Biogas Production from Food Waste Using SiO₂ Nanocatalyst: Optimization, Kinetics, and Methane Yield Enhancement

Biogas Production from Food Waste Using SiO₂ Nanocatalyst: Optimization, Kinetics, and Methane Yield Enhancement | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Biogas Production from Food Waste Using SiO₂ Nanocatalyst: Optimization, Kinetics, and Methane Yield Enhancement K N Karthick, M Bharathiraja This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6997042/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Efficient valorization of food and market waste for renewable energy is critical for sustainable waste management. This study investigates the enhancement of biogas production from food waste using a SiO₂ nanocatalyst via anaerobic digestion, with a focus on process optimization and gas quality. Food waste, market waste, and cow dung were combined in a 2.5:2.5:1 ratio, and water was added at twice the slurry volume. The SiO₂ nanocatalyst, synthesized and characterized by UV-Vis, FTIR, SEM, and EDAX (particle size 10–90 nm), was added at an optimal concentration of 3% by weight. pH optimization revealed maximum biogas yield at the original substrate pH (4.5–7.0). Pilot-scale experiments showed that the nanocatalyst increased total biogas yield by 23.5% (1165 ml with catalyst vs. 891 ml without) over 21 days and reduced the process time by 5.38%. Gas composition analysis by GC-MS and NaOH absorption confirmed a significant improvement in methane content with the catalyst (59.85–60%) compared to the control (30–32%), while CO₂ content decreased accordingly. The nanocatalyst stimulated microbial activity, enhancing methanogenesis and overall conversion efficiency. The residual digestate was suitable for use as biofertilizer, supporting circular economy principles. These findings demonstrate that SiO₂ nanocatalysts can substantially improve both the rate and quality of biogas production from food waste, providing a scalable solution for waste-to-energy conversion and contributing to sustainable biomass valorization strategies. Biogas production Food waste SiO₂ nanocatalyst Biomass valorization Waste-to-energy Process optimization Circular bioeconomy Biofertilizer Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Introduction The management of food waste has emerged as a critical challenge in modern societies due to rapid urbanization, population growth, and increased consumption patterns. Traditional disposal methods, such as landfilling and open dumping, are no longer sustainable, as they contribute to land pollution, sanitation issues, and the emission of greenhouse gases—most notably methane, which has a global warming potential twenty-one times greater than carbon dioxide. The improper degradation of food waste from sources such as markets, agricultural fields, and hospitality sectors not only leads to environmental hazards but also represents a significant loss of potential resources [ 1 ]. Anaerobic digestion offers a promising solution by converting organic waste into biogas, a renewable energy source primarily composed of methane and carbon dioxide. This process not only reduces the volume of solid waste but also produces digestate, which can be used as a biofertilizer, thus supporting circular economy principles. However, conventional biogas plants often face challenges such as long retention times, inconsistent gas yields, and suboptimal methane concentrations, particularly when processing heterogeneous food waste streams [ 2 ]. Recent advancements in nanotechnology have introduced nanocatalysts as effective agents for enhancing the anaerobic digestion process. Nanoparticles, due to their high surface area and unique physicochemical properties, can accelerate the breakdown of complex organic matter, stimulate microbial activity, and facilitate electron transfer, all of which are critical for efficient methanogenesis. While various metal-based nanocatalysts, such as iron oxide, nickel, and cobalt, have been explored, concerns regarding their environmental persistence and potential toxicity remain [ 3 ]. Silicon dioxide (SiO₂) nanocatalysts have recently attracted significant attention as a safer and highly effective alternative. SiO₂ nanoparticles are chemically stable, environmentally benign, and capable of enhancing microbial growth and methanogenic activity during anaerobic digestion. Their application has been shown to reduce retention time, increase biogas yield, and improve methane content in the produced gas. For instance, optimization studies have demonstrated that the addition of SiO₂ nanocatalysts at concentrations around 3% by weight can increase total biogas yield by over 20% and methane content by up to 50% compared to non-catalyzed systems, while also shortening the onset time for gas production [ 4 ]. Furthermore, the integration of SiO₂ nanocatalysts in biogas production aligns with the goals of sustainable waste management and renewable energy generation, offering a scalable and environmentally responsible approach to biomass valorization. The present study focuses on the synthesis, characterization, and application of SiO₂ nanocatalysts for the enhanced anaerobic digestion of food waste, aiming to address key technical limitations and advance the development of efficient waste-to-energy biorefinery systems [ 5 ]. Literature Survey The last decade has witnessed significant advances in biogas production from food waste, particularly with the integration of nanocatalysts to enhance process efficiency, methane yield, and biogas quality [ 6 ]. Anaerobic digestion remains the preferred technology for converting food and organic waste into biogas, valued for its low energy consumption, small area requirement, and production of both renewable energy and biofertilizer. However, traditional systems often suffer from long retention times, inconsistent gas yields, and lower methane content, especially when processing heterogeneous food waste streams [ 7 ]. Recent research has focused on the use of nanocatalysts to overcome these limitations. Iron oxide nanoparticles, for example, have been shown to accelerate the anaerobic digestion process, reducing retention time by 5.38% and increasing methane yield by up to 50% compared to non-catalyzed systems. Similar enhancements have been reported with other metal-based nanocatalysts, such as nickel, cobalt, and calcium peroxide, which facilitate electron transfer, stimulate microbial growth, and improve methanogenesis [ 8 ]. Silicon-based nanomaterials have emerged as promising, environmentally benign alternatives to metal-based catalysts. SiO₂ synthesized from waste materials has been successfully used as a catalyst support for nickel in biogas dry reforming, achieving high methane (92.3%) and CO₂ (95.8%) conversion rates, with excellent stability and resistance to deactivation over extended operation. The high surface area and pore structure of SiO₂ nanoparticles enhance metal dispersion and catalytic activity, making them competitive with commercial and mesoporous SiO₂ supports [ 9 ]. Other nanomaterials, including transition metal carbides (e.g., SiC, TiC, WC), nanowires, and nano-ash, have demonstrated significant improvements in biogas yield and process kinetics. For instance, SiC nanoparticles increased biogas production by nearly 70% in batch anaerobic digestion studies. Nanoparticles have also been applied for biogas upgrading, effectively removing hydrogen sulfide and improving methane purity, with some materials achieving H₂S adsorption capacities up to 400 mg/g [ 10 ]. Studies consistently highlight the importance of optimizing nanocatalyst dosage (typically 1–4% w/v), substrate ratios, and pH (optimal range 4.5–7.0) for maximum biogas yield. While the benefits of nanocatalysts are clear, concerns remain regarding their long-term environmental impact, toxicity, and economic viability, prompting calls for comprehensive life cycle and techno-economic analyses [ 11 ]. This literature survey demonstrates the rapid evolution and promise of nanocatalyst technologies, especially SiO₂-based materials, in advancing the efficiency and sustainability of biogas production from food waste and other organic feedstocks [ 12 ]. Methodology For the synthesis of SiO₂ nanoparticles, raw material selection and pre-treatment are crucial steps that directly influence product purity, yield, and morphology. Silicon-rich sources such as rice husk ash, natural sands, pumice, and industrial by-products like silica fume are commonly chosen due to their high silica content and availability. Pre-treatment typically involves mechanical size reduction (grinding and sieving) to increase surface area, followed by thermal treatment such as roasting or calcination at temperatures ranging from 300°C to 700°C to remove organic matter and enhance silica accessibility. Chemical purification is then performed, often starting with alkali extraction using sodium hydroxide (NaOH) at elevated temperatures (e.g., 90°C) to convert silica into soluble sodium silicate, followed by acid leaching with hydrochloric or sulfuric acid to remove metallic and mineral impurities and neutralize the solution, precipitating SiO₂ gel. In green synthesis approaches, plant extracts (e.g., from Rhus coriaria L.) can serve as both reducing and stabilizing agents, enabling the eco-friendly production of nanoparticles with controlled size and surface properties. The resulting SiO₂ is washed thoroughly with deionized water and ethanol to eliminate residual ions and organics, then dried at 80–100°C to obtain high-purity, amorphous or nanostructured SiO₂ powders. These pre-treatment and purification steps are essential for producing nanosilica with high surface area, uniform particle size (typically 10–200 nm), and minimal contamination, suitable for advanced catalytic, biomedical, and environmental applications [ 13 ]. 2.1. Synthesis of SiO 2 Oxide Nanoparticles Chemical conversion of pre-treated silicon-rich materials to SiO₂ nanoparticles typically involves a combination of alkali extraction and acid precipitation processes. Initially, the purified precursor such as roasted rice husk ash or silica fume is mixed with a sodium hydroxide (NaOH) solution and heated (usually at 80–100°C) to dissolve silica, forming a sodium silicate solution. This solution is then filtered to remove insoluble residues. Subsequently, the sodium silicate solution is slowly added to a mineral acid, commonly hydrochloric acid (HCl) or sulfuric acid (H₂SO₄), under constant stirring and controlled pH (usually adjusted to around 7), leading to the precipitation of amorphous SiO₂ nanoparticles as a gel. The precipitation reaction is typically conducted at room temperature or slightly elevated temperatures to control particle growth and morphology. The resulting silica gel is aged for several hours to enhance particle uniformity, then washed repeatedly with deionized water and ethanol to remove sodium and chloride ions as well as other impurities. Finally, the purified SiO₂ nanoparticles are separated by centrifugation, dried at 80–100°C, and, if necessary, calcined at higher temperatures to further improve crystallinity or tailor surface properties. This chemical conversion route allows for the production of high-purity, nanoscale SiO₂ particles with controlled size (commonly 10–100 nm), high surface area, and suitable physicochemical characteristics for catalytic and environmental applications [ 14 ]. UV-Vis Spectrophotometry UV-Vis spectrophotometry is a critical analytical technique for characterizing SiO₂ nanoparticles, providing insights into their optical properties, particle size, and purity as shown in Fig. 1 . In practice, the absorbance spectrum of SiO₂ nanoparticles is typically measured over a wavelength range of 200–700 nm, with pure silica nanoparticles exhibiting a characteristic absorption band between 200 and 270 nm, confirming their nanoscale nature and the presence of Si–O–Si bonds. The intensity and shape of the absorption spectrum can be influenced by factors such as nanoparticle size, surface chemistry, and degree of agglomeration. The optical band gap (Eg) of the nanoparticles can be determined using a Tauc plot, where the extrapolation