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This study explores the potential of converting food waste (FW) in South Africa to biogas via anaerobic digestion (AD) using the Aspen Plus Simulator version 11. The simulation modeled the AD process, focusing on hydrolysis, acidogenesis, acetogenesis, and methanogenesis stages, with unconverted substrate recycling at the acetogenesis stage, employing a Non-Random Two-Liquid (NRTL) model for the polar mixture components. The FW used contained 49.86 % volatile solids (VS) of carbohydrates, 39.31 % VS of proteins, and 10.83 % VS of lipids. The results revealed that biogas yield at mesophilic temperature (37 °C) was 50 % higher than at thermophilic temperature (55 °C) with a residence time of 35 days, and methane composition was 45.98 % higher. Methane and carbon dioxide percentage compositions increased with hydraulic retention time (HRT), varying between 37.5–45.5 % and 34.3–39.9 % at mesophilic conditions. Economic analysis indicated a profitable outlook, with a payout period of 3 years, 5 months, and a 15-year positive revenue forecast. The project exhibited an internal rate of return (IRR) of 59.6629 %, suggesting strong economic viability and potential for investment. This study underscores the potential for optimized AD processes to enhance biogas production from FW in South Africa, presenting a viable, eco-friendly waste management solution.

Globalization has led to a rapid rise in energy consumption, making climate change one of the world's most pressing issues. As wastewater treatment plants (WWTPs) contribute to climate change by emitting greenhouse gases (GHGs), this study estimated the total GHG emissions of WWTPs by classifying them as either direct or indirect carbon emissions. The effectiveness of the use of solar photovoltaic systems and biogas produced by WWTPs in increasing energy recovery and reducing GHG emissions was investigated. This study demonstrated that the use of an up-flow anaerobic sludge blanket (UASB) reactor with a biogas flow of 9 120.77 m3/d and an activated sludge processing system (ASPS) reactor with a biogas flow of 14 004 m3/d, in addition to the energy production from the UASB reactor (6 421.8 MW⸱h per year) and the ASPS reactor (9 860.0 MW⸱h per year), yielded a reduction of 3 316.85 and 5 092.69 t of CO2 equivalent per year, respectively. Furthermore, the co-design of wastewater processes could be utilized to optimize biogas energy recovery. Moreover, the use of solar photovoltaic systems reduced GHG emissions from WWTPs. This is important to the transition to renewable energy because it resulted in a 10%–40% reduction in carbon emissions from WWTPs. Integrating renewable energy sources, biogas, and solar energy could provide up to 88% of the annual energy requirements of WWTPs. Recommendations are provided for further research considering the limited availability of integrated resources for studying the simultaneous utilization of photovoltaic and biogas systems.

Natural resources deterioration, as well as greenhouse gas (GHG) emissions are a critical global problem, derived mainly from the use of fossil fuels. In recent years, several Latin American countries have sought alternatives to replace fuels with biofuels. In this regard, this article aims to make a bibliographic review focused on the analysis of the current situation of biofuel production and research development in Argentina, Brazil, Mexico, Chile, Costa Rica and Colombia. For this, seventy-seven investigations extracted in the last ten years from the databases ResearchGate, ScienceDirect, MDPI, Academic Google, Scopus, ScienceDirect, EBSCO and Elsevier were analyzed. Also, and for the same period, a bibliometric analysis of 355 investigations of the Web of Science database was carried out. The article presents the production figures, technologies, advances and challenges for the production of biofuels in these countries. Brazil stands out as a leader in the region and stands out worldwide in the generation of clean energy through the implementation of a biofuels policy and its incorporation into the transport sector. From this review, it is possible to know the state of production and research on biofuels in these countries and the challenges they face in achieving advances that do not reflect the comparative advantages they have due to the availability of raw materials for their production.

The presented set of data brings results of the experimental production of biogas and methane from silages of alternative substrates consisting of maize and three leguminous species with a potential to make the production of biogas more friendly to the environment because the cultivation of legumes is generally considered to be more environment friendly than the cultivation of maize: white sweet clover (Melilotus albus Medik.), fodder vetch (Vicia villosa Roth.) and white lupin (Lupinus albus L.). Obtained data allow to compare the composition of experimental substrates and their important parameters (VS, DM, NDF, ADF, CF, starch, cellulose, hemicellulose, CP, lipids and ADL) as well as the yield of biogas, methane and methane in biogas from silage produced as a monosubstrate from the biomass of maize shreddings on the one side with silages produced from the mixture of biomass from maize and diverse legumes on the other side. This set of data can contribute to awareness about possibilities for reducing environmental risks connected with the cultivation of maize in growers of energy crops and operators of biogas plants. The reason is that a considerable number of farmers do not use new technologies of growing biomass for the production of biogas as they cannot quantify the potential impact on biogas yield and hence on the profitability of biogas plant operation. The measured values demonstrate that silages made from the mixed culture were reaching at least the same production of biogas and its quality as the monocultural maize silage.

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.

Although poultry is the largest meat by volume produced in Fiji, there has not been any established study, nor application of the anaerobic digestion (AD) of poultry manure (PM) in the country. This paper aims to determine the techno-economic feasibility of the AD of PM to power a poultry farm in Fiji. A pilot scale study was first conducted with mono-digestion batches of poultry manure, and co-digestions with kitchen waste (KW) and newspaper waste (NPW). Solid state anaerobic digestion (SSAD) was employed in all the batches, and the key operational parameters of AD were studied, along with its influence on biogas production. The pilot study revealed that even slight changes in environmental temperature had the greatest effect on biogas production. The most resilient to the temperature changes were the co-digested feedstocks of KW. Yet, given a substantial AD period, the anaerobes in the mono-digesters were able to eventually acclimatize to the SSAD environment, and produce the overall highest biogas production. The pilot study results were then used to conduct a feasibility study of the full-scale design. The analysis showed that the SSAD system would generate 189.46 MWh of electricity annually, with a levelized cost of energy of FJ$0.17/KWh.

The wastewater circular economy promises improved environmental impacts within the food-water-energy nexus. This requires verification as the global sanitation sectors seek to improve environmental impacts and achieve integrated water management. Life cycle assessment (LCA) has been used to compare novel technologies for wastewater treatment and recovery, but research addressing plant-wide improvements of co-product resource recovery using real data from full-scale plants is still needed, particularly in a Latin American context. In Chile, two wastewater treatment plants (WWTPs) have embraced the circular economy configuration, recovering treated effluent, biosolids, and biogas, in addition to implementing advanced nitrogen removal using different technologies. The LCA of these two WWTPs demonstrated that Plant A improved 8 out of 10 impact categories compared to the baseline conventional scenario, while Plant B improved 5 categories out of 10. The analysis of the two plants showed the influence of influent quality on environmental impacts and the trade-off that occurs between the different technologies implemented. Plant B generated larger environmental credits through increased biogas and biosolids recovery due to thermal hydrolysis pre-treatment and anaerobic digestion, combined with cogeneration of heat and power. Plant A implemented water recovery, which provided benefits on a smaller magnitude but to more impact categories. Therefore, both plants improved environmental impacts through the wastewater circular economy, but further improvements in system configurations are recommended in each.

