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Journal ArticleDOI

Techniques for transformation of biogas to biomethane

TL;DR: A number of techniques have been developed to remove H 2 S from biogas, such as pressure swing adsorption, membrane separation, physical or chemical CO 2 -absorption as discussed by the authors.
Abstract: Biogas from anaerobic digestion and landfills consists primarily of CH 4 and CO 2 . Trace components that are often present in biogas are water vapor, hydrogen sulfide, siloxanes, hydrocarbons, ammonia, oxygen, carbon monoxide and nitrogen. In order to transfer biogas into biomethane, two major steps are performed: (1) a cleaning process to remove the trace components and (2) an upgrading process to adjust the calorific value. Upgrading is generally performed in order to meet the standards for use as vehicle fuel or for injection in the natural gas grid. Different methods for biogas cleaning and upgrading are used. They differ in functioning, the necessary quality conditions of the incoming gas, the efficiency and their operational bottlenecks. Condensation methods (demisters, cyclone separators or moisture traps) and drying methods (adsorption or absorption) are used to remove water in combination with foam and dust. A number of techniques have been developed to remove H 2 S from biogas. Air dosing to the biogas and addition of iron chloride into the digester tank are two procedures that remove H 2 S during digestion. Techniques such as adsorption on iron oxide pellets and absorption in liquids remove H 2 S after digestion. Subsequently, trace components like siloxanes, hydrocarbons, ammonia, oxygen, carbon monoxide and nitrogen can require extra removal steps, if not sufficiently removed by other treatment steps. Finally, CH 4 must be separated from CO 2 using pressure swing adsorption, membrane separation, physical or chemical CO 2 -absorption.
Citations
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Journal ArticleDOI
TL;DR: A critical review that summarizes state-of-the-art technologies for biogas upgrading and enhancement with particular attention to the emerging biological methanation processes.

815 citations


Cites background or methods from "Techniques for transformation of bi..."

  • ...However, in cases that the biogas contains high concentrations of H2S, steam or inert gas are used in the desorption process to avoid formation of elemental sulphur by the application of air stripping, which will in turn lead to operational problems (Ryckebosch et al., 2011)....

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  • ...clogging) derived from either the increased concentration of solid CO2 or presence of rest impurities limit the wider establishment of this technique (Bauer et al., 2013a; Muñoz et al., 2015; Ryckebosch et al., 2011)....

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  • ...The raw biogas can be upgraded up to 96–98% methane concentration; however, up to 4% methane can be lost within the off-gas stream (Table 1) (Bauer et al., 2013a; Ryckebosch et al., 2011)....

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  • ...The separation is carried out by initially drying and compressing the raw biogas up to 80 bars followed by a stepwise temperature drop up to −110 °C (Ryckebosch et al., 2011)....

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  • ...The absorption column is usually filled with random packing material to increase the gas-liquid mass transfer (Ryckebosch et al., 2011)....

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Journal ArticleDOI
TL;DR: In this paper, the authors systematically review the state-of-the-art of biogas cleaning and upgrading technologies, including product purity and impurities, methane recovery and loss, upgrading efficiency and the investment and operating costs.
Abstract: Biogas is experiencing a period of rapid development and biogas upgrading is attracting increasing attention. Consequently, the market for biogas upgrading is facing significant challenges in terms of energy consumption and operating costs. Selection of upgrading technology is site-specific, case-sensitive and dependent on the biogas utilisation requirements and local circumstances. Therefore, matching the technology selected for use to specific requirements is significantly important. This paper systematically reviews the state-of-the-art of biogas cleaning and upgrading technologies, including product purity and impurities, methane recovery and loss, upgrading efficiency and the investment and operating costs. In addition, the potential utilisation of biogas and the corresponding requirements on gas quality are investigated in depth. Based on the results of comparisons between the technical features of upgrading technologies, the specific requirements for different gas utilizations and the relevant investment and operating costs, recommendations are made regarding appropriate technology.

610 citations

Journal ArticleDOI
TL;DR: In this article, the authors systematically review the state of the art of biogas upgrading technologies with upgrading efficiency, methane (CH 4 ) loss, environmental effect, development and commercialization, and challenges in terms of energy consumption and economic assessment.

