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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 cassava stem is found to be one of few crop residues containing starch (up to 42% of dry mass) that may be converted to fuel ethanol. The current study was to evaluate the influence of parameters genotype, growth location and harvest time on cassava stem starch contents and yields as well as consequences in ethanol production (non-cellulosic process), based on 180 samples from a full factorial design experiment (3 varieties × 3 locations × 5 harvest times) in Guangxi, China. The potential utilization of stem starch and soluble sugar that varied 14–42% and 3–12.1% of dry mass, respectively, can correspond to an increase of 26% in ethanol production compared to that produced by roots only. The cassava stem starch content was significantly affected by all three studied parameters and location had the largest effect followed by variety and harvest time, while the stem starch yield was significantly affected by location only. The starch and soluble sugar content were significantly correlated with soil properties, e.g., soil pH and organic carbon, S and P contents. A general and positive correlation was also found between the stem and root starch, suggesting a promising potential of using stem starch without reducing root starch production. [ABSTRACT FROM AUTHOR]

This study investigated the shifts of bacterial and archaea diversity suffering the organic load shocks during the start-up. To demonstrate the effects of organic load shock, six reactors was operated in different OLR for 31 days. The community was analyzed using denaturing gradient gel electrophoresis (DGGE) and quantitative PCR. Findings revealed that bacteria diversity was the poorest and archaea quantity was the fewest when suffering OLR shock. MST and MSC were found to the more vulnerable methanogenic archaea groups during organic overloading. Our results explained why gradually increasing OLR is good for favoring the growth of an active biofilm and reactor successful startup quickly during the start-up from the perspective of microbial. [ABSTRACT FROM AUTHOR]

The objective of the present study is to assess the effect of the total solids (TS) content on the digestion performance, methanogenic pathways, and economic evaluation of anaerobic co-digestion with dairy manure and maize stover. The results showed that the cumulative methane yields decreased with increasing TS content, which was consistent with the maximum methane production rate and hydrolysis rate. The pH, alkalinity, soluble chemical oxygen demand, ammonium nitrogen, and volatile fatty acid content increased with increasing TS content. Analysis of the microbial community showed that the abundance of Methanosaeta decreased and Methanosarcina increased with increasing TS content, which led to the succession of the methanogenesis pathway from the acetoclastic pathway to the mixotrophic and hydrogenotrophic pathways. Results of the economic analysis indicated that the profitability of AD system increased with increasing TS content, resulting in more solid digestate being produced under the analysis conditions. [Display omitted] • TS content influences methane yield and volumetric methane productivity. • The succession from Methanosaeta to Methanosarcina with increasing TS content. • Increasing the TS content increases the net present value of anaerobic co-digestion. • The solid digestate determines the net present value of anaerobic co-digestion. • 14% TS is recommended for co-digestion with dairy manure and maize straw. [ABSTRACT FROM AUTHOR]

Abstract: The effect of temperature on the functionality of microbial community structure in a low temperature, anaerobic fixed-bed reactor was studied by decreasing the operating temperature from 18°C to 5°C. The reactor was productive within 20days and produced stable methane content in biogas (above 77%) throughout the trial period. At 17°C and 15°C, chemical oxygen demand (COD) removal efficiency and biogas production of reactor were significantly reduced. These might be temperature thresholds when fixed-bed reactors are operated under low temperatures. The methanogen community composition was analyzed using 16S rRNA gene clone library screening and quantitative PCR. At low ambient temperatures, Methanomicrobiales were dominant methanogens, and they preferentially adhered to the carbon fiber carrier. The results indicated that 16S rRNA levels of Methanomicrobiales and Methanosaetaceae in adhering sludge were higher than in deposited sludge, and they all contributed to the efficient performance of the fixed-bed reactor at low operating temperatures. [Copyright &y& Elsevier]

