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For optimum methanization of cotton residues, four (4) samples were made up in vases, with cotton residues as the main component. The first sample consisted of 30g of cotton residue and 270 ml of inoculum, the second of 30g of cotton residue, 270 ml of inoculum and 0.1g of sodium, the third of 15 g of cotton residue, 270 ml of inoculum and 15g of cow dung, and the fourth of 15g of cotton residue, 270 ml of inoculum, 15g of cow dung and 0.1g of sodium. It took 75 days to digest the 30 g of organic matter contained in each sample. The results of this study showed that the sample 4, made up of cotton residue, inoculum, cow dung and sodium, gave the highest biogas volume (1.068 m3), methane volume (0.66 m3) and methane content in the biogas (89%). The best conditions for optimal biogas production from cotton residues are those of a combination of cotton residues, inoculum, cow dung and sodium ash. The results of this study provide knowledge for choosing the optimum conditions for the methanization of organic matter from agricultural waste. [ABSTRACT FROM AUTHOR]

The severe environmental pollution in many countries is caused by indiscriminate discharge of large quantities of food waste (FW), fat oil and grease (FOG) and sewage sludge (SS) to the environment. There are many possible treatment routes, but anaerobic digestion (AD) is now well accepted for treating several kinds of organic wastes. But AD of FW alone presents some operational challenges because of substrates and variability. Anaerobic co-digestion of two or more substrates is better than single substrate digestion. This can use a plant’s unused capacity, in line with the trend to renewable energy. Co-digestion technology, although well established in many European countries, is still in its infancy in Ireland. There are problems with different regulatory arrangements. They should be resolved. The paper reviews anaerobic co-digestion technology is reviewed, with special focus on possible application in Ireland. [ABSTRACT FROM AUTHOR]

Biogas is a valuable renewable energy that can be used as a fuel or as raw material for the production of hydrogen, synthesis gas and chemicals. Apart from its main constituent of CH 4 and CO 2 , it also contained various undesirable contaminants. The removal of these contaminants such as H 2 S will significantly improve the quality of the biogas for further use. This work involved the valorization of calcium carbonate (CaCO 3 )-based solid wastes for the removal of H 2 S from the biogas stream. The solid wastes were analyzed by different physicochemical methods CaCO 3 was found as the main component of both solid wastes, while trace amounts of other elements such as Mg, Al, etc. were also present. The solid wastes were dispersed in water and the resulted suspensions were tested for the removal of H 2 S from the gas phase, using a triphasic gas/liquid/solid glass reactor at room temperature and pressure. A commercial activated carbon (AC) and a pure commercial calcite were also used for comparison purpose. In addition, mixtures of AC with CaCO 3 waste in different ratios were also tested. The influence of the matrix of gas (air or biogas) on the removal of H 2 S was evaluated. Both solid wastes showed higher performance compared to the pure commercial calcite for H 2 S removal. The coupling of a CaCO 3 waste and AC allowed improving the sorption performance compared to pure commercial CaCO 3 and AC used alone. The results obtained open a new promising way for the valorization of CaCO 3 -based wastes for H 2 S removal from biogas. [ABSTRACT FROM AUTHOR]

Biogas, one of potential renewable energies, could play an effective role in fulfilling the world's energy demand. The presence of elevated concentrations of H2S in biogas is problematic because of its highly corrosiveness and toxicity. Recently, there has been interest in utilizing biochar as alternative adsorbent to remove H2S from biogas. In this study, the adsorption capacity of banana peel biochar (BPB) and banana empty fruit bunch biochar (BEFBB) wastes for removing H2S from biogas was investigated. Biochar was produced through the pyrolysis process. Firstly, physical and chemical properties of biochar (moisture content, volatile compound content, ash content, fixed carbon, iodine number, pH, and BET surface) were determined. BEFBB possessed higher fixed carbon content (38.05%), iodine number (146.98 ± 2.29 mg g−1), pH value (8.7 ± 0.3), and larger BET surface (3.18 m2 g−1) than BPB. Secondly, the effect of biochar types and biochar pellet sizes on the adsorption capacity was investigated. The adsorption experiment was carried out, using anaerobically digested biogas, in a packed column containing 10 g of biochar with the pallet size of 1.0 cm of diameter, the initial H2S concentration of 500 ppm at the flowrate of 500 mL min−1. Adsorption efficiency curves showed that the two types of biochar presented high removal capacity for H2S but very low removal capacity for CH4 and CO2. The breakthrough adsorption capacity of BPB and BEFBB was found to be 5.85 mg g−1 and 7.65 mg g−1, respectively, consisting well with their physiochemical characterizations. Then, the effect of biochar pellet sizes on the removal efficiency was studied at three different pallet sizes (0.50 cm, 1.00 cm, and 1.50 cm of diameter). Smaller pellet size adsorbent showed higher removal efficiency than larger pellet size owning to its larger surface area. The FTIR analysis result of BEFBB shown that carboxylic and hydroxide radical groups were most likely responsible for H2S adsorption. Finally, the SEM/EDX results showed significant changes in morphological and chemical properties after the adsorption process. Therefore, BPB and BEFBB could be used as an alternative adsorbent for removing H2S from biogas. [ABSTRACT FROM AUTHOR]

