Biogas is increasingly recognized as a key renewable energy source for decentralized power generation, particularly in rural and agricultural communities worldwide. However, the direct use of raw biogas, typically containing high levels of carbon dioxide (CO2), results in low heating value, reduced thermal efficiency, and operational problems such as equipment corrosion and clogging. Enhancing biogas quality through cost-effective CO2 removal is therefore essential for maximizing energy output and improving system reliability, especially in resource-limited settings. This study proposes a simple, low-cost, and practical upgrading process suitable for decentralized biogas systems by employing adsorption and absorption techniques using readily available materials. Experiments were conducted with a fixed-bed adsorption column and a packed-column scrubber using wood chips, diatomite, activated carbon, sodium hydroxide solution, calcium carbonate, ethylamine, and water. The fixed-bed adsorption system using sodium-hydroxide-coated wood chips at a flow rate of 10-15 L/min achieved a CO2 removal efficiency of 68%, increasing methane concentration to 79.6 (+/- 0.9)%. The packed-column scrubber using 0.5 M NaOH demonstrated a comparable CO2 removal efficiency of 66%, yielding upgraded biogas with 85 (+/- 3)% methane. The NaOH solution remained effective for 50-60 minutes before reaching saturation. The resulting upgraded biogas exhibited a methane content exceeding 80% and an average heating value of 29.11 MJ/m3. Moreover, increasing NaOH concentration further enhanced CO2 removal and methane purity. The findings highlight the potential of simple, locally sourced adsorption and absorption systems to deliver significant improvements in biogas quality, offering aviable pathway for boosting energy efficiency, extending equipment lifespan, and supporting sustainable energy development in rural and off-grid communities worldwide.
The plant-mediated synthesis of zinc oxide nanoparticles (ZnO NPs) using Morus alba L. leaf extract has been developed as a low-cost, environmentally benign, and simple approach. Characterization techniques such as UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to confirm biosynthesis, crystalline nature, morphology, dimensions, and elemental composition of the ZnO NPs. XRD confirmed the hexagonal wurtzite phase of ZnO with an average crystallite size of 30.54 nm. X-ray dispersive spectroscopy suggests that the composition of ZnO NPs is represented by the emission of 76% of the total energy by zinc and 13% by oxygen. The antibacterial activity of the biosynthesized ZnO NPs was evaluated, which indicates significant inhibition of bacterial strains, including Vibrio cholera and Escherichia coli (O157:H7), as compared to native ZnO. The maximum inhibition zones of ZnO NPs at a 50 mg/mL concentration were observed for V. cholerae and E. coli (O157:H7) at 24.3 +/- 2.4 and 16.5 +/- 2.7 mm, respectively. Moreover, the photocatalytic activity of the synthesized ZnO NPs was examined through the photodegradation of a methylene blue (MB) solution under solar light irradiation. The photodegradation efficiency of MB increased by 50% at ZnO NP concentrations of 30 ppm. This suggests that the synthesized ZnO NPs exhibited promising photocatalytic and biological properties in various applications.
. The enduring popularity of clay bricks as a construction material can be attributed to their affordability. Nevertheless, the elevated temperatures necessary to attain the desired physical and mechanical characteristics result in substantial energy consumption and the emission of thermal pollutants. Accurately classifying clay bricks is essential in evaluating their suitability for construction purposes, with compressive strength being a critical parameter. The present study introduces new projected forward-backward algorithms for solving constrained convex minimization problems by using line search techniques to classify the compressive strength of clay bricks. The algorithm performs better than current methodologies, displaying exceptional As a numerical result, the finding highlight the significance of water absorption for classifying compressive strength. The bulk density is directly influenced by the size of additives, whereas the firing temperature, firing shrinkage, and apparent porosity exhibit interrelationships throughout the firing process. A comprehensive understanding of these parameters is pivotal in enhancing the clay brick manufacturing process and facilitates informed decision-making about material selection and structural design. Moreover, the algorithm can enhance machine learning methodologies in materials science and engineering applications.
