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The existing research on voltage-source converter HVDC (VSC-HVDC) system stability mostly focuses on small-signal stability analysis methods. However, when large-signal disturbances occur, the intrinsic nonlinearity of the VSC-HVDC system becomes inevitable so that the small-signal studies are no longer valid. In this paper, a large-signal stability analysis method of the VSC-HVDC system is proposed based on the estimation of domain of attraction (DOA). This method can not only analyze the asymptotic stability of the operating point, but also answer the question of how large deviations from the operating point can be tolerated by the system. By using Takagi-Sugeno (T-S) fuzzy model and Lyapunov stability theorem, the DOA of the VSC-HVDC System at the operating point is estimated, and the large-signal stability of VSC-HVDC System is analyzed. On this foundation, the influence of system parameters on the large-signal stability is studied. The results can be used to guide the adjustment of system parameters to solve the problem of system instability. The time-domain simulations conducted in Matlab/Simulink are used to test the stability of the system under large-signal disturbance in the range of DOA. The simulation results verify the feasibility and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Flexible interconnection transformation of a distribution network using all-control power electronics technology will help to overcome the technical bottleneck of distributed generation (DG) penetration and high-quality power supply in the traditional distribution network. However, the flexible interconnection form that uses back-to-back power electronic converters to replace tie switches has disadvantages such as high cost and large footprint, so its mass promotion and application are bound to be limited. Therefore, a new topology of flexible interconnected distribution network with embedded DC system (FDN+EDC) with a better economy is proposed. Firstly, the topology of FDN+EDC is introduced to improve the controllability level of the distribution network under high percentage DG penetration, and is compared with the conventional flexible interconnection method. Secondly, in order to realize the coordinated optimal economic operation of source, network and load in the FDN+EDC, a dynamic reconfiguration model of switches status and continuous adjustment of flexible interconnection device (FID) are proposed. Then, to achieve a fast and globally optimal solution of the model, a hierarchical coordinated optimization strategy is designed based on an improved particle swarm algorithm for the optimization of discrete and continuous variables. Finally, the validity of the algorithm is verified, and an 88-node FDN+EDC is constructed to verify the advantages of the proposed embedded DC flexible interconnection topology and realize the joint optimal dispatch of network-source-load. [ABSTRACT FROM AUTHOR]

• Compared with the traditional flexible interconnection method, the EDC-DN power supply architecture proposed in this paper does not simply use MTDC to achieve feeder interconnection but first optimizes and adds dynamic reactive power compensation devices based on voltage source converters in the context of a high percentage of DG access to the grid, and then the dynamic reactive power compensation equipment between different feeders is interconnected on the DC side by adding additional lines, thus weakening the voltage fluctuation of the grid when DG is connected while achieving closed-loop flexible interconnection between multiple feeders. This can achieve closed-loop flexible interconnection between multiple feeders while weakening the voltage fluctuation of the grid when DG is connected, provide a flexible active power adjustment path for high proportional DG access to DN, and realize power mutual aid between different feeders and network-level bearing of DG. • For the issue of power supply recovery after EDC-DN fault, a comprehensive analysis was conducted on the impact of different fault locations on the power supply recovery process. The collaborative plan between EDC and DAS was first proposed, clarifying the information interaction content between the distribution network automation central station, feeder sub-station, and EDC sub-station during the power supply recovery process. An EDC-DN two-stage power supply restoration architecture considering EDC continuous regulation, combinatorial optimization of interconnection switch and sectionalizing switch is proposed and designed, which fills the technical gap in the integration of EDC and DAS systems. • This paper demonstrates the real-time dynamics of EDC in the EDC-DN power supply restoration process through simulation. The restoration process includes a fast restoration phase based on EDC continuous regulation of power supply, a non-fault section transfer process based on mechanical switch action, and an economically optimal operation phase using an optimal combination of switches to reconfigure the distribution network topology. The current power supply restoration strategy of SOP focuses on the final restoration state of EDC continuous regulation and switch combination rather than on the whole process of power supply restoration. This paper considers the real-time dynamics of the entire EDC-DN power supply restoration process. It fills the technical gap in the current SOP power supply restoration without considering the intermediate process. The flexible interconnection device (FID) enables multiple distribution feeders in closed-loop mode to support a higher proportion of distributed generation (DG) and large-scale new loads connected to the distribution network (DN). Moreover, the closed-loop operation mode based on FIDs provides an effective technology roadmap for high-quality and highly reliable power users, especially the quick restoration of power supply after the failure of DN. This paper proposes a new supply shape in which the multi-terminal DC links are flexibly embedded in the AC DN (EDC-DN) to realize closed-loop operation, achieving lower investment costs than the existing mode that replaces tie switches with soft open points (SOPs). Meanwhile, a two-stage power supply quick recovery control technology is proposed for the EDC-DN, including the fast power supply recovery stage based on EDC and the optimizing restoration stage based on network reconfiguration. Firstly, the role of EDC in the process of power supply restoration of three different faults on AC feeder is analyzed. Secondly, a detailed power supply recovery process is proposed, which is based on a distribution automation system (DAS) and the real-time control capability of EDC. Thirdly, the power supply restoration second stage is implemented, which is based on network reconfiguration with switch combination and EDC continuous variable optimization. Finally, a 58-node DN with an EDC system was constructed using PSCAD/MTDC simulation software to verify the effectiveness of the two-stage strategy for EDC-DN power restoration. © 2017 Elsevier Inc. All rights reserved. [ABSTRACT FROM AUTHOR]