[Display omitted] • Fluid shear as a novel force was effective in driving biomass pretreatment reactions. • 90% of lignin and hemicellulose in biomass could be separated by fluid shearing. • Glucose yield via enzymatic hydrolysis tripled after fluid-shear pretreatment. • The obtained lignin kept a structure similar to that of native lignin. • Mechanism of biomass pretreatment by fluid shearing was preliminarily revealed. Pretreatment is the initial stage of lignocellulosic biorefinery process, but is limited by the time-consuming processes, harsh conditions and/or undesirable products. Herein, a mild (<60 °C) and highly efficient pretreatment strategy is developed. The novel mechanocatalytical reaction system driven by fluid shear force helps to exfoliate cellulose from lignocellulose, and the heat generated by the shear process can be used to precipitate and recover the dissolved cellulose from the precooled NaOH/urea solution. The regenerated cellulose shows satisfying crystal structure (cellulose II), significantly decreased crystallinity and nearly tripled enzymolysis glucose yield. Almost 90% of lignin and hemicellulose could be rapidly separated. The separated lignin shows a nearly native structure with 64% β-O-4 linkage, which is even higher than the ball-milling lignin (60%). This research provides a theoretical guidance for the mild pretreatment of lignocellulosic biomass, which will push the application of mechanocatalytical reaction system in biorefinery processes on a large scale. [ABSTRACT FROM AUTHOR]

In pursuit of low-carbon development, the production of diverse functional materials from renewable resources, especially lignocellulosic biomass, is of vital importance. Lignin is a major component of lignocellulose, and it is nature's only true high-volume aromatic polymer, which has the advantages of biodegradability, biocompatibility, and low acquisition cost. After modification by a variety of physicochemical strategies, it can be applied as an alternative to basic industrial materials, including polyurethanes, phenolic, and epoxy resins, which stands comparably to conventional synthetic polymers in terms of both performance and reduced cost. To further unlock the potential of lignin, an alluring opportunity is the exploitation of lignin for high-value materials, especially nanomaterials, that find extensive applications in energy and environment areas. This review provides a systematic summary and perspective of research that has been devoted to lignin transformation to high-value materials, ranging from industrially well-established engineering materials to the recently emerged nanomaterials that were used for energy and environment applications. Latest cutting-edge innovations on lignin modification, controlled depolymerization, and assembly during the last five years are summarized. Structure-function relationships of lignin materials in terms of their specific applications are analyzed. Furthermore, challenges and future opportunities for lignin conversion to high-value materials are also provided. We wish this review will stimulate further advances in lignin based high-value materials, and promote "waste" into "wealth". • Lignin-based materials are the way of high-value utilization of biomass. • The development of lignin chemistry is reviewed in this paper. • The modification methods of lignin are summarized. • The application of lignin-based polymer materials is evaluated. • Lignin-based nanomaterials and lithium battery materials are summarized. [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]

[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]

Cassava ( Manihot esculenta Crantz) stems, being waste residues after harvesting starchy roots, are a potential biofuel resource. However high concentrations of ash and elements Cl, K, etc. in the stems may cause severe deposition, corrosion and particle emissions, in addition to slagging during combustion. This study tests washing by water as a pretreatment to reduce the problems. A 3-level full factorial designed experiment was conducted with washing time (< 1800 s) and temperature (20–40 °C) as factors and fuel characteristics as responses. The effect of milling particle size was also examined in a supplementary experiment. After washing, the net calorific value of the biomass tended to be higher, though not significant. Both washing time and temperature increased C but decreased H, while N and S content decreased with time only. A short washing of 50 s decreased the ash content by approximately 50% and Cl around 75%, followed by K and P that decreased to 50% after 5 min. Smaller milling size resulted in a larger amount of starch washed away, but no significant change in content of total ash and individual elements, except for Cl which was significantly higher in the smaller particles. The effect of washing on the ash composition is visualized in a ternary diagram, showing that the risk for slagging and fine particle emissions is reduced. A reduction in the risk of corrosion is also predicted as indicated by a relatively higher ratio of S/Cl and lower Cl/(K + Na). Thus, in addition to extraction of starch, the washing can also improve fuel quality of the residual biomass. [ABSTRACT FROM AUTHOR]

