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• This study included 314 intact Chinese urban families with preschool-aged children. • Latent profile analysis was used to find distinct patterns of family relationships. • Mothers and fathers reported marital, coparenting, and parent-child relationships. • Four family relationship profiles emerged based on reports of dyadic relationships. • Child social and behavioral competence differed across the four profiles. Guided by family systems theory, this study examined how distinct patterns of family relationships were related to child social and behavioral competence among 314 intact Chinese urban families with preschool-aged children. Four distinct patterns of family relationships were identified using latent profile analysis: unbalanced, compensatory, moderately cohesive , and highly cohesive families. In unbalanced families, mothers perceived their marital, coparenting, and parent-child relationships as low in quality, yet fathers perceived them to have moderate quality. Compensatory families exhibited poor marital and coparenting relationships but high mother-child closeness. Highly cohesive families displayed high quality across all dyadic relationships, while moderately cohesive families showed moderate relationship quality. Children from highly cohesive families had the highest social and behavioral competence. Children from moderately cohesive families exhibited better social skills and fewer problem behaviors compared to unbalanced families, but were on par with those from compensatory families. No difference in social skills was found between children from unbalanced and compensatory families, but children in the former group displayed more problem behaviors. The findings shed light on the unique family relationship configurations among Chinese urban families with preschool-aged children. They highlight the value of using individual-centered approaches to understand holistic family relationship patterns from a family systems perspective. The findings also underscore the need to develop interventions tailored to families according to their unique family relationship profiles. [ABSTRACT FROM AUTHOR]

• Establish efficient acetogenesis system for anaerobic co-digestion. • Leachate in HSAD is more suitable for pig manure digestate. • Highest concentration of T-VFAs was found to be 45.4 g/L with reflux ratio of 32:1. • The reflux frequency of 8 times/d can achieve better hydrolysis and acidification effect. In this study, food waste and maize straw were used as feedstock, and the two-phase high-solid anaerobic digestion (TP-HSAD) technology was used to optimize the process parameters of leachate reflux in acid-production stage. Results indicated that compared with other waste activated sludge, pig manure digestate (PM) as leachate can achieve better hydrolysis and acidification effect. The increase of leachate reflux ratio can shorten the fermentation time of the acid-producing stage and increase the fermentation efficiency. When the reflux ratio was 32:1, peak concentration of volatile fatty acids (VFAs) was 45.4 g/L and the volatile solids (VS) removal rate was 61.7%. Reflux frequency has minimal effect on the concentration of VFAs and the degree of degradation of VS, but a higher reflux frequency will prolong the reaction time of acid-production stage. When PM is used as reflux leachate, the HSAD reactor can improve the hydrolysis and acidification of the anaerobic fermentation. [ABSTRACT FROM AUTHOR]

To optimize the energy yield (EY) of food waste (FW) via hydrothermal carbonization (HTC), a response surface method was applied. Hydrochars and spent liquor were further conducted to evaluate their characterization and anaerobic digestion potential. Results found that optimal parameters for HTC of FW were suggested as temperature of 260 °C, reaction time of 4 h and moisture of 80%, with higher EY of 66.1%. Higher heating value, good combustion quality, lower H/C and O/C ratios indicated that hydrochar could be utilized as a safe solid fuel. Biochemical methane potential (BMP) experiment showed that spent liquor and hydrochars could be used as feedstocks for anaerobic digestion. Interestingly, hydrochars added in the spent liquor could promote the specific methane yield, which was 2.53 times higher than no addition of hydrochars. The finding of this study could provide useful information for HTC of FW and the utilization of hydrochars and spent liquor. [ABSTRACT FROM AUTHOR]

In this study, an integrated process was developed to produce methane and high-quality bio-briquette (BB) using corn straw (CS) through high-solid anaerobic digestion (HS-AD). CS was anaerobic digested by using a leach bed reactor at four leachate recirculation strategies. After digesting for 28 days, highest methane yield of 179.6 mL/g-VS, which was corresponded to energy production of 5.55 MJ/kg-CS, was obtained at a higher initial recirculation rate of 32 L-leachate per day. Compared with bio-briquette manufactured from raw CS and lignite, the compressive, immersion and falling strength properties of bio-briquette made from AD-treated CS (solid digestate) and lignite were significantly improved. A preferred BB can be obtained with side compressive strength of 863.8 ± 10.8 N and calorific value of 20.21 MJ/kg-BB. The finding of this study indicated that the integrated process could be an alternative way to produce methane and high-quality BB with CS. [ABSTRACT FROM AUTHOR]

Efficient hydrolysis of pectic materials to sugars requires the synergistic action of endo- and exo-polygalacturonases. Two novel polygalacturonases (exo- Te PG28a and endo- Te PG28b) were identified in Talaromyces leycettanus JCM12802, overexpressed in Pichia pastoris , and characterized in this report. The specific activities of Te PG28a and Te PG28b towards polygalacturonic acid were 280 ± 9 and 25,900 ± 502 U/mg, respectively. Both enzymes exhibited optimal activities at pH 3.5 and retained highly stable over a broad pH range of 2.0–7.0. Distinct from most fungal polygalacturonases that have low temperature optima, Te PG28a and Te PG28b were optimally active at 70 °C. When treated the grape juice with the enzyme combination (the unit ratio of Te PG28a: Te PG28b was 1:4), higher pectin-degrading efficiency (up to 140%) was achieved, and light transmittance was improved from 14% to 82%. These favorable enzymatic properties make Te PG28a and Te PG28b attractive for the applications in the juice industry. [ABSTRACT FROM AUTHOR]

