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![The schematic flow chart of (a) direct and (b) indirect upgrading biogas using microalgae (adapted from [104]).](publication/355412559/figure/fig2/AS:1083062418968579@1635233611778/The-schematic-flow-chart-of-a-direct-and-b-indirect-upgrading-biogas-using-microalgae.png)
The schematic flow chart of (a) direct and (b) indirect upgrading biogas using microalgae (adapted from [104]).
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![Figure 9. PSA technique flow chart for H2S removal (adapted from [24]).](publication/355412559/figure/fig3/AS:1083062418972672@1635233611816/PSA-technique-flow-chart-for-H2S-removal-adapted-from-24_Q320.jpg)
Biogas is one of the most attractive renewable resources due to its ability to convert waste into energy. Biogas is produced during an anaerobic digestion process from different organic waste resources with a combination of mainly CH4 (~50 mol/mol), CO2 (~15 mol/mol), and some trace gasses. The percentage of these trace gases is related to operatin...
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... second step is the regeneration of the carbonate solution. Figure 7 demonstrates direct and indirect biogas upgrading with microalgae. ...
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... second step is the regeneration of the carbonate solution. Figure 7 demonstrates direct and indirect biogas upgrading with microalgae. ...
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... it is known to be less efficient in obtaining stable and low sulphur contents required for biomethane production. The disadvantages of the method are that oxygen can affect the anaerobic digestion Figure 7. The schematic flow chart of (a) direct and (b) indirect upgrading biogas using microalgae (adapted from [104]). ...
Citations
... CO 2 , the second most abundant component in biogas, is produced at certain stages of the production process. CO 2 can be used as a source of electron acceptor by methanogenic bacteria, and its amount in raw biogas is determined by operational factors such as digester liquid volume, temperature, and pressure [54]. When CO 2 combines with water, it forms carbonic acid, which can damage process equipment [54]. ...
... CO 2 can be used as a source of electron acceptor by methanogenic bacteria, and its amount in raw biogas is determined by operational factors such as digester liquid volume, temperature, and pressure [54]. When CO 2 combines with water, it forms carbonic acid, which can damage process equipment [54]. ...
Exploring alternative energy sources is vital amid increasing human fuel consumption. Globally, biogas, rich in methane, hydrogen sulfide, and carbon dioxide, addresses energy demands through biomass anaerobic digestion (AD). Efficient digestate management, employing techniques like solid‐liquid separation and composting, is crucial for environmental protection. The goal is to optimize nutrient‐rich byproduct utilization while minimizing negative impacts. This review analyzes diverse substrates, emphasizing challenges and benefits. Key considerations include nutrient ratios, moisture content, co‐digestion, organic loading rate, and retention time. The study explores temperature's impact on microbial growth, biogas impurities, and upgradation techniques, including biological methods. Fermentation, microbial electrochemical techniques, and biochar use for enhanced AD are introduced. Discussing digestate's multifaceted aspects, the review highlights its nutrient value and diverse applications in aquaculture, animal feed, fermentation, bioremediation, and fine chemical production.
... Feedstock from sewage digesters generates biogas ranging from 55-65% CH 4 , 35-45% CO 2, a minimal amount of nitrogen, and some other impurities including hydrogen sulfide, oxygen, siloxanes, hydrogen, and ammonia [6]. Biogas application as a fuel engine needs more than 96% energy value, and therefore, a purification process is required [7]. Purification necessitates the elimination of pollutants like hydrogen sulfide, water vapor, nitrogen, siloxanes, ammonia, and oxygen, while biogas upgrading requires the removal of CO 2 in biogas, which enhances its calorific value. ...
The availability of pollutants in biogas especially carbon dioxide hinders its application in the enginery parts by minimizing its calorific standards. The presence of CO2 contributes to global warming which is a worry globally. Thus, upgrading technologies is needed for safe utilization on small-scale and wide-range. The commercial technologies mostly discussed in the literature are pressure swing adsorption, membrane separation, physical scrubbing, and water scrubbing. These techniques are costly concerning investment, and operation costs, and are energy-intensive, especially on a small scale. Thus, difficult to apply especially in low-income economies, and necessitates the development of natural, low-cost sorbents for biogas upgrading like biomass, eggshell waste, and clay soil. The current review critically evaluates the potentiality of new approaches using low-cost sorbents for biogas upgrading. The review proposed that activating and additional of pore-forming materials in the adsorbents is necessary to significantly enhance their performance.