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]

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]

Napier grass is potentially a viable feedstock for biofuel production. The present study investigated biological pretreatment of Napier grass by three microbial consortia followed by saccharification and anaerobic digestion. The pretreatment efficiencies of three microbial consortia were compared in terms of degradation ability, saccharide and biogas yield. The lignocellulose loss rates of Napier grass varied largely. The biomass pretreated by the consortium WSD-5 gave 43.4% and 66.2% total sugar yield under low and moderate loadings of commercial enzyme mixtures, while the highest yield was 83.2% pretreated by the consortium MC1 under a high enzyme loading. The maximum methane yield of pretreated samples by the consortia MC1, WSD-5 and XDC-2 were 259, 279, 247 ml/g VS, respectively, which were 1.39, 1.49 and 1.32 times greater than the values of the untreated controls. This study showed that pretreatments by MC1, WSD-5 and XDC-2 were capable of significantly enhancing both the saccharide and methane yields from Napier grass. [ABSTRACT FROM AUTHOR]

Highlights: [•] The two-phase anaerobic co-digestion of CD with PM was evaluated using 4 SBRs and a CSTR. [•] Co-acidification of PM and CD promoted the production and accumulation of VFAs, SCOD and NH4–N. [•] Methanogenic fermentation of the acidification products was efficient and steady. [•] Co-digestion of PM and CD supported higher quantity and diversity of methanogens. [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: The microbial consortium WSD-5 is composed of bacteria and fungi, and the cooperation and symbiosis of the contained microbes enhance the degradation ability of WSD-5. Experiment results showed that the highest cellulase and hemicellulase were obtained when ventilation volume was 4L/min, stirring rate was 0rpm, and substrate loading rate was 3%. After 6days of cultivation, a 67.60% loss in wheat straw dry weight was observed. The crude enzyme secreted from WSD-5 after optimization was evaluated by experiments of saccharification and acidification. The maximum concentration of reducing sugars was 3254mg/L after 48h saccharification. The concentration of sCOD peaked on day 2 with a value of 4345mg/L during acidification, and the biogas yield and methane yield were 22.3% and 32.3% higher than un-acidified samples. This study is the first attempt to explore both the saccharification and the acidification ability of crude enzymes secreted by microbial consortium. [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]

The use of the conventional dual closed-loop control strategy by photovoltaic (PV) plants with grid-connected inverters may weaken the damping of a power system, which may aggravate low-frequency oscillations (LFOs). This influence will become more severe as the penetration of PV plants increases. Therefore, it is necessary to incorporate damping controls into PV plants to suppress LFOs. This paper proposed an additional compound damping control (ACDC) system that combines additional damping control (ADC) for the inverter with ADC-based dynamic power compensation control (DPCC), allowing hybrid energy storage systems (HESSs) to suppress LFOs. First, the feasibility of suppressing low-frequency oscillations in PV plants is demonstrated by the torque method and a small signal model. Then, an additional damping controller is added to the active power control link of the PV inverter to enhance the damping abilities of the system. However, given that the damping performance of PV plants with only ADC is limited by the compensated power, PV plants require devices that can rapidly compensate for the damping power. Therefore, we added the HESS to the DC bus and proposed DPCC. Finally, a three-machine nine-node system for a PV plant was modeled and simulated in the PSCAD platform. The simulation results showed that the proposed control strategy could provide effective damping for interarea oscillation. [ABSTRACT FROM AUTHOR]

The utilization of biomass for the production of agricultural green inputs is regarded as a crucial strategy for achieving low-carbon development in agriculture, while also fully harnessing the potential of renewable resources. Pesticides, as a vital agricultural input, often encounter issues pertaining to inefficient usage, resulting in significant environmental pollution and economic losses. As a main component of lignocellulosic biomass, lignin has become one of the most appealing biopolymers for the construction of advanced pesticide delivery systems. This review aims to provide a thorough summary of the advancements in lignin-based controlled release formulations (LCRFs) for the precise delivery of pesticides. The research in this field has experienced rapid growth in the past five years, making it an important area of study. Common LCRFs are introduced, and the factors influencing the release of active ingredients (AIs) within different LCRFs are analyzed. Special emphasis is placed on intelligent-responsive LCRFs, encompassing an overview of the existing formulations and an exploration of their potential application scenarios and development strategies. It is crucial to promote innovation in pesticide formulations based on the actual demands of agricultural production. We hope this review will stimulate the high-value utilization of lignin and the green development of plant protection technologies. [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]

Highlights • A hybrid DE/WOA method is proposed for parameter extraction of PV models. • DE/WOA can combine the exploration of DE with the exploitation of WOA well. • Thirteen numerical benchmark functions are firstly employed to verify DE/WOA. • DE/WOA is then applied to three different benchmark test PV models. • DE/WOA is finally applied to a practical PV power station in China. Abstract Parameter extraction of solar photovoltaic (PV) models is a typical complex nonlinear multivariable strongly coupled optimization problem. The original differential evolution (DE) is good at exploring the search space and locating the region of global optimum, but it is slow at exploitation of the solutions. Quite the opposite, the original whale optimization algorithm (WOA) is good at exploiting the population information, but it easily suffers from premature convergence. In such a context, in this paper, an effective hybrid method named DE/WOA by combining the exploration of DE with the exploitation of WOA is proposed for extracting the accurate parameters of PV models. A set of 13 numerical benchmark functions with different characteristics is firstly employed to verify the performance of DE/WOA. Then, DE/WOA is applied to parameter extraction of three PV models, i.e., single diode, double diode, and PV module models. Finally, DE/WOA is implemented to a practical PV power station in the Guizhou Power Grid of China to further validate its effectiveness under different irradiances, temperatures, and dynamic weather conditions. All the experimental results comprehensively demonstrate that DE/WOA performs significantly better than the original DE, WOA, and five advanced variants of them and is highly competitive with some recently-proposed parameter extraction methods. [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]