To obtain high calorific biogas via anaerobic digestion without additional upgrading equipment, a two-phase pressurized biofilm system was built up, including a conventional continuously stirred tank reactor and a pressurized biofilm anaerobic reactor (PBAR). Four different pressure levels (0.3, 0.6, 1.0 and 1.7 MPa) were applied to the PBAR in sequence, with the organic loading rate maintained at 3.1 g-COD/L/d. Biogas production, gas composition, process stability parameters were measured. Results showed that with the pressure increasing from 0.3 MPa to 1.7 MPa, the pH value decreased from 7.22 ± 0.19 to 6.98 ± 0.05, the COD removal decreased from 93.0 ± 0.9% to 79.7 ± 1.2% and the methane content increased from 80.5 ± 1.5% to 90.8 ± 0.8%. Biogas with higher calorific value of 36.2 MJ/m 3 was obtained at a pressure of 1.7 MPa. Pressure showed a significant effect on biogas production and gas quality in methanogenesis reactor. [ABSTRACT FROM AUTHOR]

Online imaging requires that the reconstruction of current frame only depends on the previous frames, and real time imaging is the desired case. In this work, we propose a novel scheme for real time dynamic magnetic resonance imaging (dMRI) reconstruction. Different from previous methods, the reconstructions of the second frame to the last frame are independent in our scheme, which only require the first frame as the reference image. Therefore, this scheme can be naturally implemented in parallel. After the first frame is reconstructed, all the later frames can be processed as soon as the k-space data are acquired. As an extension of the conventional spatial total variation, a new online model called dynamic total variation is used to exploit the sparsity on both spatial and temporal domains in dMRI. In real time dMRI, each frame is required to be reconstructed very fast. We then design a novel reweighted least squares algorithm to solve the challenging problem. Motivated by the special structure of partial Fourier transform in sparse MRI, this algorithm is accelerated by the preconditioned conjugate gradient descent method. The proposed method is compared with 4 state-of-the-art online and offline methods on two in-vivo cardiac dMRI datasets. The experimental results show that our method significantly outperforms previous online methods, and is comparable to the offline methods in terms of reconstruction accuracy. [ABSTRACT FROM AUTHOR]

Approximately 400 000 t of DDTs/HCHs-contaminated soil (CS) needed to be co-processed in a cement kiln with a time limitation of 2 y. A new pre-processing facility with a “drying, grinding and DDTs/HCHs vaporizing” ability was equipped to meet the technical requirements for processing cement raw meal and the environmental standards for stack emissions. And the bottom of the precalciner with high temperatures >1000 °C was chosen as the CS feeding point for co-processing, which has rarely been reported. To assess the environmental performance of CS pre- and co-processing technologies, according to the local regulation, a test burn was performed by independent and accredited institutes systematically for determination of the clinker quality, kiln stack gas emissions and destruction efficiency of the pollutant. The results demonstrated that the clinker was of high quality and not adversely affected by CS co-processing. Stack emissions were all below the limits set by Chinese standards. Particularly, PCDD/PCDF emissions ranged from 0.0023 to 0.0085 ng I-TEQ Nm −3 . The less toxic OCDD was the peak congener for CS co-processing procedure, while the most toxic congeners (i.e. 2,3,7,8-TeCDD, 1,2,3,7,8-PeCDD and 2,3,4,7,8-PeCDD) remained in a minor proportion. Destruction and removal efficiency (DRE) and destruction efficiency (DE) of the kiln system were better than 99.9999% and 99.99%, respectively, at the highest CS feeding rate during normal production. To guarantee the environmental performance of the system the quarterly stack gas emission was also monitored during the whole period. And all of the results can meet the national standards requirements. [ABSTRACT FROM AUTHOR]

The cement production process may be a potential source of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, “dioxins”), due to the widespread distribution of dioxins and potential precursors in raw materials and to conditions favorable to de novo formation in the heat exchangers. The emission, gas/particle distribution, and mass balance of PCDD/Fs were investigated at a typical state-of-the-art Chinese cement kiln. Input and output inventories were established for three campaigns, including two in normal operation and one while co-processing refuse derived fuel (RDF). Sample analysis from stack gas, cement kiln dust, raw meal, fly dust and clinker for the analysis of PCDD/Fs were reported in this study. Dioxins were also analyzed at various positions in the pre-heater, presenting an adsorption–desorption circulation process of PCDD/Fs. The over-all dioxin mass balance was negative, indicating that this cement kiln is not a source but a sink process of dioxins. [ABSTRACT FROM AUTHOR]

Highlights: [•] Co-digestion of CM and CS were investigated under batch and continuous conditions. [•] CSTR showed stable methane yield of 223±7mL/gVSadded at OLR of 4gVS/L/d. [•] Post-digestion of digestate gave extra energy yield up to 2.6MJ/kgVSadded. [•] Pyrolysis of digestate could produce valuable pyrolysis gas with LCV of 10.9MJ/m3. [ABSTRACT FROM AUTHOR]

Highlights: [•] Methane production potential, BD, and kinetics of various substrates were compared. [•] Both of elemental and organic analysis could be used to calculate the TMY and BD. [•] 15% VS of lignin was a critical point in AD of lignocellulosic and manure wastes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Synergistic effects were found in CS:CM ratios of 3:1 and 1:1. [•] In W-AD and HSS-AD, highest methane yields were obtained at CS:CM ratio of 3:1. [•] Highest volumetric productivity of 14.2L/L was found in SS-AD at CS:CM of 1:1. [•] VFA/TA value of 0.4 was a more important criterion than NH3-N or FA concentration. [ABSTRACT FROM AUTHOR]