[Display omitted] • Illumination and photoactivated nanomaterials were employed for anaerobic digestion. • Incorporating Fe 3 O 4 into g-C 3 N 4 formed an excellent electron transfer mediator. • The highest methane enhancement (23%) was obtained under optimized conditions. • Photoelectrons improved the electron transfer efficiency of microorganisms. • Enhanced acetoclastic methanogenic pathway contributed to methane enhancement. This study proposes a novel anaerobic digestion (AD) strategy combining recyclable photoactivated nanomaterials with illumination to enhance electronic transfer for anaerobic microorganisms. Results showed that 7000 Lux illumination increased methane production yield and rate. Incorporating Fe 3 O 4 into graphite carbon nitride (g-C 3 N 4) created a recyclable Fe 3 O 4 /g-C 3 N 4 (FG) nanocomposite with improved light absorption, conductivity, redox properties, and methane promotion. The highest methane yield from corn straw was achieved with 7000 Lux and 1.5 g/L FG nanocomposite, 22.6% higher than the dark control. The AD system exhibited increased adenosine triphosphate content, improved redox performance, reduced electron transfer resistance, and higher photocurrent intensity. These improvements bolstered the microorganisms and key genes involved in hydrolysis and acidification, which in turn optimized the acetoclastic pathway. Furthermore, this strategy promoted microorganisms associated with direct interspecies electron transfer, fostering a favorable environment for methanogenic activities, paving the way for future anaerobic reactor developments. [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]

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 composite microbial system of MC1 was used to degrade corn stalk in order to determine properties of the degraded products as well as bacterial composition of MC1. Results indicated that the pH of the fermentation broth was typical of lignocellulose degradation by MC1, decreasing in the early phase and increasing in later stages of the degradation. The microbial biomass peaked on the day 3 after degradation. The MC1 efficiently degraded the corn stalk by nearly 70% during which its cellulose content decreased by 71.2%, hemicellulose by 76.5% and lignin by 24.6%. The content of water-soluble carbohydrates (WSC) in the fermentation broth increased progressively during the first three days, and decreased thereafter, suggesting an accumulation of WSC in the early phase of the degradation process. Total levels of various volatile products peaked in the third day after degradation, and 7 types of volatile products were detected in the fermentation broth. These were ethanol, acetic acid, 1,2-ethanediol, propanoic acid, butanoic acid, 3-methyl-butanoic acid and glycerine. Six major compounds were quantitatively analysed and the contents of each compound were ethanol (0.584 g/L), acetic acid (0.735 g/L), 1,2-ethanediol (0.772 g/L), propanoic acid (0.026 g/L), butanoic acid (0.018 g/L) and glycerine (4.203 g/L). Characterization of bacterial cells collected from the culture solution, based on 16S rDNA PCR-DGGE analysis of DNAs, showed that the composition of bacterial community in MC1 coincided basically with observations from previous studies. This indicated that the structure of MC1 is very stable during degradation of different lignocellulose materials. [Copyright &y& Elsevier]

The development of a highly active and robust catalyst for the conversion of lignin, the largest volume of renewable aromatic resource in nature, to value-added aromatics is of great importance in sustainable chemistry. However, the condensation of lignin depolymerization intermediates into recalcitrant macromolecules restricts high yields of desired products, and this remains a great challenge in lignin valorization. Here, a serious of bifunctional Ru–ZnO/SBA-15 catalysts were synthesized for lignin conversion to aromatics. Roles of Ru and ZnO in these catalysts for lignin conversion were in-depth analyzed. The effect of the ratio of Ru to ZnO was studied. Other reaction conditions including temperature and time were systematically optimized. More than 51.3% yields of aromatics were obtained over Ru–10ZnO/SBA-15 at 240 °C for 4 h. Structure-activity relationship research of the catalyst revealed that the high yield of product could be attributed to the following three reasons: 1) the Lewis acidic sites on Ru/SBA-15 are significantly improved after ZnO modification, and thus promotes the C–O bond cleavage; 2) the oxophilic ZnO is beneficial to absorb the substrate and reaction intermediates, and therefore enhances the hydrodeoxygenation activity of the adjacent Ru; 3). The interaction between Zn and Ru in Ru–ZnO/SBA-15 changes Ru electronic properties and leads to the formation of highly active catalytic sites with high electron density. These results indicated that the bifunctional Ru–ZnO/SBA-15 catalyst with high catalytic activity could be a good choice for lignin conversion to high-yield aromatics. [Display omitted] [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]

