Search Results (1,674)

Population growth drives increasing energy demands, agricultural production, and organic waste generation. The organic waste contributes to greenhouse gas emissions and increasing landfill burdens, highlighting the need for novel closed-loop technologies that integrate water, energy, and food resources. Within the context of the Water–energy–food Nexus (WEF), wastewater can be recycled for food production and food waste can be converted into clean energy, both contributing to environmental impact reduction and resource sustainability. A novel household-scale, closed-loop WEF system was designed, installed and operated to manage organic waste while retrieving water for irrigation, nutrients for plant growth, and biogas for energy generation. The system included a biodigester for energy production, a sand filter system to regulate nutrient levels in the effluent, and a hydroponic setup for growing food crops using the nutrient-rich effluent. These components are operated with a daily batch feeder coupled with automated sensors to monitor effluent flow from the biodigester, sand filter system, and the feeder to the hydroponic system. This novel system was operated continuously for two months using typical household waste composition. Controlled experimental tests were conducted weekly to measure the nutrient content of the effluent at four locations and to analyze the composition of biogas. Gas chromatography was used to analyze biogas composition, while test strips and In-Situ Aqua Troll Multi-Parameter Water Quality Sonde were employed for water quality measurements during the experimental study. Experimental results showed that the system consistently produced biogas with 76.7% (±5.2%) methane, while effluent analysis confirmed its potential as a nutrient source with average concentrations of phosphate (20 mg/L), nitrate (26 mg/L), and nitrite (5 mg/L). These nutrient values indicate suitability for hydroponic crop growth and reduced reliance on synthetic fertilizers. This novel system represents a significant step toward integrating waste management, energy production, and food cultivation at the source, in this case, the household. Full article

The investigation into the complementary roles of essential oils (EOs) and organic acids in enhancing rumen physiology is increasingly gaining recognition within the field of animal nutrition. Essential oils are known for their antimicrobial effects, which can specifically target certain microbial populations in the rumen, thereby impacting fermentation processes, methane output, and nutrient digestion. In addition, the integration of organic acids plays a crucial role in stabilizing rumen pH and steering the metabolic activities of bacterial populations toward propionate production, a process essential for energy metabolism in ruminants. The concurrent use of essential oils and organic acids may yield synergistic benefits that could further optimize ruminal fermentation efficiency, enhance feed conversion rates, and lower methane emissions. This systematic review used the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The literature search was meticulously designed to encompass parameters related to ruminant species, feed additives, essential oils, organic acids, synergistic effects, and rumen physiology. The efficacy of both organic acids and essential oils is highly dependent on their concentration and the specific combinations utilized. When certain essential oils are used in conjunction with selected organic acids, they may mitigate any potential negative effects on fermentation, thereby fostering a more favorable environment for the proliferation of beneficial microbial communities. Understanding the relationship between essential oils and organic acids is essential for the formulation of diets that enhance rumen health while concurrently reducing environmental pressures through diminished methane emissions. Future research should prioritize long-term in vivo investigations to gain more comprehensive insights into the interactions among these dietary components and identify the optimal combinations for ruminant feeding strategies. Full article

Deep coalbed methane reservoirs must utilize hydraulic fracturing technology to create high-conductivity sand-filled fractures for economical development. However, the mechanism by which proppant embedment affects fracture width in coal rock is not yet clear. In this article, using the discrete element particle flow method, we have developed a numerical simulation model that can replicate the dynamic process of proppant embedment into the fracture surface. By tracking particle positions, we have accurately characterized the dynamic changes in fracture width and proppant embedment depth. The consistency between experimental measurements of average fracture width and numerical results demonstrates the reliability of our numerical model. Using this model, we analyzed the mechanisms by which different proppant particle sizes, number of layers, and closure stresses affect fracture width. The force among particles under different proppant embedment conditions and the induced stress field around the fracture were also studied. Numerical simulation results show that stress concentration formed by proppant embedment in the fracture surface leads to the generation of numerous induced micro-fractures. As the proppant grain size and closure stress increase, the stress concentration formed by proppant embedment in the fracture surface intensifies, and the variability in fracture width along the fracture length direction also increases. With more layers of proppant placement, the particles counteract some of the closure stress, thereby reducing the degree of proppant embedment around the fracture surface. Full article