Due to the diversity of microbiota and the high complexity of their interactions that mediate biogas production, a detailed understanding of the microbiota is essential for the overall stability and performance of the anaerobic digestion (AD) process. This study evaluated the microbial taxonomy, metabolism, function, and genetic differences in 14 full-scale biogas reactors and laboratory reactors operating under various conditions in China. This is the first known study of the microbial ecology of AD at food waste (FW) at a regional scale based on multi-omics (16S rRNA gene amplicon sequencing, metagenomics, and proteomics). Temperature significantly affected the bacterial and archaeal community structure (R2 = 0.996, P = 0.001; R2 = 0.846, P < 0.002) and total inorganic carbon(TIC) slightly changed the microbial structure (R2 = 0.532, P = 0.005; R2 = 0.349, P = 0.016). The Wood-Ljungdahl coupled with hydrogenotrophic methanogenic pathways were dominant in the thermophilic reactors, where the acs , met F, coo A, mer, mch and ftr genes were 10.1-, 2.8-, 16.2-, 1.74-, 4.15-, 1.04-folds of the mesophilic reactors (P < 0.01). However, acetoclastic and methylotrophic methanogenesis was the primary pathway in the mesophilic reactors, where the ack A, pta , cdh and mta genes were 2.2-, 3.2-, 14.3-, 1.88-folds of the thermophilic group (P < 0.01). Finally, the Wilcoxon rank-sum test was applied to explain the cause of the temperature affecting AD microbial activities. The findings have deepened the understanding of the effect of temperature on AD microbial ecosystems and are expected to guide the construction and management of full-scale FW biogas plants. • Performance overview of full-scale AD reactors by various omics. • The mesophilic and thermophilic reactors are dominated by different methane metabolism pathways. • The genomics research test explains the cause of the temperature affecting AD microbial activities. [ABSTRACT FROM AUTHOR]

Abstract: This paper aims to study the co-processing of POPs (DDTs and HCHs) contaminated soil as an alternative raw material for sustainable clinker production. The milling system designed solely to contaminated soil was introduced with hot air (250-350°C) to dry water and simultaneously vaporize POPs. The gaseous POPs was directly destroyed in the precalciner, while the milled soil with partly removal of organic pollutants was homogenized in a sealed silo and then took part in clinker sintering. According to the experiment results the moisture content reached an average of 0.4%, and the average 200μm and 80μm sieve residues were 1.9% and 19.0% respectively after grinding. Furthermore, clinkers and emission which were produced with contaminated soil as SiO2 substitute were monitored. There was no DDTs and HCHs residue both in clinkers and in exhaust, which demonstrated the success of eliminating organic pollutants and utilizing the soil as alternative SiO2 materials in our cement plant. [Copyright &y& Elsevier]

Abstract: This paper tentatively studies dioxins formation and suppression mechanisms in RDF ▪ (Refuse derived fuel)cement kiln co-processing by analyzing the dioxin concentrations of solid and gas samples of the critical points where dioxins are more likely to form in kiln system based on cement kiln co-processing technical characteristics and a few of recognized dioxins formation mechanisms and factors. Testing results show that trace amount of dioxins could be detected in all of the solid and gas samples from main points of preheater. The raw mill and bag filter play a key role on dioxins absorption and capture from gas, absorption rate of both reaches up to 91.6%.Dionxins concentration of emission is below the international standard limit of 0.1ng TEQ/Nm3. ▪ Materials with high heat value such as plastics, paper, wood, textile, etc. derived from raw MSW [Copyright &y& Elsevier]

Abstract: With the increasing of sludge emissions and people''s increasing demand for better dwelling environment, resource utilization of sludge receives much concern in recent years. Currently, the co-processing of sludge in cement kiln has been considered as a sustainable way to dispose sludge in Japan as well as Europe and the United States. Huaxin has begun the co-processing of sludge in cement kiln since 2008. So far, 65000 tons of sludge has been successfully disposed. This paper focus on 3 ways of co-processing sludge in cement kiln through certain project examples. [Copyright &y& Elsevier]

Abstract: In September 2009, 350 tons of Obsolete Pesticides (OP) including 160 tons of DDT (dichlorodiphenyltrichloroethane, a Persistent Organic Pollutant, POP) has been successfully disposed as a business case in Huaxin Jinmao Cement Company at Suzhou, China. Disposal of the Ops was carried out in a New Suspension Pre-calciner (NSP) kiln with clinker capacity of 3’200 tons per day. Before disposal campaign, a comprehensive trial burn scheme designed beforehand was conducted to find out the optimized operation parameters such as feeding rates and to get insight of Destruction Removal Efficiency (DRE) of DDT and as well as the emission level of Dioxins/Furans. In the trial, DDT feeding rates ranged from 150kg/h, 500kg/h, 1’000kg/h and up to 2’000kg/h at maximum. The results revealed that DRE of 99.99999% and emission of Dioxins/Furans well below 0.1 ng TEQ/Nm3 were found out when 2 tons of DDT preparations of 30% chlorine content in the highest among the series are fed to the kiln. [Copyright &y& Elsevier]

