Biogas Utilization Research Articles

Novel sulfide-driven denitrification methane oxidation (SDMO) system based on SBR-MBfR and EGSB-MBfR

Traditional denitrification process consumes external organic carbon leading to an increase in treatment costs and carbon emission. A novel sulfide-driven denitrification methane oxidation (SDMO) system, which could simultaneously utilize CH4 and H2S in biogas as electron donors for denitrification to reduce the cost and carbon emission, has been successfully operated in two kinds of reactors SBR-MBfR and EGSB-MBfR for ∼ 200 days in this study. The performance and microbial community were explored meanwhile machine learning approach have been used for predicting the complex effects on SDMO’s denitrification efficiency. Result shows SBR-MBfR’s superior performance with the maximum nitrate removal efficiency > 90 % while the denitrification rates and biological activity were also better than EGSB-MBfR. The autotrophic denitrification (Auto-D) contributed 5 % much more for nitrate removal in SBR-MBfR than EGSB-MBfR while denitrification anaerobic methane oxidation (DAMO) was more prominent in EGSB-MBfR. Nineteen machine learning models were used for operation data training and random forest regressor was demonstrated to be the optimal model for predicting nitrate removal efficiency in SDMO. According to random forest regressor’s analysis, HRT presented the highest importance in affecting SDMO nitrate removal efficiency. After the introduction of biogas for domestication, Auto-D bacteria Thiobacillus was the dominant bacteria in both systems occupying > 20 % and the abundance would increase gradually from ∼ 20 % to ∼ 60 % as H2S content rising. A hidden positive correlation between DAMO bacteria Candidatus Methylomirabilis and Thiobacillus was uncovered by mantel test analysis here, implying the integrating of Auto-D and DAMO process for nitrate removal. This study not only provides insights into the novel SDMO technology but also offers a potential advancement in simultaneously low-carbon wastewater treatment and biogas utilization.

Sustainability Assessment of Agricultural Waste Biogas Production System in China Based on Emergy and Carbon Evaluation Methods

Biogas production is widely recognized as an effective solution for addressing agricultural waste treatment in rural areas. However, its development is often hindered by economic and environmental constraints. This study combined emergy evaluation and carbon footprint analysis methods to establish a new environmental radius assessment model for evaluating the ecological performance and optimization direction of an agricultural waste biogas production system, using a biogas production company in China as a case study. Compared with the straw return model and straw power generation model, the results of emergy indicators and carbon accounting showed that the biogas production model had a lower environmental load and higher economic output and level of emergy sustainability. Additionally, the biogas production system was found to reduce 0.47 kg of carbon emissions per 1 kg of agricultural waste utilized. The application of the biogas production model in rural areas had high ecological sustainability and carbon emission reduction benefits. Environmental radius assessment results confirmed that the reasonable changes in resource collection distance could further enhance the ecological sustainability, carbon mitigation ability, and economic benefits of the biogas production system. The environmental radius assessment method offers a new approach to the location planning of agricultural waste biogas utilization companies in rural areas.

Anaerobic digestion of agricultural waste for biogas production and sustainable bioenergy recovery: a review

AbstractAnaerobic digestion constitutes a sustainable method for waste management and renewable energy generation, addressing significant environmental and societal challenges. The growing global waste crisis and the increasing momentum toward sustainable energy solutions emphasize the critical need to enhance anaerobic digestion technology for improved efficiency and environmental advantages. This process mitigates waste accumulation, enhances energy security, and reduces greenhouse gas emissions, providing a feasible solution within the framework of a circular bioeconomy. Here, we review the principles of anaerobic digestion and biogas production, focusing on agricultural waste and the utilization of biogas for energy within a sustainable framework. We specifically explore biogas applications in rural and industrial settings, assess the environmental impacts, and discuss the regulatory landscape with insights from China and Europe. This study reveals that the strategic implementation of anaerobic digestion can markedly improve energy yield and sustainability, demonstrating how focused policies and advanced technological practices can optimize biogas utilization. The review enhances comprehension of environmental impacts, emphasizing insights from China and Europe as key examples.