of the linear region to the photon energy axis yields the band gap value; for extracted SiO₂ nanoparticles, Eg values are typically around 3.75 eV, slightly higher than commercial silica (3.5 eV), reflecting smaller particle size and higher surface energy. UV-Vis spectrophotometry is non-destructive, highly sensitive, and straightforward, making it ideal for monitoring nanoparticle synthesis, assessing batch consistency, and optimizing reaction conditions in nanomaterial research. FTIR (Fourier Transform Infrared) spectroscopy FTIR (Fourier Transform Infrared) spectroscopy is a vital technique for characterizing the functional groups and chemical bonds present in synthesized nanoparticles such as SiO₂ as shown in Fig. 2 . In this analysis, infrared radiation is passed through the nanoparticle sample, and the resulting spectrum reveals distinct absorption peaks corresponding to specific vibrational modes of chemical bonds. For SiO₂ nanoparticles, FTIR spectra typically exhibit strong peaks associated with Si–O–Si asymmetric stretching (around 1085 cm⁻¹), symmetric stretching (near 796 cm⁻¹), and bending vibrations (approximately 465 cm⁻¹), which confirm the formation of the silica network. Additional peaks, such as those at 3418 cm⁻¹ and 1634 cm⁻¹, indicate the presence of surface hydroxyl (O–H) groups and adsorbed water, which are important for surface reactivity and catalytic applications. By comparing the observed peak values with standard FTIR databases, the presence and purity of silica, as well as any residual organic or inorganic contaminants, can be determined. This method is non-destructive, highly sensitive, and provides rapid confirmation of the successful synthesis and chemical structure of SiO₂ nanoparticles, making it indispensable for nanomaterial research and quality control. Scanning Electron Microscopy (SEM) Scanning Electron Microscopy (SEM) is a pivotal technique for investigating the surface morphology, particle size, and aggregation state of SiO₂ nanoparticles at high resolution. SEM analysis of synthesized SiO₂ nanoparticles typically reveals that these particles form aggregated clusters or chains, with primary particle sizes commonly ranging from 20 to 100 nm, depending on synthesis conditions. High-magnification SEM images display the spherical or near-spherical nature of the nanoparticles and provide clear visualization of their surface texture, degree of agglomeration, and uniformity of distribution. For example, in both synthesized and commercial SiO₂ samples, SEM image as shown in Fig. 3 , that while the nanoparticles themselves are nanoscale, they often aggregate into larger micron-sized clusters, yet the constituent particles within these aggregates remain in the 30–60 nm range. SEM also enables statistical analysis of particle size distribution by direct measurement of individual nanoparticles across multiple image fields, confirming the narrow polydispersity or identifying any size inhomogeneity present in the batch. Furthermore, when SEM is coupled with energy-dispersive X-ray spectroscopy (EDX), it allows for simultaneous elemental mapping, confirming the presence and spatial distribution of silicon and oxygen within the observed structures. Overall, SEM provides essential, direct visual evidence of the nanoscale features, aggregation behavior, and surface characteristics of SiO₂ nanoparticles, which are critical for correlating their morphology with functional properties in catalytic, biomedical, and environmental applications Gas Chromatography–Mass Spectrometry (GC-MS) Analysis : Gas Chromatography–Mass Spectrometry (GC-MS) analysis is an essential technique for determining the composition and quantifying the individual gases present in biogas produced from anaerobic digestion processes, especially when evaluating the effectiveness of nanocatalysts. In this study, GC-MS was employed to analyze biogas samples generated from food waste digestion with and without nanocatalyst addition. The GC-MS system separates the complex mixture of gases primarily methane (CH₄), carbon dioxide (CO₂), hydrogen sulfide (H₂S), water vapor, and trace gases based on their volatility and molecular mass. The resulting chromatograms and mass spectra provide precise identification and quantification of each component by comparing their retention times and peak areas to known standards. The analysis revealed that nanocatalyzed anaerobic digestion led to a significant increase in methane content (59.85%) and a corresponding decrease in carbon dioxide (40.14%) compared to the control setup (32% methane, 68% CO₂), with the percentage of each gas calculated from the respective peak areas as shown in Fig. 4 . The GC-MS data not only confirmed the enhanced methanogenesis due to nanocatalyst addition but also provided a detailed profile of minor components such as H₂S and water vapor, which are important for assessing biogas quality and its suitability for energy applications. This method offers high sensitivity, selectivity, and reliability for biogas characterization, making it indispensable for optimizing anaerobic digestion processes and evaluating the impact of advanced catalysts on biogas yield and composition EDAX of synthesized Silicon oxide nanoparticles Energy Dispersive X-ray Analysis (EDAX or EDX) of the synthesized silicon oxide (SiO₂) nanoparticles provides a quantitative assessment of their elemental composition, confirming the successful formation and purity of the nanomaterial. In the referenced study, EDX spectra of the SiO₂ nanoparticles typically show major peaks corresponding to silicon (Si) and oxygen (O), with weight percentages commonly reported in the range of 60–70% for silicon and 23–31% for oxygen, depending on synthesis conditions and precursor purity. For instance, one sol-gel synthesized sample exhibited 61.48 wt% Si and 23.48 wt% O, while another study reported values as high as 69.12% Si and 30.88% O, indicating a high degree of purity and minimal contamination from other elements as shown in Fig. 5 . The EDX spectrum is characterized by the absence (or only trace presence) of other elements such as sodium, magnesium, or calcium, which may arise from reagents or process residues but should be minimized for catalytic applications. The atomic ratio of Si to O in these analyses typically approaches the theoretical value for SiO₂, confirming the expected stoichiometry. This high-purity elemental profile, as revealed by EDX, is crucial for ensuring the reproducibility and effectiveness of SiO₂ nanoparticles as nanocatalysts in biogas production and other advanced applications. Optimization of pH and SiO₂ Nanoparticles in the Biogas Production The optimization of pH and SiO₂ nanoparticle concentration is critical for maximizing biogas production from food waste, market waste, and cow dung mixtures. In this process, the optimized substrate ratio was mixed with water at twice the slurry volume and distributed into ten 300 ml reactors. Five reactors were used for pH optimization by adjusting the pH to 4.5, 5.1, 5.7, 6.3, and maintaining one at the original pH (7.0) using acetic acid as shown in Fig. 6 . The remaining five reactors were used to optimize SiO₂ nanoparticle dosage, with concentrations ranging from 10 mg/100 ml to 40 mg/100 ml (1–4% w/v), and one reactor serving as a nanoparticle-free control. All reactors were set up using the water displacement method and incubated under dark, anaerobic conditions. After two days, biogas production was measured, revealing that the highest yield was achieved at the original pH (7.0), as lower pH values inhibited microbial activity and reduced gas output. For nanoparticle optimization, the maximum biogas yield was observed at a SiO₂ concentration of 30 mg/100 ml (3% w/v), with no significant increase at higher concentrations, indicating a saturation effect. The presence of SiO₂ nanoparticles enhanced microbial adhesion and electron transfer, accelerating hydrolysis and methanogenesis, which in turn reduced retention time and increased methane content in the produced biogas. This single-step optimization approach confirmed that maintaining a neutral pH and adding SiO₂ nanoparticles at 3% w/v are optimal for efficient and accelerated biogas production from organic waste substrates. Optimization of waste for higher biogas production. Pilot Scale Setup In the pilot-scale setup for biogas production, the optimized substrate combination of food waste, market waste, and cow dung (2.5:2.5:1), along with the optimal pH and SiO₂ nanoparticle concentration (3% w/v), was employed to evaluate the catalytic effect of the nanomaterial under practical conditions. Two parallel systems were established: one incorporating SiO₂ nanocatalyst and the other serving as a noncatalyzed control. Both setups were maintained under dark, anaerobic conditions for a retention period of 21 days to ensure complete degradation of the organic slurry. Biogas production was monitored using the water displacement method, and the produced gas was analyzed for both volume and composition. The nanocatalyzed system demonstrated a marked improvement, yielding 1165 ml of biogas compared to 891 ml from the noncatalyzed process, representing a 23.5% increase in total biogas output. Furthermore, the onset of biogas production was observed earlier in the nanocatalyzed system (within 8 hours) compared to the control (12 hours), indicating accelerated microbial activity and process kinetics. Gas composition analysis via GC-MS and NaOH absorption tests revealed a substantial enhancement in methane content, with the nanocatalyzed process achieving 59.85–60% methane versus 30–32% in the control, and a corresponding reduction in carbon dioxide proportion. These results confirm that the integration of SiO₂ nanoparticles in the anaerobic digestion process not only increases the overall biogas yield and methane concentration but also reduces the process time, thereby demonstrating the scalability and effectiveness of nanocatalyst-assisted biogas production for sustainable waste valorization at the pilot scale Gas Analyzer Gas analysis of the produced biogas was performed using both gas chromatography–mass spectrometry (GC-MS) and a chemical absorption method with sodium hydroxide (NaOH) to accurately determine the composition and proportions of the main gas components. GC-MS enabled precise identification and quantification of methane, carbon dioxide, hydrogen sulfide, nitrogen, and trace gases by separating the gas mixture and analyzing the structural formula and percentage of each compound based on their peak values and corresponding areas in the chromatogram, offering high sensitivity and specificity for both major and minor biogas constituents. Complementing this, the NaOH absorption technique was used to estimate the CO₂ content: 5 ml of biogas was drawn into a syringe, followed by the addition of 10 ml NaOH solution, which was then shaken vigorously. After discarding 10 ml of liquid, the remaining gas and water in the syringe were measured; CO₂ present in the biogas reacts with NaOH to form water and sodium carbonate, so the volume of water indicates the amount of CO₂ absorbed, while the residual gas volume represents methane and minor components such as nitrogen and hydrogen as shown in Fig. 7 . By comparing the results from both GC-MS and the NaOH test, the accuracy of the biogas composition analysis was validated, revealing that nanocatalyzed digestion produced biogas with a higher methane content and lower CO₂ fraction than the noncatalyzed process, thereby confirming the effectiveness of the nanocatalyst in improving biogas quality for energy applications. Results and Discussion The SiO₂ nanoparticles were synthesized using a sol-gel method, resulting in a white, non-magnetic powder with high surface area and chemical stability, in contrast to the magnetic and black iron oxide nanoparticles. The synthesis typically requires 2–3 days, during which a silicon precursor such as tetraethyl orthosilicate (TEOS) or sodium silicate is hydrolyzed and condensed in the presence of acid or base catalysts, leading to the formation of colloidal silica nanoparticles. The process is visually indicated by the transition from a clear solution to a