To satisfy the electricity needs of a village in Tangi, northwest Pakistan, the present research can design and evaluate the environmental and economical aspects of an optimal hybrid photovoltaic-biogas-hydropower-battery energy sustainable system (PV-BG-HP-BESS). This framework integrates various renewable energy sources, delivering a modern, efficient approach to sustainable energy solutions. The HOMER Pro software is utilized to optimize the most economical and effective hybrid energy system. The results showed that the proposed hybrid system comprising 91.4 kWp PV modules, 19.6 kW hydropower, a 50 kW biogas generator (BG), 36 batteries, and a 60.6 kW converter was the most economical choice. This system, which used the cyclic charging (CC) method, had a cost of energy (COE) of 0.0728 $/kWh and a total net present cost (NPC) of $152,242. The suggested hybrid energy system for rural areas of Pakistan includes photovoltaic (PV), biogas (BG), hydro, and battery components to provide a dependable and sustainable power supply. This system minimizes the need for expensive fossil fuels while simultaneously minimizing environmental impact by lowering pollutants and greenhouse gas emissions. The system's annual electricity production is 294,782 kWh, with PV leads at 59.4%, BG at 6.02%, and hydro at 34.6%, ensuring uninterrupted power generation even in remote areas. The unmet load, extra electricity, and capacity shortage illustrate the reliability of the system and make it possible to address rural electrification challenges while supporting sustainable development and economic growth. Moreover, the outcomes of the proposed hybrid system dominate the previous studies in multiple objectives, including cost and sensitivity analysis, when compared.

The use of non-renewable energy resources such as fossil fuels accelerates climate change and environmental degradation necessitating a shift to renewable energy sources. Biogas is a renewable energy resource with great potential. However, its application is limited by the presence of contaminants such as carbon dioxide, which reduces its energy value, and density. Upgrading biogas using locally available materials solves waste management and energy sustainability challenges. In the present study, calcined eggshell waste was employed as an adsorbent for carbon dioxide. The effect of calcination temperature, adsorbent mass and adsorbent particle size was evaluated. The experimental data was fitted to adsorption isotherms, adsorption kinetic models, and breakthrough curves. Eggshells with a particle size of 280 μm, calcined at 850 °C, and mass of 75 g showed the best performance in removing carbon dioxide from biogas. It was noted that data from the experiment fitted Langmuir isotherm with RL 0.00216 while its R2 was 0.97 and Freundlich n = 0.6 while R2 = 0.97. Regarding adsorption kinetics, the intra-particle diffusion model shows good conformity with kid of 34, C of 98, and R2 of 0.977. Breakthrough analysis proved that Yoon Nelson's Model fitted well with the experimental data with an R2 of 0.989. Thus, calcined eggshell waste is a good sorbent for biogas upgrading that can solve the twin challenges of waste disposal and management and energy sustainability.

Nepal's burgeoning poultry industry which is a key sector in its economy leads to a considerable generation of slaughterhouse waste (SHW), necessitating effective and sustainable disposal methods. This study explores anaerobic digestion as an optimal solution for poultry SHW management, aiming to produce energy-rich biogas while efficiently mitigating pollution in these facilities. Particularly, the feasibility and effectiveness of co-digestion with chicken litter (CL) were investigated to enhance biogas production and waste utilization. Four distinct runs of anaerobic digestion were performed, each utilizing varying substrate compositions with SHW to CL ratios of 1:0, 4:1, 1:1, and 1:4. Throughout the process, essential parameters, including total solids (TS), volatile solids (VS), biological oxygen demand (BOD5), pH, temperature, biogas generation, were meticulously measured. The cumulative biogas production for each run was as follows: 14.87 liters and a biogas yield of 88.73 ml/gVS with a 17.39 % VS reduction for Run 1, 25.98 liters and a biogas yield of 147.21 ml/gVS with a 28.64 % VS reduction for Run 2, 78.32 liters and a biogas yield of 314.69 ml/gVS with a 54.32 % VS reduction for Run 3, and 89.195 liters and a biogas yield of 344.36 ml/gVS with a 63.05 % VS reduction for Run 4. Notably, as the proportion of CL increased in the mixture from 4:1 to 1:1, a considerable VS reduction was observed. Furthermore, when the ratio of SHW to CL reached 1:1 and 1:4, a significant BOD5 reduction of 50 % and 63.13 % was achieved, respectively, surpassing previous runs. The results reveal that the addition of CL in an appropriate ratio effectively manages poultry SHW, with the optimum SHW:CL ratio for significant biogas yield lying between 1:1 and 1:4.

This research aimed to evaluate the use of germinated papaya seeds (GPS) as co-substrate with dairy cow manure (DCM) by paying attention to the effect of GPS sprout length. Germination has been proven to increase seed's nutrient quality, however, lack of information models that optimize anaerobic co-digestion threat combinations of these treatments. The study was conducted using batch-type digesters, and central composite design (CCD). Process optimization was carried out using response surface methodology (RSM). The findings showed that the CCD model developed by RSM was significant (p 0.05) however, the combination of GPS and DCM had a significant effect (p

Air pollution, population growth, and the lack of fossil energy sources are critical factors that drive people toward clean and renewable energies in the current century. Biogas is suitable for rural farmers as a source of clean energy. Since there are many social interactions in knowledge exchange and sharing, the transfer of skills, and participation among individuals, various actors are involved in the network. The power and influence of actors and the social interactions between smallholder farmers and these actors fuel the development of biogas consumption in rural areas. Therefore, this study analyzes the social network structures and characteristics of various actors by social network analysis (SNA) in knowledge sharing, the transfer of skills, and participation networks among traditional smallholder farmers in Iran. The research sample consisted of some smallholder farmers in four provinces of Fars, Khorasan Razavi, Golestan, and Kermanshah (144 smallholder farmers). The research instrument was a questionnaire designed as a matrix. The findings showed that based on the betweenness centrality score, biogas-consuming smallholder farmers (34.56) and cooperatives of smallholder farmers (24.79) were the main actors in the network of knowledge sharing, respectively. Furthermore, biogas-consuming smallholder farmers (28.04) and pioneer smallholder farmers (27.11) were the main actors in the network of participation, respectively. The betweenness centrality score revealed that cooperatives of smallholder farmers (29.23) and opinion leaders (23.33) were the main actors in the network of skills transfer, respectively. It can be concluded that these actors had high social power and influence among smallholder farmers and can be the core of the smallholder farmers’ social networks. It means that they can influence the development of biogas consumption among Iranian smallholder farmers.

This research aims to evaluate the effect germination of papaya seeds (GPS) on methane production (batch mode) and the application of GPS in co-digestion (continuous mode). Batch mode study showed that, compare to non-germinated (NGPS), GPS can increase methane production (p

CFB boilers exhibit broad fuel adaptability. Multi-fuel co-combustion can be implemented without altering the boiler's main structure, enabling the exploration of additional fuel utilization methods. This study assesses the feasibility of biogas co-combustion in CFB boilers. In this study, the computational particle fluid dynamics (CPFD) method was used to simulate a 130 t/h biomass CFB boiler. The impact of varying proportions of biogas on combustion characteristics and NO emissions in the CFB boiler was systematically analyzed. The results indicate that the fluid velocity in the furnace remains relatively unaffected before and after co-combustion, the flow rate varied from 3 to 5 m/s for all cases. With an increase in the proportion of biogas co-combustion, the temperature inside the furnace rises. However, maintaining the biogas co-combustion ratio below 20 % keeps the temperature within a reasonable range. Beyond this threshold, particularly at a 30 % biogas co-combustion ratio, localized time-averaged temperatures in the furnace exceed 1300K, and the coking risk increases. Additionally, co-combusting biogas decreases fuel nitrogen levels and alters oxygen distribution, thereby impeding NOx formation. This results in a 14.3 % reduction in NO emissions at a 20 % co-combustion ratio and a 24.6 % reduction at a 30 % co-combustion ratio. This paper's research provides a valuable reference for co-combustion of gases in CFB boilers.