Water hyacinth is one of the most significant sources of biomass in tropical regions that can be used to create biogas. This strategy aims to improve the sustainability, precise energy content, and ease of transport of the original biofuel feedstock, as well as to extract gases. An experimental investigation on the biomethanation of water hyacinth took place in a semi-batch digester. Temperature, stirring speed, and catalyst concentration all have an impact on the rate of biogas production. The catalyst has been discovered to primarily boost the rate of biogas production from water hyacinth (Eichhornia crassipes). As the catalyst is used here to boost up the biomethanation reaction, the effect of the catalyst on different kinetic parameters is investigated. The key conclusions of the research indicate that the maximum value of acidogenic cell mass concentration is 0.13 kg/m3d while the minimum value of methanogenic cell mass concentration is 0.014 kg/m3d at 50 ppm catalyst concentration. Moreover, the maximum specific growth rate of the entire process increases as the catalyst concentration rises, reaching a maximum level of 0.312 d−1 at a 50 ppm catalyst concentration. This is proof that using a catalyst can expedite the biomethanation process. As the catalyst concentration increases, so does the overall biomass concentration. Since it increases the precision of the parameter estimates, the simultaneous estimation of the parameters is a crucial part of the estimation process. [ABSTRACT FROM AUTHOR]

Sustainable waste management and renewable energy are crucial, particularly in Cambodia, where environmental concerns are rising. Organic waste, including cow dung (CD), pig dung (PD), and vegetable waste (VW), offers a promising source for biogas production and clean and renewable energy. However, the efficiency of this biogas production depends on the type of waste and processing conditions. We evaluated the quality, composition, and volume of biogas generated from organic waste, specifically CD, PD, and VW. Three experimental conditions were tested: 10 kg of CD with 10 liters of water, 5 kg of CD mixed with 5 kg of PD and 10 liters of water, and 5 kg of CD mixed with 5 kg of VW and 10 liters of water. As a result, the conversion of pure CD yielded a total volume of biogas up to 0.391 m3, with a methane percentage (CH4) of 69.18%. The CD mixed with PD, which produced only 0.362 m3 of biogas with a CH4 of 65.51%, and CD mixed with VW, which yielded a total biogas volume of only 0.319 m3 with a CH4 of 68.17%. From the result, it can be concluded that the bioconversion of pure CD into biogas was the most efficient compared to the other two conditions. [ABSTRACT FROM AUTHOR]

The real implementation of biogas reforming at an industrial scale to obtain interesting products (like hydrogen or syngas) is a developing research field where multidisciplinary teams are continuously adding improvements and innovative technologies. These works can contribute to the proliferation of green technologies where the circular economy and sustainability are key points. To assess the sustainability of these processes, there are different tools like life cycle assessment (LCA), which involves a complete procedure where even small details count to consider a certain technology sustainable or not. The aim of this work was to review works where LCA is applied to different aspects of biogas reforming, focusing on the role of catalysts, which are essential to improve the efficiency of a certain process but can also contribute to its environmental impact. In conclusion, catalysts have an influence on LCA through the improvement of catalytic performance and the impact of their production, whereas other aspects related to biogas or methane reforming could equally affect their catalytic durability or reusability, with a subsequent effect on LCA. Further research about this subject is required, as this is a continuously changing technology with plenty of possibilities, in order to homogenize this research field. [ABSTRACT FROM AUTHOR]

The purpose of this research is to investigate a variety of approaches to the conversion of biomass, with a particular emphasis on employing anaerobic digestion and biogas upgrading systems. An analysis of the existing technologies is performed, with a focus on highlighting the benefits and downsides of each alternative. In order to assess the effects of nitrogen and oxygen in the biogas on the cryogenic distillation process, an investigation is being carried out. The findings suggest that the presence of these two chemical species in the biogas necessitates the final condensation of methane in order to separate them from one another. In conclusion, a qualitative economic analysis is carried out in order to ascertain the most cost-effective strategy that can be implemented in a typical Italian installation. According to the assumptions that were used, membrane separation is the solution that offers the most cost-effectiveness. [ABSTRACT FROM AUTHOR]

The escalating global demand for protein and the imperative to meet sustainable development goals have driven the emergence of biotransformation platforms, with methanotrophs showing significant potential in this field. In this paper, the metabolism, nutritional requirements, cultivation strategies, and bioreactors of methanotrophs are reviewed. Integrating upstream and downstream technologies is also advocated to advance the development of methanotroph biotransformation platforms toward a circular economy model. The advancements in utilizing biogas as a viable carbon source and wastewater as a nitrogen source are discussed, emphasizing the need for detailed quality control and safety assessments to ensure the suitability of single-cell protein as animal feed. In general, by integrating advanced nutrient recovery technologies to define new process routes, methanotroph biotransformation platforms can bring better environmental benefits by reducing carbon emissions and saving resources. Shifting to renewable energy is crucial for achieving environmental sustainability. By using renewable energy to power microbial fermentation, biomass dehydration, and waste recycling, the platform can offset high energy consumption and attain significant market competitiveness with traditional protein sources. [ABSTRACT FROM AUTHOR]