The ready formation of scum in vertical reactors has been a bottleneck in the digestion of lignocellulosic materials for biogas production. This study describes a single vertical reactor that integrates the acidogenic and methanogenic phases of this process. The effects of two types of maize stover feedstock (fresh and silage) and two mixing intensities (20 and 70 rpm) on methane yield were orthogonally determined. Fresh maize stover yielded approximately 14% more methane than silage maize stover. Mixing at 20 rpm contributed to methane yield, while mixing at 70 rpm blurred the phase boundary, resulting in accumulation of volatile fatty acids and loss of methanogens. The upper and lower phases clearly constituted a two-phase fermentation system. Clostridiales occupied the acidogenic phase, while the predominant bacteria in the methanogenic phase were Bacteroidetes , Chloroflexi , and Synergistetes . The absolute predominance of Methanosaetaceae clearly demonstrated that aceticlastic methanogenesis was the main route of 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]

Health status assessment is the key link of transformer-condition-based maintenance. The health status assessment method of power transformers mostly adopts the method based on the health index, which has the problems of multiple parameters of each component and strong subjectivity in the selection of weight value, which is easily causes misjudgment. However, the existing online monitoring system for dissolved gas in transformer oil (DGA) can judge the normal or abnormal state of the transformer according to the gas concentration in a monitoring cycle. Still, there are problems, such as fuzzy evaluation results and inaccurate judgment. This paper proposes a dynamic state evaluation method for power transformers based on the Mahalanobis–Taguchi system. First, the oil chromatography online monitoring time series is used to screen key features using the Mahalanobis–Taguchi system to reduce the problem of excessive parameters of each component. Then, a Mahalanobis distance (MD) calculation is introduced to avoid subjectivity in weight selection. The health index (HI) model of a single transformer is built using the MD calculated from all DGA data of a single transformer. Box–Cox transformation and 3 σ criteria determine the alert value and threshold value of all transformer His. Finally, taking two transformers as examples, we verify that the proposed method can reflect the dynamic changes of transformer operation status and give early warning on time, avoiding the subjectivity of parameter and weight selection in the health index, which easily causes misjudgment and other problems and can provide a decision-making basis for transformer condition-based maintenance strategies. [ABSTRACT FROM AUTHOR]

• Introduce the chance constrained programming to deal with the randomness of wind power, photovoltaic output and load. • The fault recovery capability of flexible interconnected distribution network considering closed-loop operation is more fully developed. • Analyze the fault recovery effect of flexible interconnected distribution network under different SOP control modes and propose a two-stage recovery strategy. • Considering more complex faults of flexible interconnected distribution network, provide an effective fault recovery strategy for concurrent faults. With the continuous exploration of the application value of flexible interconnected distribution network, Soft Open Point (SOP) as its core device, how to fully explore the self-healing control support capability of SOP and improve its power supply reliability becomes particularly important. Aiming at the problem of fault recovery of flexible interconnected distribution network with multiple AC power supply areas, firstly, the topology of flexible interconnection of distribution network and the fault recovery model of SOP are described. Secondly, the stochastic nature of wind power, photovoltaic output and load is considered, and then the chance-constrained programming is introduced to deal with. Then, aiming at the coordinated operation of flexible closed-loop network in multiple AC power supply areas, and introducing the constraint on the acting number of switches, a stochastic optimization model of flexible interconnected distribution network fault recovery is established, and then the model is transformed into a deterministic mixed integer second-order cone programming model, which can be solved by CPLEX solver. Finally, the proposed model has been tested on a modified hand-in-hand IEEE33 system with dual-terminal SOP, verifying that the strategy proposed in this paper can effectively solve the fault recovery problem of flexible interconnected distribution network with multiple AC power supply areas considering uncertainty, and showing that this strategy can maximize the self-healing capability of distribution system. [ABSTRACT FROM AUTHOR]

This paper focuses on the self-synchronization control of cascaded-type STATCOM. One module is controlled as the current source, and the rest are regulated as voltage sources. The low-bandwidth communication is just used to transmit the given reactive powers. Via the carrier of common grid current acquired locally, the self-synchronized operation of all modules is realized. When a short interruption in communication occurs, the stable operation of the system is unaffected. Thus, the system reliability is improved in case of communication failure. The small-signal stability of the proposed scheme is proven. Finally, the effectiveness of the proposed scheme is verified by both simulation and hardware-in-the-loop results. [ABSTRACT FROM AUTHOR]

