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In this study, bioaugmentation with methanogenic propionate-utilizing enrichment was investigated as a method to improve the mono-digestion performance of Pennisetum hybrid in a semi-continuous mode. The effect of bioaugmentation on the microbial community was analyzed as well. The results demonstrate that the steady-state organic loading rate (OLR) of the bioaugmented reactor increased to 4.0 g VS/(L·d) with a volumetric biogas production of 1.95 ± 0.17 m 3 /(m 3 ·d). In contrast, the non-bioaugmented reactor failed at an OLR of 2.0 g VS/(L·d) accompanied with the accumulation of volatile fatty acids (VFAs). The results of whole genome pyrosequencing analysis suggest that the decrease in relative abundance of syntrophic butyrate and propionate oxidizers, such as Syntrophomonas, Syntrophobacter, and Syntrophorhabdus , reduced the conversion efficiency of butyrate and propionate which leads to the accumulation of butyrate and propionate, influencing the performance of the mono-digestion reactor. Conversely, in the bioaugmented reactor, the higher density of protein- and amino acid-utilizing bacteria, such as Proteiniphilum , Thermovirga, and Lutaonella, as well as the syntrophic association of Syntrophomonas spp. coupled with the methanogens Methanosarcina and Methanocella has a positive effect on system stability and performance. [ABSTRACT FROM AUTHOR]

This study sought to investigate the effect of bioaugmentation on batch anaerobic digestion of chicken manure. The digestion performance with and without bioaugmentation and bioaugmented efficiency under different dosages were compared. The results demonstrated that bioaugmentation increased the methane yield and shortened the methane production time in batch reactors. Compared to the un-bioaugmented control, the methane yield of bioaugmented digesters was increased by 1.2-, 1.7-, 2.2-, 3.4-, and 3.6-fold at addition ratios of 0.07, 0.14, 0.21, 0.27, and 0.34 g VS bioaugmentation seed (BS) /g VS CM , respectively. However, higher bioaugmentation doses (0.34 g VS BS /g VS CM) did not exhibit significantly improved bioaugmentation efficiency, thus, the recommended dose is 0.27 g VS BS /g VS CM for biomethane conversion of CM. Moreover, whole genome pyrosequencing revealed that Methanoculleus and Methanobrevibacter predominated the non-bioaugmentation digesters, whereas Methanothrix , Methanobacterium , and Methanomassiliicoccus were the dominant methanogens in bioaugmentation digesters. The increased methane may be explained by an increase in the Methanothrix population, which accelerated acetic acid degradation. With bioaugmentation the mainly methanogenic pathways have become more diverse. From gene function perspective, bioaugmentation enhanced metabolic activities in digestor which function better in metabolism. [Display omitted] • Methanogenic cultures used for bioaugmentation improved anaerobic digestion. • The optimal dose was 0.27 g VS BS /g VS CM in a batch digester of chicken manure. • Bioaugmentation can reconstruct the methanogenic community. • The abundance of Methanothrix was increased with bioaugmentation. • The proportion of key gene function has changed with bioaugmentation. [ABSTRACT FROM AUTHOR]

Effects of molasses-alcoholic wastewater on the ensiling quality of napiergrass were investigated at ambient temperature, and its anaerobic digestion performance was assessed at mesophilic temperature. Results showed that the molasses-alcoholic wastewater had positive effect on silage quality and anaerobic digestion performance. Lower pH values of 5.20–5.28, lower NH 3 -N contents of 32.65–36.60 g/kg and higher lactic acid contents of 56–61 mg/kg FM were obtained for the silage samples with molasses-alcoholic wastewater addition. Higher specific biogas yield of 273 mL/g VS was obtained for the sample with 11% molasses-alcoholic wastewater added. Therefore 11% molasses-alcoholic wastewater addition was recommended. [ABSTRACT FROM AUTHOR]

Abstract: Anaerobic digestion (AD) technology for rice straw conversion to biogas was investigated for biomass utilization and bioenergy generation. The effects of solid concentration in different temperatures on AD efficiency were conducted in bottle-tests, these tests showed that higher biogas production was achieved at the mesophilic temperature. Biogas production was inhibited under thermophilic conditions, and lowest biogas production was achieved in dry thermophilic conditions. According to bottle-test results, the dry AD at ambient condition was selected for 1m3 experiment. For pilot-test, the highest methane content, total methane production and methane yield rate were 62%, 9.5m3 and 239.7L/kg VS, respectively. And sour poisoning was effectively avoided by the circulation of leachate. This study could provide useful parameters for the energy utilization of rice straw in South China. [Copyright &y& Elsevier]

Abstract: The effect of molar ratio of methanol to oil, temperature and space velocity (SV) on pre-esterification of Tung oil was carried out in pilot-scale fixed bed reactor, with solid acid catalysts. The molar ratio results showed the maximum acid value reduction efficiency (90.21%) was obtained at the molar ratio of 8:1, the acid value decreased sharply to 0.70gkg−1 of KOH. And esterification reaction attained balance when space velocity was enough, so 0.029h−1 was optimal space velocity. Furthermore, activity of reactant and rate of reaction increase with temperature increased, and the maximum conversion was achieved at 65°C, the acid value of Tung oil could be reduced to 1.4gkg−1 of KOH. [Copyright &y& Elsevier]

To investigate how the changes in performance and the microbial community of the co-digestion system of Pennisetum hybrid and pig manure, two co-digestion systems in a semi-continuous mode were established at different grass:manure mixture ratios (50:50 and 75:25), and at variable organic loading rates (OLRs). The two reactors were in a steady-state at the OLRs of 2.0–5.0 g VS/(L·d), with the specific and volumetric biogas yields of 383.86 ± 65.13 to 574.28 ± 72.04 mL/g VS and 0.87 ± 0.07 to 2.36 ± 0.13 m3/(m3·d), respectively. The co-digestion system with a mixture ratio of 75:25 failed at an OLR of 5.5 g VS/(L⋅d). This failure could be attributed to the accumulation of volatile fatty acids (VFAs) owing to the imbalance between acid-production and -oxidation bacteria. By contrast, the co-digestion system with mixture ratio of 50:50 failed at an OLR of 7.0 g VS/(L⋅d), which was likely due to mechanical issues or improper reactor configuration. The genus Proteiniphilum contributed to the increase in total ammonia nitrogen. These findings provide useful guidance for optimizing co-digestion system, enhancing reactor performance and improving the wastes treatment. • Co-digestion system with 50:50 mixture ratio obtained better stable performance. • Different issues triggered the failure co-digestion process. • Enriched protein-utilizing Proteiniphilum related to the higher ammonia level. • Shift in methanogen could enhance the stability of GP11. [ABSTRACT FROM AUTHOR]