Among the various techniques used to reduce hydrogene sulfide in biogaz avoiding harmful effects on engines, the chemical and biological treatment appears particularly promising. The main objective of this article was to develop a new process to reduce the harmful effect of hydrogen sulfide (H2S), contained in the biogas resulting from methanization, on the equipment of the wastewater treatment plant (WWTP) of FES city in particular the two cogeneration units. A multiple regime technique for biogas desulfuration, based on the chemical and biological treatment as well as internal micro-aeration of the digester was developed. Owing to the insights gained from this study, it was identified that reducing the concentration of H2S in biogas and improving methane production (biogas production increased from 3.6 M Nm³ in 2018 to 3.8 M Nm³ in 2019, a saving of about 300,000 MAD); reduction of desulfurization tower downtime from 4 times/year to 1 time/year; increasing operating time of generating sets from 8800 in 2018 to 14 400 h in 2019; electricity production increased from 5.9 GWh in 2018 to 7.2 GWh in 2019. In light of these findings, it can be affirmed that the study successfully achieved its objectives, presenting valuable avenues for future scientific exploration. [ABSTRACT FROM AUTHOR]

The escalating challenge of waste management demands innovative strategies to mitigate environmental impacts and harness valuable resources. This study investigates waste-to-energy (WtE) technologies for municipal waste management in Kočevje, Slovenia. An analysis of available waste streams reveals substantial energy potential from mixed municipal waste, biodegradable waste, and livestock manure. Various WtE technologies, including incineration, pyrolysis, gasification, and anaerobic digestion, are compared. The results show that processing mixed municipal waste using thermochemical processes could annually yield up to 0.98 GWh of electricity, and, separately, 3.22 GWh of useable waste heat for district heating or industrial applications. Furthermore, by treating 90% of the biodegradable waste, up to 1.31 GWh of electricity and 1.76 GWh of usable waste heat could be generated annually from biodegradable municipal waste and livestock manure using anaerobic digestion and biogas combustion in a combined heat and power facility. Gasification coupled with a gas-turbine-based combined heat and power cycle is suggested as optimal. Integration of WtE technologies could yield 2.29 GWh of electricity and 3.55 GWh of useable waste heat annually, representing an annual exergy yield of 2.98 GWh. Within the Kočevje municipality, this amount of energy could cover 23.6% of the annual household electricity needs and cover the annual space and water heating requirements of 10.0% of households with district heating. Additionally, CO2-eq. emissions could be reduced by up to 20%, while further offsetting emissions associated with electricity and district heat generation by 1907 tons annually. These findings highlight the potential of WtE technologies to enhance municipal self-sustainability and reduce landfill waste. [ABSTRACT FROM AUTHOR]

Renewable energies present an opportunity to enhance energy security, reduce dependence on imports, and lower greenhouse gas emissions. Natural gas, viewed as a transitional fuel from coal to renewables, lacks reliable environmental sustainability and does not contribute to EU energy independence. Recently, biomethane has been gaining attention as an alternative to natural gas. Obtained from purified or "upgraded" biogas, it offers environmental and economic advantages. Several developed technologies, including absorption, adsorption, membrane separation, and cryogenic separation, are commercially available. However, those are energy- and resource-intensive. In this context, this review aims to examine the recent advancements in biogas upgrading, particularly in physical, chemical, and biological pathways. It focuses on CO2 removal and/or conversion to methane, offering an updated overview for future studies. The technologies are classified based on the separation method (by phase addition, by solid agent, by phase creation, and by biological process), and an analysis of each category is conducted. The discussion covers the economic and environmental characteristics, process complexity, and future research prospects in sustainable technologies. This review highlights the potential of biogas upgrading technologies in contributing to sustainable development, increasing energy security, and achieving greenhouse gas reduction goals that are aligned with EU targets. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is a prevailing technology for the treatment and utilization of municipal organic solid waste (MOSW). In this technology, the macromolecular organic matter in waste degrades into small molecular substances through the anaerobic decomposition of microorganisms, producing biogas that can provide enormous energy. This paper focuses on the research progress of anaerobic digestion of various organic wastes for biogas production. The principle and process of anaerobic digestion for biogas production are introduced, along with the key factors affecting anaerobic digestion efficiency, such as temperature, pH, and sealing conditions. At the same time, the current cycle treatment technology and comprehensive treatment system of MOSW are also summarized. Furthermore, the paper explores biogas purification technologies, including desulfurization, deoxidation, drying, and decarbonization. Finally, the state-of-the-art of the utilization of MOSW for biogas production in the world and the problems faced by the utilization of MOSW for biogas production in China are reviewed. By summarizing the anaerobic digestion technology of MOSW, this review hopes to provide some reasonable solutions for the high-value utilization of MOSW. [ABSTRACT FROM AUTHOR]