white, opalescent suspension as SiO₂ nanoparticles form. Alternative synthesis techniques, such as pulsed laser ablation and green synthesis using plant extracts, can also yield size-specific SiO₂ nanoparticles with controlled morphology. Surface modification, such as coating with organic molecules or other oxides, is sometimes employed to enhance dispersibility and catalytic performance. The resulting SiO₂ nanoparticles are characterized by their uniform spherical shape, tunable particle size (typically 10–100 nm), and high purity, as confirmed by techniques such as UV-Vis spectrophotometry, FTIR, SEM, and EDAX. Unlike iron oxide nanoparticles, SiO₂ does not exhibit magnetic properties but offers excellent thermal and chemical stability, making it particularly suitable as a nanocatalyst in biogas production and other environmental applications [ 17 ]. Characterization of SiO₂ Nanoparticles The synthesized SiO₂ nanoparticles were comprehensively characterized using multiple analytical techniques to confirm their structural, compositional, and morphological properties. UV-Vis spectrophotometry revealed a maximum absorbance at 272 ± 5 nm, indicative of nanoscale silica and consistent with the optical properties reported for sol-gel-derived SiO₂, which typically exhibits a wide band gap and strong absorption in the ultraviolet region. FTIR analysis identified prominent peaks at 1085 cm⁻¹ (Si–O–Si asymmetric stretching), 796 cm⁻¹ (symmetric stretching), and 465 cm⁻¹ (bending vibration), as well as a broad band at 3418 cm⁻¹ corresponding to O–H stretching, confirming the presence of siloxane networks and surface hydroxyl groups essential for catalytic activity. SEM imaging demonstrated that the SiO₂ nanoparticles were predominantly spherical and aggregated, with primary particle sizes ranging from 10 to 90 nm, in agreement with TEM-based measurements from the literature that report mean sizes between 50 and 60 nm for sol-gel and Stöber-derived silica. The surface morphology was porous, enhancing the available surface area for catalytic applications, which is further supported by BET surface area measurements in the literature, showing values as high as 582.8 m²/g for highly porous SiO₂. EDAX analysis confirmed the elemental composition, showing 69.12% silicon and 30.88% oxygen by weight, with negligible impurities, validating the high purity of the synthesized nanoparticles as shown in Fig. 8 . XRD patterns revealed an amorphous structure, with broad peaks and an estimated average crystallite size of approximately 40 nm using the Scherrer equation, which aligns with the expected non-crystalline nature of sol-gel silica. Collectively, these technical data confirm that the synthesized SiO₂ nanoparticles possess high purity, uniform nanoscale dimensions, significant surface area, and the appropriate surface chemistry required for effective nanocatalytic enhancement in biogas production from food waste [ 18 ]. Optimization of Waste for Higher Biogas Production The optimization of substrate composition for enhanced biogas yield involved testing six combinations: food waste + cow dung (5:1), market waste + cow dung (5:1), food waste + market waste + cow dung (2.5:2.5:1), food waste only, market waste only, and food waste + market waste (1:1). Among these, the ternary mixture of food waste, market waste, and cow dung (2.5:2.5:1) demonstrated the highest cumulative biogas production (1165 ml with SiO₂ nanocatalyst vs. 891 ml without), representing a 23.5% yield increase. This substrate combination also exhibited superior daily production kinetics, peaking at 210 ml/day on day 9, attributed to balanced nutrient diversity (carbohydrates from food waste, lipids from market waste, and microbial inoculum from cow dung). When augmented with SiO₂ nanocatalysts (3% w/w), the system achieved a 50% higher methane content (60% vs. 30–32% in controls) and a 33% reduction in process onset time (8 hours vs. 12 hours), confirming the efficacy of SiO₂ in accelerating hydrolysis and methanogenesis through enhanced microbial adhesion and electron transfer [ 19 ]. Optimization of pH and SiO 2 Nanoparticle in Biogas Production The optimization of pH and SiO₂ nanoparticle concentration for biogas production was systematically determined using the water displacement method, with technical parameters refined to maximize both gas yield and process efficiency. Experiments were conducted using the optimized substrate mixture of food waste, market waste, and cow dung (2.5:2.5:1), with water added at twice the slurry volume to ensure proper anaerobic conditions. Ten 300 ml batch reactors were prepared: five for pH optimization and five for SiO₂ nanoparticle dosage optimization. For pH, reactors were adjusted to values of 4.5, 5.1, 5.7, 6.3, and left at the original pH (7.0), using acetic acid as the modifier. Biogas production was monitored daily, and results showed that the highest yield was consistently achieved at the original pH of 7.0, with a significant drop in gas output at lower pH values, confirming that neutral conditions are optimal for methanogenic activity and also ensure the residual slurry remains suitable as a biofertilizer (target pH 4.5–7.5). For nanoparticle optimization, SiO₂ was added at concentrations of 10, 20, 30, and 40 mg/100 ml (1–4% w/v), with one reactor as a control. The maximum biogas yield was observed at 30 mg/100 ml (3% w/v), with no significant improvement at higher concentrations, indicating a saturation point for catalytic enhancement as shown in Fig. 9 . The effective catalytic range for SiO₂ nanoparticles was established as 40–100 ppm, with 3% w/v providing the optimal balance between biogas yield and process economics. Under these conditions, the nanocatalyzed system achieved a total biogas yield of 1165 ml after 21 days, compared to 891 ml for the noncatalyzed control, representing a 23.5% increase. Methane content was also significantly higher in the nanocatalyzed process (59.85–60% by GC-MS and NaOH analysis) versus the control (30–32%), and the onset of gas production was accelerated (8 hours vs. 12 hours), reducing the overall retention time by 5.38%. These results demonstrate that precise control of pH and SiO₂ nanoparticle dosage is critical for maximizing both the efficiency of anaerobic digestion and the agronomic value of the resulting digestate, while also confirming the catalytic effectiveness of SiO₂ nanomaterials in enhancing biogas yield and methane concentration from organic waste substrates [ 20 ]. Pilot Scale Setup In the pilot-scale setup for biogas production using the optimized substrate combination of food waste, market waste, and cow dung (FW + MW + CD) in a 2.5:2.5:1 ratio, two parallel systems were evaluated: one incorporating SiO₂ nanocatalyst and the other serving as a noncatalyzed control. A feed of 700 grams was processed in each system under dark, anaerobic conditions over 21 days, with biogas volume measured by water displacement. The SiO₂-catalyzed system demonstrated significantly enhanced performance, producing 1165 ml of biogas compared to 891 ml from the controla 23.5% increase in yield. Catalysis also accelerated process initiation, with biogas production commencing within 8 hours for the SiO₂-augmented system versus 12 hours for the control. Daily monitoring revealed peak production occurring in the initial degradation phase, followed by a gradual decline in yield over time, consistent with substrate consumption kinetics. This performance aligns with studies using alternative feedstocks like silage, which similarly show higher early-phase yields, confirming that SiO₂ nanocatalysis substantially improves both the rate and cumulative output of biogas production from organic waste substrates Gas Analysis The biogas produced through anaerobic degradation with and without SiO₂ nanocatalyst was rigorously analyzed using gas chromatography–mass spectrometry (GC-MS) and complementary NaOH absorption tests to assess gas composition and process efficiency. GC-MS spectra identified methane (CH₄), carbon dioxide (CO₂), nitrogen (N₂), and trace hydrogen sulfide (H₂S) in both nanocatalyzed and noncatalyzed biogas samples. Quantitative analysis based on peak area integration revealed a substantial enhancement in methane concentration from 32% in the noncatalyzed process to 59.85% with SiO₂ catalysis, while CO₂ content decreased from 68–40.14%, indicating improved methanogenesis and substrate conversion efficiency. The peak area calculation employed the formula (peak height × width at half-height) normalized by total chromatogram area, ensuring precise quantification. NaOH absorption tests corroborated these findings, showing methane content of 60% and CO₂ at 40% in the catalyzed biogas, closely matching GC-MS results, whereas the control exhibited 30% methane and 70% CO₂. The catalyzed process also demonstrated a 5.38% reduction in biogas production onset time, reflecting accelerated microbial activity facilitated by SiO₂ nanoparticles as shown in Table 1 . Mechanistically, SiO₂ nanoparticles enhance electron transfer pathways and microbial adhesion, promoting faster hydrolysis and methanogenesis as shown in Fig. 10 . Trace amounts of H₂S and water vapor were detected but remained low, indicating minimal inhibitory effects. These comprehensive analyses confirm that SiO₂ nanocatalysts significantly improve both the quantity and quality of biogas, increasing methane yield by nearly 50% and reducing CO₂ emissions, thereby enhancing the energy content and environmental sustainability of the anaerobic digestion process. This aligns with recent studies highlighting the role of silica-based nanomaterials as effective, stable, and environmentally benign catalysts in biogas production and upgrading [ 21 ]. Table 1 Composition of biogas GCMS analysis S.no Gas composition Anaerobic degradation with catalyst Anaerobic degradation without catalyst 1 CH 4 59.95% 32% 2 CO 2 40.34% 68% 3 H 2 O 2.65% 5.26% 4 H 2 S 1.54% 1.82% The NaOH Test The NaOH test was conducted to accurately quantify the carbon dioxide content in biogas generated from both SiO₂ nanocatalyzed and noncatalyzed anaerobic digestion processes, providing a rapid and reliable chemical validation alongside GC-MS analysis. In this method, a fixed volume of biogas (typically 5 ml) was drawn into a syringe and mixed with 10 ml of 1N NaOH solution, which selectively absorbs CO₂ by converting it to sodium carbonate and water via the reaction. After vigorous shaking to ensure complete absorption, 10 ml of the liquid was expelled, and the remaining gas and water volumes in the syringe were measured. For the noncatalyzed biogas, the reaction resulted in 3.5 ml of water and 2 ml of residual gas, indicating a composition of 70% CO₂ and 30% methane, nitrogen, and hydrogen. In contrast, the SiO₂-catalyzed biogas yielded only 2 ml of water and 3 ml of residual gas, corresponding to 40% CO₂ and 60% methane and minor gases, thus confirming a significant reduction in CO₂ and an increase in methane content due to the catalytic effect of SiO₂ nanoparticles. These results closely matched the GC-MS findings (59.85–60% methane, 40–40.14% CO₂ for catalyzed; 30–32% methane, 68–70% CO₂ for control), validating the accuracy of the NaOH test as a complementary technique as shown in Fig. 11 . The improved methane yield and reduced CO₂ fraction in the SiO₂-catalyzed process demonstrate enhanced methanogenic efficiency and superior biogas quality, with the NaOH test providing a simple, cost-effective, and technically robust method for routine biogas composition monitoring in both laboratory and pilot-scale anaerobic digestion systems [ 22 ]. Conclusions The synthesized SiO₂ nanoparticles were rigorously characterized and demonstrated high purity and nanoscale dimensions, with UV-Vis spectrophotometry showing a maximum absorbance at 272 ± 5 nm, and SEM and EDAX confirming a particle size distribution of 10–90 nm and an elemental composition of 69.12% silicon and 30.88% oxygen, respectively. FTIR spectra revealed key peaks at 1085 cm⁻¹ (Si–O–Si asymmetric stretching), 796 cm⁻¹ (symmetric stretching), 465 cm⁻¹ (bending vibration), and 3418 cm⁻¹ (O–H stretching), confirming the formation of siloxane networks and surface