Trichloromethane is often used as a chemical inhibitor to pretreat the inoculum to improve hydrogen yield in dark fermentation. In this study, five different doses of trichloromethane were used for ...methanogenic inhibition of methanogenic microbial community operating in stable (inoculum A) and anaerobic microbial community in natural environment (lake bottom slit, inoculum B). High concentrations of trichloromethane inhibited the activity of microbial community in the reactors and hindered the production of hydrogen and methane. At the same time, it would greatly reduce the pH, causing it to fall below the threshold of suitable hydrogen yield. In turn, ethanol-type fermentation was triggered, and the ethanol content of the system increased with increasing concentration of trichloromethane addition. The comprehensive assessment concluded that a 0.10% (v/v) trichloromethane concentration gave the best hydrogen yield performance in both inoculums. However, anaerobic microbial community in natural environment was able to produce hydrogen more efficiently than the operationally stable methanogenic microbial community. The highest cumulative hydrogen yield was 111.16, 34.36, and 72.76 mL/g VS in phase I (day 1–10), phase II (day 11–20), and the whole stage, respectively. In addition, the butyrate production in the reactor at this concentration was considerable, with an average yield of 21.3 g/L.
Graphical Abstract
•The range of proportions is lessened by considering C/N ratio and LCP composition.•The interaction of C/N ratio and LCP composition influence methane production.•Optimizing the C/N ratio and LCP ...composition can improve AD performance.
The anaerobic co-digestion (AcoD) of FWs produces variable methane yields, mainly due to variable carbon/nitrogen (C/N) ratio and proportions of lipids (L), carbohydrates (C), and proteins (P) in different FW samples. In this study, a significant interaction between C/N ratio and LCP composition was found and contributed to the differing trends between special (SMP) and theoretical methane production. The highest SMP of 595 mL CH4 gVS−1 occurred at C/N of 25 and LCP of 63.25:22.62:14.13, followed by 592 mL CH4 gVS−1 at C/N of 30 and LCP of 48.94:39.74:11.32, which also reflected their interaction. Attributing to their interactive effect on obtaining optimal process parameters and microbial community, the inhibition threshold of lipid as well as the methane yield was increased. Understanding the interaction between C/N ratio and LCP composition is an effective and promising way to obtain suitable mixture ratios of organic wastes under AcoD.
In order to promote China's biogas industry development, this paper comprehensively compared the biogas status and related policies between China and Europe and tried to find the shortage and ...potential implications. China has access to abundant biomass resources, with considerable biogas potential and an annual theoretical output of 73.6 billion m3. Household-based biogas digesters coexist with medium and large-scale biogas plants (MLBPs) in China. Although the number of MLBPs in China was almost two times higher than Europe, the annul biogas production yield was only half of those in Europe. In China, biogas is mainly used for heating and cooking, and its power generation capacity is far lower than that in Europe. Overall, biogas industry is more commercialized in Europe than China. In terms of biogas related policies, China has an advantage in quantity, but is weak in their implementation. Biogas related policies in China mainly focus on agricultural and rural development, while in Europe, they are aimed at increasing the utilization of renewable energy and reducing greenhouse gas emissions. In addition, policies in China are mostly filled with encouragement, lacking detailed subsidy schemes and modes, whereas in European countries are more targeted and scientific. Based on the dissimilarity of current status and the disparity in policies, a series of countermeasures and suggestions for the development of the Chinese biogas industry are presented.
•China's biomass sources have lower utilization rate compared to Europe.•Biogas industry in Europe is more industrialized and commercialized than in China.•The related-biogas policy framework of Europe is more mature and perfect.•European biogas policy provide valuable reference for China's biogas development.•China's biogas industry has great potential for development.