In addition to agriculture, Brazil stands out as one of the main meat exporters. In beef production, the waste from the slaughter of a 400-kg bovine produces about 26 kg of waste. In pig farming, the waste generated in the slaughter of a 90-kg pig corresponds to 2.7 kg. Both residues are potential substrates for the production of bioenergy through anaerobic digestion and co-digestion. Likewise, the biogas plants in operation in the country annually generate 1.83 BNm3 of biogas, and the sector is expanding since the national production capacity is 42.7 Bm3/year. This biogas generated through the biological process is an energy source that stands out due to the growing demand for technologies that offer clean energy. Renewable energy sources can ensure greater diversity in the world's energy matrix, in addition to reducing greenhouse gases emissions and dependence on fossil fuels. Therefore, this review addresses the fundamentals of anaerobic digestion and co-digestion, the environmental impacts of biogas and biomethane, and Brazil's energy potential for biogas production. In addition, we discussed the biogas purification technologies, the applications of biomethane, and the current scenario and perspectives of Brazilian biogas involving government initiative policies, technical regulation, international panorama, and economic, environmental, and legislative aspects. [ABSTRACT FROM AUTHOR]

With urban dry and wet waste classification utilized, kitchen waste is sorted out and used for achieving anaerobic biogas, in which biogas solid residue is produced meanwhile. The purpose of this article is to clarify the pyrolysis characteristics of the biogas solid residue using thermo-gravimetric analyzer and Py-GC/MS. The main research results include: (1) The dried biogas solid residue sample has more volatile matter, accounting for 62%.The ash accounting for 37.52%. (2) There are two dominant pyrolysis peaks in thermal gravimetric curves of biogas solid residue, located at low temperature about 200–300 °C. The lower activation energy of pyrolysis rate under 100–250 oC is related to the previous anaerobic digestion process. The third peak position occurs at 750 °C due to calcination of CaCO3 in ash. (3) The amount of alcohols and acid in pyrolysis gas increases first and then decreases with the increase of temperature. The pyrolysis of ether organics mainly occurs at lower temperature, 200 °C. Those productions are assumed to be derived from lipid degradation during pyrolysis. (4) The ash of biogas solid residue obtained under 400 oC is rich in Na, K and Cl. A proper approach could convert biogas solid residue to more amount of pyrolysis gas, keeping the temperature under 600 °C. And most Na, K and Cl retain in the residue, as beneficiates the biogas quality and favors the following-up combustion behavior avoiding slagging problem in combustion chamber. [ABSTRACT FROM AUTHOR]

Fuel cells powered by biogas for decentralised cogeneration of heat and power are an attractive alternative to combustion technologies. However, biogas contains sulfur-based compounds (H2S, COS, DMS, siloxanes), which are harmful to fuel cells. This work was carried out in the framework of the European project Waste2Watts, involving the laboratories of Politecnico di Torino, ENEA, and PSI. The aim is to design and test a flexible and cost-effective cleaning unit to remove impurities for the use of biogas in high-efficiency fuel cell systems. The focus is on small- to medium-sized farms for which deep cleaning of biogas by adsorption materials is a suitable techno-economic solution to avoid intensive gas processing treatments. The ability of commercial adsorption materials (activated carbons, metal oxides, and metal hydroxides) to remove hydrogen sulphide and carbonyl sulphide was tested under different biogas compositions (oxygen and humidity). After evaluating the results, three plant configurations were proposed to optimally utilise the potential of the sorbents. Indeed, the RGM3 sorbent has proven to be an effective solution for removing H2S and COS under humid conditions (50% RH), whilst R7H and R8C sorbents are better suited for removing H2S and COS, respectively, in dry biogas conditions. [ABSTRACT FROM AUTHOR]

The rapid population growth in Indonesia is leading to increased energy demands and the depletion of global energy sources. One promising to meet these escalating energy needs in the adoption of renewable energy sources like biogas. This study employs qualitative research methods to measure the response of the Islamic boarding school community in Central Java towards biogas utilization. Data analysis was conducted interactively, narratively describing insights gleaned from questionnaires completed by respondents. The findings reveal a varied response within Central Java Islamic Boarding School Community towards embracing biogas as part of efforts to enhance the national renewable energy mix. However, there is a consensus on certain aspects: respondents generally support biogas utilization as long as it is safe, sourced from clean materials, and developed in suitable locations. The exploration among ten boarding schools suggests that the government's renewable energy initiatives require further optimization in terms of socialization and engagement with Islamic boarding schools. [ABSTRACT FROM AUTHOR]

Dry reforming of methane (DRM) has attracted great interest for the production of syngas and/or hydrogen in a more environmentally friendly way. It is especially advantageous in this case to use biogas—as a mixture of methane, CO2, and traces of further gases—as a feedstock replacement for natural gas. Nevertheless, industrial implementation of DRM is currently limited because of its inherent process restrictions. The biggest challenge of dry reforming is the deposition of carbon on the catalyst, known as "coking." The focus of this theoretical study is to evaluate the feasibility of a biogas dry reforming process in a liquid metal (Sn) bubble column reactor. This technology has already been proven suitable for methane pyrolysis to obtain hydrogen, preventing issues related to reactor clogging or catalyst deactivation caused by carbon deposition. Results show that at high operating temperatures and atmospheric pressure, a product gas primarily composed of H2 and CO would be obtained. CO2 and water vapor may also be present in the final product depending on the operating conditions. The molten tin inside the reactor would, according to the presented theoretical considerations, not be affected by the formation of carbides and oxides. Additionally, the syngas composition (the H2 : CO ratio) could be adjusted by using different CH4 : CO2 feed ratios. [ABSTRACT FROM AUTHOR]