477 citations

Journal ArticleDOI
TL;DR: This review critically presents and discusses the state of the art of biogas upgrading technologies with special emphasis on biotechnologies for CO2, H2S, siloxane and halocarbon removal.
Abstract: The lack of tax incentives for biomethane use requires the optimization of both biogas production and upgrading in order to allow the full exploitation of this renewable energy source. The large number of biomethane contaminants present in biogas (CO2, H2S, H2O, N2, O2, methyl siloxanes, halocarbons) has resulted in complex sequences of upgrading processes based on conventional physical/chemical technologies capable of providing CH4 purities of 88–98 % and H2S, halocarbons and methyl siloxane removals >99 %. Unfortunately, the high consumption of energy and chemicals limits nowadays the environmental and economic sustainability of conventional biogas upgrading technologies. In this context, biotechnologies can offer a low cost and environmentally friendly alternative to physical/chemical biogas upgrading. Thus, biotechnologies such as H2-based chemoautrophic CO2 bioconversion to CH4, microalgae-based CO2 fixation, enzymatic CO2 dissolution, fermentative CO2 reduction and digestion with in situ CO2 desorption have consistently shown CO2 removals of 80–100 % and CH4 purities of 88–100 %, while allowing the conversion of CO2 into valuable bio-products and even a simultaneous H2S removal. Likewise, H2S removals >99 % are typically reported in aerobic and anoxic biotrickling filters, algal-bacterial photobioreactors and digesters under microaerophilic conditions. Even, methyl siloxanes and halocarbons are potentially subject to aerobic and anaerobic biodegradation. However, despite these promising results, most biotechnologies still require further optimization and scale-up in order to compete with their physical/chemical counterparts. This review critically presents and discusses the state of the art of biogas upgrading technologies with special emphasis on biotechnologies for CO2, H2S, siloxane and halocarbon removal.

464 citations


Cites background or methods from "Techniques for transformation of bi..."

  • ...These solvents allow for a decrease in both the absorbent recycling rates and 188 plant sizing, with the subsequent decrease in investment and operating costs (Petersson and 189 Wellinger, 2009; Ryckebosch et al, 2011)....

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  • ...The oxidation of H2S and further regeneration of this adsorbent 699 material can be stoichiometrically described as follows (equations 6,7,8): 700 701 Fe2O3 + 3H2S Fe2S3 + 3H2O (6) 702 2Fe(OH)3 + 3H2S Fe2S3 + 6H2O (7) 703 31 2Fe2S3 + 3O2 2Fe2O3 + 6S (8) 704 705 These chemical reagents are often immobilized onto wood chips or red mud (a waste from 706 aluminum manufacture) in order to increase the superficial area of the adsorbent, which 707 significantly decreases as a result of aggregation due to biogas water condensation (Persson 708 et al, 2006)....

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  • ...CH4 concentrations of 96–98 % are guaranteed by most membrane manufacturers in gas–liquid or multiple-stage gas–gas units, while single-pass gas–gas units provide a biomethane with CH4 concentrations of 92–94 % and off-gas permeates with CH4 concentrations of 10–25 % that need to be further treated (Ryckebosch et al. 2011; Andriani et al. 2014)....

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  • ...activated alumina, zeolite and polymeric sorbents (Patterson et al. 2011; Ryckebosch et al. 2011)....

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  • ...Lower dewpoints down to -18 ºC require the compression of 1025 the biomethane prior to cooling (Ryckebosch et al, 2011)....

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Journal ArticleDOI
TL;DR: A review of the state-of-the-art of biogas cleaning and upgrading technologies, including its composition, upgrading efficiency, methane recovery and loss, is presented in this paper.
Abstract: Biogas is a valuable renewable energy and also a secondary energy carrier produced from biodegradable organic materials via anaerobic digestion. It can be used as a fuel or as starting material for the production of chemicals, hydrogen and/or synthesis gas etc. The main constituents of biogas are methane (CH4) and carbon dioxide (CO2), with various quantities of contaminants, such as ammonia (NH3), water vapour (H2O), hydrogen sulfide (H2S), methyl siloxanes, nitrogen (N2), oxygen (O2), halogenated volatile organic compounds (VOCs), carbon monoxide (CO) and hydrocarbons. These contaminants presence and quantities depend largely on the biogas source, which could be anaerobic digestion of many substrates and landfill decompositions. The removal of these contaminants especially H2S and CO2 will significantly improve the quality of the biogas for its further uses. In parallel, biogas upgrading market is facing challenges in term of operating costs and energy consumption. The selection of appropriate technology depends on the specific biogas requirements, site specific, local circumstances and is case sensitive. This paper reviews the present state-of-the-art of biogas cleaning and upgrading technologies, including its composition, upgrading efficiency, methane recovery and loss. In addition, biogas production, utilization and the corresponding requirements on gas quality for grid injection and vehicle usage are investigated. Based on the results of comparisons of various technologies, recommendations are made on further research on the appropriate low cost technologies, especially using solid waste as low cost materials for biogas purification and upgrading.

449 citations


Cites background or methods from "Techniques for transformation of bi..."

