Enhancing solubilisation and methane production kinetic of switchgrass by microwave pretreatment

Abstract

This study investigated the effects of microwave pretreatment of switchgrass in order to enhance its anaerobic digestibility. Response surface analysis was applied to screen the effects of temperature and time of microwave pretreatment on matter solubilisation. The composite design showed that only temperature had a significant effect on solubilisation level. Then the effects of the microwave pretreatment were correlated to the pretreatment temperature. The sCOD/tCOD ratio was equal to 9.4% at 90°C and increased until 13.8% at 180°C. The BMP assays of 42 days showed that microwave pretreatment induced no change on the ultimate volume of methane but had an interesting effect on the reaction kinetic. Indeed, the time required to reach 80% of ultimate volume CH 4 is reduced by 4.5 days at 150°C using the microwave pretreatment.

Microwave Pretreatments of Switchgrass Leaf and Stem Fractions to Increase Methane Production

“…In our study, the solubilization of both the leaf and stem switchgrass fractions were significantly affected by the microwave final temperature (P<0.0001), holding time (leaf: P=0.0111; stem: P=0.0002), and heating rate (leaf: P=0.0010; stem: P=0.0002). However, the exposure time had a smaller influence on the solubilization (sCOD/tCOD) of whole fresh plants for switchgrass (Jackowiak et al 2011b). Interestingly enough, a study on whole wheat straw showed that the solubilization (sCOD/tCOD) increased with longer holding times at the target temperature (Jackowiak et al 2011a).…”

“…The sVS/VS increase ranged from 1.5% to 154.0% in the leaf fraction, and from 2.1% to 130.3% in the stem fraction (Table 3), depending on the microwave final temperature, holding time, and heating rate. Jackowiak et al (2011b) also reported that microwave pretreatment improved the solubilization of switchgrass, but whole plants were used in that study. In our study, the solubilization of both the leaf and stem switchgrass fractions were significantly affected by the microwave final temperature (P<0.0001), holding time (leaf: P=0.0111; stem: P=0.0002), and heating rate (leaf: P=0.0010; stem: P=0.0002).…”

“…This results in rapid, uniform, and volumetric heating, which reduces processing times and saves energy (Thostenson and Chou 1999). In previous studies, when microwave technology was used to pretreat switchgrass, there was no change in the ultimate volume of methane produced, but the time required to obtain 80% of the maximum methane volume was reduced by 4.5 days after a 150 C pretreatment (Jackowiak et al 2011b). Similar trials with wheat straw showed that methane production was improved by 28% after a microwave pretreatment at 150 C (Jackowiak et al 2011a).…”

Microwave-assisted extraction of lignin from triticale straw: Optimization and microwave effects

“…Microwave energy has been recently explored as a potential technology to enhance the pretreatment of various lignocellulosic materials for the production of biofuels (Eskicioglu et al, 2007a,b;Taherzadeh and Karimi, 2008;Alvira et al, 2010;Shi et al, 2011;Jackowiak et al, 2011). It has more rarely been applied to the specific extraction of lignin, either as a pretreatment technique prior to enzymatic mild acidolysis (Zoia et al, 2008)o ri n combination with ionic liquids (Tan et al, 2009;Sun et al, 2009;Fu et al, 2010).…”

Comparison of Pretreatment Strategies for Conversion of Coconut Husk Fiber to Fermentable Sugars

“…Alkaline pretreatment is believed to cause swelling of the lignocellulosic structure, leading to an increase in internal surface area, separation of structural linkage between lignin and carbohydrates, and the disruption of lignin structure (Ong et al 2010;Kashaninejad and Tabil 2011). As described in the literature, microwave treatment produces a rapid volumetric heating throughout the material, resulting in alteration of physio-chemical characteristics of the material, which enables and accelerates the breaking down of the lignin-hemicellulose complex and increases the exposure of cellulose surface to cellulase (Ma et al 2009;Jackowiak et al 2011). In addition, Gabhane et al (2011) reported that microwave treatment has better efficacy (more than 10% improvement in sugar yield) on garden biomass than autoclave and hot plate treatment techniques.…”