Anaerobic digestion is a promising alternative to disposal organic waste and co-digestion of mixed organic wastes has recently attracted more interest. This study investigated the effects of ...temperature and carbon-nitrogen (C/N) ratio on the performance of anaerobic co-digestion of dairy manure (DM), chicken manure (CM) and rice straw (RS). We found that increased temperature improved the methane potential, but the rate was reduced from mesophilic (30∼40°C) to thermophilic conditions (50∼60°C), due to the accumulation of ammonium nitrogen and free ammonia and the occurrence of ammonia inhibition. Significant ammonia inhibition was observed with a C/N ratio of 15 at 35°C and at a C/N ratio of 20 at 55°C. The increase of C/N ratios reduced the negative effects of ammonia and maximum methane potentials were achieved with C/N ratios of 25 and 30 at 35°C and 55°C, respectively. When temperature increased, an increase was required in the feed C/N ratio, in order to reduce the risk of ammonia inhibition. Our results revealed an interactive effect between temperature and C/N on digestion performance.
► Co-digestion of multi-substrates, dairy, chicken manure and wheat straw was conducted. ► Anaerobic co-digestion was optimized by feeding composition (DM/CM) and C/N ratio. ► Higher synergetic ...effect showed in mixed DM, CM and WS than single manure with WS. ► C/N ratios of 25:1 to 30:1 resulted in stable pH, low ammonium nitrogen and free NH3. ► Maximize methane potential realized with DM/CM of 40.3:59.7 and C/N of 27.2:1.
This study investigated the possibilities of improving methane yield from anaerobic digestion of multi-component substrates, using a mixture of dairy manure (DM), chicken manure (CM) and wheat straw (WS), based on optimized feeding composition and the C/N ratio. Co-digestion of DM, CM and WS performed better in methane potential than individual digestion. A larger synergetic effect in co-digestion of DM, CM and WS was found than in mixtures of single manures with WS. As the C/N ratio increased, methane potential initially increased and then declined. C/N ratios of 25:1 and 30:1 had better digestion performance with stable pH and low concentrations of total ammonium nitrogen and free NH3. Maximum methane potential was achieved with DM/CM of 40.3:59.7 and a C/N ratio of 27.2:1 after optimization using response surface methodology. The results suggested that better performance of anaerobic co-digestion can be fulfilled by optimizing feeding composition and the C/N ratio.
•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.
•Five different initial pHs were controlled in co-digestion of kitchen waste with cow manure.•The modified Gompertz equation was used to predict the potential of methane production.•The highest CH4 ...yield was achieved at initial pH of 7.5.
This study investigated the effects of different initial pH (6.0, 6.5, 7.0, 7.5 and 8.0) and uncontrolled initial pH (CK) on the lab-scale anaerobic co-digestion of kitchen waste (KW) with cow manure (CM). The variations of pH, alkalinity, volatile fatty acids (VFAs) and total ammonia nitrogen (NH4+–N) were analyzed. The modified Gompertz equation was used for selecting the optimal initial pH through comprehensive evaluation of methane production potential, degradation of volatile solids (VS), and lag-phase time. The results showed that CK and the fermentation with initial pH of 6.0 failed. The pH values of the rest treatments reached 7.7–7.9 with significantly increased methane production. The predicted lag-phase times of treatments with initial pH of 6.5 and 7.5 were 21 and 22days, which were 10days shorter than the treatments with initial pH of 7.0 and 8.0, respectively. The maximum methane production potential (8579mL) and VS degradation rate (179.8mL/g VS) were obtained when the initial pH was 7.5, which is recommended for co-digestion of KW and CM.