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]

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]

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] • Mild pretreatments for near-complete saccharification of desirable lignocelluloses. • Integrated green-like biomass pretreatments to achieve maximum cellulosic ethanol. • Green-like pretreatments selectable for generation of nanomaterials and nanocarbon. • Distinct pretreatment mechanisms accounting for biomass recalcitrance reduction. • A novel strategy for cost-effective biofuels and functional materials at high value. Lignocellulose represents the most abundant carbon-capturing substance that is convertible for biofuels and bioproduction. Although biomass pretreatments have been broadly applied to reduce lignocellulose recalcitrance for enhanced enzymatic saccharification, they mostly require strong conditions with potential secondary waste release. By classifying all major types of pretreatments that have been recently conducted with different sources of lignocellulose substrates, this study sorted out their distinct roles for wall polymer extraction and destruction, leading to the optimal pretreatments evaluated for cost-effective biomass enzymatic saccharification to maximize biofuel production. Notably, all undigestible lignocellulose residues are also aimed for effective conversion into value-added bioproduction. Meanwhile, desired pretreatments were proposed for the generation of highly-valuable nanomaterials such as cellulose nanocrystals, lignin nanoparticles, functional wood, carbon dots, porous and graphitic nanocarbons. Therefore, this article has proposed a novel strategy that integrates cost-effective and green-like pretreatments with desirable lignocellulose substrates for a full lignocellulose utilization with zero-biomass-waste liberation. [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]

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]

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]

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]

Highlights: [•] Stepwise increase of OLR concentration for four anaerobic reactors impact ability and threshold. [•] Fixed-bed anaerobic reactor biological parameter dynamics using quantitative methods. [•] Main bacteria functional groups identified as bacteroidetes bactericum and uncultured chloroflexi bacterium. [•] Main archaea functional groups identified as methanomicrobiales. [ABSTRACT FROM AUTHOR]

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

[Display omitted] • Anaerobic digestion by-products were used to pretreated corn straw. • Methane production was improved by 50.97% after CO 2 -liquid digestate pretreatment. • The dense structure of straw could be effectively destroyed after pretreatment. • Pretreatment at 170 ℃ hindered methane production due to formation of inhibitors. • Mechanism behind CO 2 -liquid digestate pretreatment was elucidated. The development of biogas projects feed by lignocellulosic biomass has been constrained by the high cost of pre- and post-treatment. In this study, a novel strategy for pretreatment by using two by-products, i.e., CO 2 and liquid digestate (LD), generated from anaerobic digestion (AD) was developed to overcome these shortcomings. Results showed that corn straw pretreated in LD pressurized under 1 Mpa CO 2 at 55 ℃ resulted in increased glucose and xylose contents and a 9.80% decrease in cellulose crystallinity. After 45 days of AD conversion, the methane yield increased by 50.97% compared with untreated straw. However, pretreatment in LD pressurized under 1 Mpa CO 2 at 170 ℃ produced 5-hydroxymethylfurfural and furfural, which led to a decrease in methane production from the straw in the subsequent AD conversion. The alteration of the microbial community in the pretreated slurry at 55 °C was another potential contributor to the enhanced performance of AD. [ABSTRACT FROM AUTHOR]

