Effect of organic loading on anaerobic digestion of cow dung: Methane production and kinetic study.

Organic loading influences the effectiveness of producing biogas through anaerobic digestion. This study set out to investigate the effect of organic loading on the anaerobic mesophilic digestion of cow dung, the parameters involved in the digestion process and to evaluate the kinetics. Anaerobic digestion of cow dung at different organic loading (gVS/L) of 14 gVS/L, 18gVS/L, 22 gVS/L, 26 gVS/L and 30 gVS/L were investigated. Increasing the organic loading increased the methane yield of the cow dung. The highest cumulative methane yield was observed at 30 gVS/L with 63.42 mL CH4/gVS while the highest biogas yield was reported at 192.53 mL/gVS with the highest methane content of 89%. In addition, the modified Gompertz model equation with an R2 of 0.9980 demonstrated strong consistency and a good fit between predicted and experimental data. The high number of substrates added to the systems when increasing the organic loading increased the λ and slow down the nutrient transport and hydrolysis. This study provides current information on the effects of organic loading on the anaerobic digestion of cow dung in batch mode, including experimental conditions and operational parameters.

Membrane-Based Electrolysis for Hydrogen Production: A Review.

Hydrogen is a zero-carbon footprint energy source with high energy density that could be the basis of future energy systems. Membrane-based water electrolysis is one means by which to produce high-purity and sustainable hydrogen. It is important that the scientific community focus on developing electrolytic hydrogen systems which match available energy sources. In this review, various types of water splitting technologies, and membrane selection for electrolyzers, are discussed. We highlight the basic principles, recent studies, and achievements in membrane-based electrolysis for hydrogen production. Previously, the Nafion™ membrane was the gold standard for PEM electrolyzers, but today, cheaper and more effective membranes are favored. In this paper, CuCl-HCl electrolysis and its operating parameters are summarized. Additionally, a summary is presented of hydrogen production by water splitting, including a discussion of the advantages, disadvantages, and efficiencies of the relevant technologies. Nonetheless, the development of cost-effective and efficient hydrogen production technologies requires a significant amount of study, especially in terms of optimizing the operation parameters affecting the hydrogen output. Therefore, herein we address the challenges, prospects, and future trends in this field of research, and make critical suggestions regarding the implementation of comprehensive membrane-based electrolytic systems.

Hydrolysis and characterization of sugar recovery from bakery waste under optimized subcritical water conditions.

Subcritical water hydrolysis process for sugar recovery from leftover croissants (LC) and leftover doughnuts (LD) was optimised using response surface methodology with three process parameters as dependent variables and sugar yield as the response. The process parameters: temperature (160-200 °C), time (5-15 min), and solid loading (10-50%), on the sugar yield were investigated. For the LC sample, the optimised process conditions were determined to be: 200 °C, 6.17 min, and 10% solid loading producing an 80% hydrolysis yield of 466.11 ± 0.67 mg/g. Comparatively, the LD sample optimisation parameters were: 200 °C, 5 min, and 10% solid loading producing a 76.18% hydrolysis yield of 394.34 ± 0.33 mg/g. The sugar extracts were further characterise; which through scanning electron microscopy revealed the LC had most starch granules rupture during hydrolysis, while Fourier-transform infrared spectroscopy detected the presence of monosaccharides and oligosaccharides for both LC and LD. 5-hydroxymethylfurfural (5-HMF), a sugar degradation by-product, was also detected with 39.16 ± 0.61 and 20.59 ± 0.81 mg/g for the LC and LD, respectively, at optimal conditions.

Subcritical Water Technology for Extraction of Phenolic Compounds from Chlorella sp. Microalgae and Assessment on Its Antioxidant Activity.

Chlorella sp. microalgae is a potential source of antioxidants and natural bioactive compounds used in the food and pharmaceutical industries. In this study, a subcritical water (SW) technology was applied to determine the phenolic content and antioxidant activity of Chlorella sp. This study focused on maximizing the recovery of Chlorella sp. phenolic content and antioxidant activity measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay as a function of extraction temperature (100-250 °C), time (5-20 min) and microalgae concentration (5-20 wt. %) using response surface methodology. The optimal operating conditions for the extraction process were found to be 5 min at 163 °C with 20 wt. % microalgae concentration, which resulted in products with 58.73 mg gallic acid equivalent (GAE)/g phenolic content and 68.5% inhibition of the DPPH radical. Under optimized conditions, the experimental values were in close agreement with values predicted by the model. The phenolic content was highly correlated (R² = 0.935) with the antioxidant capacity. Results indicated that extraction by SW technology was effective and that Chlorella sp. could be a useful source of natural antioxidants.