[Display omitted] • Syngas biomethanation was completed under higher CO concentration (40%) and higher processing capacity (12.6 m3/m3/d). • Biomethanation with syngas as the only carbon source can operate continuously and stably for a long time. • The syngas biomethanation path is shown by combination of theoretical calculation and practice. Syngas from pyrolysis/gasification process is a mixture of CO, CO 2 and H 2 , which could be converted to CH 4 , so called syngas biomethanation. Its development is obstructed due to the low productivity and CO inhibition. The aim of this study was to demonstrate the feasibility of using syngas as the only carbon source containing high CO concentration (40%) for biomethanation. Lab-scale thermophilic bioreactor inoculated with anaerobic sludge was operated continuously for over 900 h and the shift of microbial structure were investigated. Results showed that thermophilic condition was suitable for syngas biomethanation and the microbes could adapt to high CO concentration. Higher processing capacity of 12.6 m3/m3/d was found and volumetric methane yield of 2.97 m3/m3/d was observed. These findings could strengthen the theoretical basis of syngas biomethanation and support its industrialization in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • Changing properties to explore biochar on methane production of anaerobic digestion. • Surface area and ordered graphitization do not influence methane production. • Aromatic functional groups have a major effect on electron transfer. • Uniform dispersion provides stable environment for microorganisms. This study evaluated the effects of bio-based carbon materials on methane production by anaerobic digestion. The results showed that biochar and hydrochar can promote cumulative methane yield by 15% to 29%. However, there was no statistical significance (p > 0.05) between hydrochar and biochar produced at different temperature on methane production. 16S rRNA gene sequencing and bioinformatics analysis showed that biochar and hydrochar enriched microorganism that might participate in direct interspecies electron transfer (DIET) such as Pseudomonadaceae , Bacillaceae , and Clostridiaceae. The the surface properties of the modified biochar were characterized with BET, Raman, FTIR and XPS. Bio-based carbon materials with uniform dispersion provided a stable environment for the DIET of microorganisms and electrons are transferred through aromatic functional groups on the surface of materials. This study reveals bio-based carbon materials surface properties on methane production in anaerobic digestion and provides a new approach to recycling spent coffee grounds. [ABSTRACT FROM AUTHOR]

The stability of corn stover high-solid anaerobic digestion is affected by the low efficiency of solid-liquid mass transfer while the total volatile fatty acids accumulation often occurs during the process leading to acidification of the system and influencing the functional anaerobic microbial community of the system. Therefore, the problems of slow start and unstable process often occurred. In this study, the effects of different leachate spraying working conditions on total volatile fatty acids and microbial community structure were studied. Three batch tests of three 45 L leach bed reactors (LBRs) were conducted with continuously domesticated leachate and operated at different process (total solids of 15–30%, spray time of 2–6 min and spray interval of 3–8 h) to determine the relative influence of biotic and abiotic factors on microbial community structure and methanogenesis. Consequently, that within a certain range of parameter setting, biotic effects please an important role than abiotic effects, revealing microbiological mediation of methanogenesis. Higher methane yield of 188.2 mL/g VS was obtained under the conditions of 30%TS, spray time of 4 min in the first two weeks and 2 min in the third week, and spray interval of 6 h. The sludge reacting for two months was used as inoculum. After two months' cultivation, the seeding sludge became stability and increased activity, and the microbial colony richness and diversity tend to be stable regardless of the operational parameters. This study enriches the understandings of biotic and abiotic factors of microbial community structure and methanogenesis in high-solid anaerobic digestion. Image 1 • The spray of leachate helps rapid start-up and stable operation of the process. • 188.2 mL/g VS of methane yield was achieved under specific operating conditions. • Biotic effect pleases an important role than abiotic effect. • Long-term AD can optimize the microbial community in leachate. [ABSTRACT FROM AUTHOR]

• The gas-liquid mass transfer influenced more than temperature. • Product quality can be improved by promoting the H 2 /CO ratio. • Some 80% methane content can be reached after addition of Fe2+, Co2+ and Ni2+. • Trace elements addition did not affect the microbial community structure. Synthesis gas (Syngas) biomethanation is an environmentally friendly technology for fuel calorific value improvement. However, the slow mass transfer and poor product quality limit its development. In this study, the effects of temperature, hydrogen/carbon monoxide (H 2 /CO) ratio and trace element addition on simulated syngas biomethanation were investigated in three batches of experiments. Results showed that (1) the temperature influenced little on the quality of produced biogas; (2) the methane content in the biogas production were 66.37 ± 4.04%, 70.61 ± 6.06% and 73.35 ± 2.39% respectively with the H 2 /CO ratio of 3:1, 4:1 and 5:1; (3) after the addition of Fe, Co and Ni elements, the biogas quality was significantly improved (methane content was 79.76 ± 7.35%), but the microbial community structure did not change. This experiment provided a guidance for improving the biogas production performance of syngas biomethanation. [ABSTRACT FROM AUTHOR]

Monophenols form humic acids (HA) through polycondensation reaction in the anaerobic digestion (AD) process, which will inhibit AD process. Currently, metal ions are the option for in-situ relieving HA inhibition during AD, but excess metal ions are harmful to microorganisms. In this study, carbon quantum dots (CQDs, a non-metallic materials) were proposed to relieve HA inhibition in-situ. We investigated the effect of HA on AD acidification and methanation stage, and synthesized CQDs using sodium citrate (s-CQDs) and p-phenylenediamine (p-CQDs) as precursors to relieve the HA inhibition in-situ. Results showed that s-CQDs (3.0 g/L) significantly increased the cumulative CH 4 yield from AD of ethanol with 1.0 g/L HA (1.9 times higher than that without s-CQDs). Microbiological analysis indicated the most dominant methanogen was Methanosarcinaceae , with richness of 89.7%. Compared to the HA inhibition system, the relative abundance of Methanosarcinaceae increased by 87.5%. The analysis of interaction mechanism between CQDs and HA indicated that s-CQDs has an in-situ binding effect to HA by reacting with -OH, C C, and -COOH. This study provided a novel means for in-situ relieving HA inhibition, and illustrated the interaction mechanism between CQDs and HA, which will guide the application in production of bioenergy. [Display omitted] • CQDs was able to relieve the HA inhibition on microorganisms in-situ. • 3.0 g/L s-CQDs increased the cumulative CH 4 yield of ethanol AD with 1.0 g/L HA to 350.0 ± 5.0 mL/g VS. • 3.0 g/L s-CQDs significantly promoted the abundance of Methanosarcinaceae to reached 89.7%. • s-CQDs has a binding effect to HA by reacting with -OH, C C, and -COOH. [ABSTRACT FROM AUTHOR]

