In this study, the effects of co-digestion operating conditions for the enhancement of biogas production from Miscanthus Fuscus mixed with cow dung, was investigated. The aforementioned organic wastes are good substrate resources for anaerobic co-digestion (AD) due to their high content of easily biodegradable materials. This source of effective and ecofriendly technology as AD is for generating energy from organic waste. Response surface methodology (RSM) based on the Box-Behnken (BBD) design was employed to evaluate and optimise four process variables: pH, temperature, and hydraulic retention time (HRT) and feedstock inoculum (F/I) ratio on the biogas production. This study signifies the interactions between the process conditions, and identifies the most significant variables of control in order to maximise the biogas production. A developed regression model established the relationship between the significant effect of the input variables and the response. The analysis of variance (ANOVA) showed a high coefficient of determination value (R 2 = 0.9997) at 95% confidence level. The results show that the F/I ratio has a major impact on biogas production. The model developed predicted values which were well fitted (P<0.005) with the values obtained from the experimental data. Thus, the regression model confirmed findings. The RSM and BBD employed proved to be economical and a reliable tool for modelling, optimizing and studying the interactive effects of the four process factors (pH, temperature, HRT and F/I ratio) for the biogas production.
Drinking water quality of surface and underground water within 1.34 km from a waste landfill site in Kumasi, Ghana was investigated. Physico‐chemical properties and heavy metal concentrations were analysed to determine water quality and pollution indices. It was found that turbidity of 83% of hand dug wells, 50% of the streams and 33% of boreholes were higher than World Health Organisation (WHO) standards for drinking water. Water quality index (WQI) showed that 25% of the water sources are of excellent quality, while 50%, 15% and 5% are good quality, poor quality, very poor quality and unsuitable for drinking, respectively. Heavy metal pollution index (HPI) indicated that the water sources were above the critical limit for drinking water (HPI > 100). Principal component analysis (PCA) revealed 75.30% and 70.88% of the total variance for the physico‐chemical parameters and heavy metals, respectively. The findings concluded that cadmium concentrations in all the water sources were extremely higher (0.0122–0.1090 mg/L) than WHO limit (0.003 mg/L), rendering them unwholesome for consumption.
In this study, 19 experiments were conducted with 25 pouch cells of NMC cathode to investigate thermal runaway and the release of gases from lithium-ion batteries (LIBs). Single cells, double cells, and a four-cell battery stack were forced to undergo thermal runaway inside an air-tight reactor vessel with a volume of 100 dm3. The study involved two series of tests with two types of ignition sources. In the Series 1 tests, a heating plug was used to initiate thermal runaway in LIBs in the ranges of 80–89% and 90–100% SOC. In the Series 2 tests, a heating plate was used to trigger thermal runaway in LIBs in the ranges of 30–50%, 80–89%, and 90–100% SOC. Thermal runaway started at an onset temperature of 344 ± 5 K and 345 K for the Series 1 tests and from 393 ± 36 K to 487 ± 10 K for the Series 2 tests. Peak reaction temperatures ranged between 642 K and 1184 K, while the maximum pressures observed were between 1.2 bar and 7.28 bar. Thermal runaway induced explosion of the cells and lead to a rate of temperature increase greater than 10 K/s. The amounts of gases released from the LIBs were calculated from pressures and temperatures measured in the reactor. Then, the gas composition was analyzed using a Fourier transform infrared (FTIR) spectrometer. The highest gaseous production was achieved at a range of 90–100% SOC and higher battery capacities 72 L, 1.8 L/Ah (Series 1, battery stack) and 103 L, 3.2 L/Ah (Series 2, 32 Ah cell)). Among the gases analyzed, the concentration of gaseous emissions such as C2H4, CH4, and C2H6 increased at a higher cell capacity in both series of tests. The study results revealed characteristic variations of thermal behavior with respect to the type of ignition source used.
There has been a rising global concern of mercury because of its persistent nature, long-range transport and toxicity. Mercury possesses serious health effects on living organisms and the environment. Mercury, mostly in inorganic form, is present in almost all categories of rocks. It may be released through natural occurrences and/or anthropogenic activities such as aluminum production. Stable organic mercury compounds, for example methyl mercury (CH3Hg), are formed by the attachment of mercury to one or two carbon atoms. Depending on the source of bauxite, a substantial amount of elemental mercury is released by aluminum industries. Emitted elemental mercury contributes to increasing global atmospheric reserve of mercury hence decreasing mercury emissions plays a key role in lowering the contribution of anthropogenic activities to the global atmospheric mercury budget. In general, all three forms of mercury (elemental, inorganic and organic mercury) have the potential of causing adverse health effects at sufficiently high doses. Mercury emissions are readily absorbed through the alveoli membranes and gastrointestinal tract affecting other systems. Fetuses and individuals often exposed to mercury (chronic exposure) are two classes of people who are more susceptible to harm caused by mercury. This paper discusses mercury metal and oxide emission from the aluminum industry.
Biomethane produced by anaerobic digestion of organic waste is a renewable and sustainable energy that can supplement global energy needs. Existing literature shows that different mixing ratios of the same co-substrates have an impact on biomethane production. In this study, the impact of different mixing ratios of cattle blood and rumen contents on biomethane production was investigated. The physicochemical characteristics of seven samples with different blood and rumen contents were determined. Their biomethane yield was then assessed in laboratory-scale batch digesters at 37 o C (mesophilic). The biomethane yields of the samples gave a mean value of 11.25±13.34 which indicates significant variability (p < 0.05). The sample containing 10 ml of bovine blood and 50 ml of rumen contents (S 6 ) gave the highest biomethane yield and can be considered for optimization of biomethane production from these feedstocks.
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