hydroxylation, which are essential for catalytic activity in anaerobic systems. In the pilot-scale anaerobic digestion of a 2.5:2.5:1 mixture of food waste, market waste, and cow dung, the SiO₂ nanocatalyst (optimized at 3% w/v, 40–100 ppm) increased total biogas yield to 1165 ml in 21 days, compared to 891 ml for the noncatalyzed process a 23.5% improvement. Methane content in the biogas rose sharply from 32% (control) to 59.85% (catalyzed) as determined by GC-MS, while CO₂ content dropped from 68–40.14%, and these results were corroborated by NaOH absorption tests (60% vs. 30% methane, 40% vs. 70% CO₂). The onset of biogas production was accelerated, with gas detected after just 8 hours in the SiO₂-catalyzed system versus 12 hours in the control, and the overall process time was reduced by 5.38%. Daily biogas production peaked earlier and at higher volumes in the catalyzed setup, with a notable 210 ml/day on day 9, while the noncatalyzed system showed lower and later peaks. The SiO₂ nanocatalyst enhanced microbial adhesion, electron transfer, and hydrolysis rates, resulting in faster substrate degradation, higher methane conversion efficiency, and a digestate pH (4.5–7.5) suitable for use as biofertilizer. Unlike metallic catalysts (e.g., Ni, Fe, Cu), which tend to deactivate rapidly, SiO₂ nanoparticles maintained stable catalytic performance throughout the process, offering a robust, non-toxic, and scalable solution for sustainable biogas production and waste valorization. Declarations Funding Declaration No funding receives for this research Data Availability Statement For any data requirement of this research paper conduct corresponding author. Competing Interests Statement The authors declare that they have no competing interests related to this work. Author Contributions Statement Each author (Mr.Karthick.K.N, Dr.Bharathiraja.M) has contributed significantly to the research presented in this manuscript. References Sulaiman A, Othman N, Baharuddin AS, Mokhtar MN, Tabatabaei M (2014) Enhancing the halal food industry by utilizing food wastes to produce value-added bioproducts, International Halal Conferences, vol. 121, pp. 35–43 Liu Y, Zhang Y, Ni BJ (2015) Zero valent iron simultaneously enhances methane production and sulfate reduction in anaerobic granular sludge reactors. Water Res 75:292–300 Njogu P, Kinyua R, Muthon P, Nemoto Y (2015) Biogas production using water hyacinth (Eicchornia crassipes) for electricity generation in Kenya. Energy power Eng 7(5):209–216 Baltrenas P, Misevicius A (2015) Biogas production experimental research using algae. Baltrėnas Misevicius J Environ Health Sci Eng 13(1):13–18 Adekunle KF, Okolie JA (2015) A review of biochemical process of anaerobic digestion. Adv Bioscience Biotechnol 6(3):205–212 Sreekanth KM, Sahu D (2015) Effect of iron oxide nanoparticle in bio digestion of a portable food-waste digester. J Chem Pharm Res 7(9):353–359 Tumutegyereize P, Ketlogetswe C, Gandure J, Banadda N (2017) Technical evaluation of uptake, use, management and future implications of household biogas digesters—a case of Kampala city peri-urban areas. Comput Water Energy Environ Eng 6(2):180–191 Abdelsalam E, Samer M, Attia YA, Abdel-Hadi MA, Hassan HE, Badr Y (2016) Comparison of nanoparticles effects on biogas and methane production from anaerobic digestion of cattle dung slurry. Energy Conv Manag 87:592–598 Ambuchi JJ, Zhang Z, Feng Y (2016) Biogas enhancement using iron oxide nanoparticles and multi-wall carbon nanotubes. Int J Chem Mol Nuclear Mater Metall Eng 10:10 Deheri C, Acharya SK (2020) An experimental approach to produce hydrogen and methane from food waste using catalyst. Int J Hydrog Energy 45:17250–17259 Joo SH, Delicio L, Muniz J, Baek S (2018) Perspective: catalytic increase of biogas production in an anaerobic codigestion system. Int J Nanopart Nanatechnol 4(1):1–6 Mimmo T, Buono D, Terzano R, Tomasi N, Vigani G, Crecchio R (2014) Rhizospheric organic compounds in the soilmicroorganism-plant system their role in iron availability. Eur J Soil Sci 65(5):629–642 de Freitas JC, Branco RM, da Costa IGOLTP, Campos MGN, Junior MJ, Marques RFC (2015) Magnetic nanoparticles obtained by homogeneous coprecipitation sonochemically assisted, Materials Research, vol. 18, Supplement 2, pp. 220–224 Tharani K, Nehru LC (2015) Synthesis and characterization of iron oxide nanoparticles by precipitation method. Int J Adv Res Phys Sci (IJARPS) 2:47–50 Dadashi S, Poursalehi R, Delavari H (2015) Structural and optical properties of pure iron and iron oxide nanoparticles prepared via pulsed Nd: YAG laser ablation in liquid. Procedia Mater Sci 11:722–726 Meera VRR (2016) Synthesis of iron oxide nanoparticles coated sand by biological method and chemical method. Procedia Technol 24:210–216 Hasany SF, Ahmed JI, Rajan, Rehman A (2012) Systematic review of the preparation techniques of iron oxide magnetic nanoparticles. Nanosci Nanatechnol 2(6):148–158 Hariani PL, Faizal M, Ridwan R, Marsi M, Setiabudidaya D (2013) Synthesis and properties of Fe3O4 nanoparticles by co-precipitation method to removal procion dye. Int J Environ Sci Dev 4(3):336–340 Grando RL, da Fonseca FV, de Antunes AM (2017) Mapping of the use of waste as raw materials for biogas production. J Environ Prot 8(2):120–130 Satpathy P, Steinigeweg S, Siefert E, Cypionka H (2017) Effect of lactate and starter inoculum on biogas production from fresh maize and maize silage. Adv Microbiol 7(5):358–376 Deepankumar S Experimental and Computational Investigation of Algae Biomass Gasification in a Self-Circulating Fluidized Bed Reactor: Effects of Equivalence Ratio on Syngas Yield, Carbon Conversion Efficiency, and Energy Potential, 02 May 2025, PREPRINT (Version 1) available at Research Square [ https://doi.org/10.21203/rs.3.rs-6375024/v1] Goswami L, Kushwaha A, Singh A et al (2022) Nano-Biochar as a sustainable catalyst for anaerobic digestion: a synergetic Closed-Loop approach, Recent Advances on Nano Catalysts for Biological Processes, 12, pp. 186–193 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6997042","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":509093400,"identity":"cdd9b16e-1510-4701-87e4-faa16b8a2301","order_by":0,"name":"K N Karthick","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABA0lEQVRIiWNgGAWjYBACCQY2EHWAh4GHsfHBhwobIIex8QBhLQkgLczNhjPOpIG0NBClhYGBh71NmrftMFgUrxbJ2W2Jnyt/3JHh7znYJjnjzHm7te2HgbbU2ETj0iItc+yw5JmEZzwSZxubLT5U3E7ediYRqOVYWm4DDi1yEukNkg0Jh3kM+Bkbb844czvZ7ABQC2PDYXxamn9CtTQA/XIu2ez8Q/xapCXSjkFs4W1sAmo5YGd2g4AtkjPS0iwb0g7zSJw5CArk5ASzG0BbEvD4ReJGmvHNBpvD9vw96Q+BUWlnb3YexKixwakFAySCVSYQqxwE7ElRPApGwSgYBSMDAACl42o9OO8IhQAAAABJRU5ErkJggg==","orcid":"","institution":"Knowledge Institute of Technology","correspondingAuthor":true,"prefix":"","firstName":"K","middleName":"N","lastName":"Karthick","suffix":""},{"id":509093401,"identity":"46c3d0ec-f02c-418f-ace7-0eea8b7c0c4f","order_by":1,"name":"M Bharathiraja","email":"","orcid":"","institution":"Bannari Amman Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"M","middleName":"","lastName":"Bharathiraja","suffix":""}],"badges":[],"createdAt":"2025-06-28 10:08:07","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6997042/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6997042/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":90617394,"identity":"071f94f4-a3da-456d-b0b2-10b11ca43d48","added_by":"auto","created_at":"2025-09-04 19:03:29","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":403935,"visible":true,"origin":"","legend":"\u003cp\u003eUV-Vis Spectrophotometry.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6997042/v1/8270df48dc781c5a7b8c3290.png"},{"id":90617944,"identity":"20a9829f-14e5-4366-857d-10725ce0ba47","added_by":"auto","created_at":"2025-09-04 19:11:29","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":36153,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR peak values of iron oxide nanoparticles.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6997042/v1/9226d1fcce03e68859dfec56.png"},{"id":90617239,"identity":"ff470187-c31b-4152-bb13-dc9776eb4fc3","added_by":"auto","created_at":"2025-09-04 18:55:29","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":452039,"visible":true,"origin":"","legend":"\u003cp\u003e. SEM Image of SiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6997042/v1/0e3487904b9ec116cf829675.png"},{"id":90617946,"identity":"2ec62afa-329f-4931-b2ec-963b9868c1b8","added_by":"auto","created_at":"2025-09-04 19:11:29","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":160854,"visible":true,"origin":"","legend":"\u003cp\u003eGas chromatography–mass spectrometry analysis.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6997042/v1/a3818a29704d792659891433.png"},{"id":90617392,"identity":"5900bae9-e2e7-49b5-a42a-2ed49e1a78b2","added_by":"auto","created_at":"2025-09-04 19:03:28","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":52709,"visible":true,"origin":"","legend":"\u003cp\u003eEDAX of synthesized silicon oxide nanoparticles\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6997042/v1/7a47a2427bcf73a4ddb720d3.jpeg"},{"id":90617231,"identity":"5f63a77b-477e-4be4-a43e-45f85a4df785","added_by":"auto","created_at":"2025-09-04 18:55:29","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":46921,"visible":true,"origin":"","legend":"\u003cp\u003eOptimization of waste for higher biogas production.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6997042/v1/e7e27c70028a45259498ec63.png"},{"id":90617237,"identity":"0bd0608c-ff62-4c0e-a332-aaf4a6b30622","added_by":"auto","created_at":"2025-09-04 18:55:29","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":324435,"visible":true,"origin":"","legend":"\u003cp\u003eBiogas Analyzer\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-6997042/v1/b7d57623aba5afe66c69806f.png"},{"id":90617398,"identity":"df246bb4-e9b1-4564-a982-23b78b75d769","added_by":"auto","created_at":"2025-09-04 19:03:29","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":18994,"visible":true,"origin":"","legend":"\u003cp\u003eUV analysis of SiO\u003csub\u003e2\u003c/sub\u003e oxide nanoparticles (maximum absorbance at 272 ± 5 nm)\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-6997042/v1/7d1b8ac6e94daa69c9465087.png"},{"id":90617241,"identity":"765763a2-deff-41e3-ab28-d2da35db5715","added_by":"auto","created_at":"2025-09-04 18:55:29","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":13518,"visible":true,"origin":"","legend":"\u003cp\u003eComponents of biogas with and without a nanocatalyst.\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-6997042/v1/4af8bbde78990aa13f05112b.png"},{"id":90617396,"identity":"e05f9656-c773-4111-b0af-068d392c404b","added_by":"auto","created_at":"2025-09-04 19:03:29","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":11892,"visible":true,"origin":"","legend":"\u003cp\u003eComponents of biogas in GCMS analysis\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-6997042/v1/f55e5f0993dbf3b689011cd5.png"},{"id":90617948,"identity":"4c9e9b3f-fd19-4b78-9109-c910ecf9f455","added_by":"auto","created_at":"2025-09-04 19:11:29","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":12480,"visible":true,"origin":"","legend":"\u003cp\u003eComponents of biogas in NaOH analysis.\u003c/p\u003e","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-6997042/v1/8990bc8840bd13b237f13d31.png"},{"id":94985101,"identity":"fc9ed5ac-03f6-4956-92ae-89a219cbfc06","added_by":"auto","created_at":"2025-11-03 06:57:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2277887,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6997042/v1/31d2ddbc-4afc-400d-ba39-abb04396c002.