The biomethane production from lignocellulose via anaerobic digestion has always suffered from low carbon conversion rate, due to the stubborn structure of lignocellulose and the inefficiency of the current anaerobic digestion systems. The integrated two-phase anaerobic reactor can form a highly efficient anaerobic digestion system with an upper acidogenic phase and a lower methanogenic phase. However, the acidogenic phase can be overaccelerated, leading to acidification failure of the whole digestion system. In this study, the acidogenesis liquid digestate (ALD) generated from the acidogenic phase was applied to impregnate corn straw coupled with disc refining (DR) to enhance biomethane production by forming a thorough and stable integrated two-phase anaerobic system. The concentration of volatile fatty acids in the acidogenic phase is adjusted by this pretreatment technology to approximately match the efficiency of methanogenic bacteria in the methanogenic phase. The acetic acid in ALD was proved to be an effective acid to swell lignocellulose and improved the performance of the acid impregnation coupled with disc refining (AIDR) pretreatment. A 47.13% higher biomethane yield was obtained from corn straw after AIDR pretreatment. Moreover, energy conversion efficiency and economic analysis indicated this anaerobic digestion process with AIDR pretreatment had a $ 21.06 ton−1 higher net profit than that without any pretreatment. This novel anaerobic digestion process creates a synergistic processing technology that integrates biomass pretreatment with a two-phase anaerobic digestion system, resulting in destroying the compact structure of lignocellulose, enhancing biomethane production efficiency, and improving the economic competitiveness of biomass conversion to biomethane. [Display omitted] • A strategy integrated pretreatment and two-phase anaerobic digestion was unveiled. • Acid impregnation coupled with disc refining was used to pretreat corn straw. • Biomethane production was improved by 47.13% after employing the novel strategy. • Mechanism for improving biomethane production by the novel strategy was elucidated. [ABSTRACT FROM AUTHOR]

[Display omitted] Ca(OH) 2 induces a controlled-release catalytic system for the efficient conversion of high-concentration glucose to relatively high yield of lactic acid under mild conditions. • High concentration of glucose was converted to high yield of lactic acid (LA). • Ca(OH) 2 formed a controlled release catalytic system for glucose conversion to LA. • Ba(OH) 2 played a synergistic effect with Ca(OH) 2 in glucose conversion to LA. • Over 40 % yield of LA was obtained from high concentration of glucose (>0.5 M). The catalytic conversion of carbohydrate to platform chemicals, e.g. lactic acid (LA), is the key to unlock the potential of biomass. In this study, we report that the combination of Ba(OH) 2 and Ca(OH) 2 can efficiently catalyse high-concentration (> 0.5 M) of glucose to relatively high yield of LA (> 40 %) under mild conditions (60 °C). Both glucose conversion and LA yield were sensitive to the pH of the catalytic system. A high loading of Ba(OH) 2 led to a high initial pH of the reaction solution, resulting in serious side reactions. While, a low loading of Ba(OH) 2 led to a quike decrease of OH− and Ba2+ both of which were continuously consumpted by the formed LA. The combination of Ca(OH) 2 with Ba(OH) 2 could significantly improve LA yield, since Ca(OH) 2 , with limited solubility, could act as a controlled-release catalyst for the real-time supply of OH− and Ca2+. OH− was indispensable for glucose isomerization to fructose as well as for fructose retro-aldol reaction to C 3 intermediates. Ca2+ could combine with LA to form stable calcium lactate, liberating Ba2+ to catalyse the conversion of C 3 intermediates to LA. Under the preliminary optimized reaction conditions, the yield of LA could be reached to 42.55 % and 38.32 % from 0.5 M and 1 M glucose, respectively. This catalytic system has advantages of mild reaction condition, short reaction time, and capable of conversion of high-concentration substrates, enabling it with a great potential for practical applications. [ABSTRACT FROM AUTHOR]