Metallic nanoparticles derived from biosynthesis are both cost-effective and biocompatible. In the present work,
Aspergillus niger
cell-free filtrate was used to biosynthesize gold nanoparticles ...(AuNPs) in one step, which served as the catalyst in the removal of multiple contaminants. The reaction solution was visually observed to be purple and had an UV–vis characteristic absorption peak near 540 nm, which supported the biosynthesis of AuNPs. To better understand biosynthesis, the influences of key factors such as precursor concentration, biomass amount, pH and temperature were examined. The biosynthetic AuNPs were subjected by DLS, zeta potential, XRD, TGA, XPS, TEM and FTIR measurements, respectively. The extracellular proteins from the cell-free filtrate were responsible for the reduction and stabilization of AuNPs. In particular, the catalytic mechanism and the reaction kinetics of novel AuNPs in degrading different types of contaminants were investigated. The moderate AuNPs could catalyze the complete degradation of nitro-aromatics and several dyes within 20 min. Especially to remove methyl orange and Congo red, biosynthetic AuNPs showed overwhelming catalytic performance with the rate constants of 0.283 min
−1
and 0.516 min
−1
. As a result, the nanoparticles synthesized by this facile and sustainable approach have considerable potential for pollution treatment.
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•Glucose fosters dominance of Clostridium_sensu_stricto_1, with 235.00 mL H2/gVS.•Starch leads to a diverse and stable microbial population, with 234.34 mL H2/gVS.•Oil favors ...fat-degrading Anaerovibrio, hindering H2 production, with 30.22 mL/gVS.•Propionate accumulation correlates with carbon source complexity.
This study investigated how glucose, starch, and rapeseed oil, three common food waste components with diverse molecular and physicochemical characteristics, influenced hydrogen production and microbial communities in dark fermentation under varying carbon/nitrogen (C/N) ratios. The results indicated that glucose and starch groups, significantly increased hydrogen yields to 235 mL H2/gVS (C/N = 40) and 234 mL H2/gVS (C/N = 40), respectively, while rapeseed oil, with a lower yield of 30 mL H2/gVS (C/N = 20), demonstrated a negative impact. Additionally, an accumulation of propionate was observed with increasing carbon source complexity, suggesting that simpler carbon sources favored hydrogen production and bacterial growth. Conversely, lipid-based materials required rigorous pre-treatment to mitigate their inhibitory effects on hydrogen generation. Overall, this study underscores the importance of carbon source selection, especially glucose and starch, for enhancing hydrogen production and microbial growth in dark fermentation, while highlighting the challenges posed by lipid-rich substrates that require intensive pre-treatment to optimize yields.
Promoting the biomass industry in China would provide significant ecological, economic, and societal benefits by ameliorating soil and groundwater pollution and providing a sustainable energy source. ...However, although there is great potential for expanding the biomass industry in China, it currently faces large obstacles, with respect to its utilization, low economic performance, and other limitations. This study conducts a comprehensive literature review on biomass utilization methods, and establishes a new recycling model that couples the use of anaerobic digestion (AD) and its byproducts with biochar. In the model, biomass waste is used for biogas and biochar production, and biogas residues are further cracked into biochar. Biochar is also used as an additive to modify the AD process and promote methane production. In addition to its single application, biochar is further used in combination with biogas slurry or residue as a soil conditioner to repair soil and promote the growth of crops. This circulation model differs from models in which biomass alone is used in biogas or biochar production, and it combines all processes to promote the use of biomass, increase its conversion efficiency and strength the applications of such processes in the agricultural sector. Previous reports have shown that each part of the model can play a positive role in improving overall efficiency. Therefore, the application of the combined circulation model would be beneficial in biomass utilization and as such is a promising method for promoting the sustainable development of energy and agriculture in China, while protecting the environment.
•Biomass waste is used for biogas and biochar production.•Biochar is effective to modify the AD process and promote methane production.•Biogas residues are further cracked into biochar.•Biochar combined with biogas slurry or residue can serve as a soil conditioner.•A new recycling model is established by coupling biochar with anaerobic digestion.
The modification of substrate concentration and acidification level in inoculum treatment can significantly enhance hydrogen production while reducing costs. Hydrogen production showed a significant ...variation with food waste (FW) concentration, ranging from 10 to 120 gVS/L. Insufficient acidity at lower FW concentrations of 10, 20, and 40 gVS/L limited hydrogen production to 9.14, 5.70, and 7.78 mL/gVS, respectively, hindering hydrogen-producing bacteria dominance. However, higher FW concentrations facilitated rapid and strong substrate acidification at fermentation onset, effectively inhibiting the non-hydrogen producing bacteria and leading to a vast hydrogen production capacity of 68.63–120.78 mL/gVS. Rapid and substantial FW acidification is vital for effective inoculum treatment, highlighting its crucial role in this study. The findings support the potential use of FW inoculum treatment in generating highly productive microbial communities for hydrogen production.
