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Ethanol production from rape straw: Part of an oilseed rape biorefinery

Abstract

Agricultural residues from rapeseed biodiesel industry (rapeseed cake, rape straw, crude glycerol), which represent the 82%wt. of the oilseed rape, currently have only low-grade applications in the market. For this, a scenario was built on exploiting qualities of rapeseed biodiesel residues for forming added-value products, and expanding and upgrading an existing biodiesel plant, to an oilseed rape biorefinery by 2020 in European ground. Selection of products was based on a technological feasibility study given the time frame, while priority was given to Low-Value-High-Volume readily marketed products, like production of energy and feed. Products selected except rapeseed biodiesel, were ethanol, biogas, enzymes energy, chemical building blocks, and superior quality animal fodder. The production lines were analyzed and prospects for 2020 were projected on a critical basis. Particular merit was given to two products, ethanol from cellulose, and cellulolytic enzymes from rape straw. Cellulosic ethanol from rape straw was optimized for all production steps, i.e. for thermo-chemical pretreatment, enzyme hydrolysis, and fermentation of C6 sugars. Thermo-chemical pretreatment was studied with Wet oxidation technique at different conditions of temperature, reaction time, and oxygen pressure, but also factors like pre-soaking straw in warm water, or recycling liquid were also studied. Wet oxidation has been  More>>
Authors:
Publication Date:
Dec 15, 2010
Product Type:
Technical Report
Report Number:
RISO-PhD-71(EN)
Resource Relation:
Other Information: Thesis or Dissertation; TH: Thesis (Ph.D.); 239 refs.
Subject:
09 BIOMASS FUELS; BIOETHANOL; BRASSICA; STRAW; BIOFUELS; CELLULOSE; ENZYMATIC HYDROLYSIS; BIOMASS CONVERSION PLANTS; WET OXIDATION PROCESSES; FERMENTATION; OPTIMIZATION
OSTI ID:
1001401
Research Organizations:
Technical Univ. of Denmark, Risoe National Lab. for Sustainable Energy. Biosystems Div., Roskilde (Denmark)
Country of Origin:
Denmark
Language:
English
Other Identifying Numbers:
Other: ISBN 978-87-550-3865-3; TRN: DK1101003
Availability:
Also available at http://www.risoe.dtu.dk/rispubl/reports/ris-phd-71.pdf; OSTI as DE01001401
Submitting Site:
DK
Size:
152 p. pages
Announcement Date:
Jan 14, 2011

Citation Formats

Arvaniti, E. Ethanol production from rape straw: Part of an oilseed rape biorefinery. Denmark: N. p., 2010. Web.
Arvaniti, E. Ethanol production from rape straw: Part of an oilseed rape biorefinery. Denmark.
Arvaniti, E. 2010. "Ethanol production from rape straw: Part of an oilseed rape biorefinery." Denmark.
@misc{etde_1001401,
title = {Ethanol production from rape straw: Part of an oilseed rape biorefinery}
author = {Arvaniti, E}
abstractNote = {Agricultural residues from rapeseed biodiesel industry (rapeseed cake, rape straw, crude glycerol), which represent the 82%wt. of the oilseed rape, currently have only low-grade applications in the market. For this, a scenario was built on exploiting qualities of rapeseed biodiesel residues for forming added-value products, and expanding and upgrading an existing biodiesel plant, to an oilseed rape biorefinery by 2020 in European ground. Selection of products was based on a technological feasibility study given the time frame, while priority was given to Low-Value-High-Volume readily marketed products, like production of energy and feed. Products selected except rapeseed biodiesel, were ethanol, biogas, enzymes energy, chemical building blocks, and superior quality animal fodder. The production lines were analyzed and prospects for 2020 were projected on a critical basis. Particular merit was given to two products, ethanol from cellulose, and cellulolytic enzymes from rape straw. Cellulosic ethanol from rape straw was optimized for all production steps, i.e. for thermo-chemical pretreatment, enzyme hydrolysis, and fermentation of C6 sugars. Thermo-chemical pretreatment was studied with Wet oxidation technique at different conditions of temperature, reaction time, and oxygen pressure, but also factors like pre-soaking straw in warm water, or recycling liquid were also studied. Wet oxidation has been extensively tested in the past for different substrates, and gives promising results with indicators that are important for cellulosic ethanol production; C6 sugars recovery, high digestibility for enzymes, and limited formed degradation products. Here, optimal pretreatment conditions for rape straw were first presoaking rape straw at 80 deg. C for 20 minutes, and then wet-oxidize with 12 bar of oxygen at 205 deg. C for 3 minutes. Recovery of cellulose and hemicellulose under these conditions was 105% and 106% respectively, while recovery of lignin was 86%. When this solution was fermented via Simultaneous Saccharification and Fermentation (SSF) assisted by liquefaction step, with Cellubrix L and baker's yeast achieved ethanol yield was 67% based on sugars in raw material (12.5% DM). Optimization of ethanol production from rape straw then focused to enzymatic hydrolysis and benchmarking available commercial enzyme mixtures. It was found that hydrolysis rate increased considerably, if adequate amount of beta-glycosidase is present in enzyme mixture. Best mixture of enzymes was Celluclast 1.5L supplemented by Novozym 188 (5:1 v/v ratio), which in 24 hours it hydrolyzed 77% of pretreated rape straw C6 sugars. In an attempt to produce enzymes from pretreated rape straw, the most promising carbon source was a mixture of cellulose and hemicellulose (81:19 w/w sugars ratio). The produced cellulolytic enzymes in turn hydrolyzed pretreated rape straw by 70% in 24 hours enzyme hydrolysis test. These enzymes were produced after 11 days of fermentation with enzyme yielded 109 FPU/g sugars (pretreated rape straw). Finally, ethanol fermentation was optimized using the selected pretreatment method, and best enzyme mixture. Assessment of optimal fermentation conditions included determination of optimal highest fermenting temperature among three strains; the best pH pattern for maximum ethanol production; and finally assessing potentials of fermentations at increased dry matter. Results have shown that S. cerevisiae has thermotollerance up to 37 deg. C, and that pH was the catalytic factor for the progress of ethanol fermentation as well as contamination by lactic acid bacteria, in both shake flasks and scale up experiments. Highest ethanol yield was 77% achieved with 16% DM at 37 deg. C by an isolate strain from baker' yeast within 120 hours of SSF. (Author)}
place = {Denmark}
year = {2010}
month = {Dec}
}