The methane yield and microbial community resulting from co-digestion of dairy manure and switchgrass at different mixing ratios [4:0, 3:1, 2:2, 1:3, and 0:4 based on total solids (TS) content] were evaluated. The results indicated that switchgrass is an excellent feedstock for biogas production when co-digested with dairy manure. Mono-digestion of a high dose (>4% TS) of switchgrass led to volatile fatty acid accumulation and process failure, whereas co-digestion of switchgrass and dairy manure could increase the buffering capacity and improve the fermentation efficiency. The optimal mixture ratio of dairy manure and switchgrass was 2:2, with a methane yield that was 39% higher than that obtained by digestion of the individual substrates. The added amount of 8% TS at the 2:2 ratio achieved the highest methane yield of 158.6 mL/g VS, which corresponded to a 1.3-fold increase in the volumetric productivity of methane compared to mono-digestion of 4% TS switchgrass. Quantitative polymerase chain reaction and clone library analyses showed significant differences in the bacterial community resulting from the different co-substrate ratios. Planctomycetes (28%), Chloroflexi (24%), and Bacteroidetes (24%) were the dominant phyla in digesters with a co-substrate ratio of 2:2. [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]

Antibiotic mycelial dreg (AMD) has been categorized as hazardous waste due to the high residual hazardous contaminants. Inappropriate management and disposal of AMD can cause potential environmental and ecological risks. In this study, the potential of pleuromutilin mycelial dreg (PMD) as a novel feedstock for preparing tetracycline hydrochloride (TC) adsorbent was explored to achieve safe management of PMD. The results suggested that residual hazardous contaminants were completely eliminated after pyrolysis. With the increase of pyrolysis temperature, the yields, H/C, O/C, (O + N)/C, and pore size in PMD-derived biochars (PMD-BCs) decreased, while BET surface area and pore volume increased, resulting in the higher stability of the PMD-BCs prepared from higher temperatures. The TC adsorption of the PMD-BCs increased from 27.3 to 46.9 mg/g with the increase of the pyrolysis temperature. Surprisingly, pH value had a strong impact on the TC adsorption, the adsorption capacity of BC-450 increased from 6.5 to 71.1 mg/g when the solution pH value increased from 2 to 10. Lewis acid-base interaction, pore filling, π-π interaction, hydrophobic interaction, and charge-assisted hydrogen bond (CAHB) are considered to drive the adsorption. This work provides a novel pathway for the concurrent detoxification and reutilization of AMD. [Display omitted] • PMD was pyrolyzed into biochar for efficient antibiotic adsorption. • Hazardous contaminants were completely eliminated by pyrolysis at above 350 °C. • Pyrolysis temperature greatly influenced the physicochemical properties of PMD-BCs. • Higher pyrolysis temperature benefited the TC adsorption onto PMD-BCs. • A low temperature (450 °C) is recommended for the pyrolysis treatment of PMD. [ABSTRACT FROM AUTHOR]

[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]

Korshinsk peashrub branches (Korpb) are agroforestry byproducts that accumulate in millions of tons per year and need to be reasonably utilized. To maximate the utilization value of Korpb, an integrated process was proposed and conducted by using Korpb as the main substrate ingredient for Pleurotus tuoliensis cultivation and also performing anaerobic digestion (AD) of spent mushroom substrate (SMS) for biogas production. The results indicated that the cultivation substrate including Korpb could obtain higher mushroom yields than a conventional substrate, and AD of SMS added the value of Korpb. Preliminary calculation suggested that, for every t of P. tuoliensis production, 1.65 t Korpb was consumed and 314 m3 biogas was produced from corresponding amount of SMS, bringing a total economic profit of $906.1. In addition, this integrated strategy has positive ecological and social benefits. The maximization of Korpb value can not only promote the biological conversion of Korpb to circle economy, but also be beneficial for the development of environment, energy conservation and edible fungus industry. • Korpb is a lignocellulose biomass resource with great potential. • Integration of P. tuoliensis cultivation and AD of SMS maximized the value of Korpb. • The economic profit achieved $906.1 for every t of P. tuoliensis production. • The integrated strategy has positive ecological and social benefits. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid metaheuristic optimizer called CHDJ to identify accurate and reliable values for the model parameters of solid oxide fuel cells (SOFC). CHDJ is a hybridizer of differential evolution (DE) and Jaya algorithm. The core of CHDJ lies in a developed competitive hybrid operation. In this operation, three vectors including the DE mutant vector, the Jaya mutant vector, and the crossover vector that constituted by the foregoing two mutant vectors form a tri-competitive mechanism together. This mechanism can contribute to exploring the global space extensively and exploiting the local region meticulously to generate promising candidate solutions. To verify the performance of CHDJ, two SOFC models including a cylindrical cell and a tubular stack operating at different pressures and temperatures are employed. Experimental results demonstrate that these three vectors interact and cooperate organically. They make CHDJ take full advantages of the exploration of DE and the exploitation of Jaya effectively. The optimal values of the mean square error (MSE) between the measured voltage and the calculated voltage obtained by CHDJ on the cylindrical cell at 1073K, 1173K, 1213K, and 1273K are 2.9215E-06, 1.4610E-06, 1.9093E-06, and 2.4682E-06, respectively. On the tubular stack, for the operating conditions of 3atm constant pressure at 873K, 923K, 973K, 1023K, and 1073K, the optimal MSE values are 2.7489E-05, 1.6169E-04, 6.9207E-04, 1.4833E-03, and 1.5876E-03, respectively. For the operating conditions of 1073K constant temperature under 1atm, 2atm, 3atm, 4atm, and 5atm, the results are 1.5293E-03, 1.6289E-03, 1.5876E-03, 1.5868E-03, and 1.5870E-03, respectively. Comparisons with other algorithms show that CHDJ achieves better overall performance. It can skip local optima and find optimal solutions, and thus can serve as a hopeful candidate method for parameter identification of SOFC models. • A hybrid algorithm (CHDJ) is proposed for parameter identification of SOFC models. • A competitive hybrid operation based on a tri-competitive mechanism is designed. • Exploration of differential evolution and exploitation of Jaya are integrated. • CHDJ is applied to one cylindrical cell and one tubular stack. • CHDJ is verified from parameter accuracy, robustness, convergence, and statistics. [ABSTRACT FROM AUTHOR]