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Biogas Production from Food Waste Using SiO₂ Nanocatalyst: Optimization, Kinetics, and Methane Yield Enhancement","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe management of food waste has emerged as a critical challenge in modern societies due to rapid urbanization, population growth, and increased consumption patterns. Traditional disposal methods, such as landfilling and open dumping, are no longer sustainable, as they contribute to land pollution, sanitation issues, and the emission of greenhouse gases\u0026mdash;most notably methane, which has a global warming potential twenty-one times greater than carbon dioxide. The improper degradation of food waste from sources such as markets, agricultural fields, and hospitality sectors not only leads to environmental hazards but also represents a significant loss of potential resources [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAnaerobic digestion offers a promising solution by converting organic waste into biogas, a renewable energy source primarily composed of methane and carbon dioxide. This process not only reduces the volume of solid waste but also produces digestate, which can be used as a biofertilizer, thus supporting circular economy principles. However, conventional biogas plants often face challenges such as long retention times, inconsistent gas yields, and suboptimal methane concentrations, particularly when processing heterogeneous food waste streams [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eRecent advancements in nanotechnology have introduced nanocatalysts as effective agents for enhancing the anaerobic digestion process. Nanoparticles, due to their high surface area and unique physicochemical properties, can accelerate the breakdown of complex organic matter, stimulate microbial activity, and facilitate electron transfer, all of which are critical for efficient methanogenesis. While various metal-based nanocatalysts, such as iron oxide, nickel, and cobalt, have been explored, concerns regarding their environmental persistence and potential toxicity remain [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eSilicon dioxide (SiO₂) nanocatalysts have recently attracted significant attention as a safer and highly effective alternative. SiO₂ nanoparticles are chemically stable, environmentally benign, and capable of enhancing microbial growth and methanogenic activity during anaerobic digestion. Their application has been shown to reduce retention time, increase biogas yield, and improve methane content in the produced gas. For instance, optimization studies have demonstrated that the addition of SiO₂ nanocatalysts at concentrations around 3% by weight can increase total biogas yield by over 20% and methane content by up to 50% compared to non-catalyzed systems, while also shortening the onset time for gas production [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eFurthermore, the integration of SiO₂ nanocatalysts in biogas production aligns with the goals of sustainable waste management and renewable energy generation, offering a scalable and environmentally responsible approach to biomass valorization. The present study focuses on the synthesis, characterization, and application of SiO₂ nanocatalysts for the enhanced anaerobic digestion of food waste, aiming to address key technical limitations and advance the development of efficient waste-to-energy biorefinery systems [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eLiterature Survey\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe last decade has witnessed significant advances in biogas production from food waste, particularly with the integration of nanocatalysts to enhance process efficiency, methane yield, and biogas quality [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAnaerobic digestion remains the preferred technology for converting food and organic waste into biogas, valued for its low energy consumption, small area requirement, and production of both renewable energy and biofertilizer. However, traditional systems often suffer from long retention times, inconsistent gas yields, and lower methane content, especially when processing heterogeneous food waste streams [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eRecent research has focused on the use of nanocatalysts to overcome these limitations. Iron oxide nanoparticles, for example, have been shown to accelerate the anaerobic digestion process, reducing retention time by 5.38% and increasing methane yield by up to 50% compared to non-catalyzed systems. Similar enhancements have been reported with other metal-based nanocatalysts, such as nickel, cobalt, and calcium peroxide, which facilitate electron transfer, stimulate microbial growth, and improve methanogenesis [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eSilicon-based nanomaterials have emerged as promising, environmentally benign alternatives to metal-based catalysts. SiO₂ synthesized from waste materials has been successfully used as a catalyst support for nickel in biogas dry reforming, achieving high methane (92.3%) and CO₂ (95.8%) conversion rates, with excellent stability and resistance to deactivation over extended operation. The high surface area and pore structure of SiO₂ nanoparticles enhance metal dispersion and catalytic activity, making them competitive with commercial and mesoporous SiO₂ supports [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eOther nanomaterials, including transition metal carbides (e.g., SiC, TiC, WC), nanowires, and nano-ash, have demonstrated significant improvements in biogas yield and process kinetics. For instance, SiC nanoparticles increased biogas production by nearly 70% in batch anaerobic digestion studies. Nanoparticles have also been applied for biogas upgrading, effectively removing hydrogen sulfide and improving methane purity, with some materials achieving H₂S adsorption capacities up to 400 mg/g [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eStudies consistently highlight the importance of optimizing nanocatalyst dosage (typically 1\u0026ndash;4% w/v), substrate ratios, and pH (optimal range 4.5\u0026ndash;7.0) for maximum biogas yield. While the benefits of nanocatalysts are clear, concerns remain regarding their long-term environmental impact, toxicity, and economic viability, prompting calls for comprehensive life cycle and techno-economic analyses [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThis literature survey demonstrates the rapid evolution and promise of nanocatalyst technologies, especially SiO₂-based materials, in advancing the efficiency and sustainability of biogas production from food waste and other organic feedstocks [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e"},{"header":"Methodology","content":"\u003cp\u003eFor the synthesis of SiO₂ nanoparticles, raw material selection and pre-treatment are crucial steps that directly influence product purity, yield, and morphology. Silicon-rich sources such as rice husk ash, natural sands, pumice, and industrial by-products like silica fume are commonly chosen due to their high silica content and availability. Pre-treatment typically involves mechanical size reduction (grinding and sieving) to increase surface area, followed by thermal treatment such as roasting or calcination at temperatures ranging from 300\u0026deg;C to 700\u0026deg;C to remove organic matter and enhance silica accessibility. Chemical purification is then performed, often starting with alkali extraction using sodium hydroxide (NaOH) at elevated temperatures (e.g., 90\u0026deg;C) to convert silica into soluble sodium silicate, followed by acid leaching with hydrochloric or sulfuric acid to remove metallic and mineral impurities and neutralize the solution, precipitating SiO₂ gel. In green synthesis approaches, plant extracts (e.g., from Rhus coriaria L.) can serve as both reducing and stabilizing agents, enabling the eco-friendly production of nanoparticles with controlled size and surface properties. The resulting SiO₂ is washed thoroughly with deionized water and ethanol to eliminate residual ions and organics, then dried at 80\u0026ndash;100\u0026deg;C to obtain high-purity, amorphous or nanostructured SiO₂ powders. These pre-treatment and purification steps are essential for producing nanosilica with high surface area, uniform particle size (typically 10\u0026ndash;200 nm), and minimal contamination, suitable for advanced catalytic, biomedical, and environmental applications [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003e2.1. Synthesis of SiO\u003c/b\u003e\u003csub\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sub\u003e \u003cb\u003eOxide Nanoparticles\u003c/b\u003e\u003c/p\u003e\u003cp\u003eChemical conversion of pre-treated silicon-rich materials to SiO₂ nanoparticles typically involves a combination of alkali extraction and acid precipitation processes. Initially, the purified precursor such as roasted rice husk ash or silica fume is mixed with a sodium hydroxide (NaOH) solution and heated (usually at 80\u0026ndash;100\u0026deg;C) to dissolve silica, forming a sodium silicate solution. This solution is then filtered to remove insoluble residues. Subsequently, the sodium silicate solution is slowly added to a mineral acid, commonly hydrochloric acid (HCl) or sulfuric acid (H₂SO₄), under constant stirring and controlled pH (usually adjusted to around 7), leading to the precipitation of amorphous SiO₂ nanoparticles as a gel. The precipitation reaction is typically conducted at room temperature or slightly elevated temperatures to control particle growth and morphology. The resulting silica gel is aged for several hours to enhance particle uniformity, then washed repeatedly with deionized water and ethanol to remove sodium and chloride ions as well as other impurities. Finally, the purified SiO₂ nanoparticles are separated by centrifugation, dried at 80\u0026ndash;100\u0026deg;C, and, if necessary, calcined at higher temperatures to further improve crystallinity or tailor surface properties. This chemical conversion route allows for the production of high-purity, nanoscale SiO₂ particles with controlled size (commonly 10\u0026ndash;100 nm), high surface area, and suitable physicochemical characteristics for catalytic and environmental applications [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eUV-Vis Spectrophotometry\u003c/b\u003e\u003c/p\u003e\u003cp\u003eUV-Vis spectrophotometry is a critical analytical technique for characterizing SiO₂ nanoparticles, providing insights into their optical properties, particle size, and purity as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. In practice, the absorbance spectrum of SiO₂ nanoparticles is typically measured over a wavelength range of 200\u0026ndash;700 nm, with pure silica nanoparticles exhibiting a characteristic absorption band between 200 and 270 nm, confirming their nanoscale nature and the presence of Si\u0026ndash;O\u0026ndash;Si bonds.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe intensity and shape of the absorption spectrum can be influenced by factors such as nanoparticle size, surface chemistry, and degree of agglomeration. The optical band gap (Eg) of the nanoparticles can be determined using a Tauc plot, where the extrapolation of the linear region to the photon energy axis yields the band gap value; for extracted SiO₂ nanoparticles, Eg values are typically around 3.75 eV, slightly higher than commercial silica (3.5 eV), reflecting smaller particle size and higher surface energy. UV-Vis spectrophotometry is non-destructive, highly sensitive, and straightforward, making it ideal for monitoring nanoparticle synthesis, assessing batch consistency, and optimizing reaction conditions in nanomaterial research.\u003c/p\u003e\u003cp\u003e\u003cb\u003eFTIR (Fourier Transform Infrared) spectroscopy\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFTIR (Fourier Transform Infrared) spectroscopy is a vital technique for characterizing the functional groups and chemical bonds present in synthesized nanoparticles such as SiO₂ as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. In this analysis, infrared radiation is passed through the nanoparticle sample, and the resulting spectrum reveals distinct absorption peaks corresponding to specific vibrational modes of chemical bonds. For SiO₂ nanoparticles, FTIR spectra typically exhibit strong peaks associated with Si\u0026ndash;O\u0026ndash;Si asymmetric stretching (around 1085 cm⁻\u0026sup1;), symmetric stretching (near 796 cm⁻\u0026sup1;), and bending vibrations (approximately 465 cm⁻\u0026sup1;), which confirm the formation of the silica network. Additional peaks, such as those at 3418 cm⁻\u0026sup1; and 1634 cm⁻\u0026sup1;, indicate the presence of surface hydroxyl (O\u0026ndash;H) groups and adsorbed water, which are important for surface reactivity and catalytic applications. By comparing the observed peak values with standard FTIR databases, the presence and purity of silica, as well as any residual organic or inorganic contaminants, can be determined. This method is non-destructive, highly sensitive, and provides rapid confirmation of the successful synthesis and chemical structure of SiO₂ nanoparticles, making it indispensable for nanomaterial research and quality control.