... In addition, various aspects of biogas upgrading, adsorbent materials, and adsorption processes for CO 2 capture, providing valuable insights into enhancing carbon capture efficiency in biogas upgrading systems were covered. 57,[103][104][105][106][107][108][109][110][111][112][113] This collection of studies investigates diverse approaches to enhance carbon capture efficiency in biogas upgrading. Phalakornkule et al. present a bio-based adsorbent, chitosan-impregnated palm shell activated carbon, showcasing superior CO 2 adsorption selectivity and dual functionality for gas purification and storage. ...
Biogas results from the anaerobic digestion of organic materials, a reliable and sustainable process that simultaneously manages organic waste and generates renewable energy. However, the presence of secondary impurities, such as carbon dioxide (CO2) and other gases, in raw biogas diminishes its efficacy, significantly lowering its energy content and restricting its utility across industry sectors. Moreover, these impurities contribute to various health and environmental concerns, including their role in exacerbating climate change and global warming. Consequently, efficient separation of CO2 is essential for upgrading biogas. The interest in utilizing biogas as a transportation fuel or as a substitute for natural gas has spurred the advancement of biogas upgrading technologies. While various methods exist for biogas upgrading, those relying on carbon dioxide absorption stand out as particularly significant. Carbon capture efficiency in biogas upgrading pertains to the ability of a method to effectively capture and separate CO2 from biogas, typically composed of methane (CH4) and other gases. This process is crucial for producing high-quality biogas with minimal carbon emissions, thus promoting environmental sustainability. Enhancing the carbon capture efficiency of the biogas upgrading process is essential for reducing greenhouse gas emissions and promoting cleaner energy production. The efficacy of CO2 separation relies on adsorbents and adsorption isotherms, which are integral components of this process. Improving these elements is vital for enhancing biogas purity, ensuring its suitability for various applications, and mitigating its environmental footprint. Traditional methods enhance the carbon capture efficiency by employing adsorbents, such as zeolites and activated carbon, as well as by optimizing adsorption isotherms. Surface modifications and adjustments to process parameters have also led to improved CO2 selectivity over other gases. Traditional methods still have drawbacks, such poor selectivity, difficulties with regeneration, and scalability. These limitations draw attention to the necessity of ongoing optimization, investigating substitute materials, and gaining a thorough grasp of how capacities, kinetics, and selectivity interact. Adsorbents and adsorption isotherms are the main topics of this study’s thorough analysis, which examines the state of the art in increasing carbon capture efficiency in biogas upgrading. It discusses conventional methods, their drawbacks, and suggests alternate materials, customized adjustments, and optimization techniques as a means of achieving ongoing progress. It is suggested that customized changes, ongoing optimization, and investigation of substitute materials be used to increase the effectiveness of carbon capture. To guarantee consistency, the study suggested specific rules for the procurement, preparation, and calcining of materials such as eggshells. In addition, to balancing CO2 and CH4 adsorption, improving adsorbent composition and addressing scalability, long-term stability, and practical implementation challenges are critical. The results of this study direct future studies toward a more sustainable and efficient energy landscape by adding to our understanding of carbon capture in biogas upgrading.
... Currently, the most common technologies for biogas enrichment to biomethane are the following [9], [10]: ...
The EU countries are implementing biomethane production projects from biogas, supplying it to the natural gas distribution grid, or using it as motor fuel. It is also extremely relevant for Ukraine, supposing the problems with gas import due to Russian aggression. Biogas production from landfills, agriculture waste, and sewage is already implemented in Ukraine, so the next step must be biomethane production on an industrial scale and the selection of biogas separation technology is important. Using 11 years of industrial experience in biogas production from landfills, wide experience of the different methane-containing gases separations, and small companies’ industrial possibilities, the most applicable separation technologies for Ukraine were selected: amine, water, and combined water amine carbon dioxide separation. These technologies had compared using computer simulation with real landfill biogas flow rate debt. Results of a software simulation of the most applicable water-amine absorption technology were verified using a laboratory setup. For carbon dioxide concentration in biogas at 32–42 % vol., the specific energy consumption when using water absorption is on average 2 times less compared to amine absorption, but at the same time, the loss of methane due to its solubility in water during water absorption amounted to 7.1–7.6 %, with practically no losses in amine absorption, and minor losses at 0.17–2.8 % in combined water-amine technology. The energy consumption of combined water-amine absorption is comparable to that of water absorption due to: a) reduction of heat losses for the regeneration process of saturated amine absorbent, as part of carbon dioxide has already been removed with water technology; b) using the methane excess to compensate power consumption of the biogas compressor during the preliminary water absorption of carbon dioxide and/or to compensate heat costs of the saturated amine absorbent regeneration
... In 2020, according to statistics [4] of municipal waste deposited in operation landfills, an amount of about 286 kg/capita of waste was recorded [5]. For a population of about 19.02 million inhabitants [6], in December 2021 Romania is estimated to have produced about 19,290 t/year of waste, an upward trend compared to the period 2015-2019, when about 259 kg/capita of municipal waste was recorded [7]. ...
