Showing papers on "Methane published in 2011"
TL;DR: It is concluded that greater stewardship, data, and—possibly—regulation are needed to ensure the sustainable future of shale-gas extraction and to improve public confidence in its use.
Abstract: are consistent with deeper thermogenic methane sources such as the Marcellus and Utica shales at the active sites and matched gas geochemistry from gas wells nearby. In contrast, lower-concentra- tion samples from shallow groundwater at nonactive sites had isotopic signatures reflecting a more biogenic or mixed biogenic/ thermogenic methane source. We found no evidence for contam- ination of drinking-water samples with deep saline brines or frac- turing fluids. We conclude that greater stewardship, data, and— possibly—regulation are needed to ensure the sustainable future of shale-gas extraction and to improve public confidence in its use.
1,285 citations
TL;DR: In this article, the authors evaluate the greenhouse gas footprint of natural gas obtained by high-volume hydraulic fracturing from shale formations, focusing on methane emissions, and find that 3.6% to 7.9% of the methane from shale-gas production escapes to the atmosphere in venting and leaks over the life time of a well.
Abstract: We evaluate the greenhouse gas footprint of natural gas obtained by high- volume hydraulic fracturing from shale formations, focusing on methane emissions. Natural gas is composed largely of methane, and 3.6% to 7.9% of the methane from shale-gas production escapes to the atmosphere in venting and leaks over the life- time of a well. These methane emissions are at least 30% more than and perhaps more than twice as great as those from conventional gas. The higher emissions from shale gas occur at the time wells are hydraulically fractured—as methane escapes from flow-back return fluids—and during drill out following the fracturing. Methane is a powerful greenhouse gas, with a global warming potential that is far greater than that of carbon dioxide, particularly over the time horizon of the first few decades following emission. Methane contributes substantially to the greenhouse gas footprint of shale gas on shorter time scales, dominating it on a 20-year time horizon. The footprint for shale gas is greater than that for conventional gas or oil when viewed on any time horizon, but particularly so over 20 years. Compared to coal, the footprint of shale gas is at least 20% greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years.
1,261 citations
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.
1,117 citations
TL;DR: Graphene chemical vapor deposition growth on copper foil using methane as a carbon source is strongly affected by hydrogen, which appears to serve a dual role: an activator of the surface bound carbon that is necessary for monolayer growth and an etching reagent that controls the size and morphology of the graphene domains.
Abstract: We show that graphene chemical vapor deposition growth on copper foil using methane as a carbon source is strongly affected by hydrogen, which appears to serve a dual role: an activator of the surface bound carbon that is necessary for monolayer growth and an etching reagent that controls the size and morphology of the graphene domains. The resulting growth rate for a fixed methane partial pressure has a maximum at hydrogen partial pressures 200–400 times that of methane. The morphology and size of the graphene domains, as well as the number of layers, change with hydrogen pressure from irregularly shaped incomplete bilayers to well-defined perfect single layer hexagons. Raman spectra suggest the zigzag termination in the hexagons as more stable than the armchair edges.
855 citations
TL;DR: In this article, the first application of common hydrocarbon processing catalysts to microalgae liquefaction in water was reported, in which six different heterogeneous catalysts were tested under inert (helium) and high-pressure reducing (hydrogen) conditions.
Abstract: We produced crude bio-oils from the microalga Nannochloropsis sp. via reactions in liquid water at 350 °C in the presence of six different heterogeneous catalysts (Pd/C, Pt/C, Ru/C, Ni/SiO2−Al2O3, CoMo/γ-Al2O3 (sulfided), and zeolite) under inert (helium) and high-pressure reducing (hydrogen) conditions. To our knowledge, this is the first application of common hydrocarbon processing catalysts to microalgae liquefaction in water. In the absence of added H2, all of the catalysts tested produced higher yields of crude bio-oil from the liquefaction of Nannochloropsis sp., but the elemental compositions and heating values of the crude oil (about 38 MJ/kg) were largely insensitive to the catalyst used. The gaseous products were mainly H2, CO2, and CH4, with lesser amounts of C2H4 and C2H6. The Ru and Ni catalysts produced the highest methane yields. Only the zeolite catalyst produced significant amounts of N2. Typical H/C and O/C atomic ratios for the crude bio-oil are 1.7 and 0.09, respectively. In the presen...