Antarctic krill (Euphausia superba) are an essential source of food for whale, seal, several fish, squid and seabird species in the Southern Ocean. Krill also play a major role in biogeochemical cycling and are the target of a growing commercial fishery. Krill can be detected and quantified with echosounders, particularly in swarms, and monitoring krill abundance and distribution is integral to assessing the status of regional populations and managing fisheries. We used echosounders to investigate the hemispherical distribution and behaviour of krill swarms during the Antarctic Circumpolar Expedition (ACE), a multidisciplinary exercise that included measurements of atmospheric chemistry. Krill swarms were grouped using hierarchical clustering into four principal types: small swarms (on average 2 m high, 25 m long); large swarms (13 m high and 341 m long); deep swarms, which were also densely packed (average depth of 52 m); and shallower swarms, which had lower densities (average depth of 28 m). We found a weak negative relationship between the concentration of atmospheric methane close to the sea surface and the presence of krill. High densities of krill were found in the Amundsen Sea, an area purported to be of increasing importance for krill as the climate changes. Full article

Industrial park (IP) expansions in Mediterranean peri-urban areas can generate conflicts between economic development and agricultural heritage preservation. This paper develops a theoretically derived circular land use symbiosis model based on Hubs for Circularity (H4C) principles, using Fosso Imperatore IP in southern Italy as an illustrative case. This model proposes a transferable three-zone gradient design that enables the transformation of industrial–agricultural boundaries when combined with appropriate governance mechanisms and stakeholder engagement. Zone A concentrates vertical industrial development with rooftop agriculture; Zone B creates mixed agro-industrial interfaces; and Zone C enhances agricultural productivity through industrial resources. The model’s components (gradient zonation, temperature–cascade matching, and bidirectional resource flows) constitute generalizable design principles. When applied to Fosso Imperatore, where farmers oppose expansion that threatens culturally significant San Marzano tomato production, the model shows how 547 tons of organic waste could generate 87,520 m³ of methane, while industrial waste heat cascades from 150–200 °C to 25–40 °C of greenhouse heating across distances of 3 km. Implementation constraints include regulatory gaps and limited empirical data. This study operationalizes H4C through spatial design, showing how benefit-sharing mechanisms can transform stakeholder conflicts into collaboration. The model provides a replicable framework for Mediterranean contexts where industrial expansion encounters agricultural heritage. Full article

Addressing the challenge of efficient gas control in high-gas coal mines with ultra-long panels, this study focuses on the No. 8 coal seam in the Baode Mine. A multi-parameter integrated methodology was developed to establish a hierarchical classification system of Gas Geological Units (GGUs), aiming to identify regions suitable for large-scale gas extraction. The results indicate that the overall structure of the No. 8 coal seam is a simple monocline. Both gas content (ranging from 2.0 to 7.0 m³/t) and gas pressure (ranging from 0.2 to 0.65 MPa) generally increase with burial depth. However, local anomalies in these parameters, caused by geological structures and hydrogeological conditions, significantly limit the effectiveness of large-scale drainage using ultra-long boreholes. Based on key criteria, the seam was classified into three Grade I and ten Grade II GGUs, distinguishing anomalous zones from homogeneous units. Among the Grade II units, eight (II-i to II-viii) were identified as anomalous zones with distinct geological constraints, while two (II-ix and II-x) exhibited homogeneous gas geological parameters. Practical implementation of large-scale gas extraction strategies—including underground ultra-long boreholes and a U-shaped surface well—within the homogeneous Unit II-x demonstrated significantly improved gas drainage performance, characterized by higher methane concentration, greater flow rate, enhanced temporal stability, and more favorable decay characteristics compared to conventional boreholes. These findings confirm the critical role of GGU delineation in guiding efficient regional gas control and ensuring safe production in similar high-gas coal mines. Full article

This study investigates the combustion behavior of H₂–CH₄ mixtures with oxygen-enriched air, achieved through injecting ozone (O₃) into the air intake of the burner fan. The motivation for this approach lies in the high reactivity of hydrogen compared to methane, with the aim of promoting a more favorable oxidizing environment for overall combustion. The research combines theoretical analysis with experimental validation using a diffusion-type burner operating at a fuel flow rate of 1.2 Nm³/h. For this flow rate, the ozone injection led to an equivalent O₂ concentration of approximately 21.7%. At this enrichment level, flame temperature was calculated to increase by 70–90 °C. The burner was specifically designed for the diffusion combustion of H₂–CH₄ mixtures and features three fuel injection nozzles, each surrounded by five air inlets. Experiments employed premixed H₂-CH₄ gas cylinders (Linde) with hydrogen concentrations of 20% and 30%, respectively. The results confirmed slight combustion intensification due to elevated oxygen concentration, with no issues related to flame stability or pulsations observed. Core flame temperature and flue gas emissions, including CO₂, were measured. The results support the further development of this combustion technology by increasing the allowable oxygen concentration limit. Full article

