The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
David Jeison - One of the best experts on this subject based on the ideXlab platform.
-
a review on the state of the art of physical chemical and biological technologies for biogas upgrading
Reviews in Environmental Science and Bio\ technology, 2015Co-Authors: Leslie Meier, Israel Díaz, Raúl Muñoz, David JeisonAbstract: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.
-
A review on the state-of-the-art of physical/chemical and biological technologies for biogas upgrading
Reviews in Environmental Science and Biotechnology, 2015Co-Authors: Raúl Muñoz, Leslie Meier, Israel Díaz, David JeisonAbstract: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.
Raúl Muñoz - One of the best experts on this subject based on the ideXlab platform.
-
a review on the state of the art of physical chemical and biological technologies for biogas upgrading
Reviews in Environmental Science and Bio\ technology, 2015Co-Authors: Leslie Meier, Israel Díaz, Raúl Muñoz, David JeisonAbstract: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.
-
A review on the state-of-the-art of physical/chemical and biological technologies for biogas upgrading
Reviews in Environmental Science and Biotechnology, 2015Co-Authors: Raúl Muñoz, Leslie Meier, Israel Díaz, David JeisonAbstract: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.
Fiona Seh Lin Keng - One of the best experts on this subject based on the ideXlab platform.
-
Emission of selected Halocarbons by seaweeds inhabiting a coral reef / Fiona Keng Seh Lin
2020Co-Authors: Fiona Seh Lin KengAbstract:Since the discovery of the Antarctic stratospheric ozone hole in 1985 there has been increasing scientific interest in the Halocarbon species that can cause ozone destruction. Although an important region for Halocarbons in terms of atmospheric circulation, the tropics are underrepresented in terms of Halocarbon measurements, especially those biogenic short-lived Halocarbon compounds. A fringing coral reef flat at Cape Rachado, west coast Peninsular Malaysia was selected for a study on the emissions of Halocarbons by seaweeds. A portable, automated gas chromatograph with electron capture detector was used to measure a suite of Halocarbon species trimonthly over a 15-month period at the study site. The measurements of the Halocarbon atmospheric mixing ratios were then correlated to the seaweed standing biomass to investigate its influence on the Halocarbon mixing ratios at the survey site. Although it was found that the atmospheric mixing ratio for the biogenic Halocarbon compounds were poorly correlated (ρ < 0.5) to some of the important seaweed species at the sampling site, there was no significant correlation between the total seaweed standing biomass with the atmospheric concentration of biogenic Halocarbon compounds. This may be due to many contributing factors such as localized emissions, wind direction and speed that might influence the Halocarbon contents in the atmosphere. To better understand the Halocarbon emissions by the seaweeds, a laboratory-based incubation study was conducted to observe if the Halocarbon emissions by the seaweeds varied with irradiance. Three selected seaweed species, Sargassum binderi Sonder ex J. P a g e | i v Agardh, Padina australis Hauck, and Turbinaria conoides (J. Agardh) Kutzing were collected from the sampling site and exposed to a range of irradiance in the laboratory. The Halocarbon contents in the seawater were then analyzed using a purge-and-trap system attached to a gas chromatograph with mass selective detector. Release of Halocarbons especially dibromochloromethane, CHBr2Cl (r= 0.79; p< 0.01) was found to be influenced by irradiance. Correlations were also observed between emission of certain Halocarbons with photosynthetic activity, especially bromoiodomethane, CH2BrI (r = 0.85; p< 0.01) and bromoform, CHBr3 (r = 0.79; p< 0.01) suggesting that environmental factors such as light can affect the release of these volatile halogenated compounds by the seaweeds into the atmosphere. From this study, it was also found that upon comparison with temperate and polar brown seaweeds, tropical species, such as Turbinaria conoides, may emit higher levels of bromoform, CHBr3 and other Halocarbons. It is therefore important to investigate the contribution of tropical seaweeds towards the local atmospheric composition of Halocarbons.