INTEGRATED TECHNOLOGY OF BIOGAS UTILIZATION OF SOLID HOUSEHOLD WASTE LANDFILLS WITH THE PRODUCTION OF ELECTROCITY, HEAT AND CARBON DIOXIDE

The presence of carbon dioxyl as a non-combustible admixture in the landfill biogas of solid household waste and the absorption of ambient air into the layer of landfill waste, and therefore its entry into the landfill gas, significantly reduces the concentration of methane in it, which affects the efficient operation of the gas piston engine of the power plant and the reduction of volumes electricity generation. With the use of computer modeling for the composition of biogas with an increased content of N2 and a reduced concentration of CH4 £ 32 %, calculations were made on the enrichment of biogas to concentrations of CH4 in it of 36–44 % due to the use of CO2 amine absorption technologies, in which the costs for the regeneration of the absorbent are compensated by the produced thermal energy of the gas piston engine of the power plant. The removal of carbon dioxide from biogas makes it possible to simultaneously increase the concentration of methane in it at the input to the heat engine, which contributes to the stable and efficient operation of the gas piston engine of the power plant and the increase in the amount of electricity generation as a result of energy utilization of landfill gas. The use of complex biogas utilization technology in the cogeneration mode allows obtaining not only electricity, but also heat, which can be used in absorption amine technologies for CO2 extraction from biogas and thus reducing carbon dioxide emissions into the atmosphere. Bibl. 17, Fig. 9, Tab. 3.

Experimental Studies on Utilization of Biogas with Biodiesel/Diesel Blends in a CI Engine

The present study covers the utilization of a gaseous alternative fuel, raw biogas, in a diesel engine. Biogas alone cannot run a diesel engine, because gaseous fuel cannot burn by compression. It can be supplied to the CI engines in dual fuel mode by using an air-biogas mixer device. In this work, it is aimed to investigate the performance and emission characteristics of a biogas-biodiesel/diesel dual fuel mode diesel engine by employing a venturi gas mixer device for providing a homogeneous mixture. The performance and emission characteristics of the engine operated by dual-fuel mode were experimentally investigated, and compared to diesel. The results indicated that biogas inducted at a flow rate of 1L/min was found to have better performance and lower emission, than that of the other flow rates. On the other hand, dual-fuel mode with a biogas flow rate of BD10 BG@1L/min showed an average reduction in BTE of 9.94% and an average increment of 8.82% in BSFC as compared to diesel. Whereas an increment in CO and HC by 5.18% and 3.01% respectively and an average reduction in NOx emissions by 14.91% as compared to diesel. Keywords: Alternative Fuel, Biogas, Biodiesel, Diesel Engine, Dual-fuel, Venturi Gas Mixer

Greenhouse Gas Mitigation Potential of the Enhanced Rice Straw Biogas System in the Philippines

Abstract Rice straw is an agricultural waste produced abundantly every rice cropping cycle. Its disposal or removal from the field is a problem to rice farmers every start of the next cropping cycle due to its labor-intensive collection from the field. One traditional practice is soil incorporation; however, rice straw does not degrade easily, and this management practice releases significant amount of greenhouse gas emissions to the environment. An attempt to solve this issue is to utilize rice straw with cattle manure as feedstock for biogas production and use the energy generated for rice post-harvest processing such as grain drying and milling. An Enhanced Rice Straw Biogas facility was constructed in Victoria, Laguna, Philippines and a trial lagoon run was conducted from June to October 2021. The data from the initial run was used as input to the modified Aston-developed Mass Energy Balance Model to determine the biogas production potential of rice straw and cattle manure as bioenergy feedstocks. The proposed system can produce 8,803,567.99 L (296.19 L/kg VS) of biogas which can be converted to 19,502.97 MW electricity and 84,512.86 MJ heat. From the energy generated per batch, 18,417.21 kg rice grain (dry season) or 15,752.79 kg rice grain (wet season) can be dried and milled, with an excess of equivalent kerosene (696.93 L for dry season or 248.46 L for wet season) and electricity (3,745.12 kWh for dry season or 6,182.23 kWh for wet season). Due to biogas utilization, an estimated 3,351 L of fossil-based kerosene and 12,185.91 kWh of electricity equivalent can be avoided. This low GHG emission rice production system (Aston Model) has a theoretical annual carbon footprint of 153,134 kg CO2e and a 28.21% reduction of greenhouse gas emissions compared to the conventional rice production system.