• High near-infrared reflectance thermochromic materials limits heat gain in winter. • UV absorber could alleviate light aging of thermochromic materials to some extent. • Relative position of ice-melting coating didn't affect functional fillers release. • Composite coating achieved 9 °C cooling effect and freezing temperature of −5 °C. • Skid and temperature change resistance of composite coating were investigated. As the main type of urban roads, the surface temperature of asphalt pavement can reach 70 °C in summer because high heat absorption, causing pavement disease and aggravating the heat island effect. Solar reflective coating is an effective way to tackle the problem in summer but may bring certain negative effects in winter. In this paper, a kind of composite coating containing thermochromic (TCM) materials and snow melting and ice suppression (SMIS) functional fillers was developed. The reflective properties, thermal behavior and road performance of the pavement coatings were investigated. The results showed that the optimal TiO 2 contents in TCM-black coating for pavement was 3 wt% to make full use of optical variation range. Long-term solar radiation destroyed the structure of thermochromic microcapsules and caused degradation of color and visible reflectance of TCM coatings, which could be alleviated by ultraviolet absorbers and light stabilizers. The optimal double-layer coating structure with TCM on the top and SMIS at the bottom could achieve cooling effect of 9 °C, pavement icing temperature of −5 °C and faster ice melting rate. The skid and temperature change resistance with the coatings also met requirements. This study provides a reference for developing novel pavement materials with balanced cooling effect and ice suppression capacity for mitigating heat island effect, improving driving safety, and ensuring the optimal service state and longer service life of pavement at the same time. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Continuous stirred-tank reactor (CSTR) has a "short-circuit" problem. • The Gradient anaerobic digestion reactor (GADR) can solve the problem of CSTR. • GADR can stably carry out semi-continuous dry anaerobic digestion. • GADR can improve the biogas yield of straw raw materials that are unique to China. • The biogas production efficiency and microbial community were analyzed. In China, the problem of low biogas yield of traditional biogas projects has become increasingly prominent. This study investigated the effects of different hydraulic retention times (HRTs) on the biogas production efficiency and microbial community under pilot conditions. The results show that the "Gradient anaerobic digestion reactor" can stably carry out semi-continuous dry anaerobic digestion and improve biogas yield. The highest volatile solids (VS) biogas yield (413.73 L/kg VS and 221.61 L CH 4 /kg VS) and VS degradation rate (48.41%) were observed at an HRT of 25 days. When the HRT was 15 days, the volumetric biogas yield was the highest (2.73 L/L/d, 1.43 L CH 4 /L/d), but the VS biogas yield and degradation rate were significantly decreased. Microbial analysis showed that HRT significantly affected microbial community. It provides basic data support for the development of a new anaerobic digestion process and the practical application of the straw biogas project in China. [ABSTRACT FROM AUTHOR]

• The interval temperature digester exhibited the highest methane yield. • The decomposition rate of organic matter increases with increasing temperature. • Methanogenesis, rather than hydrolysis, is limited at the thermophilic temperature because of the loss of Methanosarcina. • Efficient methanogenesis occurs under the balance between hydrolysis and methanogenesis at interval temperature. • Our findings may provide insight into the temperature control in AD systems. Anaerobic digestion (AD) at mesophilic and thermophilic interval temperatures has received increasing attention due to an unexpectedly higher methane yield. However, there is no general consensus and the mechanisms of microbial regulation under interval temperature remain unclear. Therefore, this study evaluated the effect of conventional and interval temperatures on methanogenesis performance and microbial regulation in continuous AD of wilted corn straw. The results demonstrated that the hydrolysis rate increased with increasing temperatures, probably due to the predominant Firmicutes and Proteobacteria, whose abundance in D55 was more than 72% and 19%, respectively. However, in the stable period (31–55 d) experiments, digesters D35, D45, and D55 achieved an average methane yield of 224 ± 34, 311 ± 55, and 261 ± 49 N mL/g VS/d, respectively. Interval temperature substantially enhanced methane yield by 39.4% and 19.0% compared to that from mesophilic and thermophilic digesters, respectively. A higher proportion of Methanosarcina (94.42–94.73%) promoted the acetoclastic methanogenesis at interval temperature, implying that methanogenesis, rather than hydrolysis, is limited at the thermophilic temperatures because of the loss of Methanosarcina. Furthermore, a high abundance of essential genes involved in methane metabolism was found to stimulate methane production in the interval temperature digester. These findings revealed that the interval temperatures may be a balanced zone between hydrolysis and methanogenesis for achieving higher methane yield and provided a new perspective strategy for AD. [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]

