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

Abstract

The objective of this study was to determine the effectiveness of microwave pretreatments on methane production from two switchgrass tissues (leaf vs. stem). The methane production from the leaf fraction was significantly affected by the microwave final temperature, while production from the stem fraction was affected by the combination of the microwave final temperature and heating rate. Thus, the highest methane yield from the leaf (134.81 mL CH4/g of volatile solids (VS)) was obtained at 100 °C, while the highest yield from the stem (99.35 mL CH4/g VS) was obtained at 150 °C, with a heating rate of 10 °C/min. Although methane production from the leaf fraction was merely enhanced by 9.1% after microwave pretreatments, the time required to reach 80% of ultimate methane production was reduced by 12 days. For the stem fraction, methane production was improved by 5.2% after microwave pretreatment, and the time to obtain 80% of ultimate methane production increased.

Comparison of pretreatment methods that enhance biomethane production from crop residues - a systematic review

“…According to information in Table 3, physical methods appear to be the fastest amongst the pretreatment methods. This is more so for microwave (MW) pretreatment (Wu et al, 2015;Kumar and Sharma, 2017). This is in agreement with Yuan et al…”

“…Physical pretreatment appears to be generally effective as shown in Table 5. For example, hot water pretreatment increased methane yield from rice straw by 222% (Ge et al, 2016) and MW method increased methane yield by 28% (Wu et al, 2015). Baeta et al (2016) reported that autohydrolysis is a highly effective process.…”

Improving the Anaerobic Digestion of Switchgrass via Cofermentation of Rumen Microorganisms (Rumen Bacteria, Protozoa, and Fungi) and a Biogas Slurry

“…However, the methane production of the above groups was higher than those of other results. For example, the reported methane production values of switchgrass leaves and stems were 134.81 and 99.35 mL/g VS, respectively, when they were fermented by municipal sludge at 37 °C for 60 days . Another study using a biogas slurry as the sole inoculum achieved methane production of 135.31 mL/g VS at 35 ± 1 °C after 44 days of fermentation from switchgrass …”

“…At the initial stage of fermentation, gas production and composition were measured every other day as their changes were obvious. Gas production was monitored using the saturated brine displacement method . Liquid samples were collected every few days and were kept at −20 °C to test other indicators.…”

Microwave irradiation – A green and efficient way to pretreat biomass

“…The microwave digestion vessel of CEM Corporation uses Teflon as lining, advanced composite materials as outside material which increases pressure resistance and can ensure high pressure and temperature required for pretreatment. The temperature and pressure in the vessel could be monitored with sensors (Fan et al, 2013;Hu and Wen, 2008;Jackowiak et al, 2011a;Jackowiak et al, 2011b;Li et al, 2014c;Wu et al, 2015). The digestion vessel of Milestone Co. uses tetrafluorometoxil (TFM) material, which is an analog of Teflon but with a better property in some ways (Chen et al, 2012a;Lu and Zhou, 2011).…”