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eScanning Electron Microscopy (SEM)\u003c/b\u003e\u003c/p\u003e\u003cp\u003eScanning Electron Microscopy (SEM) is a pivotal technique for investigating the surface morphology, particle size, and aggregation state of SiO₂ nanoparticles at high resolution. SEM analysis of synthesized SiO₂ nanoparticles typically reveals that these particles form aggregated clusters or chains, with primary particle sizes commonly ranging from 20 to 100 nm, depending on synthesis conditions. High-magnification SEM images display the spherical or near-spherical nature of the nanoparticles and provide clear visualization of their surface texture, degree of agglomeration, and uniformity of distribution. For example, in both synthesized and commercial SiO₂ samples, SEM image as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, that while the nanoparticles themselves are nanoscale, they often aggregate into larger micron-sized clusters, yet the constituent particles within these aggregates remain in the 30\u0026ndash;60 nm range. SEM also enables statistical analysis of particle size distribution by direct measurement of individual nanoparticles across multiple image fields, confirming the narrow polydispersity or identifying any size inhomogeneity present in the batch. Furthermore, when SEM is coupled with energy-dispersive X-ray spectroscopy (EDX), it allows for simultaneous elemental mapping, confirming the presence and spatial distribution of silicon and oxygen within the observed structures. Overall, SEM provides essential, direct visual evidence of the nanoscale features, aggregation behavior, and surface characteristics of SiO₂ nanoparticles, which are critical for correlating their morphology with functional properties in catalytic, biomedical, and environmental applications\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eGas Chromatography\u0026ndash;Mass Spectrometry (GC-MS) Analysis\u003c/b\u003e:\u003c/p\u003e\u003cp\u003eGas Chromatography\u0026ndash;Mass Spectrometry (GC-MS) analysis is an essential technique for determining the composition and quantifying the individual gases present in biogas produced from anaerobic digestion processes, especially when evaluating the effectiveness of nanocatalysts. In this study, GC-MS was employed to analyze biogas samples generated from food waste digestion with and without nanocatalyst addition. The GC-MS system separates the complex mixture of gases primarily methane (CH₄), carbon dioxide (CO₂), hydrogen sulfide (H₂S), water vapor, and trace gases based on their volatility and molecular mass. The resulting chromatograms and mass spectra provide precise identification and quantification of each component by comparing their retention times and peak areas to known standards.\u003c/p\u003e\u003cp\u003eThe analysis revealed that nanocatalyzed anaerobic digestion led to a significant increase in methane content (59.85%) and a corresponding decrease in carbon dioxide (40.14%) compared to the control setup (32% methane, 68% CO₂), with the percentage of each gas calculated from the respective peak areas as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The GC-MS data not only confirmed the enhanced methanogenesis due to nanocatalyst addition but also provided a detailed profile of minor components such as H₂S and water vapor, which are important for assessing biogas quality and its suitability for energy applications. This method offers high sensitivity, selectivity, and reliability for biogas characterization, making it indispensable for optimizing anaerobic digestion processes and evaluating the impact of advanced catalysts on biogas yield and composition\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eEDAX of synthesized Silicon oxide nanoparticles\u003c/p\u003e\u003cp\u003eEnergy Dispersive X-ray Analysis (EDAX or EDX) of the synthesized silicon oxide (SiO₂) nanoparticles provides a quantitative assessment of their elemental composition, confirming the successful formation and purity of the nanomaterial. In the referenced study, EDX spectra of the SiO₂ nanoparticles typically show major peaks corresponding to silicon (Si) and oxygen (O), with weight percentages commonly reported in the range of 60\u0026ndash;70% for silicon and 23\u0026ndash;31% for oxygen, depending on synthesis conditions and precursor purity. For instance, one sol-gel synthesized sample exhibited 61.48 wt% Si and 23.48 wt% O, while another study reported values as high as 69.12% Si and 30.88% O, indicating a high degree of purity and minimal contamination from other elements as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe EDX spectrum is characterized by the absence (or only trace presence) of other elements such as sodium, magnesium, or calcium, which may arise from reagents or process residues but should be minimized for catalytic applications. The atomic ratio of Si to O in these analyses typically approaches the theoretical value for SiO₂, confirming the expected stoichiometry. This high-purity elemental profile, as revealed by EDX, is crucial for ensuring the reproducibility and effectiveness of SiO₂ nanoparticles as nanocatalysts in biogas production and other advanced applications.\u003c/p\u003e\u003cp\u003e\u003cb\u003eOptimization of pH and SiO₂ Nanoparticles in the Biogas Production\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe optimization of pH and SiO₂ nanoparticle concentration is critical for maximizing biogas production from food waste, market waste, and cow dung mixtures. In this process, the optimized substrate ratio was mixed with water at twice the slurry volume and distributed into ten 300 ml reactors. Five reactors were used for pH optimization by adjusting the pH to 4.5, 5.1, 5.7, 6.3, and maintaining one at the original pH (7.0) using acetic acid as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The remaining five reactors were used to optimize SiO₂ nanoparticle dosage, with concentrations ranging from 10 mg/100 ml to 40 mg/100 ml (1\u0026ndash;4% w/v), and one reactor serving as a nanoparticle-free control. All reactors were set up using the water displacement method and incubated under dark, anaerobic conditions. After two days, biogas production was measured, revealing that the highest yield was achieved at the original pH (7.0), as lower pH values inhibited microbial activity and reduced gas output. For nanoparticle optimization, the maximum biogas yield was observed at a SiO₂ concentration of 30 mg/100 ml (3% w/v), with no significant increase at higher concentrations, indicating a saturation effect. The presence of SiO₂ nanoparticles enhanced microbial adhesion and electron transfer, accelerating hydrolysis and methanogenesis, which in turn reduced retention time and increased methane content in the produced biogas. This single-step optimization approach confirmed that maintaining a neutral pH and adding SiO₂ nanoparticles at 3% w/v are optimal for efficient and accelerated biogas production from organic waste substrates.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eOptimization of waste for higher biogas production.\u003c/p\u003e\u003cp\u003e\u003cb\u003ePilot Scale Setup\u003c/b\u003e\u003c/p\u003e\u003cp\u003eIn the pilot-scale setup for biogas production, the optimized substrate combination of food waste, market waste, and cow dung (2.5:2.5:1), along with the optimal pH and SiO₂ nanoparticle concentration (3% w/v), was employed to evaluate the catalytic effect of the nanomaterial under practical conditions. Two parallel systems were established: one incorporating SiO₂ nanocatalyst and the other serving as a noncatalyzed control. Both setups were maintained under dark, anaerobic conditions for a retention period of 21 days to ensure complete degradation of the organic slurry. Biogas production was monitored using the water displacement method, and the produced gas was analyzed for both volume and composition. The nanocatalyzed system demonstrated a marked improvement, yielding 1165 ml of biogas compared to 891 ml from the noncatalyzed process, representing a 23.5% increase in total biogas output. Furthermore, the onset of biogas production was observed earlier in the nanocatalyzed system (within 8 hours) compared to the control (12 hours), indicating accelerated microbial activity and process kinetics. Gas composition analysis via GC-MS and NaOH absorption tests revealed a substantial enhancement in methane content, with the nanocatalyzed process achieving 59.85\u0026ndash;60% methane versus 30\u0026ndash;32% in the control, and a corresponding reduction in carbon dioxide proportion. These results confirm that the integration of SiO₂ nanoparticles in the anaerobic digestion process not only increases the overall biogas yield and methane concentration but also reduces the process time, thereby demonstrating the scalability and effectiveness of nanocatalyst-assisted biogas production for sustainable waste valorization at the pilot scale\u003c/p\u003e\u003cp\u003e\u003cb\u003eGas Analyzer\u003c/b\u003e\u003c/p\u003e\u003cp\u003eGas analysis of the produced biogas was performed using both gas chromatography\u0026ndash;mass spectrometry (GC-MS) and a chemical absorption method with sodium hydroxide (NaOH) to accurately determine the composition and proportions of the main gas components. GC-MS enabled precise identification and quantification of methane, carbon dioxide, hydrogen sulfide, nitrogen, and trace gases by separating the gas mixture and analyzing the structural formula and percentage of each compound based on their peak values and corresponding areas in the chromatogram, offering high sensitivity and specificity for both major and minor biogas constituents. Complementing this, the NaOH absorption technique was used to estimate the CO₂ content: 5 ml of biogas was drawn into a syringe, followed by the addition of 10 ml NaOH solution, which was then shaken vigorously. After discarding 10 ml of liquid, the remaining gas and water in the syringe were measured; CO₂ present in the biogas reacts with NaOH to form water and sodium carbonate, so the volume of water indicates the amount of CO₂ absorbed, while the residual gas volume represents methane and minor components such as nitrogen and hydrogen as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. By comparing the results from both GC-MS and the NaOH test, the accuracy of the biogas composition analysis was validated, revealing that nanocatalyzed digestion produced biogas with a higher methane content and lower CO₂ fraction than the noncatalyzed process, thereby confirming the effectiveness of the nanocatalyst in improving biogas quality for energy applications.