Waste to energy: Enhancing biogas utilization in dual-fuel engines using machine learning based prognostic analysis

Alternative fuels derived from organic matter like biomass can be a viable solution in the present scenario of increasing greenhouse gases. In the present study, waste food and animal refuse-derived biogas were tested as fuel in a diesel engine. To further enhance the waste-to-energy perspective waste cooking oil biodiesel − diesel blends were used as pilot fuel. A comprehensive set of operational settings including fuel injection timing, pressure, compression ratios, different flow rates of biogas, and engine loads were tested. Four machine learning approaches Linear Regression (LR), Decision Tree (DT), Extreme Gradient Boosting (XGBoost), and Gaussian Process Regression (GPR) were employed to develop prognostic models. The developed models for engine performance and emission were predicted with high accuracy with R2 values as high as 0.9962 for brake-specific fuel consumption and 0.9948 for brake thermal efficiency. The prediction errors were low 0.06 for BTE during model training and 0.18 during the model testing phase while it was almost negligible in the case of BSFC. All models were compared using statistical metrics and violin plots. The DT-based forecasting models were observed to be the best among all the models both based on statistical measures as well as violin plots.

Thermo-enviro-economic analyses of a landfill biogas-fed polygeneration process combined with a liquefied natural gas cold energy utilization unit

Landfill biogas offers a promising opportunity to supply society’s energy requirements, following the waste-to-energy approach, which issuitable for sustainable production. However, structural modification for its utilization is the main gap, requiring additional research efforts. Considering this issue, the current study aims to design an eco-friendly polygeneration method for landfill biogas utilization for a cutting-edge heat recovery system that integrates a cold energy recovery and utilization unit for liquefied natural gas. The liquefied natural gas recovery section, the organic Rankine cycle with a zeotropic mixture, and the Kalina cycle are all started using the flue gas from the combustion of biogas in a cascade process. In addition, the waste heat of the Kalina cycle is recovered by a single-effect desalination cycle and liquefied natural gas recovery section. Also, a water electrolysis process is integrated into the whole system. As a result, the products include hydrogen, electricity, natural gas, hot and cold water, and freshwater. The Aspen HYSYS software is utilized to design the system and investigate its thermodynamic, environmental, and economic aspects. The results demonstrate an energy efficiency of 57.54 % and an exergy efficiency of 18.78 %. Also, the carbon dioxide footprint associated with the system equals 0.34 kg/kWh, and the specific cost of products is 73.96 $/GJ. An optimal exergy efficiency of 25.8 % and a specific cost of products of 69.7 $/GJ are obtained by means of an intelligent optimization approach that ultimately makes use of non-dominated sorting genetic algorithm-II and artificial neural networks.

Exergetic investigation of the influence of injector location in HCCI engines utilizing DEE as pilot fuel and biogas as primary fuel

