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Spent mushroom substrate (SMS) is a potential biomass material generated during mushroom cultivation. In this study, the methane yield and microbial community resulting from co-digestion of SMS and dairy manure (DM) at different mixing ratios (0:4, 1:1, 3:1, and 1:3), were evaluated. Co-digestion analysis showed that the methane yield from the mixtures was 6%–61% higher than the yield from SMS or DM alone, indicating a synergistic effect of co-digestion of SMS with DM. For the SMS of F.velutipes (SFv) and P.erygii var. tuoliensis (SPt), co-digestion of DM/SMS at a ratio of 1:1 was optimal, but for the SMS of P. eryngi (SPe), co-digestion of DM/SMS at a ratio of 3:1 was ideal. The pH at all co-digestion ratios was in the range of 6.8–8.0, indicating that adding DM could increase the systemic buffering capacity. Methanosaetaceae was shown to be the predominant methanogens present during the co-digestion of DM/SMS. [ABSTRACT FROM AUTHOR]

Molasses is a typical feedstock for fermentation, but the effluent is hard to treat. In this study, molasses containing a high concentration of organic matter was treated by a two-stage Fix-bed reactor system with an increased organic loading rate (OLR). The results indicated at high molasses loading rate, the two-stage system was more efficient (i.e. organic matter removal, the COD of effluent and biogas production) than the single-stage system. The relative abundance of Anaerolineaceae and W5_norank was higher in the first stage (R1), where these organisms digest carbohydrates, while the second stage (R2) had higher relative abundance of Synergistaceae and SB-1_norank , which digest VFAs and decomposition-resistant compounds to produce compounds used by hydrogen methanogens. The qPCR analysis demonstrated that the Methanosaetaceae dominated the archaeal community in the first stage (R1), while Methanomicrobiales and Methanobacteriales were predominant in the second stage (R2), where they were involved in hydrogen production. [ABSTRACT FROM AUTHOR]

Potato pulp waste is a potential biomass material and easily acidified substrate for anaerobic digestion. The present study evaluated the methane yield and microbial community resulted from biochar amendment for the co-digestion of potato pulp waste and dairy manure at different feed-to-inoculum ratios (2:1, 1:1, 1:2, and 1:3) and potato pulp waste to dairy manure ratios (4:0, 3:1 and 1:1). The results indicated that the digesters with a high feed-to-inoculum ratio (2:1, 1:1) and without biochar lead to volatile fatty acid accumulation and process failure, whereas the addition of biochar and/or co-digestion can increase the buffer capacity and improve the digestion efficiency. The biogas and methane yields of the digesters with biochar were 1.1–2.8 and 1.4–5.3 times higher, respectively, than those without biochar. The maximum biogas and methane yields of 476 and 200 mL/g TS, respectively, were achieved with a feed-to-inoculum ratio of 1:2, potato pulp waste to dairy manure ratio of 4:0, and biochar addition. Biochar and co-digestion can also enhance the relative abundance of the bacterial community. Methanomicrobiales and Methanosaetaceae were the main methanogens present in the anaerobic digestion of PPW. This paper provides a theoretical basis of easily acidified substrates used for biogas production. • Potato pulp waste is a potential feedstock for biogas production but easily acidifies. • Effects of biochar and co-digestion on anaerobic digestion were evaluated. • Different ratios of feedstocks and feed to inoculum were considered. • Diversity of the microbial community was analyzed. • Biochar and co-digestion increase the buffer capacity and digestion efficiency. [ABSTRACT FROM AUTHOR]

Silage processing has a crucial positive impact on the methane yield of anaerobic treated substrates. Changes in the characteristics of switchgrass after ensiling with different additives and their effects on methane production and microbial community changes during anaerobic digestion were investigated. After ensiling (CK), methane yield was increased by 33.59% relative to that of fresh switchgrass (FS). In comparison with the CK treatment, methane production was improved by 17.41%, 13.08% and 8.72% in response to ensiling with LBr + X, LBr and X, respectively. A modified Gompertz model predicted that the optimum treatment was LBr + X, with a potential cumulative methane yield of 178.31 mL/g total solids (TS) and a maximum biogas production rate of 44.39 mL/g TS·d. Firmicutes and Bacteroidetes were the predominant bacteria in FS and silage switchgrass; however, the switchgrass treated with LBr + X was rich in Synergistetes , which was crucial for methane production. [ABSTRACT FROM AUTHOR]

