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Combined ethanol and methane production from switchgrass (Panicum virgatum L.) impregnated with lime prior to steam explosion

Capecchi, Lorenzo; Galbe, Mats LU ; Wallberg, Ola LU ; Mattarelli, Paola and Barbanti, Lorenzo (2016) In Biomass & Bioenergy 90. p.22-31
Abstract

Pretreatments are crucial to achieve efficient conversion of lignocellulosic biomass to soluble sugars. In this light, switchgrass was subjected to 13 pretreatments including steam explosion alone (195 °C for 5, 10 and 15 min) and after impregnation with the following catalysts: Ca(OH)2 at low (0.4%) and high (0.7%) concentration; Ca(OH)2 at high concentration and higher temperature (205 °C for 5, 10 and 15 min); H2SO4 (0.2% at 195 °C for 10 min) as reference acid catalyst before steam explosion. Enzymatic hydrolysis was carried out to assess pretreatment efficiency in both solid and liquid fraction. Thereafter, in selected pretreatments the solid fraction was subjected to simultaneous... (More)

Pretreatments are crucial to achieve efficient conversion of lignocellulosic biomass to soluble sugars. In this light, switchgrass was subjected to 13 pretreatments including steam explosion alone (195 °C for 5, 10 and 15 min) and after impregnation with the following catalysts: Ca(OH)2 at low (0.4%) and high (0.7%) concentration; Ca(OH)2 at high concentration and higher temperature (205 °C for 5, 10 and 15 min); H2SO4 (0.2% at 195 °C for 10 min) as reference acid catalyst before steam explosion. Enzymatic hydrolysis was carried out to assess pretreatment efficiency in both solid and liquid fraction. Thereafter, in selected pretreatments the solid fraction was subjected to simultaneous saccharification and fermentation (SSF), while the liquid fraction underwent anaerobic digestion (AD). Lignin removal was lowest (12%) and highest (35%) with steam alone and 0.7% lime, respectively. In general, higher cellulose degradation and lower hemicellulose hydrolysis were observed in this study compared to others, depending on lower biomass hydration during steam explosion. Mild lime addition (0.4% at 195 °C) enhanced ethanol in SSF (+28% than steam alone), while H2SO4 boosted methane in AD (+110%). However, methane represented a lesser component in combined energy yield (ethanol, methane and energy content of residual solid). Mild lime addition was also shown less aggressive and secured more residual solid after SSF, resulting in higher energy yield per unit raw biomass. Decreased water consumption, avoidance of toxic compounds in downstream effluents, and post process recovery of Ca(OH)2 as CaCO3 represent further advantages of pretreatments involving mild lime addition before steam explosion.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Anaerobic digestion, Energy yield, Lime, Simultaneous saccharification and fermentation, Steam explosion, Switchgrass
in
Biomass & Bioenergy
volume
90
pages
10 pages
publisher
Elsevier
external identifiers
  • Scopus:84963864011
ISSN
0961-9534
DOI
10.1016/j.biombioe.2016.03.035
language
English
LU publication?
yes
id
84356c92-14d6-4892-be6f-46e1eaf9e1a7
date added to LUP
2016-05-10 07:34:03
date last changed
2016-10-13 05:08:24
@misc{84356c92-14d6-4892-be6f-46e1eaf9e1a7,
  abstract     = {<p>Pretreatments are crucial to achieve efficient conversion of lignocellulosic biomass to soluble sugars. In this light, switchgrass was subjected to 13 pretreatments including steam explosion alone (195 °C for 5, 10 and 15 min) and after impregnation with the following catalysts: Ca(OH)<sub>2</sub> at low (0.4%) and high (0.7%) concentration; Ca(OH)<sub>2</sub> at high concentration and higher temperature (205 °C for 5, 10 and 15 min); H<sub>2</sub>SO<sub>4</sub> (0.2% at 195 °C for 10 min) as reference acid catalyst before steam explosion. Enzymatic hydrolysis was carried out to assess pretreatment efficiency in both solid and liquid fraction. Thereafter, in selected pretreatments the solid fraction was subjected to simultaneous saccharification and fermentation (SSF), while the liquid fraction underwent anaerobic digestion (AD). Lignin removal was lowest (12%) and highest (35%) with steam alone and 0.7% lime, respectively. In general, higher cellulose degradation and lower hemicellulose hydrolysis were observed in this study compared to others, depending on lower biomass hydration during steam explosion. Mild lime addition (0.4% at 195 °C) enhanced ethanol in SSF (+28% than steam alone), while H<sub>2</sub>SO<sub>4</sub> boosted methane in AD (+110%). However, methane represented a lesser component in combined energy yield (ethanol, methane and energy content of residual solid). Mild lime addition was also shown less aggressive and secured more residual solid after SSF, resulting in higher energy yield per unit raw biomass. Decreased water consumption, avoidance of toxic compounds in downstream effluents, and post process recovery of Ca(OH)<sub>2</sub> as CaCO<sub>3</sub> represent further advantages of pretreatments involving mild lime addition before steam explosion.</p>},
  author       = {Capecchi, Lorenzo and Galbe, Mats and Wallberg, Ola and Mattarelli, Paola and Barbanti, Lorenzo},
  issn         = {0961-9534},
  keyword      = {Anaerobic digestion,Energy yield,Lime,Simultaneous saccharification and fermentation,Steam explosion,Switchgrass},
  language     = {eng},
  month        = {07},
  pages        = {22--31},
  publisher    = {ARRAY(0x9631110)},
  series       = {Biomass & Bioenergy},
  title        = {Combined ethanol and methane production from switchgrass (Panicum virgatum L.) impregnated with lime prior to steam explosion},
  url          = {http://dx.doi.org/10.1016/j.biombioe.2016.03.035},
  volume       = {90},
  year         = {2016},
}