To address the global demand for sustainable energy, integrating biogas into internal combustion engines is becoming more important. Homogeneous Charge Compression Ignition (HCCI) engines, known for high efficiency and low emissions, offer a promising solution. This study investigates the optimal injector location for using biogas in HCCI engines, with diethyl ether (DEE) as the pilot fuel, evaluating three positions: (i) at the port, (ii) 6 cm away (Manifold 1), and (iii) 10 cm away (Manifold 2). Through experiments and simulations, the impact of injector location on engine performance is analyzed across various parameters, including methane fractions, engine loads, and exhaust gas compositions. Results show that port injection achieves the highest first law and exergy efficiencies but increases emissions of hydrocarbons (HC), carbon monoxide (CO), and smoke. At 15 Nm load, Manifold 1 shows a 27.34 % reduction in exergy efficiency compared to port injection, while Manifold 2 exhibits an 18.49 % decrease at higher loads. Despite lower efficiencies, Manifold 1 effectively reduces harmful emissions. The study also considers exergo-economic and sustainability aspects, highlighting that while port injection is optimal for efficiency, Manifold 1 excels in minimizing HC and CO emissions, with a 50 % reduction in HC and 71.43 % reduction in CO emissions at 15 Nm load compared to port injection. Manifold 2 achieves the lowest smoke emissions across all loads. This investigation provides crucial insights into optimizing HCCI engines for biogas utilization, emphasizing injector location, fuel composition, and operating parameters to enhance performance and reduce environmental impact.

Assessing performance variability in a dual-fuel diesel engine using diesel and biogas: an experimental study across different compression ratios

The increasing concerns about energy security and environmental sustainability have intensified the search for alternative fuels. This study investigates the performance and emission characteristics of a dual-fuel diesel engine utilizing purified biogas and diesel across various compression ratios. A single-cylinder, direct-injection, water-cooled, variable compression ratio diesel engine was adapted to operate in dual-fuel mode, running experiments at compression ratios of 12, 14, 16, 18, and 20 with a constant injection timing of 23° before top dead center under different load conditions. The study reveals a peak brake thermal efficiency of 33.25% at a compression ratio of 20, demonstrating the potential of biogas as a viable alternative fuel. Notably, while carbon monoxide and hydrocarbon emissions decreased with higher compression ratios, nitrogen oxide emissions increased, highlighting a trade-off in emission characteristics. This work contributes to the understanding of biogas utilization in diesel engines, offering insights into optimizing engine performance and emissions through compression ratio adjustments. The findings can inform future developments in sustainable energy solutions.

Renewable fuel-powered micro-gas turbine and hydrogen fuel cell systems: Exploring scenarios of technology, control, and operation

Two technology options, a proton exchange membrane (PEM) fuel cell and a recuperated micro-gas turbine (MGT) consisting of equipment with variable efficiencies and a controllable bypass valve, are modeled numerically. The validated simulations are studied under multiple scenarios, including technology, control, and operation. Under the technology scenario, the PEM fuel cell depicts higher net heat energy (1390.5 kW) with an overall efficiency of 93.27 %, significantly reducing thermal dissipation compared to the MGT, which has a low heat-to-power ratio (0.69) with the same hydrogen combustion rate (0.018 kg s−1). Following the fuel scenario, at 40 %-part load and 100 % bypass valve position, the highest net power (137.08 kW) and heat generation (635.07 kW) are achieved when 0.009 kg s−1 of hydrogen is combusted in MGT, exceeding other fuel utilization. In addition, the heating control strategy determines the availability status of the proposed technologies. The observed operational trends indicate effective fulfillment of urban heating needs by hydrogen combustion during Winter and Fall. However, the utilization of biogas leads to significant functional limitations. Finally, the operating function of the PEM fuel cell under off-design conditions is evaluated, resulting in notable enhancements in energy outputs and hydrogen consumption when considering the combination of control parameters compared to their individual evaluations.

Methylosinus trichosporium OB3b drives composition-independent application of biogas in poly(3-hydroxybutyrate) synthesis

Biological conversion of biogas into poly(3-hydroxybutyrate) (PHB) via Type II methanotrophs holds great promise. However, a prerequisite for widespread biogas utilization is a comprehensive understanding of the effects of biogas composition on methanotrophic PHB synthesis. Herein, we explore the effects of biogas composition on the microbial growth and PHB accumulation of Methylosinus trichosporium OB3b under five different artificial biogas conditions with varying the ratio of methane (CH4) to carbon dioxide (CO2), the two main components of raw biogas. Stoichiometric and kinetic analyses revealed that increased CO2 concentrations correlated with higher maximum specific growth rates (0.021–0.029 h−1) and maximum CH4 utilization rates (0.029–0.042 mg CH4/mg TSS-h). Besides, no significant correlation was found between the CH4-to-CO2 ratio and other growth parameters. Consistent PHB contents (20.2–25.3 wt%) were achieved, irrespective of the CH4-to-CO2 ratio. Furthermore, the ability of M. trichosporium OB3b to grow and synthesize PHB (13.2 wt%) was confirmed using pilot-scale biogas. Our findings highlight the potential of biogas as a feedstock for producing valuable biodegradable polymers, thus contributing to waste-derived fuel (WDF) innovation and environmental sustainability.