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•Acidification-based inoculum treatment of substrate enables cost-efficient H2 production.•Variation in hydrogen production observed based on food waste concentrations.•Limited acidity inhibits H2 production in low food waste concentration groups.•Rapid and strong acidification of substrate is crucial for successful inoculum pretreatment.•Inoculum treatment by food waste can generate productive microbial communities for H2 production.
Few studies have addressed how to blend wastes for anaerobic co-digestion. This study investigated the effects of waste sources on anaerobic co-digestion (AcoD) performance, by varying the quality of ...food wastes (FWs) from six sources in Xi'an region, China that were individually co-digested with pre-treated corn straw and cattle manure. These effects were analysed in terms of their volatile solid (VS) ratios, C/N ratios, and the chemical composition of the FWs. The results indicated that the VS ratios were not suitable as a common mixture method because the VS ratios at which the best methane potentials occurred differed significantly among the six FW groups. The C/N ratios within a 17-24 range resulted in better methane potentials when the FWs were co-digested with other wastes. Synergistic effects were found among the carbohydrates, proteins, and lipids of the FWs; however, the optimum ratios of these components could not be determined. Thus, the C/N ratio is recommended as a mixture method when co-digesting FWs with other organic wastes in selected region.
In order to mitigate the serious high-temperature corrosion problem caused by gaseous alkali metal salts on the heating surface of boilers, the adsorption effect of kaolinite for alkali metal vapor ...stood out among many silicon-aluminum-based adsorbents. To improve the adsorption capacity of kaolinite for alkali metal vapor, a novel multi-step modification method was proposed in this reported work. The multi-step modification method consisted of the following four steps, which were pre-intercalation, replacement intercalation, multiple intercalation, and exfoliation, and it was found that the multi-step modification method resulted in the increase of the particle size, the expansion of the interlayer spacing, and the expansion of the porosity structure of kaolinite. The physicochemical analyses showed that the multi-step modification method made it easier to dehydrate kaolinite to produce metakaolinite. In addition, it was found that the multi-step modification method led to the generation of a new crystalline phase of kaolinite, which was formed by the dehydration and condensation of methanol and AlOH groups. It also led to the pre-removal of some of the hydroxyl groups in kaolinite. The insoluble sodium loading capacity of the multi-step modified kaolinite was enhanced by 64.47% and the insoluble potassium loading capacity was enhanced by 29.68% under the adsorption condition of 850 °C for 45 min. Therefore, the multi-step modification method enhanced the alkali metal vapor adsorption capacity of raw kaolinite under high-temperature environment, which laid a certain foundation for subsequent research in this field.
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The effects of chemical composition (carbohydrates, lipids, and protein) on the anaerobic co-digestion performance of food wastes (FW) were investigated from the viewpoints of methane production, ...dynamic parameters, and microbial community structure. The results of this study showed that a notable gasification rate was positively correlated with the proportion of the composition. A T2 reactor, which consisted of 60% carbohydrates, 20% lipids, and 20% protein, held a higher gasification rate of 65.09% compared to other groups, while its process parameters showed some deficiency regarding the stability of digestion, especially for low biochemical methane potential (BMP), which was not beneficial for the actual practice. A T4 reactor, with a highest gasification rate of 70.68%, held the maximum BMP (497.44 mL/g VS). The stable chemical parameters achieved the optimal proportion, consisting of 40% carbohydrates, 40% lipids, and 20% protein. Furthermore, its microbial populations were rich and achieved a balance of the two main dominant communities of acetoclastic methanogens and hydrogenotrophic methanogens, whose relative abundance was close. It was obvious that interactive effects were caused by different proportional composition, which led to constantly changing chemical parameters and microbial community.
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