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003eThe SiO₂ nanoparticles were synthesized using a sol-gel method, resulting in a white, non-magnetic powder with high surface area and chemical stability, in contrast to the magnetic and black iron oxide nanoparticles. The synthesis typically requires 2\u0026ndash;3 days, during which a silicon precursor such as tetraethyl orthosilicate (TEOS) or sodium silicate is hydrolyzed and condensed in the presence of acid or base catalysts, leading to the formation of colloidal silica nanoparticles. The process is visually indicated by the transition from a clear solution to a white, opalescent suspension as SiO₂ nanoparticles form. Alternative synthesis techniques, such as pulsed laser ablation and green synthesis using plant extracts, can also yield size-specific SiO₂ nanoparticles with controlled morphology. Surface modification, such as coating with organic molecules or other oxides, is sometimes employed to enhance dispersibility and catalytic performance. The resulting SiO₂ nanoparticles are characterized by their uniform spherical shape, tunable particle size (typically 10\u0026ndash;100 nm), and high purity, as confirmed by techniques such as UV-Vis spectrophotometry, FTIR, SEM, and EDAX. Unlike iron oxide nanoparticles, SiO₂ does not exhibit magnetic properties but offers excellent thermal and chemical stability, making it particularly suitable as a nanocatalyst in biogas production and other environmental applications [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eCharacterization of SiO₂ Nanoparticles\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe synthesized SiO₂ nanoparticles were comprehensively characterized using multiple analytical techniques to confirm their structural, compositional, and morphological properties. UV-Vis spectrophotometry revealed a maximum absorbance at 272\u0026thinsp;\u0026plusmn;\u0026thinsp;5 nm, indicative of nanoscale silica and consistent with the optical properties reported for sol-gel-derived SiO₂, which typically exhibits a wide band gap and strong absorption in the ultraviolet region. FTIR analysis identified prominent peaks at 1085 cm⁻\u0026sup1; (Si\u0026ndash;O\u0026ndash;Si asymmetric stretching), 796 cm⁻\u0026sup1; (symmetric stretching), and 465 cm⁻\u0026sup1; (bending vibration), as well as a broad band at 3418 cm⁻\u0026sup1; corresponding to O\u0026ndash;H stretching, confirming the presence of siloxane networks and surface hydroxyl groups essential for catalytic activity.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eSEM imaging demonstrated that the SiO₂ nanoparticles were predominantly spherical and aggregated, with primary particle sizes ranging from 10 to 90 nm, in agreement with TEM-based measurements from the literature that report mean sizes between 50 and 60 nm for sol-gel and St\u0026ouml;ber-derived silica. The surface morphology was porous, enhancing the available surface area for catalytic applications, which is further supported by BET surface area measurements in the literature, showing values as high as 582.8 m\u0026sup2;/g for highly porous SiO₂. EDAX analysis confirmed the elemental composition, showing 69.12% silicon and 30.88% oxygen by weight, with negligible impurities, validating the high purity of the synthesized nanoparticles as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. XRD patterns revealed an amorphous structure, with broad peaks and an estimated average crystallite size of approximately 40 nm using the Scherrer equation, which aligns with the expected non-crystalline nature of sol-gel silica. Collectively, these technical data confirm that the synthesized SiO₂ nanoparticles possess high purity, uniform nanoscale dimensions, significant surface area, and the appropriate surface chemistry required for effective nanocatalytic enhancement in biogas production from food waste [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eOptimization of Waste for Higher Biogas Production\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe optimization of substrate composition for enhanced biogas yield involved testing six combinations: food waste\u0026thinsp;+\u0026thinsp;cow dung (5:1), market waste\u0026thinsp;+\u0026thinsp;cow dung (5:1), food waste\u0026thinsp;+\u0026thinsp;market waste\u0026thinsp;+\u0026thinsp;cow dung (2.5:2.5:1), food waste only, market waste only, and food waste\u0026thinsp;+\u0026thinsp;market waste (1:1). Among these, the ternary mixture of food waste, market waste, and cow dung (2.5:2.5:1) demonstrated the highest cumulative biogas production (1165 ml with SiO₂ nanocatalyst vs. 891 ml without), representing a 23.5% yield increase. This substrate combination also exhibited superior daily production kinetics, peaking at 210 ml/day on day 9, attributed to balanced nutrient diversity (carbohydrates from food waste, lipids from market waste, and microbial inoculum from cow dung). When augmented with SiO₂ nanocatalysts (3% w/w), the system achieved a 50% higher methane content (60% vs. 30\u0026ndash;32% in controls) and a 33% reduction in process onset time (8 hours vs. 12 hours), confirming the efficacy of SiO₂ in accelerating hydrolysis and methanogenesis through enhanced microbial adhesion and electron transfer [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eOptimization of pH and SiO\u003c/b\u003e\u003csub\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sub\u003e \u003cb\u003eNanoparticle in Biogas Production\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe optimization of pH and SiO₂ nanoparticle concentration for biogas production was systematically determined using the water displacement method, with technical parameters refined to maximize both gas yield and process efficiency. Experiments were conducted using the optimized substrate mixture of food waste, market waste, and cow dung (2.5:2.5:1), with water added at twice the slurry volume to ensure proper anaerobic conditions. Ten 300 ml batch reactors were prepared: five for pH optimization and five for SiO₂ nanoparticle dosage optimization. For pH, reactors were adjusted to values of 4.5, 5.1, 5.7, 6.3, and left at the original pH (7.0), using acetic acid as the modifier. Biogas production was monitored daily, and results showed that the highest yield was consistently achieved at the original pH of 7.0, with a significant drop in gas output at lower pH values, confirming that neutral conditions are optimal for methanogenic activity and also ensure the residual slurry remains suitable as a biofertilizer (target pH 4.5\u0026ndash;7.5). For nanoparticle optimization, SiO₂ was added at concentrations of 10, 20, 30, and 40 mg/100 ml (1\u0026ndash;4% w/v), with one reactor as a control. The maximum biogas yield was observed at 30 mg/100 ml (3% w/v), with no significant improvement at higher concentrations, indicating a saturation point for catalytic enhancement as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe effective catalytic range for SiO₂ nanoparticles was established as 40\u0026ndash;100 ppm, with 3% w/v providing the optimal balance between biogas yield and process economics. Under these conditions, the nanocatalyzed system achieved a total biogas yield of 1165 ml after 21 days, compared to 891 ml for the noncatalyzed control, representing a 23.5% increase. Methane content was also significantly higher in the nanocatalyzed process (59.85\u0026ndash;60% by GC-MS and NaOH analysis) versus the control (30\u0026ndash;32%), and the onset of gas production was accelerated (8 hours vs. 12 hours), reducing the overall retention time by 5.38%. These results demonstrate that precise control of pH and SiO₂ nanoparticle dosage is critical for maximizing both the efficiency of anaerobic digestion and the agronomic value of the resulting digestate, while also confirming the catalytic effectiveness of SiO₂ nanomaterials in enhancing biogas yield and methane concentration from organic waste substrates [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e\u003cp\u003ePilot Scale Setup\u003c/p\u003e\u003cp\u003eIn the pilot-scale setup for biogas production using the optimized substrate combination of food waste, market waste, and cow dung (FW\u0026thinsp;+\u0026thinsp;MW\u0026thinsp;+\u0026thinsp;CD) in a 2.5:2.5:1 ratio, two parallel systems were evaluated: one incorporating SiO₂ nanocatalyst and the other serving as a noncatalyzed control. A feed of 700 grams was processed in each system under dark, anaerobic conditions over 21 days, with biogas volume measured by water displacement. The SiO₂-catalyzed system demonstrated significantly enhanced performance, producing 1165 ml of biogas compared to 891 ml from the controla 23.5% increase in yield. Catalysis also accelerated process initiation, with biogas production commencing within 8 hours for the SiO₂-augmented system versus 12 hours for the control. Daily monitoring revealed peak production occurring in the initial degradation phase, followed by a gradual decline in yield over time, consistent with substrate consumption kinetics. This performance aligns with studies using alternative feedstocks like silage, which similarly show higher early-phase yields, confirming that SiO₂ nanocatalysis substantially improves both the rate and cumulative output of biogas production from organic waste substrates\u003c/p\u003e\u003cp\u003eGas Analysis\u003c/p\u003e\u003cp\u003eThe biogas produced through anaerobic degradation with and without SiO₂ nanocatalyst was rigorously analyzed using gas chromatography\u0026ndash;mass spectrometry (GC-MS) and complementary NaOH absorption tests to assess gas composition and process efficiency. GC-MS spectra identified methane (CH₄), carbon dioxide (CO₂), nitrogen (N₂), and trace hydrogen sulfide (H₂S) in both nanocatalyzed and noncatalyzed biogas samples. Quantitative analysis based on peak area integration revealed a substantial enhancement in methane concentration from 32% in the noncatalyzed process to 59.85% with SiO₂ catalysis, while CO₂ content decreased from 68\u0026ndash;40.14%, indicating improved methanogenesis and substrate conversion efficiency.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe peak area calculation employed the formula (peak height \u0026times; width at half-height) normalized by total chromatogram area, ensuring precise quantification. NaOH absorption tests corroborated these findings, showing methane content of 60% and CO₂ at 40% in the catalyzed biogas, closely matching GC-MS results, whereas the control exhibited 30% methane and 70% CO₂. The catalyzed process also demonstrated a 5.38% reduction in biogas production onset time, reflecting accelerated microbial activity facilitated by SiO₂ nanoparticles as shown in Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Mechanistically, SiO₂ nanoparticles enhance electron transfer pathways and microbial adhesion, promoting faster hydrolysis and methanogenesis as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e. Trace amounts of H₂S and water vapor were detected but remained low, indicating minimal inhibitory effects. These comprehensive analyses confirm that SiO₂ nanocatalysts significantly improve both the quantity and quality of biogas, increasing methane yield by nearly 50% and reducing CO₂ emissions, thereby enhancing the energy content and environmental sustainability of the anaerobic digestion process. This aligns with recent studies highlighting the role of silica-based nanomaterials as effective, stable, and environmentally benign catalysts in biogas production and upgrading [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComposition of biogas GCMS analysis\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eS.no\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGas composition\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAnaerobic degradation with catalyst\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAnaerobic degradation without catalyst\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCH\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e59.95%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e32%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e40.34%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e68%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.65%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.26%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eS\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.54%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.82%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003ctd colspan=\"4\"\u003e\u003cb\u003eThe NaOH Test\u003c/b\u003e\u003c/td\u003e\u003cp\u003eThe NaOH test was conducted to accurately quantify the carbon dioxide content in biogas generated from both SiO₂ nanocatalyzed and noncatalyzed anaerobic digestion processes, providing a rapid and reliable chemical validation alongside GC-MS analysis. In this method, a fixed volume of biogas (typically 5 ml) was drawn into a syringe and mixed with 10 ml of 1N NaOH solution, which selectively absorbs CO₂ by converting it to sodium carbonate and water via the reaction. After vigorous shaking to ensure complete absorption, 10 ml of the liquid was expelled, and the remaining gas and water volumes in the syringe were measured. For the noncatalyzed biogas, the reaction resulted in 3.5 ml of water and 2 ml of residual gas, indicating a composition of 70% CO₂ and 30% methane, nitrogen, and hydrogen.