520 citations
TL;DR: In this article, a thermodynamic equilibrium analysis on the multi-reaction system for carbon dioxide reforming of methane in view of carbon formation was performed with Aspen plus based on direct minimization of Gibbs free energy method.
455 citations
TL;DR: The relationship between methane emissions and salinity is not well understood in tidal marshes, leading to uncertainty about the net effect of marsh conservation and restoration on greenhouse gas balance.
Abstract: The relationship between methane emissions and salinity is not well understood in tidal marshes, leading to uncertainty about the net effect of marsh conservation and restoration on greenhouse gas balance. We used published and unpublished field data to investigate the relationships between tidal marsh methane emissions, salinity, and porewater concentrations of methane and sulfate, then used these relationships to consider the balance between methane emissions and soil carbon sequestration. Polyhaline tidal marshes (salinity >18) had significantly lower methane emissions (mean ± sd = 1 ± 2 g m−2 yr−1) than other marshes, and can be expected to decrease radiative forcing when created or restored. There was no significant difference in methane emissions from fresh (salinity = 0–0.5) and mesohaline (5–18) marshes (42 ± 76 and 16 ± 11 g m−2 yr−1, respectively), while oligohaline (0.5–5) marshes had the highest and most variable methane emissions (150 ± 221 g m−2 yr−1). Annual methane emissions were modeled using a linear fit of salinity against log-transformed methane flux (
$$ \log ({\text{C}}{{\text{H}}_4}) = - 0.056 \times {\text{salinity }} + { 1}{.38} $$
; r2 = 0.52; p < 0.0001). Managers interested in using marshes as greenhouse gas sinks can assume negligible methane emissions in polyhaline systems, but need to estimate or monitor methane emissions in lower-salinity marshes.
450 citations
TL;DR: This methane release simulates a rapid and relatively short-term natural release from hydrates into deep water and suggests that a vigorous deepwater bacterial bloom respired nearly all the released methane within this time, and that by analogy, large-scale releases of methane from hydrate in the deep ocean are likely to be met by a similarly rapid methanotrophic response.
Abstract: Methane was the most abundant hydrocarbon released during the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. Beyond relevancy to this anthropogenic event, this methane release simulates a rapid and relatively short-term natural release from hydrates into deep water. Based on methane and oxygen distributions measured at 207 stations throughout the affected region, we find that within ~120 days from the onset of release ~3.0 × 1010 to 3.9 × 1010 moles of oxygen were respired, primarily by methanotrophs, and left behind a residual microbial community containing methanotrophic bacteria. We suggest that a vigorous deepwater bacterial bloom respired nearly all the released methane within this time, and that by analogy, large-scale releases of methane from hydrate in the deep ocean are likely to be met by a similarly rapid methanotrophic response.
430 citations
TL;DR: A series of porous aromatic frameworks (PAFs) were synthesized via a Yamamoto-type Ullmann reaction containing quadricovalent Si (PAF-3) and Ge (PFAF-4) as mentioned in this paper, which exhibit high surface areas and excellent adsorption ability to hydrogen, methane and carbon dioxide.
