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Abstract: BACKGROUND: Vinasse is a wastewater from bioethanol production with a very high concentration of organic matter, usually from 40 to 80 gCOD L‐1. These features make this wastewater attractive for treatment in an anaerobic system. Anaerobic processes allow the valorisation of this highly polluting wastewater as an energy resource in an environmentally friendly way. RESULTS: A multiscale approach was followed, using batch tests, continuous bench scale reactors, and a full‐scale upflow anaerobic sludge bed (UASB) reactor. Potential inhibition due to high potassium concentrations was evaluated. Using batch tests, the IC50 potassium concentration was determined to be around 6 g L‐1, but continuous reactors could adapt the biomass to this concentration level without removal efficiency decay. A load of 20 gCOD L‐1 d with chemical oxygen demand (COD) removal efficiencies between 60% and 80% were reached in bench scale UASB and expanded granular sludge bed (EGSB) reactors. Finally, a 100 m3 UASB reactor located in a distillery was tested under industrial conditions. A load of 0.6 kgCOD kg‐1VSS d‐1 was achieved with a COD removal efficiency of 78%. CONCLUSION: Although potassium was inhibitory for the inoculum, the sludge from a continuously operated reactor can be adapted to high potassium concentrations without affecting its performance. The real possibility of working with undiluted vinasse was also verified. For distilleries like the Uruguayan case, which produces 18 000 m3 of bioethanol per year, 5x10 m3 of biogas per year, with 68% methane, could be expected, representing an energy potential of about one‐third of the main fuel produced. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND Pilot-scale studies focused on evaluating the robustness of biofilm-based anaerobic digestion processes for further application at full-scale are scarce. Therefore, the aim of this work was to evaluate the performance of a 445 L packed bed reactor (PBR) operated at different organic loading rates (OLRs between 4 and 12.5 g COD L-1 d-1) for the treatment of tequila vinasses. The reactor performance was correlated with the microbial dynamics to elucidate the specific role of the microbial communities in the degradation pathways that govern the process. RESULTS The PBR was operated for 231 days under different OLRs showing a stable performance. The COD removal and methane yield were maintained throughout the reactor operation at 86-89% and 0.24-0.28 L CH4 g-1 CODadded, respectively. Meanwhile, the highest volumetric methane production rate of 3.03 L CH4 d-1 L-1 was reached at the highest OLR, 12.5 g COD L-1 d-1. Regarding microbial dynamics, the Bacteria and Archaea populations were able to adapt to the OLR disturbances, favoring the interactions between syntrophic Bacteria and Methanosaeta at high OLRs. CONCLUSION This work contributes to the scarce information regarding anaerobic treatment of tequila vinasses at pilot-scale and demonstrates that the PBR is a promising and robust configuration that allows treating higher OLRs than currently reported technologies. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The effect of hydraulic and organic loading rate on the anaerobic digest EGSB (Expanded Granular Sludge Blanket) reactor for producing methane gas from starch wastewater was studied. The results show that, when the hydraulic loading rate of reactor is in the range of 1 - 4m/h and the influent concentration of COD Cr is in the range of 5000 - 10000mg/L, the EGSB reactor can operate stably. Under the volumetric organic loading rate of 30 kg/ (m 3 •d), the removal rate of COD is over 80%. The granular sludge in the reactor has good settleability, the proportion of granular sludge in the bottom of reactor with particle diameter larger than 1.5mm accounted for more than 75%. [ABSTRACT FROM AUTHOR]

This paper reports the results of the temperature profile of the unheated and unstirred continuous fermenting bio-slurry in a fixed-dome Deenbandhu 2000 model. The digester is a brick-built system of bulk size 6 m3. The digester was monitored for eight months, measuring internal bio-slurry temperature. A K-type nickel chromium-nickel temperature sensor with a sensitivity of approximately 41 μV °C and response time of 0.8s in liquids was positioned at the centre of the digester to measure the slurry temperature. The sensor was connected to the data logger and programmed to record temperature readings every second for the entire study period. The study results reported give a clear indication about the reaction of bio-slurry temperature in the digester at a local level, particularly for the eight months' period, which covered all seasons. The calculated values of the daily average temperature reveal that the digester was operating within the range of psychrophilic 10.32 °C and mesophilic 28.80 °C, although it sometimes operated at 35 °C and above during certain hours in summer. This study is useful for anaerobic digestion processes for biogas production. The results obtained can be used as a basis to estimate the amount of heat required to raise the temperature of digesters to reach an optimum temperature of mesophilic digesters. [ABSTRACT FROM AUTHOR]

