Evaluation of monomeric sugar yield from various grasses grown in thailand as biofuel feedstock by two-stage microwave/chemical pretreatment process

Abstract

Cogon grass (Imperata cylindrica), Guinea grass (Panicum maximum), Kans grass (Saccharum spontaneum), Giant reed (Arundo donax), and Mission grass (Pennisetum polystachyon) were locally collected to test as bioethanol feedstock. Mission grass, Kans grass, and Giant reed, showing high cellulose and hemicellulose compositions, were treated by a two-stage chemical/microwave pretreatment method. The optimum conditions of the pretreatment were investigated and the maximum monomeric sugar yields were compared. The microwave-assisted NaOH and H₂SO₄ with 15:1 liquid to solid ratio were studied by varying catalyst concentration, temperature, and time to maximize the amount of the obtained monomeric sugar. The maximum monomeric sugars from microwave-assisted NaOH pretreated Mission grass, Kans grass, and Giant reed were 6.6 (at 120 °C,10 min, 3%(w/v) NaOH), 6.8 (at 80 °C,5 min, 5%(w/v) NaOH), and 6.8 (at 120 °C,5 min, 5%(w/v) NaOH) g/100g biomass, respectively, while maximum monomeric sugars from microwave-assisted H₂SO₄ pretreatment were 34.3 (at 200 °C,5 min, 1%(w/v) H₂SO₄), 33.8 (at 200 °C,10 min, 0.5%(w/v) H₂SO₄), and 31.9 (at 180 °C,30 min, 0.5%(w/v) H₂SO₄) g/100g biomass, respectively. The structural changes in weeds were characterized by Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscope (SEM).