Biochar modification is an effective approach to enhance its ability to promote anaerobic digestion (AD). Focusing on the physical properties of biochar, the impact of different particle sizes of biochar on AD of food waste (FW) at high organic loading rate (OLR) was investigated. Four biochar with different sizes (40–200 mesh) were prepared and used in AD systems at OLR 30 g VS/L. The research results found that biochar with a volume particle size of 102 μm (RBC-P140) had top-performance in promoting cumulative methane production, increasing by 13.20% compared to the control group. The analysis results of the variety in volatile acids and alkalinity in the system did not show a correlation with the size of biochar, but small size has the potential to improve the environmental tolerance of the system to high acidity. Microbial community analysis showed that the abundance of aceticlastic methanogen and the composition of zoogloea were optimized through relatively small-sized biochar. Through revealing the effect of biochar particle size on AD system at high OLR, this work provided theoretical guidance for regulating fermentation systems using biochar. [Display omitted] • Four different sizes (40–200 mesh) of biochar were prepared via ball milling method. • The biochar with a volume particle size of 102 μm (RBC-P140) enhanced 13.2% methane accumulation production. • The small-sized biochar improved the system's tolerance to acidity condition. • The small-sized biochar optimized the aceticlastic methanogen abundance and the composition of zoogloea. [ABSTRACT FROM AUTHOR]

Exploring the complex mechanism of anaerobic digestion with hydrothermal pretreatment (HTAD) for biomass efficiently and optimising the reaction conditions are critical to improving the performance of methane production. This study used H 2 O automated machine learning (AutoML) for comprehensive prediction, analysis, and targeted optimization of the HTAD system. An IterativeImputer system for data filling was constructed. The comparison of three basic regressors showed that random forest performed optimally for filling (R2 > 0.95). The gradient boosting machine (GBM) model was searched by H 2 O AutoML to show optimal performance in prediction (R2 > 0.96). The software was developed based on the GBM model, and two prediction schemes were devised. The generalization error of the software was less than 10%. The Shapley Additive exPlanations value showed that solid to liquid ratio, hydrothermal pretreatment (HT) temperature, and particle size have greater potential for improving cumulative methane production (CMP). A Bayesian-HTAD optimization strategy was devised, using the Bayesian optimization to directionally optimize the reaction conditions, and performing experiments to validate the results. The experimental results showed that the CMP was significantly improved by 51.63%. Compared to the response surface methodology, the Bayesian optimization relatively achieved a 2.21–2.50 times greater effect. Mechanism analyses targeting the experiments showed that HT was conducive to improving the relative abundance of Sphaerochaeta, Methanosaeta, and Methanosarcina. This research achieved accurate prediction and targeted optimization for the HTAD system and proposed multiple filling, prediction, and optimization strategies, which are expected to provide an AutoML optimization paradigm for anaerobic digestion in the future. [Display omitted] • Built a machine learning framework for data filling and automated search prediction. • Developed software based on gradient boosting machine with prediction errors of 6.33%. • The solid to liquid ratio influences cumulative methane production most critically. • Bayesian optimization enhanced methane production by 51.63% over the control group. • The Methanosarcina and high energy production pathways increased after optimization. [ABSTRACT FROM AUTHOR]

The biological methanation of H 2 and CO 2 is beneficial to industrial upgrading of anaerobic digestion, efficient utilization of surplus electricity and H 2 , energy storage and peak regulation, as well as CO 2 emission reduction. Applying well-developed continuous stirred tank reactor (CSTR) for methanation is economical and convenient. In this study, the biological methanation process was conducted in a CSTR for 151 days. H 2 and CO 2 were the substrates and no external additives were added. The maximum CH 4 yield was 355.8 mL/(L·d) at a CH 4 content of 94.8%, and after double loading shock and recovery, the highest CH 4 content of 99.5% was achieved at a CH 4 yield of 249.3 mL/(L·d). The reactor could run stably at a pH around 8.5, and CO 2 flow was adjusted for pH control. As the experiment proceeded, hydrogenotrophic methanogens were enriched, and the microbial community in different stages had significant succession. Acetate was accumulated after loading shock, causing proportion increase of Natronincola , a genus of homoacetogen. Pseudomonas , an acetate-consuming and electroactive bacterium, was dominant in later period. Methanosarcina and Methanoculleus were in the majority of archaea, accounting for 80%–90%. In stable phase, 72.8% of the input CO 2 flowed to CH 4 , 17.8% consumed in rising pH, and 8.9% increased VFAs and microbes. As a complex system with competition and synergy among different reactions, the scientific design and regulation of the system to achieve an efficient methanation process is an important direction for future research. [Display omitted] • Biological methanation of H 2 /CO 2 lasted 151 days in a CSTR with no nutrients added. • Maximum CH 4 yield was 355.8 mL/(L·d) at a CH 4 content of 94.8%. • Maximum CH 4 content was 99.5% at a CH 4 yield of 249.3 mL/(L·d). • Reactor ran stably at a pH around 8.5, and CO 2 flow was adjusted for pH control. • Succession of microbial community was analyzed and carbon flow was calculated. [ABSTRACT FROM AUTHOR]

