| 1. |
- Capecchi, Lorenzo, et al.
(författare)
-
Combined ethanol and methane production from switchgrass (Panicum virgatum L.) impregnated with lime prior to steam explosion
- 2016
-
Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 0961-9534. ; 90, s. 22-31
-
Tidskriftsartikel (refereegranskat)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 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.
|
|
| 2. |
- Capecchi, Lorenzo, et al.
(författare)
-
Combined ethanol and methane production using steam pretreated sugarcane bagasse
- 2015
-
Ingår i: Industrial Crops and Products. - : Elsevier BV. - 0926-6690. ; 74, s. 255-262
-
Tidskriftsartikel (refereegranskat)abstract
- Efficient energy production relies on complementary use of crop residues, to enhance the amount of energy obtained per unit biomass. In this frame, sugarcane bagasse (SB) was pretreated and the resulting slurry and liquid fraction served, respectively, for simultaneous saccharification and fermentation (SSF) at high solid concentration (15%), and anaerobic digestion (AD). More specifically, SB was subjected to twelve pretreatments to enhance fiber deconstruction and subsequent energy output: steam explosion alone (195 degrees C for 5,10 and 15 min), after impregnation with 0.4% and 0.7% Ca(OH)(2), and at 205 degrees C for the same three times after 0.7% Ca(OH)(2) addition. After pretreatment, enzymatic hydrolysis was carried out on washed solid fraction; glucose and xylose were determined on this fraction as well as residual liquid fraction. On this latter, inhibitors (acetic and formic acid, furfural and 5-hydroxymethylfurfural) were also determined. Based on high glucose yield in enzymatic hydrolysis, three pretreatments were selected for SSF of the slurry. The same pretreatments underwent AD of the liquid fraction. Inhibitors augmented at increasing time and temperature, although never achieved critical levels. Lignin removal (range, 17-38%) was enhanced by lime addition, whereas increasing temperature and time did not contribute to delignification. Glucose yield in washed solid fraction varied accordingly. SSF exhibited the highest ethanol yield with mild lime addition (60% of theoretical) vs. steam alone (53%). However, modest yields were generally evidenced (average, 55%) as a result of high viscosity, especially in the case of high lime dose in SSF at high solid concentration. Combined energy yield (ethanol, methane and solid residue) proved lime effectiveness as catalyst in steam explosion of SB, beside two intrinsic advantages: low water consumption in SSF at high solid concentration, and the possibility of lime removal from downstream effluents through carbonation. (C) 2015 Elsevier B.V. All rights reserved.
|
|