-
The emission of volatile Halocarbons by seaweeds and their response towards environmental changes
Journal of Applied Phycology, 2020Co-Authors: Fiona Seh Lin Keng, Siew-moi Phang, Noorsaadah Abd Rahman, Emma C. Leedham Elvidge, Gill Malin, William T. SturgesAbstract:Volatile Halocarbons can deplete the protective stratospheric ozone layer contributing to global climate change and may even affect local climate through aerosol production. These compounds are produced through anthropogenic and biogenic processes. Biogenic Halocarbons may be produced as defence compounds, anti-oxidants or by-products of metabolic processes. These compounds include very short-lived Halocarbons (VSLH), e.g. bromoform (CHBr_3), dibromomethane (CH_2Br_2), methyl iodide (CH_3I), diiodomethane (CH_2I_2). Efforts to quantify the biogenic sources of these compounds, especially those of marine origin, e.g. seaweeds, phytoplankton and seagrass meadows, are often complicated by inherent biological variability as well as spatial and temporal changes in emissions. The contribution of the coastal region and the oceans to the stratospheric load of Halocarbons has been widely debated. This highlights the need to understand the factors affecting the release of these compounds from marine sources for which data for modelling purposes are generally lacking. Seaweeds are important sources of biogenic Halocarbons subjected to changing environmental conditions. Huge uncertainties in the prediction of current and future global Halocarbon pool exist due to the lack of spatial and temporal data input from coastal and oceanic sources. Therefore, investigating the effect of changing environmental conditions on the emission of VSLH by the seaweeds could help towards better estimations of Halocarbon emissions. This is especially important in light of global changes in both climate and the environment, the expansion of seaweed cultivation industry and the interactions between Halocarbon emission and their environment. In this paper, we review current knowledge of seaweed Halocarbon emissions, how environmental factors affect these emissions and identify gaps in understanding. Our aim is to direct much needed research to improve understanding of the contribution of marine biogenic sources of Halocarbons and their impact on the environment.
-
Halocarbon emissions by selected tropical seaweeds species specific and compound specific responses under changing ph
PeerJ, 2017Co-Authors: Paramjeet Kaur Mithoosingh, Fiona Seh Lin Keng, W. T. Sturges, Siew-moi Phang, Gill Malin, Emma Leedham Elvidge, Noorsaadah Abd RahmanAbstract:Five tropical seaweeds, Kappaphycus alvarezii (Doty) Doty ex P.C. Silva, Padina australis Hauck, Sargassum binderi Sonder ex J. Agardh (syn. S. aquifolium (Turner) C. Agardh), Sargassum siliquosum J. Agardh and Turbinaria conoides (J. Agardh) Kutzing, were incubated in seawater of pH 8.0, 7.8 (ambient), 7.6, 7.4 and 7.2, to study the effects of changing seawater pH on Halocarbon emissions. Eight Halocarbon species known to be emitted by seaweeds were investigated: bromoform (CHBr3), dibro-momethane (CH2Br2), iodomethane (CH3I), diiodomethane (CH2I2), bromoiodomethane (CH2BrI), bromochlorometh-ane (CH2BrCl), bromodichloromethane (CHBrCl2), and dibro-mochloromethane (CHBr2Cl). These very short-lived Halocarbon gases are believed to contribute to stratospheric halogen concentrations if released in the tropics. It was observed that the seaweeds emit all eight Halocarbons assayed, with the exception of K. alvarezii and S. binderi for CH2I2 and CH3I respectively, which were not measurable at the achievable limit of detection. The effect of pH on Halocarbon emission by the seaweeds was shown to be species-specific and compound specific. The highest percentage changes in emissions for the Halocarbons of interest were observed at the lower pH levels of 7.2 and 7.4 especially in Padina australis and Sargassum spp., showing that lower seawater pH causes elevated emissions of some Halocarbon compounds. In general the seaweed least affected by pH change in terms of types of Halocarbon emission, was P. australis. The commercially farmed seaweed K. alvarezii was very sensitive to pH change as shown by the high increases in most of the compounds in all pH levels relative to ambient. In terms of percentage decrease in maximum quantum yield of photosynthesis (Fv∕Fm) prior to and after incubation, there were no significant correlations with the various pH levels tested for all seaweeds. The correlation between percentage decrease in the maximum quantum yield of photosynthesis (Fv∕Fm) and Halocarbon emission rates, was significant only for CH2BrCl emission by P. australis (r = 0.47; p ≤ 0.04), implying that photosynthesis may not be closely linked to Halocarbon emissions by the seaweeds studied. Bromine was the largest contributor to the total mass of halogen emitted for all the seaweeds at all pH. The highest total amount of bromine emitted by K. alvarezii (an average of 98% of total mass of halogens) and the increase in the total amount of chlorine with decreasing seawater pH fuels concern for the expanding seaweed farming activities in the ASEAN region.