Assessment of the possibility of obtaining biohydrogen during decarbonization of municipal solid waste landfills

The article discusses the current problem of energy utilization of municipal solid waste, most of which is currently buried in landfills. An assessment of greenhouse gas emissions from these anthropogenic objects is provided. It is noted that a promising direction for utilization of landfill biogas is the production of biohydrogen. The authors present the results of laboratory studies on the production of biomethane from organic waste with its further conversion into biohydrogen. Using the example of a large landfill for municipal solid waste, a possible geo-ecological effect is shown by reducing greenhouse gas emissions during the energy utilization of biogas.

Revolutionizing waste from household plastics to eco-friendly diesel alternatives through catalytic degradation with biogas utilization

The study tackled the pressing environmental issue of managing both biodegradable and non-biodegradable household plastic waste, aiming to convert this waste into valuable hydrocarbons, thus addressing critical concerns over plastic pollution and the quest for renewable energy sources. In the context of escalating environmental degradation and the urgent need for sustainable alternatives to fossil fuels, the ability to transform various forms of waste into energy presents a significant stride towards ecological and energy sustainability. Utilizing an innovative methodology, the research employed catalytic degradation of mixed plastic waste, leveraging fly ash as a catalyst and biogas produced from a combination of cow dung and kitchen waste as a renewable and sustainable heat source. This process was fine-tuned across several catalyst-to-polymer (cat/pol) ratios, specifically 0.10, 0.15, and 0.20, with detailed documentation of the degradation temperatures and yields of liquid and gaseous hydrocarbons for each 1 kg batch of plastic waste. Notably, at a cat/pol ratio of 0.20, a remarkable 100% conversion rate was achieved, highlighting the efficiency of this method. Following this, the resultant oil was segmented based on boiling points for further analysis and evaluation of its utility as a diesel fuel substitute. Significant findings include the highest liquid hydrocarbon yield of 65.1% at 378 °C, achieved with the 0.20 cat/pol ratio. Moreover, fractions boiling above 100 °C were identified to possess superior heating values and cetane numbers compared to conventional diesel, particularly the fraction boiling at 100 °C–150 °C (C2), which demonstrated optimal performance and combustion qualities. This fraction achieved a maximum brake thermal efficiency of 32.92%, exhibited low smoke density and hydrocarbon emissions of 48 HSU and 32ppm, but it also resulted in a significant increase in NOx emission. Among all the fractions, diesel C2 was observed to be the best in terms of performance & combustion and was lower in emission. The conclusions drawn underscore the method’s potential to mitigate plastic pollution and reduce fossil fuel reliance by converting both biodegradable and non-biodegradable waste into useful energy. This study’s novelty lies in its comprehensive approach to waste management and energy recovery, significantly advancing over previous literature by achieving a 100% conversion rate at a specific cat/pol ratio and optimizing the output for use as a diesel alternative. It stands out by producing a fraction with both high efficiency and lower emissions, offering a scalable, sustainable solution to waste management challenges and paving the way for future innovations in sustainable energy production.