Energy sustainability, especially in agriculture, has been considered due to population growth and the lack of fossil fuel resources for future generations. Extending renewable energies, including biogas, is essential for sustainable development. This qualitative research was designed and implemented to determine how to extend biogas in rural areas in Iran. The study used grounded theory to guide data collection and analysis and model presentation. The sample included experts from the Ministry of Agriculture and Renewable Energy Organization of Iran selected by purposive sampling. Data were collected by field observations and interviews and analyzed by the coding process (open, axial, and selective coding), as a result of which ten core categories were extracted. They were presented as intervening conditions, contextual conditions, and strategies and used to develop a paradigmatic model for promoting biogas use in Iran's rural areas. Finally, based on the results, suggestions are presented to accelerate the process.

Every liter of sugarcane-based bioethanol production discharges 8–20 L of liquid waste called vinasse, which is suitable for biogas production. However, biogas production from vinasse is hindered by the presence of phenolic compounds as inhibitors in anaerobic digestion. In this study, we investigated the improvement of specific methane yield in the anaerobic digestion of vinasse by adding a solid structure as a microbial immobilization medium. The ring-shaped zeolite/bentonite mixture loaded with particular amounts of Fe(II) cations was used as the medium. The medium was tested in vinasse anaerobic digestion with initial substrate concentrations ranging from 7500 to 35,000 mg sCOD/L. The substrate concentrations affected both the soluble chemical oxygen demand (sCOD) removal rate and the methane yield. However, the amount of Fe(II) loading in the medium only affected the methane yield. Specific methane yields 85 % higher than the control was obtained with the solid medium, i.e., 399.78 mL CH4/g sCOD, by adding 45 g media/g sCOD with an Fe(II) loading of 0.0016 mg Fe/g media. Based on the results, it was possible to increase biogas productivity by adding an Fe-loaded zeolite/bentonite medium to make the anaerobic digestion of vinasse more economically feasible.

Anaerobic co-digestion offers a promising approach to enhancing biogas production from surplus by-products of wastewater treatment plants (WWTPs) and agricultural waste while reducing environmental negative impact. This study investigated the co-digestion of anaerobic thickened sewage sludge (ATSS) and rice straw (RS) under mesophilic conditions (35 ± 1 °C). In phase 1 of the experiment, lab-scale reactors with varying MRs of RS (0 %, 4 %, 8 %, and 16 % based on sludge weight) were employed to determine the optimal MR for maximizing biogas quantity and methane content. Phase 2 examined the impact of mechanical mixing (MM) on biogas production, pathogen and trace element reduction, and the calorific value (CV) of the co-digested mixture compared to the digested thickened sludge (DTS) and RS individually to assess the potential energy of co-digestion. Results revealed that the 8 % MR yielded the highest biogas volume, approximately 2.5 times that of the DTS alone, with methane and carbon dioxide contents within the typical ranges. MM in phase 2 further increased biogas volume by 2.8 times compared to DTS. The CV of the co-digested mixture was 24,937 kJ/kg and 21,929 kJ/kg for the DTS. Pathogens were effectively eliminated, and trace elements remained below the permissible limits. The 8 % MR with MM was identified as the optimal MR that produces the highest biogas quantity before reaching the turning point. Moreover, co-digestion at this MR enhanced the CV of ATSS by 14 %.

In an urban context, municipal mixed sludge (MMS) and fruit and vegetable waste (FVW) are becoming the major organic solid wastes in human society. Thus, anaerobic digestion as a low carbon energy strategy to minimize their environmental polluting risk was studied. To overcome the drawbacks of anaerobic digestion of MMS, an alternative approach is proposed, involving the addition of increasing proportions of mango peel pulp (MPP) as a co-substrate. Different ratios of MMS:MPP (v:v) were studied: 80:20 (T1), 70:30 (T2), 60:40 (T3). The increase in the organic loading rate was well incorporated by the reactor's biomass activity, and it had no negative effects on the reactor stability and performance operational parameters. Results indicated that the addition of MPP had a beneficial effect on specific methane production, where the highest value was registered in T2 (0.47 L CH4/g VS added), with a 1.8-fold increase in this operational parameter. Moreover, bioenergy recovery within the same trial followed the same profile, representing a two-fold increment.

This study aims to identify the optimal conditions for generating biogas from poultry manure with respect to pH, C/N ratio, and temperature. The study was conducted in lab batch bioreactor having a working volume of 2 l at different conditions with respect to pH, carbon to nitrogen ratio (C/N), and temperature. A full factorial design is designed to analyze the impact of the three parameters and their interactions. Experiments are replicated four times to ensure the reproducibility of data. Results indicate that temperature is the only influencing parameter on biogas production from poultry manure within a pH range of 6–8 and a C/N ratio range of 10/1 to 40/1. Moreover, there is no interaction between the three parameters, and mesophilic conditions are found to be the optimum conditions for biogas production. The maximum biogas yield of 285 ml/g VS is found in mesophilic conditions at 37 °C with a retention time of 20 days. Biogas production kinetics are similar in mesophilic and thermophilic conditions but vary in psychrophilic conditions.

The article examines municipal solid waste (MSW), specifically organic or food waste (OW), which constitutes between 42 % and 69 % of MSW globally. These wastes contain a high concentration of organic matter, nutrients and moisture, with an easily acidified pH. Its management is crucial due to its environmental impact, generating greenhouse gas emissions and pollution problems.Anaerobic Digestion (AD) is presented as a biotechnological solution to harness the energy of food waste. This process, without oxygen, decomposes organic matter by means of microorganisms, converting it into biogas, with a yield of 5–7 kWh/m³. This reduces emissions and promotes sustainable practices, which are crucial for the sustainable management and development of the ROA.The methodology used involved a systematic review in English, Portuguese and Spanish, refining the search in several databases. After a thorough selection, 18 articles met the established criteria and were critically evaluated. The meta-analysis showed low heterogeneity (Iˆ2 = 2 %). This article highlights the importance of addressing SWR through AD, highlighting their energy potential and environmental benefits to mitigate the negative impacts of MSW.The analysis of biogas production evidenced the need to standardize approaches for more efficient and sustainable solutions in future research.

In this study, first, a fed-batch biogas fermenter was established using anaerobic digester sludge treating secondary sludge from a municipal wastewater treatment plant and operated for 120 days on glycerol as the sole substrate. Then, the prefiltered effluent of the anaerobic digester unit was loaded subsequently into a stirred-tank coupled with a hollow-fibre, polydimethylsiloxane (PDMS) gas-liquid membrane contactor and a dissolved methane sensor for studying the gas recovery process under continuous biogas supply, consisting of CH4 and CO2 in different proportions (70/30 CH4/CO2 vol.%; 50/50 CH4/CO2 vol.%; 30/70 CH4/CO2 vol.%.). Experiments showed that besides the actual composition of the internal biogas, the ratio (0.5–2) of sweep gas (N2) and effluent (liquid) volumetric flow rates (G/L) could be a crucial operating factor with influence on the degassing efficiency attainable by the 1 m2 PDMS membrane module. Results were compared to the performance of the same PDMS membrane module working with synthetic anaerobic digester effluents, indicating the dissolved methane recoveries observed with the synthetic effluents (>50 %) considerably surpassed those with the real effluent (

This study investigates the performance, emission and combustion characteristics of a stationary engine under diverse operating conditions. The research focuses on the impact of waste plastic oil (WPO) blends with and without biogas addition. WPO added in diesel at various proportions such as 20%, 35% and 50% by volume. Biogas is inducted through inlet manifold. Biogas flow rate was varied. This study introduces a pioneering approach by investigating the superior performance of WPO blends coupled with the unique exploration of biogas addition, revealing intricate relationships between fuel blends and combustion characteristics for enhanced stationary engine efficiency and reduced emissions. Notably, WPO with 80% diesel (WPO20) demonstrates superior Brake Thermal Efficiency (BTE), showcasing a significant increase compared to WPO35 and WPO50 across varying load conditions. The addition of biogas to WPO20 results in a measurable reduction in BTE due to incomplete combustion, insufficient excess air, and increased emissions. Hydrocarbon (HC) emissions increase with load for WPO blends, with WPO20 exhibiting the lowest HC emissions. Carbon monoxide (CO) emissions are influenced by WPO concentration, with WPO20–B12 and WPO20–B16 dual fuel mode showing varying trends. Nitrogen oxides (NOx) emissions decrease with the addition of biogas, indicating a 10% reduction for WPO20–B16 compared to WPO20–B12. Smoke emissions increase with higher WPO concentrations but decrease with the introduction of biogas, exhibiting a 20% reduction in smoke for WPO20–B16 compared to WPO20–B12.