... This method is adopted when H2S concentrations are low. Regenerative absorption means that the water requirement used in the methane treatment and upgrading process will be much lower [19]. ...
... Currently, several basic methods are used for biogas treatment. These include the following technologies: physical absorption in water or solvents, chemical absorption, pressure absorption, membrane separation, and biological conversion [54][55][56][57][58]. ...
Pyrolysis is a thermochemical technology for converting biomass into energy and chemical products consisting of bio-gas, bio-oil, and biochar. Several parameters influence the process efficiency and properties of pyrolysis products. These include the type of biomass, biomass preliminary preparation, gaseous atmosphere, final temperature, heating rate, and process time. This manuscript provides a general summary of the properties of the pyrolytic products of waste rapeseed cake, with particular emphasis on the sorption properties of biochar. Biochar, produced by the pyrolysis process of biomass, is emerging as a powerful tool for carbon sequestration, reducing greenhouse gas emissions, and purifying water from contaminants such as potentially toxic elements and antibiotics. The review found that the biochar obtained as a result of pyrolysis of chemically modified waste rapeseed cake is characterised by its excellent sorption properties. The obtained sorbents are characterised by sorption capacity relative to the copper(II) ion, ranging from 40 mg·g −1 to 100 mg·g −1 , according to the pyrolysis conditions and chemical modification method. The purified pyrolysis gas obtained in the high-temperature process can be used to generate heat and energy. Bio-oil, with its significant combustion heat of 36 MJ·kg −1 , can be a source of environmentally friendly green biofuel.
... Purification process typically includes firstly drying by dewatering, and then removing hydrogen sulfide, and finally removing other impurities. Upgrading process simply refers to the separation of methane from carbon dioxide to obtain high methane-enriched biogas which is the socalled biomethane [6]. However, biogas upgrading systems faces challenges such as the massive digestate produced that will add more complication in terms of land use and also the consequent greenhouse gas emissions released from the digestate storage, transport, and manipulation. ...
The valorization of biogas as a renewable energy source faces a major obstacle regarding its purification. Siloxane is one of the impurities that cause problems such as damages to equipment of combustion engines, turbines, and boilers used for biogas conversion to heat and electricity. In this review, adsorption for siloxane removal is widely discussed, with two specific approaches: adsorbents sensitivity to water and regeneration, two essential points for industrial application. Thus, determining factors in adsorbents capacity, reusability, and water tolerance including textural properties, surface functional groups, and hydrophobicity are deeply analyzed. Studies oriented to the optimization of traditional adsorbents such as activated carbon, silica gel, and aluminosilicates as well as newly emerging adsorbents such as metal organic frameworks, graphene oxides, and waste-derived materials are studied in detail in terms of reusability and water tolerance. Although activated carbon is commercially used, its low selectivity, pore blockage due to siloxane polymerization, and unsuccessful regeneration make it disadvantageous. Silica gel, however, shows better reusability as a result of less adsorbent-adsorbate dissociation energy. In addition, aluminosilicates, despite its low adsorption capacity, proved to be more practical for real biogas due to their high hydrophobicity. Graphene oxide cost and energy efficiency in their synthesis make them more industrially appealing candidates despite their low adsorption capacity. Finally, metal organic frameworks demonstrated high selectivity, high adsorption capacity, and more efficient regeneration and therefore have more advantages and less drawbacks, although the number of published studies is still limited.
... On the other hand, the global awareness on the risk of the accumulation of the biogenic waste in the landfills without proper recycling is also rising with many policies aimed at turning these wastes into useful energy or green products through the integrated biorefineries. The anaerobic digestion (AD) process, which is one of the most established biofuels production technologies, is an effective method to convert the biogenic waste into useful energy [2]. Biogas which is produced by the AD process is one of the most promising alternatives to fossil fuels due to its versatile use in electricity and heat generation besides the vehicles. ...
The lignocellulosic properties of date palm waste (dry palm) differ significantly from one cultivar to another, which affects the anaerobic digestion (AD) process. This study is believed to be amongst the first to evaluate the influence of date palm cultivars on the biomethane yield in order to offer an annual, continuous and cost-effective biogas production model. In this work, 5 cultivars from date palm waste namely; H'mira (H), Teggaza (Tg), Tinacer (Ti), Aghamou (Ag) and Takarbouchet (Tk) were evaluated for biogas production. All experiments were performed for 45 days with 5 reactors in triplicate under mesophilic conditions (37 °C). The highest methane yield of 231.87 ml of CH4/g of Volatile Solid (VS) was obtained with the Ag cultivars with a difference that varied between 37% and 62% depending on the cultivar type. These results indicate that the date palm cultivars massively influence the biomethane yield, it may give an opportunity for researchers to select the most suitable cultivars for methane production and provide opportunities to valorize other cultivars on other beneficial uses, such as adsorption, thermal insulation, or charcoal production etc.