Improved combustion stability of biogas at different CO2 concentrations using inhomogeneous partially premixed stratified flames

Biogas is a renewable and clean energy source that plays an important role in the current environment of low- carbon transition. If high-content CO2 in biogas can be separated, transformed, and utilized, it not only realizes high-value utilization of biogas but also promotes carbon reduction in the biogas field. To improve the combustion stability of biogas, an inhomogeneous, partially premixed stratified (IPPS) combustion model was adopted in this study. The thermal flame structure and stability were investigated for a wide range of mixture inhomogeneities, turbulence levels, CO2 concentrations, air-to-fuel velocity ratios, and combustion energies in a concentric flow slot burner (CFSB). A fine-wire thermocouple is used to resolve the thermal flame structure. The flame size was reduced by increasing the CO2 concentration and the flames became lighter blue. The flame temperature also decreased with increase in CO2 concentration. Flame stability was reduced by increasing the CO2 concentration. However, at a certain level of mixture inhomogeneity, the concentration of CO2 in the IPPS mode did not affect the stability. Accordingly, the IPPS mode of combustion should be suitable for the combustion and stabilization of biogas. This should support the design of highly stabilized biogas turbulent flames independent of CO2 concentration. The data show that the lower stability conditions are partially due to the change in fuel combustion energy, which is characterized by the Wobbe index (WI). In addition, at a certain level of mixture inhomogeneity, the effect of the WI on flame stability becomes dominant.

Continuous biogas production and ex-situ biomethanation in a trickling bed bioreactor under mesophilic and thermophilic conditions

The utilization of biogas as a renewable energy source necessitates a reduction in its CO2 content. "Ex-situ biomethanation" is employed to convert CO2 in biogas to CH4 through hydrogenotrophic methanogens. In this study, a biogas stream (32–36 % CO2) originating from cow manure digestion was subjected to treatment in a trickle bed bioreactor (4 liters). The presence of microorganisms on the packing material was confirmed by using a 16 S rRNA test and SEM images. This study stands out by considering all four combinations of thermophilic and mesophilic conditions, monitoring the transition and steady-state phases in a two-reactor series setup. The mesophilic-thermophilic mode yielded the highest purity (92 %) with an 86 % CO2 conversion rate and an energy density of 13,870 kJ/m3. Additionally, the performance consistency was also assessed using a larger TBB (8 liters). Extending the residence time, the thermophilic-thermophilic mode yielded the highest CH4 concentration at 98 %. The 16 S rRNA results revealed that, influenced by the designated growth conditions encompassing culture media, pH, temperature, and reactor retention time, an enrichment of hydrogenotrophic methanogens occurred. Furthermore, promising results in terms of CH4 concentration and process efficiency were demonstrated by the trickled bed bioreactor employing liquid-in-gas dispersion.

Optimization of methane gas-liquid mass transfer during biogas-based ectoine production in bubble column bioreactors

Nowadays, the utilization of biogas for energy generation is hindered by the declining production costs of solar and wind power. A shift towards the valorization of biogas into ectoine, a highly valuable bioproduct priced at 1000 €⸱kg−1, offers a novel approach to fostering a more competitive biogas market while contributing to carbon neutrality. This study evaluated the optimization of CH4 gas-liquid mass transfer in 10 L bubble column bioreactors for CH4 conversion into ectoine and hydroxyectoine using a mixed methanotrophic culture. The influence of the empty bed residence time (EBRTs of 27, 54, and 104 min) at different membrane diffuser pore sizes (0.3 and 0.6 mm) was investigated. Despite achieving CH4 elimination capacities (CH4-ECs) of 10–12 g⸱m−3⸱h−1, an EBRT of 104 min mediated CH4 limitation within the cultivation broth, resulting in a negligible biomass growth. Reducing the EBRT to 54 min entailed CH4-ECs of 21–24 g⸱m−3⸱h−1, concomitant to a significant increase in biomass growth (up to 0.17 g⸱L⸱d−1) and reaching maximum ectoine and hydroxyectoine accumulation of 79 and 13 mg⸱gVSS−1, respectively. Conversely, process operation at an EBRT of 27 min lead to microbial inhibition, resulting in a reduced biomass growth of 0.09 g⸱L⸱d−1 and an ectoine content of 47 mg⸱gVSS−1. While the influence of diffuser pore size was less pronounced compared to EBRT, the optimal process performance was observed with a diffuser pore size of 0.6 mm.