Abstract: A series of porous aromatic frameworks (PAFs) were synthesized via a Yamamoto-type Ullmann reaction containing quadricovalent Si (PAF-3) and Ge (PAF-4). These PAFs are thermally stable up to 465 °C for PAF-3 and 443 °C for PAF-4, corresponding to a 5% weight loss according to the TG pattern. As PAF-1, they exhibit high surface areas (up to 2932 m2 g−1) and excellent adsorption ability to hydrogen, methane and carbon dioxide. Low pressure gas uptake experiments on PAFs show PAF-3 has the highest heat of adsorption (Qst) of hydrogen (6.6 kJ mol−1) and carbon dioxide (19.2 kJ mol−1), while PAF-4 has the highest Qst for methane adsorption (23.2 kJ mol−1) among PAFs. Gas molecule recognition at 273 K was performed and results show only greenhouse gases such as carbon dioxide and methane could be adsorbed onto PAFs.
422 citations
TL;DR: The anaerobic metabolism of the bacteria breaking coal down to methanogenic substrates, the likely rate-limiting step in biogenic gas production, is not fully understood and coal molecules are more recalcitrant to biodegradation with increasing thermal m...
Abstract: Microbial methane accumulations have been discovered in multiple coal-bearing basins over the past two decades. Such discoveries were originally based on unique biogenic signatures in the stable isotopic composition of methane and carbon dioxide. Basins with microbial methane contain either low-maturity coals with predominantly microbial methane gas or uplifted coals containing older, thermogenic gas mixed with more recently produced microbial methane. Recent advances in genomics have allowed further evaluation of the source of microbial methane, through the use of high-throughput phylogenetic sequencing and fluorescent in situ hybridization, to describe the diversity and abundance of bacteria and methanogenic archaea in these subsurface formations. However, the anaerobic metabolism of the bacteria breaking coal down to methanogenic substrates, the likely rate-limiting step in biogenic gas production, is not fully understood. Coal molecules are more recalcitrant to biodegradation with increasing thermal m...
365 citations
TL;DR: In this article, the authors discuss the catalysts that can be used for methane cracking, and their deactivation and regeneration are discussed, including carbon filament formation, the reaction mechanisms, and the models available in the literature for predicting reaction rates.
TL;DR: In this article, an atmospheric pressure chemical vapor deposition (CVD) method was developed for the growth of large-area graphene on catalytic metal substrates, which is potentially more cost-effective and compatible with industrial production than approaches based on synthesis under high vacuum, and the results showed that field effect transistors fabricated from CVD graphene made with the optimized process had room temperature hole mobilities that are a factor of 2−5 larger than those measured for samples grown on as-purchased Cu foil with larger methane concentration.
Abstract: The growth of large-area graphene on catalytic metal substrates is a topic of both fundamental and technological interest. We have developed an atmospheric pressure chemical vapor deposition (CVD) method that is potentially more cost-effective and compatible with industrial production than approaches based on synthesis under high vacuum. Surface morphology of the catalytic Cu substrate and the concentration of carbon feedstock gas were found to be crucial factors in determining the homogeneity and electronic transport properties of the final graphene film. The use of an electropolished metal surface and low methane concentration enabled the growth of graphene samples with single layer content exceeding 95%. Field effect transistors fabricated from CVD graphene made with the optimized process had room temperature hole mobilities that are a factor of 2−5 larger than those measured for samples grown on as-purchased Cu foil with larger methane concentration. A kinetic model is proposed to explain the observed...
TL;DR: In this paper, sulfate reduction and sulfur-iron geochemistry were studied in 5-6m deep gravity cores of Holocene mud from Aarhus Bay (Denmark), where sulfate is generated by reoxidation of sulfide throughout the sulfate and methane zones, which might explain the abundance of active reducers deep below the main sulfate zone.
TL;DR: In this paper, the additive effects of noble metals on the catalytic performances are summarized in terms of activity, suppression of Ni oxidation, carbon formation, self-activation, and sustainability in the daily startup and shutdown operations.