The socio-economic feasibility of biogas as a renewable source of energy has been analyzed for the energy security of India. The impact of Indian government schemes such as the National Biogas and Manure Management Programme (NBMMP) for the implementation of Bioenergy has been discussed in detail. The feasibility of a water-based scrubber (high as well as low pressure) for Bio-methane production in the Indian scenario was analyzed. Theoretical modeling for Steady-State Digester Pressure Water-based Biogas Scrubber (DP-WBS) was performed using the Sum Rate Method. Design parameters for a DP-WBS-based scrubber having a capacity of 60 Nm3/h were optimized at the digester pressure of 110 mm of the Water Column (WC). Modeling for raw biogas (CH4 64 %, CO2 30 %, H2S 1000 ppm) scrubbing was done with and without water recirculation. Sensitivity analysis shows that a 90 m3/h water flow rate and a total of 7 theoretical stages are required to reduce the CO2 concentration in biogas from 30 % to <2.58 % and H2S concentration from 1000 ppm to <20 ppm. H2S removal efficiency in the scrubber was found to be highly dependent on operating conditions at the regeneration section. [ABSTRACT FROM AUTHOR]

This paper explores the mechanisms of biochar that facilitate direct interspecies electron transfer (DIET) among syntrophic microorganisms leading to improved anaerobic digestion. Properties such as specific surface area (SSA), cation exchange capacity (CEC), presence of functional groups (FG), and electrical conductivity (EC) were found favorable for increased methane production, reduction of lag phase, and adsorption of inhibitors. It is revealed that these properties can be modified and are greatly affected by the synthesizing temperature, biomass types, and residence time. Additionally, suitable biochar concentration has to be observed since dosage beyond the optimal range can create inhibitions. High organic loading rate (OLR), pH shocks, quick accumulation and relatively low degradation of VFAs, and the presence of heavy metals and toxins are the major inhibitors identified. Summaries of microbial community analysis show fermentative bacteria and methanogens that are known to participate in DIET. These are Methanosaeta, Methanobacterium, Methanospirillum, and Methanosarcina for the archaeal community; whereas, Firmicutes, Proteobacteria, Synergistetes, Spirochetes, and Bacteroidetes are relatively for bacterial analyses. However, the number of defined cocultures promoting DIET is very limited, and there is still a large percentage of unknown bacteria that are believed to support DIET. Moreover, the instantaneous growth of participating microorganisms has to be validated throughout the process. [ABSTRACT FROM AUTHOR]

Separation of acid gases such as CO2 from biogas is a key step for its purification before biomethane is used in various applications such as injection into a pipeline or use as a vehicle fuel. In this study, the single step purification of real biogas (locally collected landfill gas) was demonstrated using (3-Aminopropyl) triethoxysilane (APTES)-grafted SBA-15. The sorbent was optimized between amine amount and accessibility to adsorption sites. In studies using a surrogate mixture of CH4/CO2 the sorbent recorded an adsorption capacity of 0.85 mmolCO2/gads under dry conditions and this decreased to 0.72 mmolCO2/gads when the surrogate biogas was saturated with steam. Even though the capacity was further decreased to 0.55 mmolCO2/gads using real landfill gas, it remained fairly stable over 5 cycles despite the presence of impurities, namely hydrogen sulfide (68 ppm). In all cases, the capacity was regenerated with a thermal treatment in inert gas at 100°C. The results suggested possibilities for a single step purification unit to remove acid gasses and water and provide potential for a streamlined operation for the separation of carbon dioxide from biogas. The enhanced economics should propel the move toward a green energy future. [ABSTRACT FROM AUTHOR]

This study demonstrates the production of synthetic methane or synthetic natural gas via methanation of carbon dioxide (CO2), which could replace natural gas. For the power-to-methane (P2M) process, a simulation of two-stage methanation with simultaneous power generation was carried out in Aspen Plus. The process is based on an assumed production capacity of 1 t/h of synthetic methane and is also capable of simultaneous methanation of CO2 and biogas. The biogas flow rate was estimated from industry data. When co-methanation is carried out, it is possible to produce up to 1.3 t/h of synthetic methane. After the production of synthetic methane, compression of the product was added to the process scheme, followed by dehydration. The dehydration of the synthetic methane was carried out via dynamic simulation in Aspen Adsorption. The steady-state operation was determined. The final dehydrated product contained on average only about 4.85 × 10−4 mol.% water (H2O) and the methane (CH4) contents were above 97 mol.%, providing a composition suitable for injection into the pipelines of many European countries. [ABSTRACT FROM AUTHOR]

