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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]

Microbial pretreatment is beneficial in some anaerobic digestion systems, but the consortia used to date have not been able to effectively increase methane production from cotton stalk. In this study, a thermophilic microbial consortium (MC1) was used for pretreatment in order to enhance biogas and methane production yields. The results indicated that the concentrations of soluble chemical oxygen demand and volatile organic products increased significantly in the early stages of pretreatment. Ethanol, acetic acid, propionic acid, and butyric acid were the predominant volatile organic products in the MC1 hydrolysate. Biogas and methane production yields from cotton stalk were significantly increased following MC1 pretreatment. In addition, the methane production rate from the treated cotton stalk was greater than that from the untreated sample. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effect of microbial pretreatment on methane production of LMSW was evaluated. [•] Soluble substrates in hydrolysate increased obviously after microbial pretreatment. [•] CH4 production yields and rates significantly increased after microbial pretreatment. [Copyright &y& Elsevier]

Abstract: The methane potential of nine varieties of fresh maize harvested at three different times and of maize silage was experimentally determined in batch assays. The ultimate methane productivity in terms of volatile solids (VS) was determined as 213.94–313.63, 195.88–334.81mL/g VS from several fresh and silage maize in three stages, respectively. The average specific methane yield of wax ripeness stage for fresh maize and full ripeness stage for silage maize were higher than that of other stages, respectively. The high-oil varieties of fresh maize and silage varieties of ensiling maize could produce more methane than general varieties in the same ripeness stage. Methane yield of ensiled materials was higher than fresh material. The methane yields of fresh and silage maize in full ripeness stage were ranged 5656–7956 and 4633–8915m3/ha, respectively. The corresponding maximum of methane yield came from fresh HO5580 and silage CAU No. 4. [Copyright &y& Elsevier]

Abstract: A microbial consortium MC1 was used to pretreat filter paper, office paper, newspaper, and cardboard to enhance methane production. The results of pretreatment indicated that sCOD of hydrolysates of the four substrates increased significantly in the early stage, and peaked on day 7. During pretreatment, ethanol, acetic acid, propionic acid, butyric acid, and glycerol were the predominant volatile organic products in hydrolysates. MC1 had strong degradation ability on the four substrates, and the weight loss of filter paper, office paper, newspaper, and cardboard reached 78.3%, 80.5%, 39.7%, and 49.7%, respectively. The results of anaerobic digestion showed that methane production yields and rates of the four substrates significantly increased after pretreatment. This study is the first attempt to explore the microbial pretreatment method for anaerobic digestion of waste paper and cardboard. Microbial consortium pretreatment could be an effective method for enhancing methane production of waste paper and cardboard into bioenergy. [Copyright &y& Elsevier]

[Display omitted] • Ensiling EWS with acetic acid or heterofermentative LAB addition was first studied. • Ensiling EWS with additives enhanced acetic acid fermentation. • Ensiling EWS with additives preserved hemicellulose and cellulose content. • Ensiling EWS with additives changed the homo-fermentation to hetero-fermentation. • Ensiling EWS with additives improved the methane yield by 17.7–23.9%. Ensiling is an effective storage strategy for agricultural biomass, especially for energy crops (mainly energy grasses and maize). However, the ensiling of excessively wilted crop straw is limited due to material characteristics, such as a high lignocellulosic content and low water-soluble carbohydrate and moisture contents. In this study, acetic acid or hetero-fermentative lactic acid bacterial community (hetero-fermentative LAB) were employed as silage additives to improve the ensiling process of excessively wilted wheat straw (EWS). The results showed that the additives inhibited the growth of Enterobacteriaceae and Clostridium_sensu_stricto_12 , whose abundances decreased from 55.8% to 0.03–0.2%, respectively. The growth of Lactobacillus was accelerated, and the abundances increased from 1.3% to 80.1–98.4% during the ensiling process. Lactic acid fermentation was the dominant metabolic pathway in the no additive treatment. The additives increased acetic acid fermentation and preserved the hemicellulose and cellulose contents, increasing the methane yield by 17.7–23.9%. This study shows that ensiling with acetic acid or hetero-fermentative LAB is an effective preservation and storage strategy for efficient methane production from EWS. [ABSTRACT FROM AUTHOR]