The electrochemical properties of biochar may be the key factor to promote anaerobic digestion, which has attracted extensive attention. However, the mechanism and the role of the electrochemical properties of biochar are remaining unclear. In this study, biochar with different electrochemical properties was prepared by pyrolysis at different temperatures (BC300/600/900) and oxidation or reduction modification (O/RBC300/600/900). The biochar was added as an additive to promote methanogenic performance of anaerobic digesters of glucose and food waste. In both anaerobic digestion systems, the cumulative methane production of food waste increased by 42.07% and the maximum methane production rate of glucose enhanced by 17.80% after BC900 treatment. RBC600 was inferior to BC900, but superior to BC600. Microbiological analysis suggests that biochar enriched the relative abundant Synergistia and Methanoculleus. This is conducive to the establishment of the direct interspecies electrons transfer (DIET). Results from correlation analysis, principal component analysis and machine learning confirmed that both of the electron donating capacities (EDC) and electrical conductivity (EC) are dominated factors affecting the cumulative methane yield. Through the analysis of electrochemical properties and preparation process of biochar, the results showed that the pyrolysis temperature increases and the content of phenolic hydroxyl decreases under medium temperature of biochar, which was beneficial to the methane production. This study found the key factors of the electrochemical properties of biochar in anaerobic digestion, provided new insights for the mechanism of biochar promoting anaerobic digestion and proposed novel directions for the preparation of biochar. [Display omitted] • BC900 increased the cumulative methane production of food waste by 42.07%. • BC900 increased the maximum methane production rate of glucose by 17.80%. • RBC600 was inferior to BC900, but superior to BC600 in anaerobic methanation. • Electron donating capacities and electrical conductivity of biochar are keys factors. • Higher pyrolysis temperature and lower phenolic hydroxyl of biochar are beneficial. [ABSTRACT FROM AUTHOR]

• Effects of metal oxide coated electrodes on EPT and WAS-FW Co-AF were investigated. • Electrogenerated RCS and 1O 2 enhanced WAS-FW disintegration and biodegradability. • RCS and 1O 2 both enriched acidogenic bacteria, while RCS inhibited methanogens. Electrochemical pretreatment (EPT) has shown to be superior in improving acidogenic co-fermentation (Co-AF) of waste activated sludge (WAS) and food waste (FW) for volatile fatty acids (VFAs). However, the influence of EPT electrode materials on the production of electrogenerated oxidants (such as singlet oxygen (1O 2) and reactive chlorine species (RCS)), as well as their effects on properties of electrodes, the microbial community structure and functional enzymes remain unclear. Therefore, this study investigated the effects of various metal oxide coated electrodes (i.e., Ti/PbO 2 , Ti/Ta 2 O 5 -IrO 2 , Ti/SnO 2 -RuO 2 , and Ti/IrO 2 -RuO 2) on EPT and subsequent Co-AF of WAS-FW. The results showed that EPT with Ti/PbO 2 , Ti/Ta 2 O 5 -IrO 2 , Ti/SnO 2 -RuO 2 and Ti/IrO 2 -RuO 2 electrodes generated 165.3–848.2 mg Cl 2 /L of RCS and 5.643 × 1011–3.311 × 1012 spins/mm3 of 1O 2 , which significantly enhanced the solubilization and biodegradability of WAS-FW by 106.4 %–233.6 % and 177.3 %–481.8 %, respectively. Especially with Ti/Ta 2 O 5 -IrO 2 as the electrode material, an appropriate residual RCS (2.0–10.4 mg Cl 2 /L) remained in Co-AF step, resulted in hydrolytic and acidogenic bacteria (e.g., Prevotella_7, accounting for 78.9 %) gradually become dominant rather than methanogens (e.g., Methanolinea and Methanothrix) due to their different tolerance to residual RCS. Meanwhile, the functional gene abundances of hydrolytic and acidogenic enzymes increased, while the methanogenic enzymes deceased. Consequently, this reactor produced the highest VFAs up to 545.5 ± 36.0 mg COD/g VS, which was 101.8 % higher than that of the Control (without EPT). Finally, the economic analysis and confirmatory experiments further proved the benefits of WAS-FW Co-AF with EPT. [Display omitted] [ABSTRACT FROM AUTHOR]

Kitchen waste (KW) when disposed properly we can still utilize its nutrients and energy through appropriate recycling process. KW-hydrochar is the major product from hydrothermal carbonization (HTC) which is regarded as a promising method in waste treatment. However, the studies which focus more about the factors in regulating the properties of hydrochar and its further influence were limited. Here, HTC temperature (195 °C, 225°Cand 255 °C) and retention time (1.5h, 4.5h, 9.0h and 12.0h) were chosen as the controlling factors to observe the influence in the surface property. Moreover, it is the first time to research the role of KW-hydrochar chemical structures in co-digestion to regulate the biogas and methane production. Meanwhile, KW-hydrochar had no further thermal treatment and its own gas production was taken into account. The results revealed that KW-hydrochar gained at 225 °C in 4.5h affected the increase in methane yield up to 19% in co-digestion. Not only the surface morphology but also some functional groups acted as key factors on this study. Redox active moieties and amine could affect the methanogenesis process in varying degrees. In the end, a sustainable pathway of "waste to clean energy" by using KW-hydrochar as an additive was proposed. Image 1 • KW-derived hydrochar used as additive in co-digestion could promote biogas yield. • KW-hydrochar obtained in 4.5h (225 °C) could realize increasing CH 4 yield up to 19%. • Some redox active moieties may have an active effect on methanogenesis process. • Functional group of amine may negatively affect the methane production upgrading. • KW-hydrochar could improve waste to clean energy conversion efficiency. [ABSTRACT FROM AUTHOR]