Highlights • Composting of biogas residues and spent mushroom substrate lasted 118 days. • Plant growth was used to evaluate the compost maturity. • Compost as tomato substrate showed better seedling quality than commercial seedling. • TOC, C/N, NH 4 +-N, NO 3 −-N, AK and lignocellulose can be used to evaluate compost maturity. Abstract Recycling of BR and SMS are crucial for the development of biogas industry and commercial mushroom cultivation. The seed germination test is limited to examine the maturity of compost because of lacking the effect of insoluble part on plant growth. The aim of this study was to evaluate the maturity of compost by analysis the relationship between agronomic parameters of plant growth with physicochemical parameters of compost. The thermophilic period (over 50 °C) was lasted 52 days. TOC, C/N, AP and NH4+-N was decreased along with composting process, while TK, TP, AK and NO 3 −-N showed an opposite trend. As for seedling quality, the raw material (T0) showed the worst plant growth but the 100% compost (T1) showed better seedling quality compared with commercial seedlings. According to the analysis of Spearman correlation, the results indicated that TOC, C/N, NH 4 +-N, NO 3 −-N, AK and lignocellulose can be used to evaluate compost maturity. [ABSTRACT FROM AUTHOR]

A composted material derived from biogas production residues, spent mushroom substrate (SMS) and pig manure was evaluated as a partial or total replacement for peat in growth medium for tomato and pepper seedlings. Five different substrates were tested: T1, compost + perlite (5:1, v:v); T2, compost + peat + perlite (4:1:1, v:v:v); T3, compost + peat + perlite (2.5:2.5:1, v:v:v); T4, compost + peat + perlite (1:4:1, v:v:v); and CK, a commercial peat + perlite (5:1, v:v). The physical-chemical characteristics of the various media were analyzed, and the germination rate and morphological growth were also measured. Real-time Quantitative PCR (qPCR) was used to quantify Fusarium concentrations. The addition of compost to peat-based growth medium increased the pH, electrical conductivity, air porosity, bulk density, and nutrition (NPK), and decreased the water holding capacity and total porosity. The use of compost did not affect the percent germination at day 15 of the tomato and pepper seedlings. The addition of compost resulted in better or comparable seedling quality compared with CK and fertilized CK. The best growth parameters were seen in tomato and pepper seedlings grown in T1 and T2, with higher morphological growth in comparison with CK and fertilized CK. However, T2 showed the highest Fusarium concentration compared to compost and all growth media. Fusarium concentrations in T1, T3, and T4 did not differ significantly from those in CK for tomato seedlings, and those in T1 and T4 were also similar to those in CK for pepper seedlings. The results suggest that biogas residues and SMS compost is a good alternative to peat, allowing 100% replacement, and that 20–50% replacement produces tomato and pepper seedlings with higher morphological growth and lower Fusarium concentrations. [ABSTRACT FROM AUTHOR]

Abstract: The development of inexpensive and effective catalysts that can produce hydrogen from methanol is attractive for the implementation of clean energy technologies. Cu-Al oxides, prepared by different methods, were tested for hydrogen production from methanol decomposition. Catalysts with spinel CuAl 2 O 4 (copper aluminate) structure as compared with non-spinel Cu-Al oxides, are more stable, and exhibit higher catalytic activity despite of their low surface area. Spinel CuAl 2 O 4 synthesized by citrate process show better performance towards methanol decomposition than that obtained by co-precipitation process. The selectivity to H 2 +CO can be improved by the impregnation of potassium in spinel CuAl 2 O 4 . However, the direct addition of potassium during the citrate process strongly inhibited the formation of CuAl 2 O 4 structure, thus leading to a low catalytic activity. CuAl 2 O 4 was found to be a reservoir of Cu, slowly releasing Cu during the catalysis of methanol decomposition and preventing Cu from quick sintering. [ABSTRACT FROM AUTHOR]

In this study, the impact of pig manure on the maturity of compost consisting of spent mushroom substrate and rice husks was accessed. The results showed that the addition of pig manure (SMS-PM) reached 50 °C 5 days earlier and lasted 15 days longer than without pig manure (SMS). Furthermore, the addition of pig manure improved nutrition and germination index. High-throughput 16S rRNA pyrosequencing was used to evaluate the bacterial and fungal composition during the composting process of SMS-PM compared to SMS alone. The SMS treatment showed a relatively higher abundance of carbon-degrading microbes (Bacillaceae and Thermomyces ) and plant pathogenic fungi (Sordariomycetes_unclassified) at the end of the compost. In contrast, the SMS-PM showed an increased bacterial diversity with anti-pathogen ( Pseudomonas ). The results indicated that the addition of pig manure improved the decomposition of refractory carbon from the spent mushroom substrate and promoted the maturity and nutritional content of the compost product. [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]

Fe is widely used as an additive in anaerobic digestion, but its bioavailability and the mechanism by which it enhances digestion are unclear. In this study, sequential extraction was used to measure Fe bioavailability, while biochemical parameters, kinetics model and Q-PCR (fluorescence quantitative PCR) were used to explore its mechanism of stimulation. The results showed that sequential extraction is a suitable method to assess the anaerobic system bioavailability of Fe, which is low and fluctuates to a limited extent (1.7 to –3.1 wt%), indicating that it would be easy for Fe levels to be insufficient. Methane yield increased when the added Fe 2+ was 10–500 mg/L. Appropriate amounts of Fe 2+ accelerated the decomposition of rice straw and facilitated methanogen metabolism, thereby improving reactor performance. The modified Gompertz model better fitted the results than the first-order kinetic model. Feasibility analysis showed that addition of Fe 2+ at ≤50 mg/L was suitable. [ABSTRACT FROM AUTHOR]