The existence of CO2 in biogas limits its utilization in engines by lowering its energy value and density. It contributes to global warming which is a major concern globally. The elimination of CO2 content from biogas will significantly improve the quality of biogas. In this study, biogas upgrading by calcined eggshell waste was systematically investigated. The influence of adsorbent particle size, mass, calcination temperature, and flow rate on carbon dioxide removal was studied in detail. Chemical adsorption of CO2 by calcined eggshells in a packed column having 280 and 400 μm, calcined under 800 °C, 850 °C, and 900 °C, with the mass of 25, 50, and 75 g was experimentally investigated at a different flow rate as 0.03 and 0.04 m3/h. The results revealed that a particle size of 280 μm, calcined at 850 °C, flow rate of 0.03 m3/h, and mass of 75 g perform better in the upgrading of carbon dioxide in biogas with RE and sorption of 82.5 %, and g 5.0 g/100 g respectively, creating methane enriched fuel. X-ray Fluorescence shows the presence of CaO automatically facilitates the whole process of purification. The pores were mesoporous as seen in the pore distribution curve via BET analysis while Scanning Electron Microscopy was for morphology purposes. The sorbent was successfully regenerated five times with a RE of 79.8 % and SC of 4.97 g/100 g in the first cycle. The results proved that calcined eggshells are a promising sorbent in biogas upgrading.

Burkina Faso is one of the countries in Africa that has problems managing organic waste such as faecal sludge. These problems are mainly related to the lack of sanitation infrastructure in most cities in the country. This study was, therefore, designed to assess the potential of sustainably managing faecal sludge and other organic wastes in Bobo-Dioulasso through biogas technology to recover energy and organic fertilizer for agricultural production. Samples of faecal sludge from nine different trucks in one-litre plastic bottles, a two-litre abattoir waste and 1 kg of fruit and vegetable waste were also collected and their physicochemical parameters were analysed at ONEA Laboratory. The laboratory results reveal that 100% faecal sludge (FS) introduced into the digester after 25 days of mesophilic digestion at 37 °C produced 4.37 l/kg of biogas, with 23% of CH4 and 1.3% and 44.2% of Total Solids (TS) and Volatile Solids (VS) respectively. A faecal sludge of 90% with slaughterhouse waste of 10% introduced yielded 17.3 l/kg of biogas with 44.4% of CH4 content and 2.38% and 61.42% of TS and VS respectively. A combination of 90% faecal sludge with 10% of fruits and vegetables waste produced 29.4 l/ kg of biogas with 42% of CH4, 4.72% of TS and 72.18% of VS. However, it was found that the settled sludge and semi-solid material collected for the same tests with respective TS (8.62%) and VS (69.1%) produced a good yield of 54.4 l/kg of biogas with 51% of CH4. The study also revealed that decantation of the waste material was more profitable for energy recovery from faecal sludge. Field surveys to assess social impacts showed that 82.8% of the households were in support of a biogas production plant and are willing to pay for biogas for cooking. The study concludes that the valorization of faecal sludge into biogas is a good solution to solving sanitation problems and contributes to energy supply as well as improving agricultural production in Bobo-Dioulasso and beyond.

Electric Vehicle (EV) usage across the world has rapidly increased in the recent times and has opened the doors for researchers working in the area of EV charging station (EVCS). The presence of EVs in India is equally growing and creating a charging infrastructure resource is a big challenge. In this paper, biogas–solar powered EVCS is proposed for a typical location in South Indian state of Karnataka. Techno economic assessment and environmental analysis of PV-Grid with Biogas Powered EVCS in a microgrid was comprehensively carried out using Hybrid Optimization of Multiple Energy Resources (HOMER) software. Results obtained demonstrated that the dependency on the grid purchase was significantly reduced with improved environment benefits in terms of lesser CO2 emissions. This study shall be beneficial in renewables based EVCS infrastructure development.

Anaerobic Digestion (AD) of mono-substrate is reported to be ineffective due to nutritional imbalance and lack of a variety of microbes. Anaerobic co-digestion of substrates is the advised alternative to mono-digestion to boost the generation of quality biogas. Brewers’ Spent Grains (BSG) contain high organic matter content and can be used in the production of biogas towards reducing the reliance on fossil fuel-based energy sources. Biogas generation from BSG can be improved through the co-digestion process via the inclusion of extra substrate. The current study explored the quality of biogas generated through co-digestion of BSG and cattle dung (CD). Digestion of two substrates was managed at a retention time of 10 days at BSG: CD ratios: 1:3, 1:2, 1:1, 2:1, 3:1, BSG and CD control experiments with substrates combination of 4.5 kg in each setup. Plastic bottles (10 L) were used as bio-digesters with substrates and water at a 1:1 ratio to allow anaerobic digestion (AD) to proceed. Results showed that BSG: CD ratios of 1:3 and 1: 2 with total solids (TS) content of 9.24% and 8.95% produced the highest quality raw biogas rich in methane. Both ratios 1:3 and 1:2 produced Methane which exhibited a 100% lower explosive limit (LEL) at an average of 40.3 ± 29.88 % LEL d−1 and 40.28 ± 33.39 LEL d−1 respectively; with a respective methane content of 54.7 ± 10.74% CH4d−1 and 51.9 ± 8.67% CH4d−1. The current study provides a facile and convenient optimal ratio between BSG and CD for the production of high-quality biogas using environmentally prevalent materials.

The metagenomic approach stands as a powerful technique for examining the composition of microbial communities and their involvement in various anaerobic digestion (AD) systems. Understanding the structure, function, and dynamics of microbial communities becomes pivotal for optimizing the biogas process, enhancing its stability and improving overall performance. Currently, taxonomic profiling of biogas-producing communities relies mainly on high-throughput 16S rRNA sequencing, offering insights into the bacterial and archaeal structures of AD assemblages and their correlations with fed substrates and process parameters. To delve even deeper, shotgun and genome-centric metagenomic approaches are employed to recover individual genomes from the metagenome. This provides a nuanced understanding of collective functionalities, interspecies interactions, and microbial associations with abiotic factors. The application of OMICs in AD systems holds the potential to revolutionize the field, leading to more efficient and sustainable waste management practices particularly through the implementation of precision anaerobic digestion systems. As ongoing research in this area progresses, anticipations are high for further exciting developments in the future. This review serves to explore the current landscape of metagenomic analyses, with focus on advancing our comprehension and critically evaluating biases and recommendations in the analysis of microbial communities in anaerobic digesters. Its objective is to explore how contemporary metagenomic approaches can be effectively applied to enhance our understanding and contribute to the refinement of the AD process. This marks a substantial stride towards achieving a more comprehensive understanding of anaerobic digestion systems.