The current challenges of commercial cyclic adsorption processes for biogas upgrading are associated with either high energy consumption or low recovery. To address these challenges, this work evaluates the performance of a range of configurations for biogas separations, including pressure swing adsorption (PSA), pressure vacuum swing adsorption (PVSA), and twin double-bed PSA, by dynamic modelling. Moreover, a sensitivity analysis was performed to explore the effect of various operating conditions, including adsorption time, purge-to-feed ratio, biogas feed temperature, and vacuum level, on recovery and energy consumption. It was found that the required energy for a twin double-bed PSA to produce biomethane with 87% purity is 903 kJ/kg CH4 with 90% recovery, compared to 961 kJ/kg CH4 and 76% recovery for a PVSA process. With respect to minimum purity requirements, increasing product purity from 95.35 to 99.96% resulted in a 32% increase in energy demand and a 23% drop in recovery, illustrating the degree of loss in process efficiency and the costly trade-off to produce ultra-high-purity biomethane. It was concluded that in processes with moderate vacuum requirements (>0.5 bar), a PVSA should be utilised when a high purity biomethane product is desirable. On the other hand, to minimise CH4 loss and enhance recovery, a twin double-bed PSA should be employed. [ABSTRACT FROM AUTHOR]

The environmental impact and the forecasted scarcity of fossil fuels have intensified research on renewable energy sources. Hydrogen is a versatile energy carrier that can be produced from renewable sources and plays a key role in achieving global decarbonization targets. Biogas, produced by anaerobic digestion of organic compounds, is rich in methane and carbon dioxide and can be used to produce renewable hydrogen by dry reforming. This review focuses on the recent advances in Ni-based catalysts for biogas reforming. The effect of supports and promoters on catalyst activity, stability, and resistance to carbon deposition will be systematically discussed. This review provides a better understanding of the influence of the synthesis method, metal-support interaction, acid/base sites, and oxygen mobility on catalytic activity. Special emphasis will be given to the development of core-shell structure catalysts and bimetallic catalysts of Ni with other transition metals and noble metals. [ABSTRACT FROM AUTHOR]

The article provides a short review on catalyst-based processes for the production of hydrogen starting from methane, both of fossil origin and from sustainable processes. The three main paths of steam- and dry-reforming, partial oxidation and thermo-catalytic decomposition are briefly introduced and compared, above all with reference to the latest publications available and to new catalysts which obey the criteria of lower environmental impact and minimize the content of critical raw materials. The novel strategies based on chemical looping with CO2 utilization, membrane separation, electrical-assisted (plasma and microwave) processes, multistage reactors and catalyst patterning are also illustrated as the most promising perspective for CH4 reforming, especially on small and medium scale. Although these strategies should only be considered at a limited level of technological readiness, research on these topics, including catalyst development and process optimization, represents the crucial challenge for the scientific community. [ABSTRACT FROM AUTHOR]

The biogas generated by anaerobic digestion consists of CH4, CO2, and traces of other gases like H2S and water vapour. Biogas utilization has numerous environmental and economic benefits. Before being used as fuel for industrial or vehicular applications, it is necessary to enrich it. Methane enriched biogas can be regarded as a substitute for fossil natural gas. The available various biogas cleaning and enrichment techniques differ in terms of working, gas quality, energy requirement, separation efficiency, and operational problems. This paper reviews the various technologies for biogas cleaning and enrichment with gas purity and impurities, CH4 recovery and loss, energy requirement, enrichment efficiency, and costs. Among the various alternatives, water scrubbing and membrane separation are the most cost-effective techniques while chemical scrubbing offers relatively high biomethane purities with less CH4 losses. The possible utilization of the biogas and the criteria for gas quality are also reviewed. [ABSTRACT FROM AUTHOR]

The aim of this work is the development of a structured catalyst for the dry reforming of biogas to be used as a pre–reformer in the indirect internal reforming configuration (IIR) of solid oxide fuel cells (SOFCs). The structured catalyst is based on NiCrAl foams coated with ruthenium (nominal loading 3.0 wt%) supported on a CaZr0.85Sm0.15O3−δ (CZS) perovskite oxide. The powder is produced by solution combustion synthesis and deposited on metallic foams by the wash–coating method. Catalytic tests for the dry reforming of methane (DRM) reaction are carried out at 850 °C, 700 °C and 550 °C for an overall 50 h with CH4/CO2 = 1 and p = 1.3 bar at different gas hourly space velocities (GHSVs). The final goal is a proof–of–concept: a laboratory validation of an IIR–SOFC fed by biogas. The carbon amount on spent structured catalysts is evaluated by thermogravimetric analysis and microstructural/compositional investigation. [ABSTRACT FROM AUTHOR]

Biodesulfurization using biotrickling filters (BTFs) under anoxic conditions is a cost-effective method for biogas clean-up. To improve the performance of BTFs, the microbial consortia from the anaerobic pond of a swine farm (SW), the denitrification pond of a tuna factory (DN), and the UASB of the concentrated latex industry (LW) were immobilized on BTFs. In this study, the efficiency of BTFs immobilized with the microbial consortia for the reduction of H2S gas combined with the reduction of nitrate contained in wastewater was investigated. The results showed that H2S was completely removed at the inlet H2S concentration of 207.8–1476 ppmv with wastewater circulation under anoxic conditions. However, only the DN-BTF achieved H2S removal of 95.2% at an inlet concentration of 2500 ppmv. An increase in the N/S ratio (0.356–2.07 mol/mol) improved the H2S removal of the SW-BTF, LW-BTF, and DN-BTF but not the BTF-C. Moreover, the DN-BTF had the highest nitrate removal rate (71.1%) with an N/S ratio of 2.07 mol/mol. When oxygen was supplied in wastewater at DO = 3.60 ± 0.41 mg/L, sulfate was generated at a higher rate, but nitrite production was lower than at DO~0. After microbial community analysis, Proteobacteria were the main phyla involved in the biodesulfurization process. [ABSTRACT FROM AUTHOR]

