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This article investigates the current status and distribution of the feedstock of biogas engineering in China, evaluates the temperature conditions for anaerobic co-digestion (AcoD), and assesses the biogas production potential of feedstock in AcoD, including six feedstocks, namely, maize straw (M), wheat straw (W), rice straw (R), pig manure (P), cow manure (C), and sheep manure (S). The total amount of M, W, and R was 3.89 × 108, 2.10 × 108, and 1.50 × 108 tons, respectively, and that of P, C, and S was 8.46 × 108, 1.31 × 109, and 4.95 × 108 tons, respectively. However, the spatial distributions and amount of those resources were found to be uneven in China. Heilongjiang has abundant maize straw, and Henan has abundant wheat resources. Sichuan is rich in cow manure, while Inner Mongolia is rich in sheep manure. The analysis of total biogas production (TBP) by mono-digestion and co-digestion (using two feedstocks at ratio of 1:9, 3:7, 5:5, 7:3 and 9:1) showed that co-digestion outperforms mono-digestion under 15 and 25 °C. Thus, it is necessary to study anaerobic co-digestion scheme (AcoDS), which will provide a reference for biogas engineering in different regions to promote the biogas yield based on their actual situation.

This study investigated the mesophilic and thermophilic anaerobic fermentation of rape straw with biochar addition. The effects of biochar on the biogas yield, degradation of lignocellulose, bacterial community, and crystallinity were explored. The results showed that the biogas yield and methane content increased as the biochar concentration was increased. The biochar concentration of 5.0% resulted in a high biogas yield in mesophilic and thermophilic anaerobic digestion at 142.2 mL/g and 193.5 mL/g, respectively, which were 40.5% and 21.0% improvements compared with the control. The corresponding methane contents were 59.4% and 57.0%, respectively. For the lignocellulose degradation, the cellulose content in the mesophilic AD decreased from 54.0% in the pretreated rape straw to between 18.7% and 25.0%. The microbial community results showed that as the biochar concentration was increased, the relative abundance of Firmicutes initially increased before it decreased. Among the microbial community results, the relative abundances of Firmicutes and Bacteroides in the biogas residue of the mesophilic anaerobic digestion were the highest in the biogas residue with the 5.0% biochar concentration sample in the mesophilic AD, at 27.06% and 39.20%, respectively. This result revealed the mechanism of biochar to improve the biogas production of rape straw in anaerobic fermentation.

In the described study, the relationships between the percentage and structure of selected lignocellulosic components and the efficiency of their anaerobic digestion and the quality of the produced biogas were analyzed. This research included various lignocellulosic raw materials. The biogas efficiency and quality tests were carried out according to DIN standard 38 414-8 (1985) and VDI standard 4630 (2016). Multiple TAPPI standards and the Seifert method were used to determine the chemical composition of the lignocellulose materials. Lignin structure analysis was performed using Fourier transform infrared spectroscopy. Wide-angle X-Ray scattering analysis was used to determine the degree of crystallinity of cellulose. The biogas was positively correlated with C=O and the syringyl to guaiacyl ratio, and negatively correlated with the crystalline structure of cellulose, lignin, cellulose, and extractives. In addition, methane was positively correlated with holocellulose and extractives and negatively correlated with the crystalline structure of cellulose, cellulose, substances soluble in NaOH, and the OH groups. The found independent features accounted for 86.0% of the biogas variability and 68.0% of the methane variability. [ABSTRACT FROM AUTHOR]