With the development of large-scale and intensive pig breeding, the harmless disposal of dead pigs has become increasingly prominent. The method to process dead pigs by biogas engineering can realize resource utilization of dead pigs and and obtain high economic benetit. In this paper, through a batch of experiments, the feasibility of anaerobic co-digestion of dead pigs and pig manure was verified, and effects of addition proportion of dead pigs and reaction temperature on biogas production from the anaerobic co-digestion were analyzed. The results showed that when the reaction temperature was 35 "C and the adding proportion of the dead pig was 12%. the fermentation could get the best effect, and the maximum of methane content could reach 64.72%, while the total biogas yield was up to 5 310 ml. which was 26% higher than single fermentation of pig manure. Meanwhile, the unit TS and VS biogas yield could rise by 30% and 22% respectively. [ABSTRACT FROM AUTHOR]

CO2 removal from biogas is becoming an important area of research to overcome the environmental issues associated with the release of CO2 into the atmosphere and the utilization of CO2 in greenhouses. In this study, a hollow fiber membrane module was used to separate CO2 from the biogas generated in a biogas plant from manure as the main raw material. The membrane module was set in a two-stage configuration and a vacuum pump was installed on the permeated side of a module to increase the concentration of CO2. The separated and purified CO2 gas was used in a greenhouse to analyze its impact on greenhouse crops. Experiments analyzing the effect of CO2 fertilization using the purified biogas were conducted in three greenhouses under different conditions. Biogas purification experiments achieved CH4 concentration of 95.3% and CO2 concentration of 93.2% at two outputs. H2S concentration was low. A small difference was observed in the average lettuce growth rates with supply of biogaspurified CO2 and with no CO2. The highest fresh weight and dry weight were measured in greenhouse supplied with biogas-purified CO2. The leaf area was the highest in greenhouse supplied with commercial CO2. A high growth rate of lettuce was observed in greenhouses supplied with CO2. The lettuce growth rates in greenhouses supplied with commercial and biogas-purified CO2 were the same. [ABSTRACT FROM AUTHOR]

This study evaluates the treatment efficacy and biogas yield of an integrated system composed of a plug-flow biodigester (with sludge recirculation) followed by polishing in a stabilization pond. The system was operated in real scale for 12 months at ambient temperature and under continuous flow. The volumetric yields of biogas varied according to the organic loads applied, between 114 and 294 Kg COD day, reaching levels of 0.026 to 0.173 m m day, with concentrations of CH between 56 and 70%. The monthly biogas productions were between 378.5 and 2186.1 m month equal to an energy potential of approximately 2070 to 19,168 KWh month.The average yearly removals of BOD and COD by the integrated treatment system were 70 and 86%, respectively. The average annual removals of NH and TKN were 88.5 and 85.5%, respectively. The pH values were always near neutral, and the alkalinity was in ranges propitious for anaerobic digestion. The results of this study indicate good efficacy in terms of removal of organic matter and nitrogen compounds, with the added benefits of generation of energy and use of the treated effluent as biofertilizer, enabling significant cost reductions to cattle farmers. [ABSTRACT FROM AUTHOR]

Production of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. Although several norms and guidelines for BMP tests exist, inter-laboratory tests regularly show high variability of BMPs for the same substrate. A workshop was held in June 2015, in Leysin, Switzerland, with over 40 attendees from30 laboratories around the world, to agree on common solutions to the conundrum of inconsistent BMP test results. This paper presents the consensus of the intense roundtable discussions and cross-comparison of methodologies used in respective laboratories. Compulsory elements for the validation of BMP results were defined. They include the minimal number of replicates, the request to carry out blank and positive control assays, a criterion for the test duration, details on BMP calculation, and last but not least criteria for rejection of the BMP tests. Finally, recommendations on items that strongly influence the outcome of BMP tests such as inoculum characteristics, substrate preparation, test setup, and data analysis are presented to increase the probability of obtaining validated and reproducible results. [ABSTRACT FROM AUTHOR]