Despite the fact that fossil fuel resources can produce a substantial amount of hydrogen, their pollution level is concerning, and their reserves are depleting. Consequently, the use of renewable resources like biogas in the production of chemicals could benefit from the high potential of these sources alone or in combination with fossil fuels. Both carbon dioxide and methane are present in biogas, making it an excellent renewable energy source. In this study, three models of hydrogen production from fossil sources (natural gas), renewable energy sources (biogas), and a combination of fossil and renewable sources were evaluated using a multicriteria decision-making technique. The calculated and compared parameters included the net energy efficiency of the process, the total carbon dioxide emission flow rate, the carbon dioxide emission intensity, the hydrogen production intensity, and the annual total cost. According to the results, the production of hydrogen from natural gas results in the highest amount of carbon dioxide emissions (8.76 m ˙ CO 2 m ˙ H 2 ) for (3.31 t H 2 t feed ) of hydrogen production. Biogas combination with natural gas (combined feedstock) has the highest exergy (80.84%) and energy (81.62%) efficiency compared to the other two methods. In addition, the TAC for the combined process is the lowest of the three scenarios (TAC = $31.35 M). Due to the limitation of fossil fuel resources, combining renewable energy sources with fossil fuels enhances the thermodynamic performance of the system while reducing the required capital. [ABSTRACT FROM AUTHOR]

The transition to a carbon-neutral economy requires innovative solutions that reduce greenhouse gas emissions (GHG) and promote sustainable energy production. Additionally, carbon dioxide removal technologies are urgently needed. The production of biomethane or biohydrogen with carbon dioxide capture and storage are two promising BECCS approaches to achieve these goals. In this study, we compare the advantages and disadvantages of these two approaches regarding their technical, economic, and environmental performance. Our analysis shows that while both approaches have the potential to reduce GHG emissions and increase energy security, the hydrogen-production approach has several advantages, including up to five times higher carbon dioxide removal potential. However, the hydrogen bioenergy with carbon capture and storage (HyBECCS) approach also faces some challenges, such as higher capital costs, the need for additional infrastructure, and lower energy efficiency. Our results give valuable insights into the trade-offs between these two approaches. They can inform decision-makers regarding the most suitable method for reducing GHG emissions and provide renewable energy in different settings. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) can be a suitable alternative for industrial waste treatment and energy recovery. In this study, the AD of açaí seeds was evaluated under mesophilic temperature and dry regime. The stirred-tank reactor, composed of açaí seeds (25%), inoculum (45%), and water (30%), was started up and operated in batch mode for 40 days. The results demonstrate that the total solids' biodegradation reached 59.38%, and the accumulated biogas produced was higher than 6 L. A stable methane content was obtained after 22 days of digestion, with a composition of around 60%. The experimental methane yield (156.65 mL CH4 g−1 TS) was higher than the theoretical methane yield (116.36 mL CH4 g−1 TS), demonstrating that the dry AD process was favorable to methane production. From the biogas combustion in a heat and power unit, 21.88 kWh of electricity and 98.48 MJ of heat could be produced from 1 ton of açaí seeds submitted to dry AD, mitigating a total of 7.15 × 10−3 tCO2eq. From the proposed industrial process intensification, the adoption of dry AD could supply 43.19% of the energy required by the açaí processing industry. Hence, the AD can be a technological route for bioenergy recovery, contributing for reducing the açaí industry's carbon footprint while promoting environmental, social, and economic benefits for the local sustainable development. [ABSTRACT FROM AUTHOR]

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. In the present work, CO2 and H2S were scrubbed from biogas generated from cow dung by employing reaction chambers of alkaline salts such as Ca(OH)2, NaOH, and KOH. Water vapor content in biogas was adsorbed by passing it through a silica gel bed. CH4 content after scrubbing had also been examined as the reduction of impurities is highly correlated to the enrichment of CH4. The biogas flow rates and the concentrations of alkaline salt solutions were varied. The test results revealed that the biogas flow rate and the concentration of the solutions were affected by biogas content. The highest CH4 content (94.80%) was obtained when the biogas flow rate was minimum (0.54 Nm3/h) and the solvent concentration was maximum (1N). However, the removal analysis of H2S was not feasible due to lower concentration of 2 ppm only in biogas. [ABSTRACT FROM AUTHOR]