Combined heat and power systems (CHPs) have received much attention in recent years due to increasing use of bio-fuels and distributed generation (DG). Conventionally, they are connected to the power grid to balance electrical demands and supplies. This research investigated an off-grid (stand-alone) biofuel micro CHP system with hybrid energy storage (HES) (including battery banks and super-capacitors) by developing an energy management strategy based on dynamic programming (DP). DP is an optimization strategy which has been applied to energy systems in recent years. However, they suffer from dimension problems when the number of variables increases. This work is the first attempt to apply the decision tree (DT) to multi-dimension DP solutions in energy systems. The energy efficiency is improved from 45.77% to 57.97% using diesel-biofuels and the system has a potential for commercial applications. The experimental test results validate its feasibility and effectiveness. [ABSTRACT FROM AUTHOR]

Although trace elements are known to aid anaerobic digestion, their mechanism of action is still unclear. High-throughput sequencing was used to reveal the mechanism by which adding trace elements affects microbial communities and their action. The results showed that the highest methane yields, with addition of Fe, Mo, Se and Mn were 289.2, 289.6, 285.3, 293.0 mL/g volatile solids (VS), respectively. The addition of Fe, Mo, Se and Mn significantly ( P < 0.05) reduced the level of volatile fatty acids (VFAs). The dominant bacteria and archaea were Bacteroidetes and Methanosaeta , respectively. Compared with the proportion of Methanosaeta in the control group, treatment with added trace elements increased Methanosaeta by as much as 12.4%. Microbial community analysis indicated that adding trace elements changed the composition and diversity of archaea and bacteria. Methane yield was positively correlated with bacterial diversity and negatively correlated with archaeal diversity for most treatments. [ABSTRACT FROM AUTHOR]

Silage efficiency is crucial for corn stalk storage in methane production. This study investigated characteristics of dynamic changes in materials and microbes during the silage process of corn stalks from the initial to stable state. We conducted laboratory-scale study of different silage corn stalks, and optimized silage time (0, 2, 5, 10, 20, and 30 days) for methane production and the endogenous microbial community. The volatile fatty acid concentration increased to 3.00 g/L on Day 10 from 0.42 g/L on Day 0, and the pH remained below 4.20 from 5.80. The lactic acid concentration (44%) on Day 10 lowered the pH and inhibited the methane yield, which gradually decreased from 229 mL/g TS at the initial state (Day 0, 2) to 207 mL/g TS at the stable state (Day 10, 20, 30). Methanosaeta was the predominant archaea in both fresh and silage stalks; however, richness decreased from 14.11% to 4.75%. [ABSTRACT FROM AUTHOR]

Bioaugmentation using microbial consortia is helpful in some anaerobic digestion (AD) systems, but accelerated acidification to produce methane has not been performed effectively with corn stalks and cow dung. In this study, the thermophilic microbial consortia MC1 was inoculated into a complex open environment (unsterilized and sterilized systems) to evaluate the feasibility of bioaugmentation to improve acidification efficiency. The results indicated that MC1 itself degraded lignocellulose efficiently, and accumulated more organic acids within 3 days. Similar trends were also observed in the unsterilized system, where the hemicellulose degradation rate and organic acid concentrations increased significantly by two-fold and 20.1% (P < 0.05), respectively, and clearly reduced the loss of product. Microbial composition did not change obviously after inoculating MC1, but the abundance of members of MC1, such as Bacillus and Clostridium , increased clearly on day 3. Finally, the acidogenic fluid improved methane yield significantly (P < 0.05) via bioaugmentation. [ABSTRACT FROM AUTHOR]

Using microbial community MC1 to pretreat lignocellulosic materials increased the yield of biogas production, and the substrate did not need to be sterilized, lowering the cost. Rotted silage maize straw carries many microbes. To determine whether such contamination affects MC1, rotted silage maize straw was pretreated with MC1 prior to biogas production. The decreases in the weights of unsterilized and sterilized rotted silage maize straw were similar, as were their carboxymethyl cellulase activities. After 5 d pretreatment, denaturing gradient gel electrophoresis and quantitative polymerase chain reaction results indicated that the proportions of five key strains in MC1 were the same in the unsterilized and sterilized groups; thus, MC1 was resistant to microbial contamination. However, its resistance to contamination decreased as the degradation time increased. Following pretreatment, volatile fatty acids, especially acetic acid, were detected, and MC1 enhanced biogas yields by 74.7% compared with the untreated group. [ABSTRACT FROM AUTHOR]

To effectively deal with the operating uncertainties of protective relays and circuit breakers existing in the power system faults, an improved fault section diagnosis (FSD) method is proposed by using Takagi–Sugeno fuzzy neural networks (T–S FNN). In this method an optimal T–S FNN-based diagnosis model is built with the idea of distributed parallel processing for each section instead of the whole power system. To obtain accurate T–S FNN-based diagnosis models, a genetic learning adaptive gaining-sharing knowledge-based algorithm (GLAGSK) is designed to optimize their structure parameters and consequent parameters. GLAGSK combines an adaptive knowledge ratio and a genetic learning strategy to balance population diversity and convergence speed to boost the optimization ability. After a fault occurs, selective optimal T–S FNN-based diagnosis models are triggered according to the alarm information. They work in parallel to improve the fault diagnosis efficiency. Simulation results of three test systems including an actual fault event show that, compared with other peer algorithms, GLAGSK can obtain more accurate T–S FNN-based diagnosis models with faster global convergence. Besides, compared with the BP and RBF neural networks and other FSD methods, the proposed FSD method based on optimal T–S FNN-based diagnosis models can diagnose different complex faults successfully with higher fault credibility. • Improved fault section diagnosis (FSD) method based on T–S FNN is proposed. • T–S​ FNN-based diagnosis model is designed for each power system section. • Enhanced metaheuristic named GLAGSK is presented to optimize T–S FNNs. • GLAGSK is boosted by adaptive knowledge ratio and genetic learning strategy. • Proposed FSD method can diagnose different complex fault scenarios accurately. [ABSTRACT FROM AUTHOR]