The selection of a suitable catalytic system for ligninOX reductive depolymerization, with a careful consideration of the reaction conditions and catalyst compositions, is crucial to successful implementation of the oxidation–reduction strategy for lignin conversion. • 43% yields of aromatics were obtained from ligninOX, while only 11% were from lignin. • High hydrogen pressure is not beneficial to the conversion of ligninOX. • Catalysts with high hydrogenation activities tend to reconvert ligninOX to lignin. • LigninOX conversion pathways under different conditions were determined. Recently, a two-step strategy involving oxidative activation and reductive depolymerization becomes very popular for lignin conversion. However, both positive and negative results are obtained, and the detailed mechanism is still unknown. This study thoroughly investigated the effects of several key factors, including hydrogen pressure, reaction temperature, and catalyst compositions, on the reductive conversion of oxidized lignin (ligninOX) to aromatics. For lignin oxidative activation, FT-IR, 2D NMR, and TG/DTG were used to prove that hydroxyl groups at lignin side chains had been successfully oxidized to carbonyl groups by AcNH-TEMPO/HNO 3 /HCl system. For ligninOX reductive conversion, pathways and mechanisms were explored, and the applicable conditions of this strategy were determined. Under relative moderate hydrogen pressure (e.g. 2 Mpa) over metal–acid catalysts, e.g. Ru/γ-Al 2 O 3 combined with Hf(OTf) 4), an obvious advantage of ligninOX conversion was found. Yield of valuable product from ligninOX was 42.98% which was much higher than that (10.99%) from unoxidized lignin. While, under high hydrogen pressure or promoted by catalysts with high hydrogenation activities, ligninOX tended to be reconverted to original lignin structures with loss of its conversion advantage. 2-phenoxyacetophenone as a ligninOX model was used to verify this speculation and to predict reaction pathways over different catalytic systems. These results proved that a catalyst with both hydrogenolysis and hydrolysis activity was essential for efficient ligninOX depolymerization. [ABSTRACT FROM AUTHOR]

The mechanisms and enhancing effects of different biochar loadings on the digesters receiving low and high excess (or anaerobic) sludge loadings were thoroughly examined in the present study. This was done to explore an efficient method for converting excess sludge to anaerobic sludge. Biochar had an obvious effect on the anaerobic digestion of excess sludge but not on the anaerobic sludge. When the amount of biochar added was equivalent to 100% of the sludge TS, the cumulative methane yields of anaerobic digestion inoculated with small and large amounts of excess sludge were respectively 30.2 and 1.7 times that of those without biochar. The number of methanogens in the digesters that received small and large inoculations of excess sludge with 100% biochar, were respectively 105.4% and 20.6% higher than those without biochar. The biochar enhanced the systems performance because it selectively enriched the Trichococcus and Methanomicrobiales tightly attach to it. This enhanced the synergy and overall activity of the system by promoting biofilm development. Ultimately, the integration of 100% biochar and excess sludge can be used as a substitute for anaerobic sludge as an inoculum by giving similar overall performance. Biochar enhanced excess sludge can be used as an attractive alternative to anaerobic sludge for anaerobic digestion. Unlabelled Image • This study provided a novel method to cultivate excess sludge to anaerobic sludge. • 100% biochar and excess sludge can substitute anaerobic sludge as inoculum. • Biochar selectively enriched Trichococcus and Methanomicrobiales in excess sludge. [ABSTRACT FROM AUTHOR]

• Different N-doped activated carbons (N-ACs) were prepared from leather wastes. • Structure-function relationships of N-ACs for adsorption and energy storage were studied. • KOH activation resulted in high surface area and pyridinic N in N-ACs. • Surface area and pyridinic N played key roles in adsorption and energy storage. The fabrication of nitrogen-doped activated carbons (N-ACs) from leather solid wastes (LSW), a huge underutilized bioresource, by different activation methods was investigated. N-AC prepared by KOH activation (named KNAC) exhibited superior physical and chemical properties with much higher BET surface area (2247 m2 g−1) and more abundant hierarchical micropores than those activated by nano-CaCO 3 (CNAC) or by direct carbonization (NNAC). KOH activation decreased the total nitrogen content in KNAC, but it increased the ratio of surface nitrogen species. KOH activation also significantly promoted the conversion of nitrogen species in the carbon material to pyridinic N. Potential applications of the prepared N-ACs were evaluated, and they were tested as adsorbents to remove phenols from water and as the anodes of lithium batteries. The high surface area, abundant micropores, and plentiful surface pyridinic N guaranteed KNAC a superior nitrogen-doped activated carbon that could serve as an excellent adsorbent to remove phenols (282 mg/g) from waste water as well as an outstanding electrode material with a high and stable charge/discharge capacity (533.54 mAh g−1 after 150th cycle). The strategy of LSW conversion to versatile N-ACs turns waste into treasure and could promote the sustainable development of our society. [ABSTRACT FROM AUTHOR]

