This study investigates how the inclusion of refuse-derived fuel (RDF) alters the surface chemistry and electrostatic behavior of oak-based biochar. Biochars were produced using downdraft gasification at 850 °C from 100% oak (HW) and a ternary blend comprising 50% oak, 30% pine, and 20% RDF (HW/SW/RDF). Characterization using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), zeta potential, pH, and electrophoretic mobility was conducted to assess surface functionality and colloidal behavior. The RDF-containing biochar exhibited a 43.3% increase in surface nitrogen content (from 0.24% to 0.90%) and a 6.6% rise in calcium content (from 2.07% to 2.27%) alongside the introduction of chlorine (0.20%) and elevated silicon levels (0.69%) compared to RDF-free counterparts. A concurrent reduction in oxygen-containing functional groups was observed, as O1s decreased from 15.75% in HW to 13.37% in HW/SW/RDF. Electrokinetic measurements revealed a notable decrease in zeta potential magnitude from −31.5 mV in HW to −24.2 mV in HW/SW/RDF, indicating diminished surface charge and colloidal stability. Moreover, the pH declined from 10.25 to 7.76, suggesting a loss of alkalinity and buffering capacity. These compositional and electrostatic shifts demonstrate that RDF inclusion significantly modifies the surface reactivity of biochar, influencing its performance in catalysis, ion exchange, and nutrient retention. The findings underscore the need for tailored post-treatment strategies to enhance the functionality of RDF-modified biochars in environmental applications.

This study presents a comprehensive characterization of oak biochar produced via downdraft gasification at 850 °C. The research employs a wide range of advanced analytical techniques to examine the biochar’s physical, chemical, and structural properties. Scanning electron microscopy (SEM) revealed a mesoporous structure, while Brunauer–Emmett–Teller (BET) analysis showed a surface area of 88.97 m²/g. Thermogravimetric analysis (TGA) demonstrated high thermal stability and carbon content (78.7%). X-ray photoelectron spectroscopy (XPS) and ultimate analysis confirmed the high degree of carbonization, with low O/C (0.178) and H/C (0.368) ratios indicating high aromaticity. Fourier transform infrared spectroscopy (FTIR) identified functional groups suggesting potential for CO₂ adsorption. The biochar exhibited a negative zeta potential (−31.5 mV), indicating colloidal stability and potential for soil amendment applications. X-ray diffraction (XRD) and Raman spectroscopy provided insights into the biochar’s crystalline structure and graphitization degree. These findings highlight the oak biochar’s suitability for diverse applications, including soil improvement, carbon sequestration, and environmental remediation. By filling knowledge gaps in oak-specific biochar research, this study underscores the benefits of optimized downdraft gasification and sets a foundation for future advancements in sustainable biochar applications.

The development of new materials capable of converting carbon dioxide (CO₂) into value-added products has emerged as a crucial strategy in addressing global climate change and promoting sustainable industrial practices.

This research delves into the co-pyrolysis of refuse-derived fuel (RDF) and oil shale (OS), utilizing a 50% weight ratio for each component. The study employs a fixed-bed reactor, augmented by electrical kiln heating, to conduct the co-pyrolysis process. A significant aspect of this research is the use of Aspen Plus software for process simulation, with the simulated results undergoing validation through experimental data. A commendable correlation was observed between the experimental outcomes and the model predictions, underscoring the reliability of the simulation approach. The investigation reveals distinct product yields from the pyrolysis of 100% RDF and 100% OS. Specifically, the pyrolysis of pure RDF yielded 45.26% gas, 20.67% oil, and 34.07% char by weight. In contrast, the pyrolysis of pure OS resulted in 14.51% gas, 8.32% liquid, and a significant 77.61% char by weight. The co-pyrolysis of RDF and OS in a 50% blend altered the product distribution to 31.98% gas, 12.58% liquid, and 55.09% char by weight. Furthermore, the Aspen Plus simulation model aligned closely with these findings, predicting yields of 31.40% gas, 11.9% oil, and 56.6% char by weight for the RDF-OS blend. This study not only elucidates the co-pyrolysis behavior of RDF and OS but also contributes valuable insights into the potential of these materials to address the pressing issue of plastic waste management and energy resource utilization. The findings underscore the efficacy of RDF and OS co-pyrolysis as a viable strategy for enhancing the value extraction from waste and underutilized energy resources, presenting a promising avenue for environmental and energy sustainability.

Two-stage anaerobic reactors are being widely used in the organic waste management industry. In these reactors, up to one-third of the chemical oxygen demand (COD) content is naturally pre-acidified in a first stage pre-acidification (PA) and then fed to a second stage digester for conversion to methane. Traditionally, all the generated gases from the PA tank will be vented to the atmosphere. Hydrogen and carbon dioxide are the main gases generated in the PA tank. A pilot-scale of two-stage anaerobic expanded granular sludge bed reactor was fabricated and used to investigate the impact of the PA gas injection into the second stage. The gas from the PA reactor was captured and stored in the storage tank. The tests were run under two temperature ranges and five organic loading rates (similar to 2, 3, 4, 5, and 6 g COD/L.day). For mesophilic range, the biogas production and energy yield increased by 10-90% and 40-130%, respectively, from without PA gas injection case compared to with PA injection case. For thermophilic range, the biogas production and energy yield increased by 12-40% and 90-140%, respectively, from without PA gas injection compared to with PA injection case. For each OLR, the gas production and energy yield were 90 to 160% more in thermophilic range than the mesophilic range for the cases with and without the PA gas injection. This implies that a higher temperature range has a significant impact on energy yield in a digester. One of the important findings was the amount of the PA gas injected into the EGSB reactor should be less than 50% of the theoretically calculated hydrogen gas based on ethanol substrate assumption.