Abstract: Nickel is an effective component for the steam reforming of methane in terms of the catalytic activity and the catalyst cost. When Ni catalysts are applied to dry reforming, oxidative reforming, and catalytic partial oxidation, it is necessary to add the properties of high resistance to oxidation, hot spot formation, and coke deposition, to the Ni catalysts. An efficient method for giving these properties while considering the catalyst cost is the modification of Ni metal particles with small amounts of noble metals. An important point is that preparation methods can affect the structure of noble metal–Ni bimetallic particles, which is connected to the catalytic performances. The additive effects of noble metals on the catalytic performances are summarized in terms of activity, suppression of Ni oxidation, carbon formation, self-activation, and sustainability in the daily startup and shutdown operations.
TL;DR: Ordered mesoporous NiO-MgO-Al2O3 composite oxides with various Ni and Mg content were facilely synthesized via one pot evaporation induced self-assembly (EISA) strategy.
Abstract: Ordered mesoporous NiO-MgO-Al2O3 composite oxides with various Ni and Mg content were facilely synthesized via one pot evaporation induced self-assembly (EISA) strategy. These mesoporous materials with large specific surface areas, big pore volumes, uniform pore sizes and superior thermal stability were investigated as the catalysts for the carbon dioxide reforming of methane reaction. These materials performed high catalytic activity as well as long stability. The improved catalytic performances were suggested to be closely associated with both the amount of laccessibler active centers for the reactants owing to their advantageous structural properties and the stabilized Ni nanoparticles by mesoporous framework matrix due to the lconfinement effectr of the mesopores. Besides, the role of the MgO basic modifier was also studied. It was observed that only moderate amount of the Mg containing (2 M%) could greatly promote the catalytic performances. The stabilized Ni nanoparticles as well as doped MgO had reinforced capacity of resistance to coke, accounting for no deactivation after 100 h long-term stability test at 700 ◦C. Therefore, the ordered mesoporous NiO-MgO-Al2O3 composite oxides promised a series of novel and stable catalyst candidates for carbon dioxide reforming of methane reaction.
TL;DR: In this paper, the authors used lithium naphthalenide (LiC10H8 ) to introduce Li ions into the [Cu3(btc)2] frameworks and showed that the excess CO2 uptakes of the lithium-doped COFs can be enhanced by four to eight times compared to the undoped COF at 298 K and 1 bar.
Abstract: Reduction of the anthropogenic emission of CO2 is currently a top priority because CO2 emission is closely associated with climate change. Carbon capture and storage (CCS) and the development of renewable and clean energy sources are two approaches for the reduction of CO2 emission. One of the most promising alternative fuels is CH4, which is the major component of natural gas. The efficient storage of CH4 is still one of the main challenges for its widespread application. Accordingly, the development of more efficient approaches for CO2 capture and CH4 storage is critically important. Recently, metal–organic frameworks (MOFs, e.g., MOF210 and NU-100) have shown great potential for gas storage because of their high specific surface area (SSA) and functionalized pore walls. However, most MOF materials still show relatively low CO2 and CH4 uptakes. To enhance CO2 and CH4 adsorption, it is imperative to develop new materials, such as covalent organic frameworks (COFs), or to modify MOFs by using postsynthetic approaches. Herein, we focus on the latter strategy. One of the modification approaches is incorporation of carbon nanotubes (CNTs) into MOFs in order to achieve enhanced composite performance, because of the unusual mechanical and hydrophobicity properties of CNTs. Another approach is doping MOFs or COFs with electropositive metals. Recent studies indicate that the surface carboxylate functional groups of a substrate could act as nucleation sites to form MOFs by heterogeneous nucleation and crystal growth. Both experimental and theoretical investigations indicate that the H2 adsorption capacities of MOFs can be enhanced significantly by doping alkali-metal ions, in particular Li ions, to the frameworks, owing to the strong affinity of Li ions towards H2 molecules. [3d, 7] Similarly, Lan et al. also showed theoretically that doping of COFs with Li ions can significantly enhance the CH4 uptake of COFs. [8] Most recently, the multiscale simulations performed by Lan et al. indicate that Li is the best surface modifier of COFs for CO2 capture among a series of metals (Li, Na, K, Be, Mg Ca, Sc and Ti). Furthermore, their simulations show that the excess CO2 uptakes of the lithium-doped COFs can be enhanced by four to eight times compared to the undoped COFs at 298 K and 1 bar. Motivated by these experimental and theoretical results, we synthesized hybrid MOF materials by using the two modification techniques outlined above, that is, 1) incorporation of CNTs into [Cu3(C9H3O6)2(H2O)3]·x H2O ([Cu3(btc)2], HKUST-1; btc = 1,3,5-benzenetricarboxylate), which is an important MOF material owing to its open metal sides and high thermal stabilities, as well as its sorption properties, 10] and 2) doping [Cu3(btc)2] with Li + ions. We used lithium naphthalenide (LiC10H8 ) to introduce Li ions into the [Cu3(btc)2] frameworks. These frameworks have Cu 2+
TL;DR: Temporal and spatial uncoupling between methanogenesis and methanotrophy was supported by field and laboratory measurements, which also helped explain the oversaturation of methane in the upper water column.