Adopting anaerobic digestion (AD) of lignocellulosic biomass to produce biomethane is an effective approach to meet the urgent demand for clean and sustainable energy in energy transition. The pretreatment kinetic mechanism is the key to enhance the lignocellulosic carbon conversion and significantly improve the efficiency of AD. Various pretreatment strategies have been proposed in the literature, while a systematical summarization of these strategies based on different driving forces is still lacking. The purpose of this review is to classify and analyze the current technologies and research achievements on lignocellulose pretreatment technologies according to different driving forces including single ones and combined ones. Features, as well as fundamental modes of conventional and recently emerged pretreatments, have been introduced. Single pretreatment methods driven by physical, chemical, or biological forces have obvious advantages and limitations for the anaerobic transformation of lignocellulosic feedstocks. Recently emerged combined pretreatment technologies powered by multiple forces have synergistic treatment effects which hold greater application potential than those driven by single forces. Besides, a comprehensive evaluation of combined pretreatments is carried out on the basis of pretreatment efficiency, cost, energy consumption, and environmental impact to detect their potential applications in the actual biogas industry. By comprehensively summarizing the current features of single and combined technologies, this review finally provides future research perspectives for biomass pretreatment. [Display omitted] • Features of different pretreatments driving by different forces were analyzed. • Conventional pretreatments driven by single forces have obvious shortcomings. • Rational integration of multiple driving forces has synergistic pretreatment effect. • Combined pretreatment strategies have greater potential than single ones. • Physical-chemical methods are most promising based on comprehensive evaluations. [ABSTRACT FROM AUTHOR]

In China, about 7.0×108 t of crop straws may be collected annually, and the amount suitable for converting to feed was approximately accounted for 85.67%. However, low digestibility and protein content prevent its use in feedlots, much of these materials were disposed by burning, which resulted in environmental pollution. A matrix formed by lignin and hemicellulose surrounds the orderly cellulose microfibrils and reduces their digestibility. The breakdown of the bonds between lignin and cellulose is the key to transform the lignocellulosic substrate into a high quality feed for ruminants. Studies have provided various results that removal of lignin enhanced the digestibility of straws. Although hemicellulose has higher potential digestibility than the other cell wall components, its degradation was not maximized because it concentrated in the primary wall, and no research results has been provided that the removal of hemicelluloses enhanced the digestibility. In order to improve the digestibility and nutrition value of air-dried corn stalk, and to develop a convenient and practical straw feed processing technology, experiments were carried out as follows: 1) Corn stalk was fermented at 60℃ in a feed fermentation machine for 5 days, after the moisture content of which was adjusted to 60%, and hemicellulose-degrading microflora WDC2 was inoculated in them; 2) Lactic acid bacteria community S FC-2 was cultivated in a fermentation tank, the working volume of which was 30 L; 3) Culture broth of SFC-2 was sprayed evenly on the corn stalk being partially degraded, at the rate of 1:1 (m/v) to produce fermented straw feed. In this study, the feasibility of bioconversion of straw as forage by dividing the fermentation into lignocellulose decomposition of corn stalk and malolactic fermentation of lactic acid bacteria, was discussed from the nutriology and the molecular ecology. The results indicated that after 5 days high-temperature fermentation, the degradation rates of cellulose, hemicelluloses and lignin were 5.36%, 18.83% and 3.29%, respectively, and in vitro digestibility of dry matter, neutral detergent fiber and acid detergent fiber improved by 13.94%, 22.56% and 21.12%, respectively. In addition, dry matter, crude protein and water soluble carbohydrate content, as well as in vitro degradation rate showed that the quality of products was stable during the continuous fermentation. The results of PCR-DGGE indicated that the diversity of microorganisms in the decomposed straw was very abundant, however, no pathogenic bacteria was detected. Meanwhile, during the continuous fermentation of lactic acid bacteria, the microbial composition of the lactic acid bacteria community, OD600 and pH value of the culture broth were all stable. However, lactic acid and ethanol content were decreased and acetic acid was increased as the cultivate time. Which indicated that the period of continuous fermentation should be controlled in 10 days for more lactic acid and less acetic acid. Compared with the untreated stalk, the crude protein content of the partially decomposed stalk mixed with the culture broth of SFC-2 increased by 36.17%. Twelve Nanyang cattles were used as experimental animal to determinate their feed intake on the treated straw, the results showed that the dry matter intake increased by 21.71%, compared to the untreated treatment. In conclusion, by coupling lignocellulose decomposition of corn stalk and malolactic fermentation of lactic acid bacteria, both digestibility and nutritive value of corn stalk and dry matter intake of beef cattle on it were improved. [ABSTRACT FROM AUTHOR]