Co-Digestion of Napier Grass and Its Silage with Cow Dung for Methane Production

Abstract

Methane production from co-digestion of grass with cow dung and silage with cow dung was conducted by a bioaugmentation technique. For self-fermentation, maximum methane yield (MY) of 176.66 and 184.94 mL CH4/g-VSadded were achieved at a ratio of grass to cow dung and silage to cow dung of 1:1, respectively. A higher maximum MY of 179.59 and 208.11 mL CH4/g-VSadded was obtained from co-digestion of grass with cow dung and silage with cow dung bioaugmented with anaerobic sludge at a ratio of 3:1. The solid residue left over after co-digestion at a ratio of 3:1 was pretreated by alkaline plus enzyme before used to produce methane and a maximum MY of 333.63 and 301.38 mL CH4/g-VSadded, respectively, was achieved. Overall power generated from codigestion of grass with cow dung plus pretreated solid residues and co-digestion of silage with cow dung plus pretreated solid residues were 0.0397 and 0.007 watt, respectively.

Co-Digestion of Napier Grass and Its Silage with Cow Dung for Bio-Hydrogen and Methane Production by Two-Stage Anaerobic Digestion Process

“…In the one-stage process, the sole enzyme pretreatment and the combined pretreatment had a methane content that exceeded 65% of the volume of biogas production (our previous experiments, [50]). In the two-stage process, the combined pretreatment gave a higher methane content in the range of 68-70% for both substrates (Figure 2).…”

“…The individual pretreament and the combined pretreatment methods were set according to Prapinagsorn et al [50].…”

“…The biogas compositions (H 2 , CH 4 and CO 2 ) were determined using gas chromatography (GC, Shimadzu 2014). Operating conditions were set according to our previous experiment [50].…”

“…The methane content in biogas produced during the methane fermentation processes by different pretreatment methods from one-stage fermentation (our previous experiments, [50]) and two-stage fermentation are shown in Figure 2. In the one-stage process, the sole enzyme pretreatment and the combined pretreatment had a methane content that exceeded 65% of the volume of biogas production (our previous experiments, [50]).…”

“…It was obtained from a local field in Khon Kaen province, Thailand. The preparation of silage followed the method of our previous experiment [50]. Grass and its silage were kept at −20 • C. Prior to usage, both substrates were thawed at room temperature (30 ± 2 • C) and chopped to a particle size of 0.5-1.0 cm in length by using a food blender.…”