During anaerobic digestion (AD) process, process parameters e.g., VFA, pH, COD removal … and kinetic parameters e.g., hydrolysis rate, lag phase and methane production potential… are the important ...indicator for illustrating AD process performance, however, the AD process performance based on these parameters remains poorly understood. To estimate process performance focusing on initial pH and substrate composition, the effects of initial pH and swine manure to corn straw ratio on biogas production and these parameters and linkages of these parameters were analyzed. Also, the methane production was optimized. The results revealed that the maximum methane yield and methane production rate were obtained with initial pH 7.5 and SM/CS ratio of 70:30. Kinetic parameters are coupled with process parameters, especially for COD removal rate, VS degradation rate, VFA and pH. Hydrolysis constant positively correlated with pH, COD removal rate and VS degradation rate, then impacted methane production and lag phase. Meanwhile, lag phase and the maximum methane production rate were directly determined by VFA and COD removal rate. The optimum initial pH and SM/CS ratio were 7.15 and 0.62, respectively, with a predicted maximum methane content of 55.12%. Thinking these findings together, they provide a scientific theory for estimating AD performance.
Prior literature indicates that compliance with International Financial Reporting Standards (IFRS) is not complete in many countries. This study examines practice under the Australian version of IFRS ...by measuring compliance with the disclosure requirements of eight standards. The study focuses on data drawn from the consolidated financial statements of a sample of the top 200 Australian listed companies. To enable a time‐series analysis of compliance over time, this study examines three reporting years: 2006, 2010 and 2014. This research identifies material non‐compliance among Australian companies, finding that some disclosure items appear to be neglected by companies, such as some of the requirements of AASB 137 Provisions. This non‐compliance raises questions about accounting and audit quality in Australia. It may suggest poor regulatory oversight.
This study examines compliance with IFRS disclosure requirements by large Australian listed companies over time from 2006 to 2014. It identifies material non‐compliance and finds that some disclosure items appear to be neglected by companies. This non‐compliance raises questions about accounting and audit quality in Australia. It may suggest poor regulatory oversight.
The contradictions between the increasing energy demand and decreasing fossil fuels are making the use of renewable energy the key to the sustainable development of energy in the future. Biogas, a ...renewable clean energy, can be obtained by the anaerobic fermentation of manure waste and agricultural straw. This study examined the initial pH value had obvious effect on methane production and the process in the thermophilic anaerobic co-digestion. Five different initial pH levels with three different manure ratios were tested. All digesters in different initial pH showed a diverse methane production after 35days. The VFA/alkalinity ratio of the optimum reaction condition for methanogens activity was in the range of 0.1–0.3 and the optimal condition that at the 70% dung ratio and initial pH 6.81, was expected to achieve maximum total biogas production (146.32mL/g VS).
•The additives of magnetite and zeolite in anaerobic digestion were studied.•Mineral additives increased methane production significantly.•Mineral additives provided a good environment for ...methanogens.•The optimum conditions for anaerobic digestion process were optimized.
To enhance biogas production and identify new additive materials for the co-digestion of wheat straw, sheep manure, and chicken manure, batch experiments were investigated in this study. Experiments were conducted on the influence of additive materials on a range of manure/straw ratios (3:7, 5:5, and 7:3) and biogas production under a mesophilic temperature (35°C). Results showed that the maximum increments of methane production (L/kg·VSadd) with the addition of 3g magnetite and 1g natural zeolite were 52.01% and 51.01%, respectively. The addition of magnetite and zeolite in the anaerobic digestion process produced a good fermentation environment. By using the response optimizer when the manure proportion was 52%, the best methane yield was obtained with the addition of 2.7g magnetite. For zeolite, the best addition dose was 1g and the optimum manure proportion is 63%. Magnetite had a more extensive increase in methane yield than zeolite.
A NiAlMnCu-containing steel during ageing at 500°C up to 100h exhibits an interesting age-hardening effect. Careful atom probe tomography investigations confirm that small clusters, enriched with Ni, ...Al, Mn and Cu, formed in the steel after a short ageing of 0.25h. Composite precipitates, consisting of a NiAl-rich and a Cu-rich component side by side, formed after 4h ageing, a phenomenon which corresponded to a peak of 445VHN in hardness. A decrease in hardness of the steel occurred after ageing for 100h, due to the coarsening of the composite precipitates. Quantitative chemical composition measurements reveal that early-stage formation of composite precipitates involves the decomposition of metastable solute clusters, and their growth is associated with the further partitioning of solutes from the ferrite matrix into the composite precipitates.
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