anhua Li

Biogas Production Potential and Kinetics of Microwave and Conventional Thermal Pretreatment of Grass

Pretreatment methods play an important role in the improvement of biogas production from the anaerobic digestion of energy grass. In this study, conventional thermal and microwave methods were performed on raw material, namely, Pennisetum hybrid, to analyze the effect of pretreatment on anaerobic digestion by the calculation of performance parameters using Logistic function, modified Gompertz equation, and transference function. Results indicated that thermal pretreatment improved the biogas production of Pennisetum hybrid, whereas microwave method had an adverse effect on the performance. All the models fit the experimental data with R2 > 0.980, and the Reaction Curve presented the best agreement in the fitting process. Conventional thermal pretreatment showed an increasing effect on maximum production rate and total methane produced, with an improvement of around 7% and 8%, respectively. With regard to microwave pretreatment, maximum production rate and total methane produced decreased by 18% and 12%, respectively.

Eruptions of two flux ropes observed by SDO and STEREO

Aims. We report for the first time the hot and cool components of two flux ropes simultaneously observed by SDO and STEREO, and the relationship between the flux rope eruptions and the coronal mass ejection (CME). Methods. Employing SDO and STEREO A and B observations, we investigated the eruptive event of two flux ropes and their associated activities in active region (AR) 11402 on January 23, 2012. Results. In SDO/AIA 94 A (∼6.4 MK) and 131 A (∼10 MK) images, a twisted flux rope appeared from 00:44 UT, which was located in AR 11402. Another longer saddle-shaped flux rope, with twisted fine structures, appeared 25 min later. This was located across the two ARs11401 and 11402. These twoflux ropes initiallyrose rapidly, then slowly, andfinally were again accelerated fast. The twoflux ropes are also identified in the STEREO A and B 195 A (∼1.4 MK), 304 A (0.06‐0.08 MK), 284 A (∼1.8 MK), and 171 A (∼1.0 MK) observations. We suggest that the flux ropes may have both hot and cool components. Investigating the flux rope eruptions with their associated CME, we find that the erupting flux ropes are co-spatial with the CME bright core and the expanding overlying flux loops with the CME bright front.

Effect of microalgae supplementation on the silage quality and anaerobic digestion performance of Manyflower silvergrass

The silage quality of Manyflower silvergrass with microalgae supplementation was investigated, and the variation in bacterial communities during ensilage period was analyzed by high-throughput sequencing technology. In addition, the specific methane yields of the silages were also evaluated. Results showed that the samples with microalgae supplementation have lower pH value and higher lactic acid concentration (8.0 mg/g FM). Meanwhile, higher NH3-N concentration was observed since microalgae were N-rich material. Microalgae additions also influenced the bacterial community structure. For the samples without microalgae, the major genus was Enterococcus from day 1 to day 3, and then Lactobacillus became the dominant genus. While the prevalent genus represented in the samples with microalgae supplementation was Lactobacillus. The specific methane yields of all samples were within the range of 153 ± 1 mL/g VS to 178 ± 11 mL/g VS and no significant difference was observed.

Superconductivity and magnetism in FeSe thin films grown by metal–organic chemical vapor deposition

High quality FeSe thin films with different ratios of Fe to Se have been grown on GaAs and Si substrates by changing the flow rate of Fe(CO)5 in a low-pressure metal–organic chemical vapor deposition (MOCVD) system. For both substrates, the films grown at a low flow rate of Fe(CO)5 are non-ferromagnetic and exhibit superconductivity at low temperature, while those grown at a high flow rate of Fe(CO)5 display ferromagnetic and semiconducting behaviors. Our results suggest that the superconducting phase does exist in a narrow range of Fe and Se concentration near stoichiometry. The introduction of excess Fe favors ferromagnetism and leads to the suppression of superconductivity.

Factors affecting the performance of a single-chamber microbial fuel cell-type biological oxygen demand sensor.

Microbial fuel cells (MFCs) are devices that exploit microorganisms as biocatalysts to degrade organic matter or sludge present in wastewater (WW), and thereby generate electricity. We developed a simple, low-cost single-chamber microbial fuel cell (SCMFC)-type biochemical oxygen demand (BOD) sensor using carbon felt (anode) and activated sludge, and demonstrated its feasibility in the construction of a real-time BOD measurement system. Further, the effects of anodic pH and organic concentration on SCMFC performance were examined, and the correlation between BOD concentration and its response time was analyzed. Our results demonstrated that the SCMFC exhibited a stable voltage after 132 min following the addition of synthetic WW (BOD concentration: 200 mg/L). Notably, the response signal increased with an increase in BOD concentration (range: 5-200 mg/L) and was found to be directly proportional to the substrate concentration. However, at higher BOD concentrations (>120 mg/L) the response signal remained unaltered. Furthermore, we optimized the SCMFC using synthetic WW, and tested it with real WW. Upon feeding real WW, the BOD values exhibited a standard deviation from 2.08 to 8.3% when compared to the standard BOD5 method, thus demonstrating the practical applicability of the developed system to real treatment effluents.