The global energy shortage and resource waste are becoming more and more prominent. With the massive production of food waste, anaerobic digestion through food waste is a key way to solve the resource shortage problem. To better study the anaerobic digestion process of food waste, a novel production prediction model of food waste process based on a long short-term memory (LSTM) method integrating the synthetic minority oversampling technique (SMOTE) based data expansion method is proposed. The minority class samples are analyzed and extended using the SMOTE, which are used as inputs of the LSTM. Then, the production prediction model can be built to reduce the influence of a few samples on the prediction model. Finally, the proposed method is applied in the methane production prediction model of actual food waste process plants. Compared with the back Propagation (BP) neural network, the extreme learning machine (ELM), the radial basis function (RBF) neural network, the support vector machine (SVM), the LSTM and the convolutional neural network (CNN), the experimental results have verified the higher applicability of the proposed method for the methane prediction result including an accuracy of 99.75% and the highest R2 of 0.9913 with minimal training and generalization errors. Moreover, by analyzing the prediction result and the actual methane production, the proposed method can effectively guide and timely adjustment the feed allocation for increasing the methane production per m3 of feed by 25.77%. [Display omitted] • Novel LSTM integrating SMOTE is proposed. • Production prediction model of food waste processes for resources saving is built. • The feed allocation can be effectively adjusted for increasing the methane production. • The methane production per m3 of feed can be increased by 25.77%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tree-based machine learning revealed the role of biochar in anaerobic digestion. • The best tree-based model achieved R2 values of 0.84 and 0.69 for the test datasets. • The most important features and their best range were analyzed by machine learning. • The software predicted anaerobic digestion performance with errors of below 20%. The ideal conditions for anaerobic digestion experiments with biochar addition are challenging to thoroughly study due to different experimental purposes. Therefore, three tree-based machine learning models were developed to depict the intricate connection between biochar properties and anaerobic digestion. For the methane yield and maximum methane production rate, the gradient boosting decision tree produced R2 values of 0.84 and 0.69, respectively. According to feature analysis, digestion time and particle size had a substantial impact on the methane yield and production rate, respectively. When particle sizes were in the range of 0.3–0.5 mm and the specific surface area was approximately 290 m2/g, corresponding to a range of O content (>31%) and biochar addition (>20 g/L), the maximum promotion of methane yield and maximum methane production rate were attained. Therefore, this study presents new insights into the effects of biochar on anaerobic digestion through tree-based machine learning. [ABSTRACT FROM AUTHOR]

Co-digestion of lignocellulosic biomass and animal manure is a common approach to increase the efficiency of methane production, but the niche differentiation and microbial metabolism of the anaerobic digestion (AD) process remain to be determined. To further explore the effect of the interaction between species and their compositional niches, the methane yield and resulting microbial community were determined by machine learning (ML) and 16S rRNA gene sequencing in mixed high-solid anaerobic digestion (HS-AD) with spray-enhanced conditions to explore the internal relationship between physical and chemical parameters and microorganisms and to speculate on the enhancement mechanism of co-digestion. In this study, three ML models (extreme learning machine (ELM), artificial neural network (ANN), and random forest (RF)) were applied to analyse and model AD of dry fermentation. The results showed that the best prediction model, based on ELM, could best predict the material biogas production in this experiment with a mean absolute error (MAE/10) of 0.678 and a coefficient of determination (R2) of 0.9574, whereas the characteristic percentage analysis of the RF model showed that butyric acid, acetic acid, and pH had three important influences on the biogas production values. Meanwhile, the results of high-throughput 16S rRNA gene sequencing and PICRUSt showed that the addition of manure containing ammonia nitrogen improved the metabolism of amino acids, enriched species capable of Clostridiales and Methanosarcinales , promoted the electronic transfer of nutrient metabolism, and thus enhanced AD. Moreover, the co-occurrence network showed that seven niches were differentiated within the HS-AD system to reduce the shock of ammonia nitrogen for methanogens. Overall, microbial analysis and ML can help understand the dynamic processes of methanogenic microorganisms and predict biogas production for the efficient operation of AD. [Display omitted] • PICRUSt showed that the addition of manure containing ammonia nitrogen enhanced archaeal methanogenesis. • ELM is the most accurate model for predicting biogas production. • The characteristic factors influencing biogas production can be derived from RF. • Network analysis shows seven niches have differentiated within the HS-AD system. [ABSTRACT FROM AUTHOR]