In recent years, significant progress has been achieved in developing the potential of anaerobic membrane bioreactors (AnMBRs). The present paper presents a comprehensive review of studies focused on biogas production via the treatment of municipal and domestic wastewater with the use of such technology. The main aim of the current work was to evaluate the impact of operating parameters on the biogas production yield. Moreover, the possibilities of applying various fouling mitigation strategies have been discussed in detail. Analyses have been performed and reported in the literature, which were conducted with the use of submerged and external AnMBRs equipped with both polymeric and ceramic membranes. It has been shown that, so far, the impact of the hydraulic retention time (HRT) on biogas yield is ambiguous. This finding indicates that future studies on this issue are required. In addition, it was demonstrated that temperature has a positive impact on process performance. However, as presented in the literature, investigations have been carried out mainly under psychrophilic and mesophilic conditions. Hence, performing further experimental studies at temperatures above 40 °C is highly recommended. Moreover, it has been shown that in order to restore the initial permeate flux, a combination of several membrane cleaning methods is often required. The findings presented in the current study may be particularly important for the determination of operating conditions and suitable fouling mitigation strategies for laboratory-scale and pilot-scale AnMBRs used for biogas production via the treatment of municipal and domestic conditions. [ABSTRACT FROM AUTHOR]

Recent trends in hydrogen production include using renewable energy sources, e.g., biogas as feedstocks for steam reforming. Crucial to the field is minimizing existing reforming reactors for their applications to fuel cell systems. Here, we present a novel design of a steam reforming reactor for an efficient biogas conversion to hydrogen. The design includes a radial division of the catalytic insert into individual segments and substituting parts of the catalytic material with metallic foam. The segment configuration is optimized using a genetic algorithm to maximize the efficiency of the reactor. Changes in the catalytic insert design influence the thermal conditions inside the reactor, leading to moderation of the reaction rate. This article presents a promising approach to producing hydrogen from renewable sources via steam reforming. A significant enhancement in the reforming process effectiveness is achieved with a notable decrease in the amount of the catalyst used. The final results demonstrate the capability for acquiring a similar level of biogas conversion with a 41% reduction of the catalytic material applied. [ABSTRACT FROM AUTHOR]

The market for biogas production has been increasing every year all over the world. The use of biogas as an energy vector is accomplished through the most diverse applications, such as direct burning (thermal energy), internal combustion engines, and fuel cells. Besides direct applications, biogas can be used as a raw material for producing high added‐value products, such as molecular hydrogen and renewable hydrocarbons, through a new enterprise concept, the biorefineries. Purity and quality control are determinant factors that enable the decision‐making regarding the end use of biogas. Physical, chemical, and biological methods can be used in biogas upgrading processes as well as a combination of different techniques. This review aims to deepen the knowledge about relevant technologies for biogas purification. It also addresses the most efficient and feasible methods, challenges to be overcome, and main demands for future studies. Therefore, the presentation, in a detailed way, of the synergistic effects caused by components contained in natural biogas and the combinatorial methods for removing these contaminants, differentiates this from other works that approach only the purification techniques but do not point out their problems and causes more comprehensively. Thus, studies related to the combined effects of contaminants would be interesting in future works. [ABSTRACT FROM AUTHOR]

Hydrogen production from biogas over alumina-supported Ce1−xNixO2−x catalysts was studied in a temperature range of 600–850 °C with an initial gas composition of CH4/CO2/H2O of 1/0.8/0.4. To achieve a high and stable hydrogen yield, highly dispersed Ni catalysts were prepared through the exsolution approach. A solid solution of Ce1−xNixO2−x was firstly formed on the surface of Al2O3 and then activated in H2/Ar at 800 °C. The genesis and properties of the Ce1−xNixO2−x/Al2O3 catalysts were established using X-ray fluorescence analysis, thermal analysis, N2 adsorption, ex situ and in situ X-ray diffraction, Raman spectroscopy, electron microscopy, EDX analysis, and temperature-programmed hydrogen reduction. The performance of Ce1−xNixO2−x/Al2O3 catalysts in biogas conversion was tuned by regulation of the dispersion and reducibility of the active component through variation of content (5–20 wt.%) and composition (x = 0.2, 0.5, 0.8) of Ce1−xNixO2−x as well as the mode of its loading (co-impregnation (CI), citrate sol–gel method (SG)). For the 20 wt.% Ce1−xNixO2−x/Al2O3 catalyst, the rate of the coke formation decreased by a factor of 10 as x increased from 0.2 to 0.8. The optimal catalyst composition (20 wt.% Ce0.2Ni0.8O1.8/80 wt.% Al2O3) and preparation mode (citrate sol–gel method) were determined. At 850 °C, the 20 wt.% Ce0.2Ni0.8O1.8/Al2O3-SG catalyst provides 100% hydrogen yield at full CH4 conversion and 85% CO2 utilization. [ABSTRACT FROM AUTHOR]

Biogas is a renewable fuel produced from modern biomass, yet biogas contains traces of hydrogen sulfide, a toxic compound, that must be removed before biogas usage. Here we review the removal of hydrogen sulfide by biological treatment, chemical treatment, porous solid treatment and photocatalysis. Adsorption and photocatalysis methods are compared by figures of merit calculations. Adsorption is used commercially but is limited by the lifespan of adsorbent materials. Photocatalysis appears as an affordable alternative, and the combination of adsorption and photocatalysis is promising. The figure of merit calculation appears as a good indicator of the performance of adsorbent materials and photocatalysts. [ABSTRACT FROM AUTHOR]