Livestock production raises significant environmental concerns, necessitating the development of sustainable feeding strategies based on non-conventional forages, such as locally available vegetation. This study evaluated the effects of a pelleted concentrate containing 10% Acacia farnesiana leaves as a dietary supplement on in vitro ruminal fermentation. Four experimental diets were formulated with increasing levels of the concentrate (0%, 25%, 50%, and 75%). Analyses were performed in triplicate and included chemical composition, in vitro gas and methane production, fermentation kinetics, ammonia nitrogen concentration (N–NH₃), in vitro dry matter digestibility (IVDMD), and metabolizable energy (ME) estimation. The results revealed no significant differences (p > 0.05) in most gas production kinetic parameters, overall fermentation patterns, or metabolizable energy. In contrast, a significant increase (p < 0.05) in secondary metabolite concentrations was detected. While methane production remained unaltered (p > 0.05), a significant linear reduction was observed for IVDMD, the lag phase (L), and N–NH₃ concentration (p = 0.0064, p = 0.0036, and p < 0.0001, respectively). These findings suggest that A. farnesiana can be incorporated into ruminant concentrates without increasing methane emissions. However, in vivo trials and mechanistic studies are required to validate and further elucidate these results. Full article

Thermo-catalytic decomposition (TCD) presents a promising pathway for producing hydrogen from natural gas without emitting CO₂. This process represents a form of fossil fuel decarbonization where the byproduct, rather than being a greenhouse gas, is a solid carbon material with potential for commercial value. This study examines the dynamic behavior of TCD, showing that carbon formed during the reaction first enhances and later dominates methane decomposition. Three types of carbon materials were employed as starting catalysts. Methane decomposition was continuously monitored using on-line Fourier transform infrared (FT-IR) spectroscopy. The concentration and nature of surface-active sites were determined using a two-step approach: oxygen chemisorption followed by elemental analysis through X-ray photoelectron spectroscopy (XPS). Changes in the morphology and nanostructure of the carbon catalysts, both before and after TCD, were examined using high-resolution transmission electron microscopy (HRTEM). Thermogravimetric analysis (TGA) was used to study the reactivity of the TCD deposits in relation to the initial catalysts. Partial oxidation altered the structural and surface chemistry of the initial carbon catalysts, resulting in activation energies of 69.7–136.7 kJ/mol for methane. The presence of C₂ and C₃ species doubled methane decomposition (12% → 24%). TCD carbon displayed higher reactivity than the nascent catalysts and sustained long-term activity. Full article

This paper investigates the combustion characteristics of promising decarbonized fuel mixtures—methane/hydrogen (CH₄/H₂) and ammonia/hydrogen (NH₃/H₂)—with a focus on how they interact with external electric fields. The key findings are that these flames possess significant electrochemical properties, allowing for non-intrusive control over their stabilization, shape, and structure using relatively weak electric fields. The research combines experimental techniques like volt-ampere characteristic (VAC) measurement and advanced Hilbert visualization to analyze flame deformation, temperature distribution, and species concentration. Two orientations of the electric field were considered: transverse and longitudinal. For the transverse field, an assessment of the degree of flame deformation was made, indicating the preservation of the laminar combustion regime. In the longitudinal electric field, a change in the combustion stabilization mode was observed, which was detected through visualization and current-voltage characteristics (CVC). Full article

This study aimed to evaluate the potential benefits of co-digesting rapeseed oil cake, a by-product of biodiesel production, with microalgal biomass. Anaerobic fermentation was carried out under mesophilic conditions using various doses of press residue as a co-substrate. The results demonstrate that the addition of rapeseed oil cake enhances biogas production. The highest biogas yield was achieved during co-digestion with 1 g VS·L⁻¹ of microalgal biomass and 0.5 g VS·L⁻¹ of rapeseed oil cake. The average methane content in the biogas was 62.42%. The average hydrogen sulfide concentration ranged from 400 to 700 ppm. The maximum energy yield of 3.76 kWh·kg⁻¹ DM was obtained from co-digesting microalgal and rapeseed oil cake biomass in a 2:1 ratio. Full article

