Search

For establishing a sustainable society, it is crucial to reuse the organic waste as a material resource. Therefore, herein, we aim to pulverize the methane fermentation residue sludge by ball milling and high-speed agitation to directly utilize it as a liquid fertilizer. The solid particles in the sludge can be below 100 µm, corresponding to the nozzle diameter of the boom sprayer by both ball milling and high-speed agitation; when ball milling was carried out for at least 1 h, the ratio of coarse particles larger than 100 µm decreased by less than 10%. In addition, the phosphate-ion concentration in the sludge increased with a decrease in the particle size of solid in the sludge mainly due to increase in its specific surface area. Furthermore, we investigated the effects of various experimental conditions for ball milling on the pulverization efficiency. Results suggests that for grinding the soft solid particles in the sludge by ball milling, the volume ratio of the total medium balls and sludge, total volumes of the balls and sludge, and inner pot volume should be larger, while the ratio of the rotation speed to the critical rotation speed should be almost the same as those reported previously in the reports on grinding of inorganic particles to attain an effective pulverization. [ABSTRACT FROM AUTHOR]

ABSTRACT The butyric acid biorefinery technology for straw is highly significant for environmental protection and the restructuring of the energy system. However, this process produces waste from alkali-heat pretreatment (PW) and butyric acid fermentation (FW). In this study, the feasibility of methane fermentation from the wastes was confirmed, with the methane production from PW and FW of 351.1 ± 11.8 and 741.5 ± 14.2 mLCH 4 /gVS, respectively. The initial pH and V FW of methane fermentation using the mixed waste of PW and FW were optimized at 7.5 and 1.8, respectively. The methane fermentation using the mixed waste was also verified by operating two anaerobic digesters in sequencing batch mode. At the V PW of methane fermentation using the mixed waste of PW and FW were optimized at 7.5 and 1.8, respectively. The methane fermentation using the mixed waste was also verified by operating two anaerobic digesters in sequencing batch mode. At the V FW / V PW of 0.25 (actual ratio), methane production was 301.20 mLCH 4 /gVS with the waste load of 0.64 kgVS/m³/d. When the V FW / V PW was 1.8 (optimal ratio), methane production reached 396.45 mLCH 4 /gVS at the waste load of 1.20 kgVS/m 3 /d. This study facilitates the comprehensive utilization of all components within rice straw.

The purpose of this study was to investigate the performance of the thermophilic and mesophilic anaerobic digestion process (TADP, MADP) fed with NaOH-microwave pretreated waste activated sludge. The experiment was conducted in anaerobic CSTR reactors. During this experiment, the reactors were stable in operation and were not inhibited by ammonia. The methane production and reduction of organic matters from MADP were less than those from TADP. The dewatering performance of mesophilic sludge was better than that of the thermophilic sludge. The experimental results showed that the continuous TADP and MADP were effective, when the reactors were fed with the waste activated sludge pretreated by NaOH-microwave. MADP was more suitable to combine the NaOH-MW pretreatment process than TADP. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the biogas productivity from selected cultivars of sorghum (Sorghum bicolor Moench) and maize (Zea mays L.) depending on the dose of mineral fertilization with nitrogen. The topic is novelty in the northern Poland area due to the fact that this crop is not very widespread here. The silage samples were derived from two experiments: (1) two factors experiment with sorghum varieties (Arbatax, KWS Maja, Herkules) and two doses of mineral nitrogen fertilization (0 and 150 kg ha−1 N) in split-plot design. (2) one-factor experiment with fodder maize, variety NK Magitop, and two doses of mineral nitrogen fertilization (0 and 150 kg ha−1 N) in a randomized complete block design. The experiment was performed in four replications in the split-plot design. Methane fermentation was carried out under mesophilic conditions. The temperature of the process was 37°C ± 1°C, while pH 7 ± 0.1. The content of total solids in the bioreactor was 7.0%. The composition of the gas produced was measured once a day with the use of an automatic biogas analyser (GFM 416, GasData). The trial was run in triplicate until the daily yield was less than 1% of the cumulative biogas yield [DIN 38 414-S8. Sediments and sediments. Determination of fermentation characteristics; 1985]. Sorghum was characterized by higher average biogas productivity (about 12%), higher methane content in biogas (about 10%), and higher methane productivity (about 43%). It can, therefore, be stated that sorghum represents as an alternative plant to maize for the purpose of biogas production. [ABSTRACT FROM AUTHOR]

The goal of this study was to establish a system for co-culturing microalgae and crop plants with biogas digestate. We examined growth performances of E. gracilis and L. sativa co-cultured using a commercial liquid fertilizer designed for soilless culture supplemented with vitamins and ammonium. This solution simulated the filtrate of nitrified biogas digestate derived from the organic fraction of municipal solid waste but was supplemented with insufficient plant nutrients (Mg, Fe and Mn). The specific growth rate of the co-cultured E. gracilis was 0.761 ± 0.081 d−1 (mean ± SE), which was the same rate that E. gracilis achieved when grown as a sole culture. There were no significant differences between L. sativa cultured with E. gracilis until the stationary growth phase of E. gracilis was reached and those cultured alone relative to biomass, RGRs (relative growth rates), or relative to SPAD values of leaves. These results suggest that E. gracilis and L. sativa could be co-cultured with the biogas digestate after being nitrified and filtered. In addition, considering concentrations of plant macronutrients in the residual solution after the co-culturing E. gracilis and L. sativa, it could be re-used as the nutrient solution for co-culturing E. gracilis and L. sativa. [ABSTRACT FROM AUTHOR]