Anaerobic digestion is a suitable technology to treat cheese whey (CW), a high-strength wastewater from cheesemaking. However, CW anaerobic digestion is limited by its high biodegradability, acidic pH, and lack of alkalinity. This publication evaluated the acidification risk of CW anaerobic digestion under psychrophilic and mesophilic conditions, aiming to improve digester design, operation, and decision-making when facing instability periods. To evaluate the acidification risk of CW anaerobic digestion, biochemical methane potential (BMP) tests were carried out at four different organic loads, each under psychrophilic (20 °C) and mesophilic (35 °C) conditions. Besides methane production, pH, soluble chemical oxygen demand, volatile fatty acid and alcohols were also monitored. Experimental results showed that CW can be successfully degraded under both temperature conditions, with methane yields of 389–436 mLCH4/gVS. The organic load had a greater impact on the accumulation of intermediate products than temperature, indicating that process inhibition by overloading is plausible under psychrophilic and mesophilic conditions. However, the degradation rate under mesophilic conditions was faster than under psychrophilic conditions. Experimental results also revealed a higher imbalance between fermentation and methanogenesis rate under psychrophilic conditions, which resulted in higher concentrations of intermediate products (volatile fatty acids and alcohols) and prolonged lower pHs. These results indicate that the degradation of intermediate products is less favourable under psychrophilic conditions compared to mesophilic conditions. This implies that psychrophilic digesters have a lower capacity to recover from process disturbances, increasing the risk of process underperformance or even failure under psychrophilic conditions.

Load growth puts pressure on existing electric infrastructure and impacts on the system's performance parameters which may necessitate network expansion. Conventionally, electric network expansion is done by building new substations or reinforcing the existing ones with new transformers and upgrading the network feeders. However, optimal allocation of combined heat and power distributed generators (CHP-DGs) on distribution networks (DNs) can be adopted for network expansion planning problem. Optimal DG allocation is an optimisation problem which requires an efficient optimisation approach. In this paper, an improved particle swarm optimisation (IPSO) based on weighted randomised acceleration coefficient and adaptive inertia weight is proposed for optimal DG allocation problem. The considered CHP-DGs include internal combustion engine (ICE) and fuel cells (FCs) powered by biogas obtained from anaerobic digestion of food wastes. The proposed IPSO is tested on IEEE 69 bus radial distribution network under single and multi-objectives considering constant and mixed seasonal voltage-dependent load models. Some of the key findings show that integrating ICE-based CHP-DGs operating at optimal power factor in winter day mixed voltage dependent load in base year achieves 97.63 % active power loss reduction in comparison to 77.14 % loss reduction for unity power factor operating FC-based CHP-DG. Economic and environmental evaluation indicate that FC-based CHP-DG records a net present value of over 29.29 million $, levelised cost of energy of 0.0493 $/kWh and zero pollutant emission in comparison with 28.40 million $, 0.0501 $/kWh and 0.2817 million kg pollutant emission for ICE-based CHP-DG over the planning horizon. In comparison with the standard PSO, the proposed IPSO performs better in terms of solution quality, convergence speed and statistical results.

The circular economy is one of the most critical challenges in the 21st century. By using waste, the consumption of valuable raw materials can be reduced. It will also reduce the amount of waste directed to landfill or incineration. Also, in biogas production terms, activities consistent with the circular economy are raised. They mainly consist of the use of waste in the anaerobic digestion process and the rational use of the digestate. For the owners of biogas plants, the essential issue is optimizing the anaerobic digestion process to produce as much biogas as possible. The work aimed to determine the profitability of the operation of agricultural biogas plants in Poland, depending on the substrate use model.The study analyzes two options for supplying agricultural biogas plants with substrates: Option I — traditional (maize silage and slurry) and Option II — waste (slaughterhouse waste and slurry). In both options, it was assumed that biogas plants would operate under the conditions of the auction system — one of the models in force in Poland. The investment balance can be significantly improved by using waste instead of maize silage. The profit for the biogas plant operating in Option I was estimated at PLN 628,360, and in Option II it was PLN 2,307,600. The conducted analysis showed that the operation of waste biogas plants is much more profitable than traditional ones. The positive impact on the natural environment will complement the economic benefits. It is because managing waste from the agri-food industry in controlled conditions will significantly contribute to energy production, considering the aspects of protection against climate change.

Biogas is obtained from the breakdown of biomass by microorganisms and bacteria in the absence of oxygen. Biogas is considered a renewable source of energy, similar to solar energy and wind energy. Biogas can be produced from biomass or bio-waste; thus, it is environmentally friendly. Biogas is obtained in a suspended monoxide decomposition process by anaerobic bacteria or in a fermentation process of decomposable materials such as agricultural manure, sewage, municipal waste, green waste (gardens and parks), plant material and agricultural products. Biogas is a renewable natural energy source that leaves effective effects on nature and industries. This gas is produced from the decomposition of organic materials, including animal manure, food waste and sewage. Fertilizers and waste produce biogas through anaerobic digestion (ie without the presence of oxygen). Biogas is a mixture of gases generated by decaying biodegradable material without the presence of oxygen. Its main contents are 50–70 % of methane (CH4) by volume, 30–50 % of carbon dioxide (CO2), and traces of other gases, like hydrogen sulfide (H2S) and water vapor (H2O). CO2, H2S, and water vapor content in biogas may affect the performance and life of the energy conversion devices; consequently, their removal before end-use is essential for improving the quality of biogas. This combination is an ideal option for making renewable energy. The most important advantages of biogas (production of energy, reduction of the amount of discarded waste, reduction of pathogens, conversion of waste containing organic matter into high quality fertilizer, protection of vegetation, soil, water, increasing productivity in the field of livestock and agriculture) and It is also one of the disadvantages of biogas (incomplete and small technologies, containing impurities, the effect of temperature on biogas production, unsuitable for urban and dense areas, not affordable). For economical use of biogas, the fermentation process can be carried out under controlled conditions in a relatively simple device called a digestion reservoir. This review summarizes the current state-of-the-art and presents future perspectives related to the anaerobic digestion process for biogas production. Moreover, a historical retrospective of biogas sector from the early years of its development till its recent advancements give an outlook of the opportunities that are opening up for process optimization.

Electrode biofilm and planktonic microorganisms are two important parts in bioelectrochemical system, but the mechanism of planktonic microorganisms affect biofilms is not clear. Waste sludge lysate produced from sludge pyrolysis contains melanoidins as complex carbon source that are refractory. Anaerobic digestion companied with weak electrostimulation is adopted to treat the wastewater and explore the mechanism in electron transfer, biofilm activity and microbial community structure. In the presence of planktonic microorganisms, electrode biofilm still plays a major role that about 70% of organics was removed by biofilm, the energy recovery efficiency increased by 10.81%, and the main electron transfer mechanism of biofilm is unchanged, but extra electron transfer pathway (Ef = 0.404 V vs Ag/AgCl) is generated. More cytochrome is produced in biofilm and charge transfer resistance decreases to facilitate electron transfer. The planktonic microorganisms cause more electrochemically active microorganisms and methanogens enrich in the electrode biofilm to enhance the direct interspecies electron transfer.