  • ...Therefore, Selexol (mixture of dimethyl ethers of polyethylene glycol), which exhibits higher affinity for H2S than water by five times can be used, resulting in smaller absorbent volume with compact size and require regeneration step [7]....

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  • ...In the gas–liquid separation, alkaline liquid is used on the microporous hydrophobic membrane, which can support H2S removal by 98% during desulphurization, leaving only 2% in the upgraded gas [7, 21, 22]....

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  • ...This last one is harmful to the environment and corrosive to the metallic parts of engines, pumps, compressors, gas storage tanks, valves and reduce the lifespan of process equipment [7, 8]....

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  • ...Although some reports [7, 8, 16, 20] reported methane losses up to 4% due to CH4 dissolution in alkanolamine....

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  • ...Membrane is based on different molecules of different sizes with different permeability through the membrane, and is also driven by pressure difference between the two sides of the membrane and the biogas temperature [7]....

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References
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Journal ArticleDOI
TL;DR: In this paper, the authors reviewed the fundamentals of siloxanes and the current problems of the associated fouling and summarized the useable methods for siloxane abatement from biogas and made some recommendations towards preventive actions.

307 citations

Journal ArticleDOI
TL;DR: In contrast to biogas drying by refrigeration, which had a poor effect on siloxane content, the installation of meadow ore adsorption beds resulted in a significantsiloxane reduction of 31-75%, depending on the site studied.

241 citations

Journal ArticleDOI
TL;DR: In this paper, fixed-site-carrier membranes were prepared for the facilitated transport of CO2 by casting polyvinylamine (PVAm) on various supports, such as poly(ether sulfone) (PES), polyacrylonitrile (PAN), cellulose acetate (CA), and polysulfone (PSO).
Abstract: Fixed-site–carrier membranes were prepared for the facilitated transport of CO2 by casting polyvinylamine (PVAm) on various supports, such as poly(ether sulfone) (PES), polyacrylonitrile (PAN), cellulose acetate (CA), and polysulfone (PSO). The cast PVAm on the support was crosslinked by various methods with glutaraldehyde, hydrochloric acid, sulfuric acid, and ammonium fluoride. Among the membranes tested, the PVAm cast on polysulfone and crosslinked by ammonium fluoride showed the highest selectivity of CO2 over CH4 (>1000). The permeance of CO2 was then measured to be 0.014 m3 (STP)/(m2 bar h) for a 20 μm thick membrane. The effect of the molecular weight of PVAm and feed pressure on the permeance was also investigated. The selectivity increased remarkably with increasing molecular weight and decreased slightly with increased pressure in the range of 1 to 4 bar. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4326–4336, 2004

213 citations

Journal ArticleDOI
TL;DR: In this paper, an experimental study of purification of a biogas by removal of its hydrogen sulphide (H2S) content was carried out by means of chemical absorption in an iron-chelated solution catalyzed by Fe/EDTA, which converted H2S into elemental sulphur (S).
Abstract: This work presents an experimental study of purification of a biogas by removal of its hydrogen sulphide (H2S) content. The H2S was removed by means of chemical absorption in an iron-chelated solution catalyzed by Fe/EDTA, which converts H2S into elemental sulphur (S). Preparation of the catalyst solution and the results of biogas component absorption in the catalyst solution (0.2 mol/L) are presented. These results are compared with those for physical absorption into pure water under similar conditions. Experimental results demonstrate that, under the same experimental conditions, a higher percentage of H2S can be removed in the catalytic solution than in water. In a continuous counter current using adequate flow-rate phases contact at room temperature and low gas pressure, the results demonstrate that is possible to totally remove the H2S from the biogas with the prepared catalytic solution.

108 citations

Journal ArticleDOI
TL;DR: This gas stream treatment process improves the quality and caloric value of the biogas and increases the methane content through the use of a chemo-autotrophic methanogen, uncoupled methanogenesis techniques and hollow fiber membranes.
Abstract: Off-gas from anaerobic digestion and landfills has significant potential as an alternative energy source. Current technologies to purify off-gas and increase its caloric value have been primarily limited to physicochemical methods. An alternative biological method has been proposed that increases the methane content. Through the use of a chemo-autotrophic methanogen (Methanobacterium thermoautotrophicum), uncoupled methanogenesis techniques and hollow fiber membranes, carbon dioxide is converted to methane and hydrogen sulfide is effectively removed from biological off-gases. This gas stream treatment process improves the quality and caloric value of the biogas. A continuous culture bench-scale system that utilizes hollow fiber membranes was employed to study the process. The gas-phase methane concentrations were found to increase from 60% to 96%.

75 citations