More information on the connection between anaerobic digestion (AD) parameters and composition of the microbial community involved in the AD process is required to gain a better understanding of how a bioreactor functions. The aim of this study was to analyse the composition of microbial communities and the dynamics of methanogens' biodiversity changes during the shift from mesophilic (38°C) to thermophilic (55°C) conditions during biogas production. The total microbial composition was examined via the metagenomic approach based on 16S rRNA gene sequencing, whereas the methanogen communities were analysed using PCR–DGGE (Polymerase Chain Reaction–Denaturing Gradient Gel Electrophoresis) of mcrA. Even though the temperature is one of the crucial parameters affecting microorganisms involved in the AD process, the results presented here revealed that there were no statistically significant differences in bacterial community composition between the mesophilic and thermophilic phases of the process. The most abundant phyla were found to be Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. However, the methanogens' community genotypic structure as examined by the PCR–DGGE method changed under thermophilic conditions. The temperature had the strongest impact on the archaeal methanogens in the fermentation chamber directly after implementing the temperature shift. A relatively higher biogas yield and average content of CH4 in the produced biogas were observed under thermophilic conditions. [ABSTRACT FROM AUTHOR]

We investigated the possibility of usingEuglena gracilisto convert digestate from methane fermentation of organic wastes into a medium for soilless crop culture. The growth ofE. graciliscultured with aqueous solutions containing filtrate of raw digestate at 1–30% (v/v) and nitrified digestate at 10–100% (v/v) was examined. Concentrations of plant macronutrient ions in nitrified digestate before and after culturingE.graciliswere also examined. Specific growth rates in aqueous solutions containing filtrate of raw digestate at 1–10% and nitrified digestate at 10–100% showed no significant differences, respectively (0.781 ± 0.031 d−1and 0.925 ± 0.033 d−1, mean ± standard error). The rates in the filtrate of nitrified digestate were significantly higher than those in the filtrate of raw digestate. Moreover, there were no significant differences between the concentrations of plant macronutrient ions other thanin the filtrate of nitrified digestate before and after culturingE. gracilis.The concentration ofdecreased significantly by 10.5% of the initial concentration. As a result, the constituent ratio of plant macronutrient ions other than magnesium in the solution after culturingE. graciliswas similar to that in a standard nutrient solution for soilless culture. [ABSTRACT FROM PUBLISHER]

A two serially connected single-chamber microbial fuel cell (MFC) was applied to the treatment of diluted molasses wastewater in a continuous operation mode. In addition, the effect of series and parallel connection between the anodes and the cathode on power generation was investigated experimentally. The two serially connected MFC process achieved 79.8% of chemical oxygen demand removal and 11.6% of Coulombic efficiency when the hydraulic retention time of the whole process was 26 h. The power densities were 0.54, 0.34 and 0.40 W m−3when electrodes were in individual connection, serial connection and parallel connection modes, respectively. A high open circuit voltage was obtained in the serial connection. Power density decreased at low organic loading rates (OLR) due to the shortage of organic matter. Power generation efficiency tended to decrease as a result of enhancement of methane fermentation at high OLRs. Therefore, high power density and efficiency can be achieved by using a suitable OLR range. [ABSTRACT FROM PUBLISHER]

Two-phase anaerobic systems are being increasingly implemented for the treatment of both sewage sludge and organic fraction of municipal solid waste. Despite the good amount of mathematical models in anaerobic digestion, few have been applied in two-phase systems. In this study, a three-reaction mechanistic model has been developed, implemented and validated by using experimental data from a long-term anaerobic two-phase (TPAD) digester treating sewage sludge. A sensitivity analysis shows that the most influential parameters of the model are the ones related to the hydrolysis reaction and the activity of methanogens in the thermophilic reactor. The calibration procedure highlights a noticeable growth rate of the thermophilic methanogens throughout the evaluation period. Overall, all the measured variables are properly predicted by the model during both the calibration and the cross-validation periods. The model's representation of the organic matter behaviour is quite good. The most important disagreements are observed for the biogas production especially during the validation period. The whole application procedure underlines the ability of the model to properly predict the behaviour of this bioprocess. [ABSTRACT FROM AUTHOR]

The objective of the present study was to determine the effectiveness of biogas production during methane fermentation of wastewaters originating from the dairy, tanning and sugar industries, by means of respirometric measurements conducted at a temperature of 35°C. Experiments were carried out with the use of model tanks of volume 0.5 dm3. A high production yield of biogas, with methane content exceeding 60%, was achieved in the case of the anaerobic treatment of wastewaters from the dairy and sugar industries. A significantly lower effect was observed in the case of tanning wastewaters. The effectiveness of the fermentation process decreased with increasing loading of the tanks with a feedstock of organic compounds. By loading a model tank with this feedstock, the effectiveness of treatment ranged from 62.8% to 71.4% residual chemical oxygen demand for dairy wastewaters and from 57.9% to 64.1% for sugar industry wastewaters. The efficiency of organic compound removal from tanning wastewaters was below 50%, regardless of the method applied. [ABSTRACT FROM PUBLISHER]