This review investigates small-scale biogas digesters' design and construction considerations to address biogas digesters' failures shortly after installation. The frequent failures of small-scale or household biogas digesters negatively affect its adoption as a clean domestic cooking fuel in developing countries, affecting the achievement of Sustainable Development Goal (SDG) 7. The study considered Scopus database-indexed peer-reviewed journals published between 2000 and 2022. Selected papers focussed on real-time monitoring, stirring mechanisms, and temperature control systems based on predefined inclusion and exclusion criteria with initial search results of 4751 documents, narrowing to 55 papers. The PRISMA 2020 statement was adopted to conduct the study. The study highlights the importance of incorporating a real-time monitoring system as a design factor in small-scale biogas digesters for successful operation and maintenance. The study's findings may be helpful to practitioners, policymakers, and researchers promoting sustainable energy and waste management solutions in low-resource settings.

Over-dependence on virgin resources has been a major topic of social and political debates as the world's population and urbanization continue to rise. The high rate of rural–urban migration and changes in standard of living habits give rise to rapid economic activities that have an enormous impact on the gradual increase in waste generation and continued demand for electricity in urban centres. The solutions to these concerns can be achieved through efficient waste management options by waste resource utilization for energy and nutrient recovery and reduced solid waste pollution footprint. This research examined the viability of present and projected municipal solid waste streams to generate green energy through field surveys by physical characterization of the waste composition, projected waste quantity based on available population and waste data for the period 2000 – 2014, modelled methane gas generated by IPCC method, and the energy value was determined respectively. The findings indicated a high organic content of 54.1% of MSW and a per capita waste generation rate of 0.49–0.57 kg/capita/day. The waste was projected to increase from 353717.41 to 2,223497 tonnes between 2014 and 2035 at a population growth rate of 9.15%. This accounted for methane gas generated estimated to be 9.85Gg/year with an energy value of 15 MW/day in 2014 and projected to increase to 33.4 MW/day by 2035. The energy value estimated represented an increase from 6.14% to 212.74% of the allocated power supply from the national grid within the projected period. However, it is worth noting that, there are some limitations associated with the research due in part to inadequate field data which was supplemented by default model values as recommended by IPCC, although within an acceptable uncertainty band of result sensitivity. Therefore, the WTE management option can serve as a pathway for green energy integration for sustainable development.

Anaerobic digestion of multiple substrates can generate more biogas while remaining stable, if positive synergistic effects are achieved. The type of co-digested substrates and the mixing ratio used, are the most important variables as each substrate has unique set of characteristics. Optimizing the volume ratios by testing various substrate mixing ratios is a popular method for determining the best-performing ratio of substrate mixture. The ternary mixture design has reportedly been found to quicken the process of testing different mixing ratios with high accuracy without running several experiments. Therefore, a ternary mixture design and a response surface approach are used in this work to ascertain the relationship between substrate mix and responses (biogas yield, methane yield, and synergy). The findings of the experiment revealed that R9 comprising 78.8 % human excreta, 11.8 % food leftovers and 9.4 % kitchen residue, had the highest methane production of 764.79 mLCH4/gVS and a synergistic index of 3.26. Additionally, the 3D response surface plots from the response surface model showed important and shared interactions between Human Excreta, (HE), Food Leftovers (FLO), and Kitchen Residue (KR). HE and KR had a similar positive synergistic effect on biogas yield, methane yield, and synergy, which was not the case for FLO. The response surface plots showed that the predicted responses (methane yield, biogas yield and synergy) increased with increasing HE and KR fractions and decreased with increasing FLO fractions in the substrate mixtures.

The use of hybrid renewable energy systems is growing as a viable option for clean power generation, fueled by the increasing demand for sustainable energy sources and the need to reduce carbon emissions. In this context, this paper evaluates the optimal configuration, as well as the economic and environmental performances of a hybrid solar PV/biogas/battery energy system designed to provide electricity to a commercial platform in Berkane- Morocco. The optimization model aims to determine the optimal capacity of renewable energy systems achieving the most cost-effective levelized cost of electricity, reducing greenhouse gas emissions, and utilizing locally available renewable energy resources. The model was developed using HOMER software incorporating real-measured data for electricity demand, solar irradiance, and biogas availability. It was found that the PV/biogas/battery combination is very optimal in terms of cost and emissions savings in comparison with the use of only one source of power generation. The optimal design of the energy system results in 231 kW of PV modules, 170 kW biogas generator, a 140-kW converter, and a 201 kWh Li-Ion battery park. The optimization results in an LCOE of 0.280 $/kWh; Moreover, the proposed system would save almost 40 % of carbon dioxide (CO2) emissions in comparison with only biogas system. A sensitivity test has been performed, showing that the proposed hybrid system is sensitive to capital subsidies and discount rates. This study demonstrates the economic viability and environmental benefits driven by the integration of the hybrid of PV/Biogas/Battery system in Morocco, making it an attractive alternative for future sustainable development.

This study investigates and describes a novel method for using biogas to run a cogeneration system that generates electricity/cooling and cools with recovered heat from liquefied natural gas (LNG). The investigated setup comprises an open-loop Brayton cycle fed by biogas, a close-loop Brayton cycle (CLBC), an LNG open power generation cycle, and a dual-stage combined cooling and power (CCP) unit composed of an organic Rankine cycle (ORC) integrated with an ejector refrigeration cycle (ERC). The performance of the system is scrutinized from many perspectives, such as the ones of energy, exergy, exergoeconomic, CO2 emmision rate, payback, and multi-objective optimization. It is deduced that TGT1 is the most influential decision variable from exergy and cost outlooks, while energy efficiency undergoes considerable changes with variation in Teva. Based on optimization, the developed unit generated 424.1 kW of cooling and 1,864 kW of net electricity, corresponding to 80.4% energy efficiency, 41.24% exergy efficiency, and 10.07 $/GJ for the unit’s overall product cost. In base and optimum design modes, the combustion chamber (1058 kW) and condenser (1023 kW) are responsible for the high levels of total exergy destruction. At a selling price of 0.27 $/kWh for cooling and 0.06 $/kWh for electricity, payback period equals 12.13 years. Furthermore, it is also expected that over the course of 20 years, the system can earn 3.5 million dollars in profits. Based on environmental aspect, the cogeneration system emits 6091 kg/ MWh of CO2, which decreased to 3913 kg/MWh after optimization.

Reducing the use of fossil fuels is an essential measure to counteract the rise in greenhouse gas emissions. In this context, biofuels and e-fuels make an important contribution to achieving climate neutrality targets, especially if their distribution can take place within existing infrastructure, as in the case of methane.The aim of this work is to carry out a techno-economic and environmental assessment of the combined production of biological and synthetic methane in a wastewater treatment plant (WWTP). Methane yield from biogas, usually associated only with biogas upgrading, is enhanced by recovering CO2 to produce additional synthetic natural gas (SNG) through a methanation process. The analysis is applied to a medium-sized WWTP in Italy, whose biogas production profile is known throughout the year.In the current scenario, SNG is not competitive on the gas market. The investment costs of the technologies and the electricity price are then varied in order to better investigate the profitability of SNG production. The results show that, considering long-term cost projections and an electricity price of about 50 €/MWh, SNG can become competitive, with a production cost of 1.4 €/Sm3. Finally, the environmental competitiveness of SNG (direct and indirect CO2 emissions) with respect to fossil natural gas is investigated: results are shown as a function of the carbon intensity of grid electricity and the share of local renewable energy. To make SNG environmentally sustainable, the renewable share must increase to 46% or, alternatively, the carbon intensity of grid electricity must decrease to 187 gCO2eq/kWh.