Organic fraction of municipal solid waste (OFMSW) has high volatile solid and moisture content, which is mainly treated via anaerobic digestion (AD). Since the composition of OFMSW is complicated and inconstant, it is difficult to maintain the AD process stable and effective. In this study, a novel two-stage AD system, including a tank-type acidogenic phase and a fixed-bed methanogenic phase, was implemented for OFMSW treatment to demonstrate the feasibility of the two-stage configuration. Results showed that 84% of potential CH 4 yield was achieved and the methane content reached 77.83% on average in methanogenic phase. The acetoclastic methanogens, Methanosaeta and Methanosarcina , which can participate in direct interspecies electron transfer, were the dominant genera in solid digestate and the biofilm. The hydrogenotrophic methanogens, Methanospirillum and Methanoculleus , accounted for high proportions in liquid digestate. Our study provides a novel approach to treat OFMSW with less water consumption, high stability and efficiency. [Display omitted] • AD with acidogenic solid stage and fixed-bed methanogenic liquid stage was applied. • CH 4 content in methanogenic phase averaged in 77.83%. • Two-stage solid-liquid AD configuration achieved 84% of the BMP. • Methanosaeta and Methanosarcina were dominant in solid digestate and biofilm. • Methanospirillum and Methanoculleus accounted high proportions in liquid digestate. [ABSTRACT FROM AUTHOR]

The pretreatment of wheat straw with potassium hydroxide (KOH) at ambient temperature (20 °C) was investigated. The pretreatment effects on chemical composition and physical structures, and subsequent enzymatic hydrolysis and anaerobic digestion were evaluated. Wheat straw at 10% total solids (TS) was treated with KOH solution for 24 h at a wide range of KOH loadings from 2% to 50% (w/w dry basis). Higher KOH loading resulted in higher lignin reduction from the straw and chemical oxygen demand (COD) in the resulting black liquor. Maximum lignin reduction of 54.7% was observed at 50% KOH loading. In comparison to untreated straw, specific hydrolysis yields achieved 14.0–92.3% over the range of 2–50% KOH loading, and methane yields increased 16.7–77.5% for KOH loadings of 10–50%, respectively. Accounting for losses during pretreatment, 20% KOH loading resulted in maximum overall reducing sugar yield and methane yield and therefore is the recommended loading for pretreatment under these conditions. [ABSTRACT FROM AUTHOR]

Getting over recalcitrance of lignocellulose is effective way to fuel production from lignocellulosic biomass. In current work, different pretreatments were applied to enhance the digestibility of corn stover (CS). Results showed that steam explosion (SE)-treated CS produced maximal methane yield (223.2 mL/g vs ) at 1.2 MPa for 10 min, which was 55.2% more than untreated (143.8 mL/g vs ). Whereas 1.5% KOH-treated CS produced maximum methane yield of 208.6 mL/g vs , and significantly ( α < 0.05) improved 45.1% with respect to untreated. Sequent pretreatment of potassium hydroxide and steam explosion (SPPE) (1.5% KOH-1.2 MPa, 10 min) achieved a very significant ( α < 0.01) improvement (80.0%) of methane yield (258.8 mL/g vs ) compared with untreated CS. Methane production could be well explained by the first-order and modified Gompertz models. Besides, SEM, FTIR, and XRD analyses validated structural changes of CS after SPPE. SPPE might be a promising method to pretreat CS in the future AD industry. [ABSTRACT FROM AUTHOR]

With the development of the world economy and society, the living standards of residents have been improved, along with a large amount of food waste and carbon dioxide (CO 2) emissions. In the face of global warming and energy shortages, food waste can be used as high-value bio-energy raw materials which is also an effective way to reduce CO 2 emissions. Therefore, this paper proposes a novel anaerobic digestion and CO 2 emissions efficiency analysis based on a Slacks-Based Measure integrating Data Envelopment Analysis (SBM-DEA) model to evaluate and optimize the process structure of anaerobic treatment of food waste. The total feed volume and the discharge volume of liquid digestate are taken as inputs, and the total methane (CH 4) production volume is taken as the desirable output and CO 2 emissions are regarded as the undesirable output to build the biogas production and CO 2 emissions evaluation model during the anaerobic digestion process. Finally, the proposed method is used in the actual anaerobic digestion process. The results show that the overall efficiency values in January, April, May, and June in 2020 are higher than those in other months. At the same time, due to the optimal allocation of slack variables of inputs and undesirable outputs, the efficiency values of other inefficient anaerobic digestion days can be improved. [Display omitted] • Novel anaerobic digestion and CO 2 emissions efficiency analysis method is proposed. • Inefficient and efficient anaerobic digestion days of food waste treatment can be effectively distinguished. • CO 2 emissions and CH 4 production optimization of food waste treatment are obtained. • Production efficiency of inefficient production configuration can be improved. [ABSTRACT FROM AUTHOR]

• Injected H 2 was 100% consumed within short period. • Hydrogen biomethanation performed superior at thermophilic temperature. • Remaining CO 2 of<10% cannot be removed by increasing H 2 content and stirring intensity. In-situ hydrogen biomethanation is a promising technology to upgrade biogas. The efficiency of biomethanation relies on various parameters, e.g. gas supplement, temperature and hydrogenotrophic methanogens. Therefore, it is important to investigate the characteristics of in-situ hydrogen biomethanation under different conditions. In this study, two experiments (lasted for 91 days and 105 days) were carried out to investigate the impacts of feeding gas and operating conditions on performances of reactors and microorganisms. During the whole experiment, no obvious fluctuation of pH and limitation of gas–liquid mass transfer were found. Results showed that the hydrogenotrophic methanogenesis performed better at thermophilic condition, while the dominant archaea genera at mesophilic and thermophilic temperature was determined to be Methanobacterium and Methanothermobacter , respectively. The highest CH 4 content (greater than 90%) was obtained when H 2 and CO 2 was feeding at ratio of 4:1 and Methanothermobacter was dominant. These findings can provide useful information for promoting hydrogen biomethanation. [ABSTRACT FROM AUTHOR]