-
Volatile Halocarbon emissions by three tropical brown seaweeds under different irradiances
Journal of Applied Phycology, 2013Co-Authors: Fiona Seh Lin Keng, Siew-moi Phang, Noorsaadah Abd Rahman, C. Hughes, E Leedham, N R P Harris, J A Pyle, Andrew D. Robinson, William T. SturgesAbstract:The emission rates of eight volatile halogenated compounds by three tropical brown seaweed species collected from Cape Rachado, west coast Peninsular Malaysia, under different irradiances have been determined. A purge-and-trap sample preparation system with a gas chromatograph and mass-selective detector was used to measure a suite of Halocarbons released by Sargassum binderi Sonder ex J. Agardh, Padina australis Hauck, and Turbinaria conoides (J. Agardh) Kützing. All species are widely distributed in Peninsular Malaysia, with S. binderi a dominant seaweed species at our survey site. Release of few Halocarbons was found to be influenced by irradiance. Correlations were also observed between emission of certain Halocarbons with photosynthetic activity, especially bromo-and iodinated compounds (0.6
-
Emission of atmospherically significant Halocarbons by naturally occurring and farmed tropical macroalgae
Biogeosciences, 2013Co-Authors: E. C. Leedham, Fiona Seh Lin Keng, Siew-moi Phang, Gill Malin, C. Hughes, William T. SturgesAbstract:Current estimates of global Halocarbon emissions highlight the tropical coastal environment as an important source of very short-lived (VSL) biogenic Halocarbons to the troposphere and stratosphere, due to a combination of assumed high primary productivity in tropical coastal waters and the prevalence of deep convective transport, potentially capable of rapidly lifting surface emissions to the upper troposphere/lower stratosphere. However, despite this perceived importance, direct measurements of tropical coastal biogenic Halocarbon emissions, notably from macroalgae (seaweeds), have not been made. In light of this, we provide the first dedicated study of Halocarbon production by a range of 15 common tropical macroalgal species and compare these results to those from previous studies of polar and temperate macroalgae. Variation between species was substantial; CHBr 3 production rates, measured at the end of a 24 h incubation, varied from 1.4 to 1129 pmol g FW −1 h −1 (FW = fresh weight of sample). We used our laboratory-determined emission rates to estimate emissions of CHBr 3 and CH 2 Br 2 (the two dominant VSL precursors of stratospheric bromine) from the coastlines of Malaysia and elsewhere in South East Asia (SEA). We compare these values to previous top-down model estimates of emissions from these regions and, by using several emission scenarios, we calculate an annual CHBr 3 emission of 40 (6–224 Mmol Br −1 yr), a value that is lower than previous estimates. The contribution of tropical aquaculture to current emission budgets is also considered. Whilst the current aquaculture contribution to Halocarbon emissions in this regional is small, the potential exists for substantial increases in aquaculture to make a significant contribution to regional Halocarbon budgets.
Israel Díaz - One of the best experts on this subject based on the ideXlab platform.
-
a review on the state of the art of physical chemical and biological technologies for biogas upgrading
Reviews in Environmental Science and Bio\ technology, 2015Co-Authors: Leslie Meier, Israel Díaz, Raúl Muñoz, David JeisonAbstract: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.
-
A review on the state-of-the-art of physical/chemical and biological technologies for biogas upgrading
Reviews in Environmental Science and Biotechnology, 2015Co-Authors: Raúl Muñoz, Leslie Meier, Israel Díaz, David JeisonAbstract: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.
Leslie Meier - One of the best experts on this subject based on the ideXlab platform.
-
a review on the state of the art of physical chemical and biological technologies for biogas upgrading
Reviews in Environmental Science and Bio\ technology, 2015Co-Authors: Leslie Meier, Israel Díaz, Raúl Muñoz, David JeisonAbstract: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.
-
A review on the state-of-the-art of physical/chemical and biological technologies for biogas upgrading
Reviews in Environmental Science and Biotechnology, 2015Co-Authors: Raúl Muñoz, Leslie Meier, Israel Díaz, David JeisonAbstract: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.