[Display omitted] • DOC was the foremost parameter influencing the phytotoxicity of LD. • Temperature accelerated the stability and phytotoxicity disappearance of LD. • Open storage of LD at 30 °C for 60 days and 20 °C for 90 days of LD was safe. • Hermetic storage of LD at 30 °C for 120 days and 20 °C for 150 days of LD was safe. • For storage at 10 °C for 180 days, additional post-treatment is required. Identifying the stability and phytotoxicity of liquid digestate (LD) is necessary for safe agricultural utilization. Storage temperature, method, and time are critical factors that affect the stability and phytotoxicity of LD. This study therefore aimed to explore the dynamics of stability, phytotoxicity, and microbial community of LD in cattle farms under different storage conditions. The results showed that the contents of solids, organic matter, nitrogen, and phosphorous decreased during storage and exhibited temperature dependency. Conversely, the seed germination index increased, which was negatively correlated with dissolved organic carbon and ammonium nitrogen and positively correlated with certain bacteria (Thermovirga and Fastidiosipila). Open storage and/or higher temperature were found to contribute to the stabilization efficiency and phytotoxicity disappearance of LD. Open storage of LD at 30 °C for 60 days and 20 °C for 90 days was safe for its agricultural utilization, while hermetic storage of LD at 30 °C for 120 days and 20 °C for 150 days was safe. However, for storage at 10 °C for 180 days, additional post-treatment is required. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of temperature rises and falls on anaerobic digestion was assessed. • 45 °C exhibits optimal methanogenic performance during temperature rises and falls. • An effective equilibrium between hydrolysis and methanation is achieved at 45 °C. • The shortest recovery time was 2 days following temperature fluctuation. This study implemented five successive temperature stages (35 °C–45 °C–55 °C–45 °C–35 °C) in a continuous stirred tank reactor, designated as D35-1, D45-1, D55, D45-2, and D35-2, respectively. The objective was to probe the mechanism of temperature transformations on methanogenesis performance, microbial community, and metabolic pathways. The suitability of 45 °C for anaerobic digestion (AD) under varying temperatures was emphatically expounded. Intriguingly, optimal methanogenesis performance was attained at 45 °C, with methane production reaching 238.51 mL/g VS/d in D45-1 and 245.91 mL/g VS/d in D45-2, signifying increases of 17.66% and 21.32% contrasted with D35-2, respectively. Additionally, considerable resistance to temperature shocks at 45 °C was also manifested, as evidenced by a recovery time of 2 days in D45-2. At 45 °C, an effective balance between hydrolysis and methanogenesis was observed, maintaining a dynamic equilibrium between acetoclastic and hydrogenotrophic methanogenesis. The primary drivers in D45-1 were Caldicoprobacter , Bathyarchaeia , and Methanosarcina , while Anaerolinea and Methanosarcina were the key determinants in D45-2. By contrast, methanogenesis was suppressed at other stages. Therefore, 45 °C emerges as a viable alternative to conventional temperatures when confronted with temperature fluctuations to optimize energy efficiency. The results provide novel insights into AD temperature management and pave the way for engineering applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two-stage anaerobic digestion affects the hydrolysis-methanogenesis process. • Aerobic or micro-aerobic hydrolysis results in carbon loss from the substrate. • Substrate type significantly affected biogas yield and microbial community. • The gradient anaerobic digestion process (GADP) improved the biogas yield. • GADP enhanced carbon recovery of substrate and synergies of microorganisms. The destruction of the synergistic effect of the hydrolysis-methanogenesis process (HMP) of substrate may lead to the serious carbon loss of substrate and low biogas yield in traditional straw biogas engineering. In this study, the influence of substrate composition on anaerobic digestion (AD) was investigated under pilot conditions, and the relationship between HMP was further investigated under full-scale plants. The results showed that straw with a high content of soluble substances had the highest methane yield (264.25 L/kg VS) and degradation rate (59.32 %). At HRT = 20 d, the full-scale plant achieved the highest biogas yield (576.92 L/kg VS, 3.47 L/L/d) and degradation rate (67.50 %). Microbial analysis showed that substrate composition affected microbial community and methanogenic metabolic pathway. The analysis results of PICRUSt2 confirm that gradient AD guarantees the synergistic relationship of HMP. This study provides the theoretical basis and engineering guidance for improving the AD process in traditional straw biogas engineering. [ABSTRACT FROM AUTHOR]

Ensilage is a commonly used method of preserving energy crops for biogas production. However, aerobic deterioration of silage is an inevitable problem. This study investigated the effect of aerobic deterioration on methane production and microbial community dynamics through anaerobic digestion (AD) of maize stalk silage, following 9 days air exposure of silage. After air exposure, hydrolytic activity and methanogenic archaea amount in AD were reduced, decreasing the specific methane yield (SMY); whereas lignocellulose decomposition during exposure improved the degradability of silage in AD and enhanced SMY, partially compensating the dry matter (DM) loss. 29.3% of the DM and 40.7% of methane yield were lost following 0–9 days exposure. Metagenomic analysis showed a shift from Clostridia to Bacteroidia and Anaerolineae in AD after silage deterioration; Methanosaetaceae was the dominant methanogenic archaea. [ABSTRACT FROM AUTHOR]