The catalytic conversion of lignocellulosic biomass to aviation fuel is identified as a key strategy to alleviate high operating costs and serious environmental pollution caused by using petroleum-derived fuels. Aviation fuel with stringent end-use requirements consists of several specific hydrocarbon compositions, and the conversion of lignocellulose to aviation fuel is more challenging than that to other fuels. In this study, the latest cutting-edge innovations on the catalytic conversion of lignocellulose to aviation fuel was summarized. Promising routes for the catalytic conversion of cellulose, hemicellulose, lignin, and their derivatives were elaborated, with emphasis on those catalytic approaches including depolymerization of C–O bonds, formation/rearrangement of C–C bonds, and hydrodeoxygenation (HDO) removal of oxygen-containing functional groups. Innovations on reaction mechanism exploration, catalyst development, solvent screening, and reaction condition optimization were introduced. It revealed that a 100% biomass-derived aviation fuel could be produced by catalytic methods with the full utilization of all lignocellulosic compositions. Straight and branched paraffins in aviation-fuel range could be generated from cellulose and hemicellulose via various intermediates including 5-hydroxymethylfurfural (HMF), furfural, levulinic acid, and γ−valerolactone. The degradation and HDO conversion of lignin could yield aromatics and cycloparaffins in aviation range. The development of hydrothermal stable catalysts for the controllable formation of C–C bonds among platform chemicals from carbohydrates as well as for the efficient HDO conversion of fuel precursors is particularly important. Image 1 • All compositions in lignocellulose can be catalytically converted to aviation fuel. • A 100% biomass-derived aviation fuel can be produced by catalytic methods. • Paraffins for aviation fuel can be produced from cellulose and hemicellulose. • Cycloalkanes and aromatics for aviation fuel can be generated from lignin. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass holds great potential in the production of renewable energy such as biomethane via anaerobic digestion. However, the digestion performance of the three main compositions of lignocellulose during biogas production is not well understood so far, and this has greatly hindered the efficient use of biomass by anaerobic fermentation. In this study, the anaerobic digestion performances of glucose, cellulose, hemicellulose, lignin, and their combinations in biomethane production were investigated. The biomethane production potential of cellulose was higher than that of hemicellulose and lignin, and high crystallinity cellulose shows adverse impact on methane production. Hemicellulose had a fast hydrolysis rate and was easier to be digested than cellulose, but it also easily led to excessive acids accumulation. Lignin showed a very limited potential in biomethane production. The co-fermentation of cellulose and hemicellulose could promote cellulose conversion and eliminate the over-acidification of hemicellulose, resulting in efficient and stable biogas production. The co-fermentation of lignin with cellulose and hemicellulose showed an inhibition in biomethane production, and lignin with different structure and sulfur content had different degree of inhibition. This study provides insights into the mechanisms of anaerobic fermentation of lignocellulosic biomass, and paves the way for the better use of biomass. • Cellulose showed the highest methane production potential than hemicellulose and lignin. • Reducing the crystallinity of cellulose was beneficial to biomethane production. • Hemicellulose and glucose were easily led to rancidity when were digested alone. • Lignin containing sulfur had a more serious inhibition on anaerobic digestion than that without sulfur. [ABSTRACT FROM AUTHOR]