... The biogas produced from AD can be converted into biomethane and bioenergy [16], while the digestate can be upgraded into fertilizer [17]. Biogas has undesirable impurities in its composition, such as carbon dioxide, water vapor, hydrogen sulfide, siloxanes, nitrogen, ammonia, oxygen, and volatile organic compounds [18]. The presence of these interferents causes corrosion in engines and other components during energy conversion, which reduces fuel quality [19,20]. ...
Bioenergy recovery from biomass by-products is a promising approach for the circular bioeconomy transition. However, the management of agri-food by-products in stand-alone treatment facilities is a challenge for the low-capacity food processing industry. In this study, the techno-economic assessment of a small-scale anaerobic digestion process was evaluated for the management of jabuticaba by-product and the production of biomethane, electricity, heat, and fertilizer. The process was simulated for a treatment capacity of 782.2 m3 y−1 jabuticaba peel, considering the experimental methane production of 42.31 L CH4 kg−1 TVS. The results of the scaled-up simulated process demonstrated the production of biomethane (13,960.17 m3 y−1), electricity (61.76 MWh y−1), heat (197.62 GJ y−1), and fertilizer (211.47 t y−1). Economic analysis revealed that the process for biomethane recovery from biogas is not profitable, with a net margin of −19.58% and an internal rate of return of −1.77%. However, biogas application in a heat and power unit can improve project feasibility, with a net margin of 33.03%, an internal rate of return of 13.14%, and a payback of 5.03 years. In conclusion, the application of small-scale anaerobic digestion can prevent the wrongful open-air disposal of jabuticaba by-products, with the generation of renewable energy and biofertilizer supporting the green economy toward the transition to a circular economy.
... It is considered a simple waste to renewable energy technology because no pre-treatment is necessary, and only a favorable environment is needed for microorganisms to decompose the organic waste [2]. The produced biogas contains 55-65% of methane (CH4), 35-45% of carbon dioxide (CO2), and impurities; 0-1% hydrogen sulfide (H2S), 0-3% nitrogen (N2) [19,20,21,22]. Apart from that, biogas could also oxygen (O2) at concentrations of 0-1%, which may come from the influent substrate or leakages [23,24]. ...
... Apart from that, biogas could also oxygen (O2) at concentrations of 0-1%, which may come from the influent substrate or leakages [23,24]. The properties of biogas are shown in Table 2 [21]. One of biogas's fundamental components is methane, an important fuel. ...
... It is a colorless gas with a substantial rotten egg-like smell and is detectable by humans even at very low concentrations from 0.05 ppm [21]. To protect industrial workers, the Occupational Safety and Health Administration (OSHA) standard limit and peak limit for hydrogen sulfide are merely 20 and 50 ppm, respectively [63]. ...
The effort of electrifying Sarawak also comes with challenges mainly caused by geographic and demographic factors. Sarawak’s population scatters over a wide spatial area, where families inhabit small villages located in areas of challenging terrains and thick jungles. As a result, electrification through grid connection becomes infeasible and uneconomic. Biogas has immense potential to contribute to energy supply, especially in rural areas. It not only reduces waste but can also be used in generating electricity and subsequently reduces the dependency on fossil fuels. Approximately 993,000 hectares of Sarawak land were planted with oil palm in 2019. The predicted biogas generation from palm oil mill effluent (POME) could create enough electricity to power nearly 2 million rural Sarawak households, in which the Sarawak population in 2020 was 2.9 million. The lagoon system and continuous stirred tank reactor are common technologies used in biogas production. Other technologies used in biogas production are the fixed dome reactor from the Chinese model and the floating dome reactor from the Indian model. The standard technology involves the combustion of biogas in a heat engine called an internal combustion engine to produce heat to generate steam that drives a turbine for electricity generation. This work studied a new biogas utilisation method, fuel cell technology. Solid oxide fuel cell (SOFC) has high efficiency of up to 60% and is generally more prominent than conventional combustion of biogas in a gas engine to generate electricity. With the continual development of biogas fuel cells, a great prospect is predicted for rural areas of Sarawak in biogas production and utilisation. Thus, biogas could contribute a larger role in contributing to a higher renewable energy mix and rural electrification in Sarawak.