Biogas is a renewable gas produced by the fermentation of biomass and is an environmentally friendly alternative to traditional fossil fuels. To overcome the problems of traditional biogas burner, such as unstable combustion, easy flameout and backfire, and low thermal intensity, a new water-cooled biogas burner based on fully premixed combustion technology was designed and developed. Then, numerical simulations and experimental investigations were conducted to explore the effects of CO2 content, excess air coefficient, heat load, and cooling water temperature on the combustion characteristics of the burner. The results revealed that the designed burner exhibited good adaptability to simulated biogas with methane concentrations ranging from 55 % to 80 %. Increasing CO2 content resulted in decreased combustion temperatures and reduced NOx and CO emissions concentration at the burner outlet. In addition, reducing the excess air coefficient enhanced the combustion heat intensity and reduced combustion heat loss. Nevertheless, excessively low excess air coefficients yielded elevated levels of NOx and CO in the flue gas. The results showed that the designed burner demonstrated stable operation at a minimum heat load of 35 %, exhibited a favorable load regulation ratio, and had low emissions. It is a promising solution for utilizing biogas as a clean and sustainable energy source.

Rice straw (RS) is a rich lignocellulosic biomass that can be employed for biogas generation through anaerobic digestion. However, lignin-silica encrustation around the holocellulose complex hinders its digestibility. Therefore, in this present study, RS was biologically pretreated with microbial consortium of Punjab Agricultural University (PAU decomposer), which is composed of Bacillus sp., Delftia sp., Pseudomonas sp., Lysinibacillus fusiform, Arthrobacter nicotianae, Paenibaccilus ehimensis, Aspergillus sp. and Trichoderma sp. Bio-digested slurry, the underutilized spent waste from cattle dung-based biogas plants was used as a growth medium for the mass multiplication of consortium. Soaked and chopped RS was pretreated with consortium and individual cultures in triplicate sets for 5 and 10 d and were analyzed for biochemical parameters along with cellulolytic activity. The pretreated straw was used for biogas production in 2 L capacity anaerobic digesters. Cellulolytic activities i.e., endoglucanase (0.071 IU/mL), exoglucanase (0.027 IU/mL) and β-glucosidase (3.734 IU/mL) of consortium treated RS were higher as compared to untreated RS. Biogas production from consortium pretreated RS was 187.45 L/kg RS which is 45.93% more as compared to untreated RS with 128.45 L/kg RS of biogas. This could be attributed to the synergistic cellulolytic activities of PAU decomposer leading to enhanced biogas production from RS.

Iron metal (Fe0) materials enhance the performance of anaerobic digestion (AD) reactors to remove pollutants. Most research focused on the materials' mechanisms and effectiveness in enhancing AD. However, there is scant information on the biogas and sludge quality and quantity and the kinetics of generated methane (CH4) of biogas from the Fe0-aided AD of domestic wastewater (DW). The information is essential for AD reactors' management. This study characterizes the sludge and biogas from Fe0-aided AD of DW and predicts the CH4 yield using the Gompertz, Logistic, and Richard models to study the impact of Fe0 materials on the composition and generation of sludge and biogas. Bench-scale reactors containing DW were fed with Fe0 and operated for 53 days in a quiescent condition, at 24 ± 3 OC room temperature, at 7.3 initial pH value. Steel wool and iron scrap were used as Fe0 sources. A parallel experiment without Fe0 was performed as an operational reference. Results indicate that Fe0 significantly enriched most of the nutrients in sludges, produced well-settling sludge (sludge volume index ≤30), and enriched the CH4 of biogas by more than 12%. Furthermore, all the tested models exhibited good fitting (error

This paper focuses on a CCHP (Combined Cooling, Heating and Power) system based on co-firing in an Internal Combustion Engine (ICE) of biogas from anaerobic digestion and syngas produced by biomass gasification. From an energy perspective, in order for the mixture to make sense, a relationship setting the threshold percentage of methane in the biogas has been established. Gasification and Organic Rankine Cycle (ORC) models developed in Aspen Plus software and thermodynamic modeling of the Internal Combustion Engine (ICE) have been validated by comparison with experimental work conducted by other authors. The results show a decrease in energy efficiency with an increase in the percentage of methane in biogas and the mass ratio of the mixture. For extraction rates of 80 % and 90 %, respectively, exergy efficiency increases with an increase in the percentage of methane in biogas and the mass ratio of the mixture. Additionally, an increase in gasification temperature improves the efficiencies, while an increase in biogas temperature reduces them. The ICE is a significant source of exergy destruction.

In this paper, the optimal utilization of local biogas production in multi-energy systems is investigated. The micro-grid policy of local biogas production, to supply the variable demand of natural gas and also to convert it into electrical energy required by an energy hub micro-grid, along with other sources of scattered energy production and national electricity and gas networks, is one of the main goals of this paper. The multi-factor intelligent optimization method is considered to investigate the non-linear and heterogeneous optimization problem in the IEEE standard 33-bus energy hub microgrid. Most of the main indicators of interest are economic savings and minimization of operating costs. The multi-objective optimization method has been chosen as a method to solve the aforementioned non-linear and heterogeneous problem. Simulation has been done in GAMS software and the results of optimal load distribution of electric energy and natural gas supply for selected energy microhub have been explained and compared. The final results show a significant reduction of 46 % (2.8 thousand dollars per day) in operating costs. Significant reduction of energy flow between local network microhubs by 39.4 % is also one of the optimization results studied. Also, the Island performance of the local energy microhub has been simulated with the desired strategy. The cost of local energy microhub energy supply in island mode has decreased by 34 % (1.4 thousand dollars per day) compared to normal mode.© 2022 Published by.

This work fashioned the conventional pyrolysis by introducing a microwave process to assess the feasibility of lemon myrtle waste (LMW) to produce biochar, bio-oil and biogas in the presence of catalyst. Microwave assisted pyrolysis (MAP) of LMW was established as a control before introducing five different catalysts in the Microwave Assisted Catalytic Pyrolysis (MACP) reaction. The catalyst includes CaO based catalyst (Dolomite and Eggshell (CES)) and Zeolite based catalyst (ZSM-5, HY-Zeolites and FCC). These catalysts were characterized using the X-Ray Diffraction (XRD) method, Brunauer-Emmet-Teller (BET) surface area, Particle Size Analyzer (PSA) and Scanning Electron Microscope (SEM) to determine their physical properties. These characterizations proved that all catalysts are suitable for the MACP reaction. The biochar, bio oil and biogas yield were determined using mass balance. Biochar quality was evaluated by its calorific value content while the bio-oil and biogas produced from the MACP was characterized using Gas Chromatography-Mass Spectrometry (GC–MS) and GC-Thermal Conductivity Detector (GC-TCD) analysis. The result shows that more than 95 % of MACP yield were biochar and biogas. MAP of LMW produced highest calorific value biochar at 21.72 MJ/kg. Dolomite catalyst produced the highest bio-oil yield of 2.27 % with the highest hydrocarbon content of 86.35 %. MACP of LMW proved that the bio-oil yield produced was increase by 0.7 % while hydrocarbon percentage was increased by 11.4 % in the presence of Dolomite catalyst. The feasibility of LMW to be used as solid fuel is successfully proven form this study.

