Biogas Production by Co-Digestion of Goat Manure with Three Crop Residues

Abstract

Goat manure (GM) is an excellent raw material for anaerobic digestion because of its high total nitrogen content and fermentation stability. Several comparative assays were conducted on the anaerobic co-digestion of GM with three crop residues (CRs), namely, wheat straw (WS), corn stalks (CS) and rice straw (RS), under different mixing ratios. All digesters were implemented simultaneously under mesophilic temperature at 35±1 °C with a total solid concentration of 8%. Result showed that the combination of GM with CS or RS significantly improved biogas production at all carbon-to-nitrogen (C/N) ratios. GM/CS (30:70), GM/CS (70:30), GM/RS (30:70) and GM/RS (50:50) produced the highest biogas yields from different co-substrates (14840, 16023, 15608 and 15698 mL, respectively) after 55 d of fermentation. Biogas yields of GM/WS 30:70 (C/N 35.61), GM/CS 70:30 (C/N 21.19) and GM/RS 50:50 (C/N 26.23) were 1.62, 2.11 and 1.83 times higher than that of CRs, respectively. These values were determined to be the optimal C/N ratios for co-digestion. However, compared with treatments of GM/CS and GM/RS treatments, biogas generated from GM/WS was only slightly higher than the single digestion of GM or WS. This result was caused by the high total carbon content (35.83%) and lignin content (24.34%) in WS, which inhibited biodegradation.

Biodigestion of cassava peels blended with pig dung for methane generation

“…It shows that the B1 and C had initial acidic condition. This agrees with Zhang et al (2013) explanation on relationship between high C/N ratio and toxicity of the reacting medium. Similarly, the pH values of other blends were responsible for the high biogas yield experienced by B2 and B3.…”

“…CN ratio is an important indicator for controlling biological treatment systems (Wang et al, 2012). It has been pointed out that high C/N ratio indicates rapid nitrogen consumption by methanogens and leads to lower gas production while low C/N ratio results in ammonia accumulation and an increase in pH values, which is toxic to methanogenic bacteria (Zhang et al, 2013). This is partly reflected in the biogas yield of the blends as B3 with the lowest C/N ratio yield the least gas among the blends and the B1 with largest C/N ratio yields moderate biogas as compared to B2 according to the explanation above but Yadika et al (2004), pointed out that during anaerobic digestion, microorganisms utilize carbon 25 to 30 times faster than nitrogen.…”

Effects of feedstock ratio and organic loading rate on the anaerobic mesophilic co-digestion of rice straw and pig manure

“…Wang et al carried out a large number of experiments on the co-digestion of dry straw and manure, including the co-digestion of WS with dairy manure (DM) and chicken manure (CM), CS with DM and CM, and RS with DM, CM, and PM (Wang et al, 2012b(Wang et al, , 2013. Zhang et al (2013) conducted the anaerobic co-digestion of goat manure (GM) with WS, CS, and RS under mesophilic temperature conditions. Wu et al (2010) also conducted similar work using PM and three agricultural residues, namely CS, WS, and, oat straw.…”

Effects of feedstock ratio and organic loading rate on the anaerobic mesophilic co-digestion of rice straw and cow manure

“…Wang et al carried out a large number of experiments on the co-digestion of dry straw and manure, including the co-digestion of wheat straw with dairy manure and chicken manure, corn straw with dairy manure and chicken manure, and RS with dairy manure, chicken manure, and pig manure (Wang et al, 2012(Wang et al, , 2013. Zhang et al (2013) conducted the anaerobic co-digestion of goat manure with wheat straw, corn straw, and RS under mesophilic temperature conditions. The results of these studies showed that the co-digestion of straw with manure significantly improves biogas production.…”