Methane production from lignocellulosic biomass using hydrothermal pretreatment

Lignocellulosic biomass is a promising raw material for energy production due to its low cost and sustainability. In this work, Egeria densa, Typha domingensis,Eichhornia crassipes, and Cyperus papyrus 'Nanus' aquatic macrophytes were evaluated as a potential to produce methane, and their biochemical transformations were investigated. All substrate produced biogas by anaerobic fermentation. The values obtained to methane yield were 170.47, 132.42, 121.90, and 180.57 mLCH(4) gSV(-1), respectively. The hydrolysis rate was higher using E. densa biomass. Total volatile acid concentrations were 32.56 mg L-1 (E. densa), 77.35 mg L-1 (T. domingensis), 22.8 (E. crassipes), and 12.4 mg L-1 (Cyperus papyrus 'Nanus'). The more significant microbiological activity was observed in the reactors using E. densa (RE) and T. domingensis (RT). The total and volatile solids removal order was RE > RT > Rec (E. crassipes) > RP (Cyperus papyrus 'Nanus'). So, for recovery of the bioenergy step, the E. densa biomass obtained the most promising results, and it was selected for hydrothermal pretreatment (HPT). After HPT, the biomass was more suitable for bioprocessing, increasing the carbohydrates available. There was a reduction in the crystallinity index due to the low lignin content and increased type II cellulose amorphous fraction. Also, the samples increased thermal stability (374 degrees C and 388 degrees C) and showed morphology with fibers partially disorganized. The methane yield was 4.2% higher as the time increased of the HPT. And the material became more vulnerable to attack by methanogenic microorganisms, resulting in greater energy production, with a potential of E. densa to generate methane.