticipated climate changes attributed to an increase of greenhouse gasses are important driving forces for finding alternative energy sources. One approach to meeting the increasing energy demands and reduction of greenhouse gas emissions is by large-scale substitution of petrochemically derived transport fuels by the use of carbon dioxide-neutral biofuels, such as ethanol derived from lignocellulosic material.

Results: This paper describes an integrated pilot-scale process where lime-treated wheat straw with a high dry-matter content (around 35% by weight) is converted to ethanol via simultaneous saccharification and fermentation by commercial hydrolytic enzymes and bakers' yeast (Saccharomyces cerevisiae). After 53 hours of incubation, an ethanol concentration of 21.4 g/liter was detected, corresponding to a 48% glucan-to-ethanol conversion of the theoretical maximum. The xylan fraction remained mostly in the soluble oligomeric form (52%) in the fermentation broth, probably due to the inability of this yeast to convert pentoses. A preliminary assessment of the distilled ethanol quality showed that it meets transportation ethanol fuel specifications. The distillation residue, which contained non-hydrolysable and non-fermentable (in)organic compounds, was divided into a liquid and solid fraction. The liquid fraction served as substrate for the production of biogas (methane), whereas the solid fraction functioned as fuel for thermal conversion (combustion), yielding thermal energy, which can be used for heat and power generation.

Conclusion: Based on the achieved experimental values, 16.7 kg of pretreated wheat straw could be converted to 1.7 kg of ethanol, 1.1 kg of methane, 4.1 kg of carbon dioxide, around 3.4 kg of compost and 6.6 kg of lignin-rich residue. The higher heating value of the lignin-rich residue was 13.4 MJ thermal energy per kilogram (dry basis).

No MeSH data available.


Related in: MedlinePlus