Methane production from lignocellulosic feedstock through high solid anaerobic digestion is a huge potential technology. However, the shortage of an efficient reactor has become a major bottleneck in developing the technology. The continuous feeding and discharge of lignocellulosic feedstock with high solids is difficult to complete. Methane production from the feedstock is low in practice. Thus, it is important to develop a new reactor with efficient feeding and discharge feedstock equipments and improve methane production by an optimized operation process. Based on synthesizing the merits of a number of techniques home and abroad, a novel anaerobic reactor was designed in this study. The reactor had two spiral equipments to implement continuous feeding and discharge feedstock with high solid content and had a high bearing capability of organic loading rate (OLR) to improve methane production. In order to provide a technology and some reliable operating parameters to efficiently produce methane from lignocellulosic feedstock, the continuous anaerobic co-digestion tests were conducted at three total solid contents of 10%, 15% and 20% using corn stalk and dairy manure as feedstock. An integrated two-phase division digestion system was constructed by controlling stirring intensity (h/d) and feeding intensity (d). The methane volumetric production rate (MVPR) of different OLRs was compared. Effects of the total solid (TS) of feedstock, stirring, feeding intensity on height, pH of function divisions, and MVPR were discussed in detail. The results showed that function divisions, including the acidification division of upside and methanogenic division of underpart in the vertical reactor, were obviously formed when TS were 10% and 15%, MVPR gradually increased, and methane content stabilized around 52% with OLR increasing. The highest MVPR reached 1.62 and 1.66 m3/(m3·d) respectively when OLR was 13.44 kg/(m3·d) at 10% TS and 20.17 kg/(m3·d) at 15% TS. MVPR significantly decreased when OLR was 20.17 kg/(m3·d) and 30.0 kg/(m3·d), respectively, which might be caused by the accumulation of volatile fatty acids. MVPR stabilized around 0.98 m3/(m3·d) with OLR increasing, then it dramatically decreased and anaerobic digestion failed when OLR reached 30.0 kg/(m3·d) at 20% TS. The results of two factors interacting declared the highest MVPR at 1.63-1.69 m3/(m3·d) The efficient acidification division and methanogenic division were formed, and the height ratio of both was 1.1-1.6:1 when stirring intensity, feeding intensity, and TS were 6-12 h/d, 6.5-10 d, and 10%-15%, respectively. In summary, the process of continuous feeding and discharge at 10%-20% TS of lignocellulosic feedstock was feasible in the anaerobic digestion reactor. The reactor was more efficient and stable to produce methane at 10% and 15% TS compared to 20% TS, and MVPR could be improved by adjusting stirring intensity and feeding intensity. Therefore, this technology has a promising prospect for industrial scale application. [ABSTRACT FROM AUTHOR]

Temperature and hydraulic retention time (HRT) control are crucial for mitigating the "short-circuit" issue and enhancing methane production in continuous stirred-tank reactors. This study focuses on the combined effects of temperature and HRT on methanation via operating the reactors at different temperatures (35 °C, 45 °C, and 55 °C) and HRT (30, 25, and 20 d) for 116 days. The results demonstrated that the digester conducted at 45 °C and an HRT of 30 d unexpectedly yielded the maximum average methane production of 296.08 ml/g volatile solids (VS). In contrast, the optimal HRT for the 35 °C and 55 °C digesters were 25 and 30 d, with a methane yield of 241.88 ml/g VS and 240.9 ml/g VS, respectively. High-throughput sequencing shows that Firmicutes, Bacteroidetes, Themotogae, Chloroflexi, and Acidobacteria dominated 90–98 % of the total bacteria. Temperature exhibited a significant influence on shaping microbial ecosystems, indicating that temperature, rather than HRT, is the primary factor to consider. Additionally, metagenomic analysis reveals that the levels of genes involved in acetoclastic and hydrogenotrophic methanogenic pathways were enhanced at 45 °C, probably improving methane yield. These findings provide new insights into "short-circuit" mitigation and strategies to strengthen methane generation from biomass. • The digester at 45 °C exhibited a higher methane yield than those at 35 °C and 55 °C. • The optimal HRT for the 35 °C, 45 °C, and 55 °C digesters were 25, 30, and 30 d, respectively. • Temperature showed more influence on microbial regulation than HRT. • The enhanced acetoclastic methanogenesis path exhibited at 45 °C. [ABSTRACT FROM AUTHOR]

Ensiling is a widely used method for preserving crop stalks as biogas feedstock. However, secondary fermentation of silage is an inevitable problem that causes significant mass and energy losses. In this study, the effect of different lactic acid bacteria (LAB) inoculants on the fermentation pattern, aerobic stability, and methane production of maize stover was investigated. Maize stover was ensiled for 50 days with or without different LAB inoculants, followed by 10 days of air exposure. Methane production from the stover after the two processes was determined through batch anaerobic digestion (AD) tests. Lactiplantibacillus plantarum enhanced the homo-fermentation and reduced the pH of silage. Lentilactobacillus buchneri improved the hetero-fermentation of hexose, while causing higher dry matter loss (DML) than other inoculants. Limosilactobacillus fermentum enhanced pentose hetero-fermentation and increased both lactic acid and acetic acid production with minor DML. All the tested inoculants reduced the DML, improved the aerobic stability, and increased the methane yield of maize stover after ensiling (by up to 18.8%) and after air exposure (by up to 41.0%), with Limosilactobacillus fermentum exhibiting superior performance. The Limosilactobacillus fermentum treatment showed smaller variations in the bacterial community in AD than other treatments during air exposure. Ruminococcaceae , SHA-31 , SB-1 , Lachnospiraceae , Marinilabiaceae, and Erysipelotrichaceae showed positive correlations with water-soluble components, whereas Anaerolinaceae was positively correlated with cellulose or hemicellulose. [Display omitted] • Maize stover was ensiled with different lactic acid bacteria for methane production. • All the inoculants improved the aerobic stability and reduced dry matter loss. • The inoculants led to up to 41% higher methane yield after air exposure. • Limosilactobacillus fermentum enhanced pentose hetero-fermentation into acetic acid. • Limosilactobacillus fermentum showed superior performance in methane preservation. [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]