Junin is a town in Ecuador known for producing alcohol on an artisanal scale, with around 45 distilleries. The artisanal alcohol production process uses firewood as fuel, dumping sugarcane bagasse (SB) outdoors, affecting the environment. The research aimed to assess the techno-economic feasibility of SB treatment for energy generation in artisanal distilleries. The alternatives for the energy use of SB were anaerobic digestion (AD) and combustion. AD evaluation used 5 inoculum-to-substrate ratios (ISR) in biomethanation potential (BMP) assays. The 2:1 ISR presented the highest methane yield for SB (195.54 NLCH4 kgVS−1). Likewise, the estimation of the energy potential by combustion was through thermogravimetric analysis (TGA), resulting in a higher heating value of 16.62 MJ/kg DM. The results of the BMP assays and TGA contributed to the formulation of three SB use scenarios: (i) AD + biogas combustion (S1), (ii) biogas for heat and power generation (S2), and (iii) SB combustion (S3). The evaluation of the techno-economic viability used the financial indicators Net Present Value (NPV) and Internal Rate of Return (IRR), among others. Some variables analyzed were the gross energy generated and the greenhouse gas emissions avoided. The financial indicators associated with S1 and S3 were the most satisfactory compared to S2, which had the highest investment recovery period (11.01 years), and the lowest IRR (13.05 %). All scenarios were feasible, with NPVs positive and IRRs higher than annual interest rate (8 %). Only S3 supplies the energy required in the distillation of ethanol (3,959.702 MJ d−1). However, S1 and S2 offer the highest GHG decreases, 16.96 tCO2e per year. These results are an initial reference for implementing biomass recovery technologies in rural areas of Ecuador as an opportunity for sustainability.

In the forthcoming era of smart energy systems, decentralised solutions are gaining increasing prominence due to their superior adaptability for interconnecting sectors, reduced inefficiencies, and environmentally friendly operation. This study introduces a new medium-scale biogas-based power plant that utilises a gas turbine to meet the energy needs of a specific locality, encompassing electricity, heating, cooling, and water supply, all whilst considering the system's environmental impact. To optimise the plant's performance, three different multi-objective optimisation scenarios employing machine learning methodologies and Greywolf algorithms with distinct objective functions are analysed. Under the base conditions, the proposed plant showcases impressive capabilities, delivering 1372 kW of electricity, 246.2 kW of heating, 293.3 kW of cooling, and 4.1 kg/s of distilled water. It operates with first and second law thermodynamics efficiencies of 72.3 % and 41.4 %, respectively, while maintaining a CO2 emission index of 0.778 kgCO2/kWh. Furthermore, the net present value and investment return period for the investment are estimated to be approximately 4.4 million USD and 4 years, respectively. Through optimisation (scenario 1) that prioritises maximising efficiency while minimising product costs and environmental impact, the following parameters are achieved: an exergy efficiency of 42.7 %, a cost of products at 28.8 $/GJ, and a reduced CO2 emission index of 0.762 kgCO2/kWh. The results reveal that the proposed system not only excels in efficiency but also proves to be economically viable and environmentally beneficial.

Brazil is the third largest beer producer in the world and has several brewing industries. These industries cover a range of production processes due to their wide variety of beverages, which leads to the generation of effluents with different physicochemical characteristics. Furthermore, these residues are usually disposed of without any treatment despite having enormous potential for biogas and bioenergy production. Biorefinery is a relevant alternative to the transition from a linear economy to a Circular Economy (CE). The Biorefinery exploits all available resources in the production of goods and contributes to sustainable development in the face of industrial production. In this context, as an alternative solution, anaerobic digestion (AD) has been commonly used as it uses different biomass sources to satisfy current energy demands. AD can be implemented to treat brewing effluent, promote its energy recovery, reduce environmental pollution, and produce environmentally friendly biological products: biogas and biofertilizer. Thus, this review explored the potential of AD for brewery waste management in association with the bio-based CE. Overall, the current manuscript emphasized the potential of brewery waste for biogas generation and energy production, discussing its adoption and challenges.

The aim of this study was to investigate the simultaneous biogas generation and leachate treatment using municipal waste and its polluted leachate at Mashhad landfill in northeast Iran. The research focused on examining the kinetic model of CH4, CO2, CO, H2S and O2 production with and without leachate recirculation (LR) through control/test wells. The findings from both wells showed an increase in logarithmic CH4 production rate, with the coefficient related to the rate of increase in methane concentration ranging from 0/52-0/64 in the control well and 0/47-0/55 in the test well, respectively. Under LR conditions, it was observed that the CH4 production rate was slower, taking an average of 120 minutes to reach 50% concentration, compared to just 15 minutes without LR. Using first-order equations, the CH4 production coefficients were measured to be 2/17 h−1 and 0/9 h−1 for the control and test wells, respectively. The analysis of recirculated leachate revealed a significant decrease (∼30%) in the total volume of leachate with 72% COD removal, which could help manage overloaded leachate problems in the landfill. The COD removal coefficient was found to be 0/036 day−1 in the control well, whereas the test well with leachate recirculation showed a more rapid decrease from 50 g.l−1 to about 14 g.l−1 with a removal coefficient of 0/012 day−1, three times higher than the control well. Additionally, nitrogen content analysis indicated that although the amount of ammonia content increased with LR, the increase was relatively low in comparison to conditions without LR, equivalent to 1394 ppm and 1000 ppm in control and test wells, respectively. This study aligns with the water-energy-nexus concept by offering a sustainable solution for waste management and energy generation, while also addressing water management challenges associated with landfill operations.

Selective CO2 adsorption for efficient carbon capture from flue gas (CO2/N2 - 15/85, v/v) and biogas (CO2/CH4 - 50/50, v/v) is important for achieving global energy and climate goals but remains a challenge due to the lack of effective adsorbents. To address this issue, we attempted to develop zeolite adsorbents by systematically investigating the effect of different extra-framework metal cations (i.e., Na+, Ca2+, Mn2+, and Ce3+-exchanged in LTA zeolites) on selective CO2 adsorption from CO2/N2 and CO2/CH4. Analyzing the isosteric heat of adsorption results showed that CO2 adsorption at moderate pressure (e.g., 15 and 50 kPa relevant to the compositions of flue gas and biogas, respectively) is governed by the gas-framework interaction. On the other hand, the adsorption of N2 and CH4 was found to be dominated by the gas-cation interaction. Therefore, we concluded that metal cations with a small charge-to-size ratio are beneficial for selective CO2 adsorption from flue gas and biogas because they tend to induce strong CO2-framework interaction (due to the enhanced charge induction to zeolite framework O) and weak N2 or CH4-cation interaction (due to the weakened gas-cation electrostatic interaction). Specifically, LTA zeolites in the form of Na+, with the smallest charge-to-size ratio of cation in this study, exhibit the highest CO2 uptake and separation factor of CO2/N2 and CO2/CH4, as demonstrated by both static single-component adsorption and dynamic binary adsorption results. In addition, the potential of metal cation-exchanged LTA zeolites for VSA and PSA processes was evaluated. Our study provides valuable insights for designing small-pore zeolites as adsorbents for carbon capture.

Currently, finding a renewable source for energy production and also the problems caused by the production and disposal of municipal solid waste have led researchers to think of ways to generate energy from waste. To produce biogas from waste, anaerobic digestion method is used. In developing countries, including Iran, the production of biogas from municipal solid waste in metropolitan areas is being studied and developed. In turn, this study investigates the potential of biogas production from municipal solid waste in Iran. First, the amount of municipal solid waste produced in Iran was estimated. Then, the biogas production potential and the generated electric power were calculated through mathematical relations. The recorded physical properties of the waste and the volume of the biogas produced by it (PCV, Pdegradable, Pdry, Pmax, Prad, Prl were calculated) showed that Iran has a high potential for biogas production from municipal solid waste. PCV, Pdegradable, Pdry, Pmax, Prad, Prl values for this type of waste in the most populous provinces of Iran (Tehran, Khorasan Razavi, Khuzestan, Fars, East Azerbaijan, Esfahan, Mazandaran, West Azerbaijan and Gilan) were 2171.02, 900.2, 356.35, 1256.45, 262.43, 315.05 MW, respectively.