To enhance the structural safety of casings in coalbed methane (CBM) wells, this study develops a finite element model of the casing-cement sheath-formation assembly using ABAQUS software (ABAQUS 6.14). The model systematically investigates the influence of cement sheath defect thickness, defect angle, and internal pressure on the casing stress distribution. The results reveal that the cement sheath defects significantly elevate the casing stress, particularly when the defect is located at the first cementing interface. Casing stress increases most sharply when the defect angle lies between 20° and 60°. Beyond 60°, the stress on the outer wall approaches the yield strength of the casing material. Furthermore, rising internal pressure intensifies stress concentration. When internal pressure exceeds 60 MPa, the outer wall becomes the most likely location for failure initiation. Optimizing the elastic modulus of the cement sheath and employing heavy-wall casing grades such as TP125V can effectively mitigate the casing stress and enhance wellbore integrity. These findings offer both theoretical insights and practical guidance for optimizing cementing design and hydraulic fracturing operations in CBM wells. Full article

Swine manure poses significant challenges for anaerobic digestion due to its low carbon-to-nitrogen (C/N) ratio and elevated ammonia concentrations, both of which restrict methane generation. This study investigated the impact of integrating low-intensity ultrasound with co-digestion of piggery wastewater and food waste leachate. Laboratory-scale upflow anaerobic sludge blanket (UASB) reactors were employed under four operational conditions to evaluate anaerobic digestion performance, track shifts in microbial community structure, and assess the abundance of antibiotic resistance genes (ARGs). Co-digestion significantly enhanced methane production, yielding 1.3–3.2 times more than manure alone, while low-intensity ultrasound further increased methane yields by approximately 36–44% at high loading rates. Moreover, coupling low-intensity ultrasound with co-digestion led to the most rapid recovery following an overloading shock. Unexpectedly, ultrasound treatment alone increased the expression of certain ARGs (tetG, sul1, ermB) and the Integrase gene (intI1), while co-digestion led to a reduction in these genetic markers. These findings clearly indicate that the concurrent application of co-digestion and low-intensity ultrasound achieved the highest methane yield, the fastest recovery after organic overloading, and greater suppression of specific ARGs. Full article

Using Excel and its Solver feature, a novel method of analyzing the component reactions of an overall reaction is outlined. As an example, autothermal reforming (300–700 °C) of acetic acid (AA), a significant component of pyrolysis oil, was considered. The overall reaction can be viewed as comprising five individual reactions: reforming, oxidation, water–gas shift, reverse Boudouard, and methanation. A laboratory apparatus was set up in which acetic acid, air, and water were continuously fed to a BASF dual-layer catalytic reactor in plug flow at 1 atm. For this setup, it is easy to construct a material balance in Excel in which five factors, f_i, are defined which represent the fraction of reactant going to each of the individual five reactions. Using the Solver feature of Excel, it can readily be determined which of the five factors f_i produce the best match of the calculated exit gas composition with the measured gas concentrations for CO, CO₂, H₂, CH₄, and O₂. Furthermore, a program such as GasEq or Aspen can then be used to calculate the theoretical equilibrium gas composition at a given condition. Using this equilibrium gas composition and Solver, the individual (f_i)_equilb can be calculated. Thus, the ratio f_i/(f_i)_equilb is an indication of how close each component reaction is to equilibrium. In this way, an idea is gained of which of the individual component reactions need to be improved or inhibited or if operating parameters should be adjusted. For the specific case of autothermal reforming of acetic acid, the steam reforming reaction requires at least 600 °C to approach equilibrium. In contrast, the oxidation reaction goes to equilibrium throughout the temperature range, completely consuming oxygen. The water–gas shift reaction appears to approach equilibrium to the extent of 71–90% throughout the temperature range. The reverse Boudouard reaction is favored at lower temperatures; in fact, coking was predicted and found at the low temperature of 300 °C. Full article

The implementation and monitoring of Republic Act (RA) 9003 of the Philippines presents significant challenges due to the vast area and limited number of implementing enforcers. RA 9003 focuses on ecological solid management systems. The law relies on citizens’ identification of violators. In this study, we developed a plastic combustion monitoring system, Green Guardian, which detects and monitors methane (CH₄), carbon dioxide (CO₂), and carbon monoxide (CO) concentrations using the Internet of Things technology. The system was tested in Barangay in Cabuyao City, Laguna, Philippines. This system supports RA 9003 implementation, enabling efficient tracking, reporting, and management of plastic combustion incidents. By using self-calibration testing, third-party testing, isolation testing, location testing, and user acceptance test (UAT), the system’s accuracy and reliability were validated. Full article