Study of the first productive active region in solar cycle 24

Context. The Sun is very quiet with less sunspots and activity since the beginning of solar cycle 24. However, the active region (AR) 11045 emerged on February 5, 2010, is associated with 43 (8 M- and 35 C-class) flares, 53 coronal mass ejections (CMEs), 29 filament eruptions, 19 extreme ultraviolet (EUV) waves and abundant jets, indicating that this AR is the first productive one of solar cycle 24. Aims. We study the AR evolution and its associated activities, and also their relationships, to understand this productive AR. Methods. We used SOHO/MDI magnetograms to study the magnetic fields, STEREO/SECCHI images to explore the activities, and GOES measurements to investigate the soft X-ray flux of the AR. Results. During the AR evolution, six pairs of main magnetic fields emerged, and 93.1% flares and 82.75% filament eruption occurred in the emergence and stable phases of the magnetic flux. However, 43.4% CMEs occurred in the decaying phase, even though there were lessflares. An example isgiven to show that an event isrelated to aflare, afilament eruption, a CME and an EUV wave from inner corona to outer corona in space, and the filament eruption and EUV wave occur near the peak time of the flare. Among the 29 filament eruptions, 79.3% are associated with CMEs, as well as 58.6%, associated with flares, and 34.5%, associated with EUV waves. During the 12-day active phase, 575 jets are detected with a daily occurrence rate of 49.3. This is the first time that so many jets have been identified in one AR, implying at least 575 lower magnetic reconnection processes during the AR evolution. We statistically studied these jets along with the AR evolution, and noticed that the jets mostly occurred surrounding the emerging flux. We also investigated the spatio-temporal relationships between the jets and the flares, and find that the jets are usually rooted around the flare cores, and the soft X-ray flux is inverse correlated with the number of the jets, especially during the beginning 9 days since the AR emergence. In comparison with AR 11045, we studied the other newly emerging AR 11045, and obtained similar results. The relationships between the jets and the flares may well represent a scenario of two-step magnetic reconnection. Using schematic diagrams, we explain the remarkable magnetic field emergence, cancelation and shear motion of AR 11045, and its associated activities.

Application of surface-modified carbon powder in microbial fuel cells

Abstract The catalytic activity of surface-modified carbon powder, Vulcan XC-72R (XC), for the oxygen reduction reaction (ORR) at an air cathode in a microbial fuel cell (MFC) has been investigated. The effects of treatment with different chemicals such as nitric acid and ammonia on the chemical characteristics of XC were studied. The catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), Boehm titration, and X-ray photoelectron spectroscopy. FTIR analysis showed that the functional groups of the materials were changed by chemical treatment, with nitric acid causing the introduction of oxygen-containing groups, and ammonia leading to the introduction of nitrogen-containing groups. Electrochemical measurements of MFCs containing various modified carbon materials as ORR catalysts were performed, and the results showed that chemically modified carbon materials are promising catalysts in MFCs.

Vertical distribution of microbial community and metabolic pathway in a methanogenic propionate degradation bioreactor

The methanogenic propionate degradation consortia were enriched in a propionate-fed semi-continuous bioreactor. The microbial community shift with depth, the microbial network and its correlation with metabolic pathway were also investigated. The results demonstrated that the maximum organic loading rate (OLR) of the reactor was 2.5g propionic acid (HPr) L-1d-1 with approximately 1.20LL-1d-1 of volumetric methane production (VMP). The organisms in the enrichment were spanning 36 bacterial phyla and 7 archaeal orders. Syntrophobacter, the main Hpr oxidizer in the digester, dominated bacteria with relative abundance changing from 63% to 37% with depth. The predominant methanogens shift from hydrogenotrophic Methanoculleus (∼60%) at the upper liquid layer to acetoclastic Methanothrix (∼51%) at the lower sediment layer in the bioreactor. These methanogens syntrophically support Syntrophobacter by degrading HPr catabolism by-products (H2 and acetate). Other bacteria could scavenge anabolic products (carbohydrate and protein) presumably derived from detrital biomass produced by the HPr-degrading community.

The future Of biogas utilizations in China

The existing energy is almost provided by carbon-containing fossil sources such as oil and coal. The rapid consumption of these fossil resources causes an accelerated release of CO2 which is a major cause of global warming and associated climate change. “Green” bio-methane (also named biogas) has the advantage for both reducing over dependency on fossil energy and reducing emissions o CO2 and other greenhouse gases (GHGs). The purpose of this work is to introduce the biogas utilization ways widely applied in China and indicate the development orientation on clean, effective and economical utilizations. Firstly, biogas in china should gradually walk out from rural family, come into centralized anaerobic digestion (CAD). Secondly, combined production of heat and power (CHP) and upgrading to vehicle fuel should be popularized extensively. Thirdly, biogas fuel cell systems and biogas chemical industry (BCI) should be exploited as a technique reservation.

Effect of pH on anaerobic fermentative products distribution for kitchen waste

Batch tests were carried out to investigate the effect of pH adjustment (control, 5.1, 5.8, 6.5, 7.2 and 7.9) on anaerobic fermentative products distribution for kitchen waste. The experimental results showed that H2 and CO2 were main gas products during the acidification stage (first 5 day) for all fermentations. After the acidification stage, fermentation type was dependent on pH. No gas produced due to the inhibition of low pH 4.5 for the control. It was hydrogen-producing fermentations when reactors operated at pH 5.0–5.5, while it was methane-producing fermentations when reactors operated at pH 6.0–7.0. The acidogenesis pathway was ethanol-type with a little volatile fatty acids (VFAs) production when the pH in reactors were lower than 5.5, while the acidogenesis pathway was VFAs-type without alcohols production when the pH in digesters were 6.0–7.0. The optimal pH value for VFAs production was 7.0 and it was about 4.5 for ethanol production. No ammonia inhibition was found in this study. The degradations of kitchen waste were inhibited by the high concentration of VFAs. The inhibitory levels of undissociated acids on acidogenesis were about 1185, 1150, 979, 460 and 178 mg/L at final actual pH 5.2, 5.4, 6.0, 6.5 and 7.0 for five fermentations with pH adjusting respectively.