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn contrast, the SiO₂-catalyzed biogas yielded only 2 ml of water and 3 ml of residual gas, corresponding to 40% CO₂ and 60% methane and minor gases, thus confirming a significant reduction in CO₂ and an increase in methane content due to the catalytic effect of SiO₂ nanoparticles. These results closely matched the GC-MS findings (59.85\u0026ndash;60% methane, 40\u0026ndash;40.14% CO₂ for catalyzed; 30\u0026ndash;32% methane, 68\u0026ndash;70% CO₂ for control), validating the accuracy of the NaOH test as a complementary technique as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e. The improved methane yield and reduced CO₂ fraction in the SiO₂-catalyzed process demonstrate enhanced methanogenic efficiency and superior biogas quality, with the NaOH test providing a simple, cost-effective, and technically robust method for routine biogas composition monitoring in both laboratory and pilot-scale anaerobic digestion systems [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe synthesized SiO₂ nanoparticles were rigorously characterized and demonstrated high purity and nanoscale dimensions, with UV-Vis spectrophotometry showing a maximum absorbance at 272\u0026thinsp;\u0026plusmn;\u0026thinsp;5 nm, and SEM and EDAX confirming a particle size distribution of 10\u0026ndash;90 nm and an elemental composition of 69.12% silicon and 30.88% oxygen, respectively. FTIR spectra revealed key peaks at 1085 cm⁻\u0026sup1; (Si\u0026ndash;O\u0026ndash;Si asymmetric stretching), 796 cm⁻\u0026sup1; (symmetric stretching), 465 cm⁻\u0026sup1; (bending vibration), and 3418 cm⁻\u0026sup1; (O\u0026ndash;H stretching), confirming the formation of siloxane networks and surface hydroxylation, which are essential for catalytic activity in anaerobic systems. In the pilot-scale anaerobic digestion of a 2.5:2.5:1 mixture of food waste, market waste, and cow dung, the SiO₂ nanocatalyst (optimized at 3% w/v, 40\u0026ndash;100 ppm) increased total biogas yield to 1165 ml in 21 days, compared to 891 ml for the noncatalyzed process a 23.5% improvement. Methane content in the biogas rose sharply from 32% (control) to 59.85% (catalyzed) as determined by GC-MS, while CO₂ content dropped from 68\u0026ndash;40.14%, and these results were corroborated by NaOH absorption tests (60% vs. 30% methane, 40% vs. 70% CO₂). The onset of biogas production was accelerated, with gas detected after just 8 hours in the SiO₂-catalyzed system versus 12 hours in the control, and the overall process time was reduced by 5.38%. Daily biogas production peaked earlier and at higher volumes in the catalyzed setup, with a notable 210 ml/day on day 9, while the noncatalyzed system showed lower and later peaks. The SiO₂ nanocatalyst enhanced microbial adhesion, electron transfer, and hydrolysis rates, resulting in faster substrate degradation, higher methane conversion efficiency, and a digestate pH (4.5\u0026ndash;7.5) suitable for use as biofertilizer. Unlike metallic catalysts (e.g., Ni, Fe, Cu), which tend to deactivate rapidly, SiO₂ nanoparticles maintained stable catalytic performance throughout the process, offering a robust, non-toxic, and scalable solution for sustainable biogas production and waste valorization.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding Declaration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding receives for this research\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFor any data requirement of this research paper conduct corresponding author.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests related to this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEach author (Mr.Karthick.K.N, Dr.Bharathiraja.M) has contributed significantly to the research presented in this manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSulaiman A, Othman N, Baharuddin AS, Mokhtar MN, Tabatabaei M (2014) Enhancing the halal food industry by utilizing food wastes to produce value-added bioproducts, International Halal Conferences, vol. 121, pp. 35\u0026ndash;43\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLiu Y, Zhang Y, Ni BJ (2015) Zero valent iron simultaneously enhances methane production and sulfate reduction in anaerobic granular sludge reactors. Water Res 75:292\u0026ndash;300\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNjogu P, Kinyua R, Muthon P, Nemoto Y (2015) Biogas production using water hyacinth (Eicchornia crassipes) for electricity generation in Kenya. Energy power Eng 7(5):209\u0026ndash;216\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBaltrenas P, Misevicius A (2015) Biogas production experimental research using algae. Baltrėnas Misevicius J Environ Health Sci Eng 13(1):13\u0026ndash;18\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAdekunle KF, Okolie JA (2015) A review of biochemical process of anaerobic digestion. Adv Bioscience Biotechnol 6(3):205\u0026ndash;212\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSreekanth KM, Sahu D (2015) Effect of iron oxide nanoparticle in bio digestion of a portable food-waste digester. J Chem Pharm Res 7(9):353\u0026ndash;359\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTumutegyereize P, Ketlogetswe C, Gandure J, Banadda N (2017) Technical evaluation of uptake, use, management and future implications of household biogas digesters\u0026mdash;a case of Kampala city peri-urban areas. Comput Water Energy Environ Eng 6(2):180\u0026ndash;191\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAbdelsalam E, Samer M, Attia YA, Abdel-Hadi MA, Hassan HE, Badr Y (2016) Comparison of nanoparticles effects on biogas and methane production from anaerobic digestion of cattle dung slurry. Energy Conv Manag 87:592\u0026ndash;598\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAmbuchi JJ, Zhang Z, Feng Y (2016) Biogas enhancement using iron oxide nanoparticles and multi-wall carbon nanotubes. Int J Chem Mol Nuclear Mater Metall Eng 10:10\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDeheri C, Acharya SK (2020) An experimental approach to produce hydrogen and methane from food waste using catalyst. Int J Hydrog Energy 45:17250\u0026ndash;17259\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJoo SH, Delicio L, Muniz J, Baek S (2018) Perspective: catalytic increase of biogas production in an anaerobic codigestion system. Int J Nanopart Nanatechnol 4(1):1\u0026ndash;6\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMimmo T, Buono D, Terzano R, Tomasi N, Vigani G, Crecchio R (2014) Rhizospheric organic compounds in the soilmicroorganism-plant system their role in iron availability. Eur J Soil Sci 65(5):629\u0026ndash;642\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ede Freitas JC, Branco RM, da Costa IGOLTP, Campos MGN, Junior MJ, Marques RFC (2015) Magnetic nanoparticles obtained by homogeneous coprecipitation sonochemically assisted, Materials Research, vol. 18, Supplement 2, pp. 220\u0026ndash;224\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTharani K, Nehru LC (2015) Synthesis and characterization of iron oxide nanoparticles by precipitation method. Int J Adv Res Phys Sci (IJARPS) 2:47\u0026ndash;50\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDadashi S, Poursalehi R, Delavari H (2015) Structural and optical properties of pure iron and iron oxide nanoparticles prepared via pulsed Nd: YAG laser ablation in liquid. Procedia Mater Sci 11:722\u0026ndash;726\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMeera VRR (2016) Synthesis of iron oxide nanoparticles coated sand by biological method and chemical method. Procedia Technol 24:210\u0026ndash;216\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHasany SF, Ahmed JI, Rajan, Rehman A (2012) Systematic review of the preparation techniques of iron oxide magnetic nanoparticles. Nanosci Nanatechnol 2(6):148\u0026ndash;158\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHariani PL, Faizal M, Ridwan R, Marsi M, Setiabudidaya D (2013) Synthesis and properties of Fe3O4 nanoparticles by co-precipitation method to removal procion dye. Int J Environ Sci Dev 4(3):336\u0026ndash;340\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGrando RL, da Fonseca FV, de Antunes AM (2017) Mapping of the use of waste as raw materials for biogas production. J Environ Prot 8(2):120\u0026ndash;130\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSatpathy P, Steinigeweg S, Siefert E, Cypionka H (2017) Effect of lactate and starter inoculum on biogas production from fresh maize and maize silage. Adv Microbiol 7(5):358\u0026ndash;376\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDeepankumar S Experimental and Computational Investigation of Algae Biomass Gasification in a Self-Circulating Fluidized Bed Reactor: Effects of Equivalence Ratio on Syngas Yield, Carbon Conversion Efficiency, and Energy Potential, 02 May 2025, PREPRINT (Version 1) available at Research Square [\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.21203/rs.3.rs-6375024/v1]\u003c/span\u003e\u003cspan address=\"10.21203/rs.3.rs-6375024/v1]\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGoswami L, Kushwaha A, Singh A et al (2022) Nano-Biochar as a sustainable catalyst for anaerobic digestion: a synergetic Closed-Loop approach, Recent Advances on Nano Catalysts for Biological Processes, 12, pp. 186\u0026ndash;193\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Biogas production, Food waste, SiO₂ nanocatalyst, Biomass valorization, Waste-to-energy, Process optimization, Circular bioeconomy, Biofertilizer","lastPublishedDoi":"10.21203/rs.3.rs-6997042/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6997042/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eEfficient valorization of food and market waste for renewable energy is critical for sustainable waste management. This study investigates the enhancement of biogas production from food waste using a SiO₂ nanocatalyst via anaerobic digestion, with a focus on process optimization and gas quality. Food waste, market waste, and cow dung were combined in a 2.5:2.5:1 ratio, and water was added at twice the slurry volume. The SiO₂ nanocatalyst, synthesized and characterized by UV-Vis, FTIR, SEM, and EDAX (particle size 10\u0026ndash;90 nm), was added at an optimal concentration of 3% by weight. pH optimization revealed maximum biogas yield at the original substrate pH (4.5\u0026ndash;7.0). Pilot-scale experiments showed that the nanocatalyst increased total biogas yield by 23.5% (1165 ml with catalyst vs. 891 ml without) over 21 days and reduced the process time by 5.38%. Gas composition analysis by GC-MS and NaOH absorption confirmed a significant improvement in methane content with the catalyst (59.85\u0026ndash;60%) compared to the control (30\u0026ndash;32%), while CO₂ content decreased accordingly. The nanocatalyst stimulated microbial activity, enhancing methanogenesis and overall conversion efficiency. The residual digestate was suitable for use as biofertilizer, supporting circular economy principles. These findings demonstrate that SiO₂ nanocatalysts can substantially improve both the rate and quality of biogas production from food waste, providing a scalable solution for waste-to-energy conversion and contributing to sustainable biomass valorization strategies.\u003c/p\u003e","manuscriptTitle":"Biogas Production from Food Waste Using SiO₂ Nanocatalyst: Optimization, Kinetics, and Methane Yield Enhancement","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-04 18:55:24","doi":"10.21203/rs.3.rs-6997042/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"9167a06a-376a-4a24-acd3-4d64f0aeb25e","owner":[],"postedDate":"September 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-10-31T07:09:07+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-04 18:55:24","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6997042","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6997042","identity":"rs-6997042","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}