This study reports a systematic investigation of vitrification-driven modification of fired clay ceramics through the co-utilization of lignite-derived bottom ash (BA) and post-consumer waste glass (WG). Clay bodies containing 2.5-10.0 wt% BA-WG (1:1 mass ratio) were fired at 900-1100 degrees C to evaluate their physical, mechanical, and chemical performance. The results reveal a competing mechanism within the clay matrix: at low additions (2.5-5.0 wt%), decomposition of BA-derived sulfate (SO42-) induces gas evolution and bloating, reducing bulk density. In contrast, at higher additions (7.5-10.0 wt%), the Na2O-CaO-SiO2-rich flux from WG dominates, promoting extensive vitrification and effective pore sealing. This vitrification-driven densification produces glass-rich matrices with reduced water absorption (similar to 7 %) and compressive strengths of 18-22 MPa, satisfying the minimum requirements of ASTM C62-17 for moderate-weathering clay bricks. Chemical durability is exceptional, with mass loss <= 0.02 % after acid immersion at pH 2 for 14 days. XRD and SEM analyses confirm that the high-flux BA-WG system fundamentally alters phase equilibria in the clay body, suppressing the formation of mullite-the typical reinforcement phase in clay and fly ash-based ceramics-and instead promoting a distinct strengthening mechanism: a continuous glassy matrix reinforced by crystalline albite (NaAlSi3O8). This vitrification-albitization pathway, distinct from conventional crystalline-reinforcement routes, provides a clay-centered route for producing mechanically robust and acid-resistant fired ceramics while valorizing two industrial waste streams, bottom ash and waste glass.
BACKGROUND AND OBJECTIVES: Hydrogen sulfide is a major contaminant in biogas that leads to corrosion of equipment, unpleasant odors, and reduced energy efficiency. Alternative approaches for the elimination of hydrogen sulfide, including chemical scrubbing and adsorption, frequently incur high costs and pose environmental challenges. In contrast, biological removal using microorganisms has emerged as a sustainable and cost-effective alternative. Therefore, the study objectives were to isolate and evaluate efficient microorganisms for hydrogen sulfide removal from biogas and to assess their performance in a biofiltration system. METHODS: Soil samples were collected from a swine farm and enriched in sulfur-based selective media to isolate hydrogen sulfide-degrading microorganisms. Two strains, Sphingomonas paucimobilis and Enterobacter cloacae, were selected based on their growth and hydrogen sulfide removal capability. The strains were fixed onto coconut husk and implemented in a laboratory-scale biofilter. Biogas composition was analyzed before treatment, and hydrogen sulfide removal efficiency was evaluated at gas flow rates of 0.3-0.5 liters per minute, corresponding to empty bed residence times of 4.0-6.6 minutes. FINDINGS: The initial hydrogen sulfide concentration in untreated biogas was 4,281 (+/- 26) part per million. Both strains exhibited the capability to mitigate hydrogen sulfide, with removal efficiencies progressively enhancing throughout the operational phase, thereby suggesting microbial adaptation and subsequent biofilm establishment on the coconut husk matrix. The biofilter inoculated with Sphingomonas paucimobilis showed a rapid increase in performance, achieving 36.5 percent removal on day 1, increasing to over 80 percent within the first week, and reaching a maximum efficiency of 84.8 percent on day 13. During the stable phase of operation, the system maintained relatively high removal efficiencies before showing a slight decline toward the end of the experiment, possibly due to substrate limitation or accumulation of metabolic by-products. Under similar operating conditions, the biofilter utilizing Enterobacter cloacae demonstrated inferior performance, reaching a maximum removal efficiency of only 76.7 percent alongside reduced long-term stability. CONCLUSION: Overall, Sphingomonas paucimobilis exhibited superior performance in hydrogen sulfide removal compared to Enterobacter cloacae. The results indicate that this strain possesses significant potential for use in biofiltration systems aimed at biogas purification, providing an ecofriendly and sustainable method for the reduction to mitigate sulfide.