The wide use of antibiotics in the animal husbandry and the relevant sustainable industries may promote the emergence of antibiotic-resistant bacteria (ARB), which constitutes a growing threat to human health. The objective of this study was to determine the abundance and diversity of sulfonamide- and tetracycline-resistant bacteria within an eco-agricultural system (EAS) in Hangzhou, China. We investigated samples at every link in the EAS, from livestock manure, to biogas residues and biogas slurry, to vegetable and ryegrass fields, to a fish pond. A combination of culture-based and 16S rRNA gene-based sequencing method was used in this study. Within the studied system, the average rate of bacterial resistance to sulfonamide (46.19 %) was much higher than that of tetracycline (8.51 %) ( p < 0.01). There were 224 isolates that were enumerated and sequenced, 108 of which were identified to species level. The genera comprising the sulfamethoxazole-resistant (SMX) bacteria were generally different from those of tetracycline-resistant (TC) bacteria. Staphylococcus and Acinetobacter were the most dominant genera of SMX bacteria (19.30 % of the total resistant bacteria) and TC bacteria (14.04 % of the total resistant bacteria), respectively. Several strains of resistant opportunistic pathogens (e.g., Pantoea agglomerans) were detected in edible vegetable samples, which may exert a potential threat to both pig production and human health. In general, this study indicates that the EAS is an important reservoir of antibiotic-resistant bacteria, some of which may be pathogenic. [ABSTRACT FROM AUTHOR]

Electrical current in the hydrolytic phase of the biogas process might affect biogas yield. In this study, four 1,150 mL single membrane-less chamber electrochemical bioreactors, containing two parallel titanium plates were connected to the electrical source with voltages of 0, -0.5, -1 and -1.5 V, respectively. Reactor 1 with 0 V was considered as a control reactor. The trend of biogas production was precisely checked against pH, oxidation reduction potential and electrical power at a temperature of 37 ±0.5 °C amid cattle manure as substrate for 120 days. Biogas production increased by voltage applied to Reactors 2 and 3 when compared with the control reactor. In addition, the electricity in Reactors 2 and 3 caused more biogas production than Reactor 4. Acetogenic phase occurred more quickly in Reactor 3 than in the other reactors. The obtained results from Reactor 4 were indicative of acidogenic domination and its continuous behavior under electrical stimulation. The results of the present investigation clearly revealed that phasic electrical current could enhance the efficiency of biogas production. [ABSTRACT FROM AUTHOR]

Background: Microbial communities are ubiquitous in nature and play a major role in ecology, medicine, and various industrial processes. In this study, we used stoichiometric metabolic modeling to investigate a community of three species, Desulfovibrio vulgaris, Methanococcus maripaludis, and Methanosarcina barkeri, which are involved in acetogenesis and methanogenesis in anaerobic digestion for biogas production. Results: We first constructed and validated stoichiometric models of the core metabolism of the three species which were then assembled to community models. The community was simulated by applying the previously described concept of balanced growth demanding that all organisms of the community grow with equal specific growth rate. For predicting community compositions, we propose a novel hierarchical optimization approach: first, similar to other studies, a maximization of the specific community growth rate is performed which, however, often leads to a wide range of optimal community compositions. In a secondary optimization, we therefore also demand that all organisms must grow with maximum biomass yield (optimal substrate usage) reducing the range of predicted optimal community compositions. Simulating two-species as well as three-species communities of the three representative organisms, we gained several important insights. First, using our new optimization approach we obtained predictions on optimal community compositions for different substrates which agree well with measured data. Second, we found that the ATP maintenance coefficient influences significantly the predicted community composition, especially for small growth rates. Third, we observed that maximum methane production rates are reached under high-specific community growth rates and if at least one of the organisms converts its substrate(s) with suboptimal biomass yield. On the other hand, the maximum methane yield is obtained at low community growth rates and, again, when one of the organisms converts its substrates suboptimally and thus wastes energy. Finally, simulations in the three-species community clarify exchangeability and essentiality of the methanogens in case of alternative substrate usage and competition scenarios. Conclusions: In summary, our study presents new methods for stoichiometric modeling of microbial communities in general and provides valuable insights in interdependencies of bacterial species involved in the biogas process. [ABSTRACT FROM AUTHOR]