A Comprehensive Review on Biomethane Production from Biogas Separation and its Techno-Economic Assessments.

Biogas offers significant benefits as a renewable energy source, contributing to decarbonization, waste management, and economic development. This comprehensive review examines the historical, technological, economic, and global aspects of biomethane production, focusing on the key players such as China, the European Union, and North America, and associated opportunities and challenges as well as future prospects from an Australia perspective. The review begins with an introduction to biogas, detailing its composition, feedstock sources, historical development, and anaerobic digestion (AD) process. Subsequently, it delves into major biomethane production technologies, including physicochemical absorption, high-pressure water scrubbing (HPWS), amine scrubbing (AS), pressure swing adsorption (PSA), membrane permeation/separation (MP), and other technologies including organic solvent scrubbing and cryogenic separation. The study also discusses general guidelines of techno-economic assessments (TEAs) regarding biomethane production, outlining the methodologies, inventory analysis, environmental life cycle assessment (LCA), and estimated production costs. Challenges and opportunities of biogas utilization in Australia are explored, highlighting and referencing global projections, polarization in production approaches, circularity in waste management, and specific considerations for Australia. The review concludes discussing future perspectives for biomethane, emphasizing the importance of technological advancements, policy support, and investment in realizing its full potential for sustainable energy and waste management solutions.

Design and Construction of an Anaerobic Digester for the Ingestion of Waste from the Cocoa Industry in Nigeria

The Anaerobic Digester designed and constructed for waste ingestion from the Nigerian cocoa industry aims to harness abundant renewable energy from crop residues like cocoa rinds and groundnuts. This study evaluates the biogas potential of these sources in contributing to the country's overall energy needs, emphasizing the imperative for environmental sustainability. Focusing on reducing fossil energy consumption, greenhouse gas emissions, and minimizing environmental impact, the project advocates for a shift towards biogas for day-to-day energy requirements, presenting direct cost savings. The utilization of fossil fuel-derived energy is known to contribute to temperature increase, greenhouse gas emissions, noise pollution, and ground-level air pollution, all of which can be mitigated through biogas utilization. This initiative involves the design and construction of a 0.24m<sup>3</sup> pilot plastic fossil plant for biogas generation, aiming to "green" various applications, including domestic and industrial usage as well as transportation. The digester, constructed from high-density polyethylene (HDPE) plastic, demonstrates leak-free operation, further supporting its potential for long-term sustainability. Results from a 28-day retention period show a cumulative biogas yield, with a daily assessment indicating a gas yield of 0.0496 m<sup>3</sup> on the 12th day. The study highlights the positive and negative influences of temperature inequality gradients ≥34°C≤38°C on biogas production. This comprehensive research contributes valuable insights for the sustainable management of waste and the utilization of biogas as a viable alternative energy source.

Proposing an innovative polygeneration process based on biogas fuel: A comprehensive thermo-enviro-economic (4E) analysis

The utilization of biogas as a renewable fuel is feasible due to its high energy density, allowing for the development of polygonation structures in a cascade configuration. However, the high initial cost associated with biogas-based high-temperature applications is the central gap considered in this study. This paper introduces a novel heat integration model that employs a novel multi-stage cascade heat recovery and cost-effective operational approach. A biogas burner, an organic Rankine cycle, a Kalina cycle, an absorption chiller cycle, a heat supplier unit, and a proton exchange membrane electrolyzer-based hydrogen generating process are all part of the proposed system. Following the structure's modeling with the Aspen HYSYS program, thermodynamic, environmental, and economic evaluations are carried out along with a thorough parametric assessment. The simulation results indicate that the system has the capability to generate 2993 kW of electricity, 23350 kg/h of hot water at 80 °C, 68120 kg/h of chilled water at 10 °C, and generate 40.32 kg/h of hydrogen. This structure's energy, exergy, and electrical efficiencies are measured at 40 %, 23.71 %, and 16.68 %, respectively. Moreover, the exergy analysis indicated that the biogas burner and ORC evaporator account for 75.1 % of the total irreversibility (13800 kW).