Abstract: The prevailing paradigm in aquatic science is that microbial methanogenesis happens primarily in anoxic environments. Here, we used multiple complementary approaches to show that microbial methane production could and did occur in the well-oxygenated water column of an oligotrophic lake (Lake Stechlin, Germany). Oversaturation of methane was repeatedly recorded in the well-oxygenated upper 10 m of the water column, and the methane maxima coincided with oxygen oversaturation at 6 m. Laboratory incubations of unamended epilimnetic lake water and inoculations of photoautotrophs with a lake-enrichment culture both led to methane production even in the presence of oxygen, and the production was not affected by the addition of inorganic phosphate or methylated compounds. Methane production was also detected by in-lake incubations of lake water, and the highest production rate was 1.8–2.4 nM⋅h−1 at 6 m, which could explain 33–44% of the observed ambient methane accumulation in the same month. Temporal and spatial uncoupling between methanogenesis and methanotrophy was supported by field and laboratory measurements, which also helped explain the oversaturation of methane in the upper water column. Potentially methanogenic Archaea were detected in situ in the oxygenated, methane-rich epilimnion, and their attachment to photoautotrophs might allow for anaerobic growth and direct transfer of substrates for methane production. Specific PCR on mRNA of the methyl coenzyme M reductase A gene revealed active methanogenesis. Microbial methane production in oxygenated water represents a hitherto overlooked source of methane and can be important for carbon cycling in the aquatic environments and water to air methane flux.
TL;DR: The synthesis and CO(2), CH(4), and N(2) adsorption properties of hierarchically porous electron-rich covalent organonitridic frameworks (PECONFs) were prepared by simple condensation reactions between inexpensive, commercially available nitridic and electron- rich aromatic building units.
Abstract: Carbon dioxide capture from point sources like coal-fired power plants is considered to be a solution for stabilizing the CO(2) level in the atmosphere to avoid global warming. Methane is an important energy source that is often highly diluted by nitrogen in natural gas. For the separation of CO(2) and CH(4) from N(2) in flue gas and natural gas, respectively, sorbents with high and reversible gas uptake, high gas selectivity, good chemical and thermal stability, and low cost are desired. Here we report the synthesis and CO(2), CH(4), and N(2) adsorption properties of hierarchically porous electron-rich covalent organonitridic frameworks (PECONFs). These were prepared by simple condensation reactions between inexpensive, commercially available nitridic and electron-rich aromatic building units. The PECONF materials exhibit high and reversible CO(2) and CH(4) uptake and exceptional selectivities of these gases over N(2). The materials do not oxidize in air up to temperature of 400 °C.
TL;DR: The impact of coal mine methane emissions in China has been drawing attention as coal production has powered its economic development as discussed by the authors, however, Chinese methane emission from coal production accounts for only a very small proportion on the environmental impact when compared to emissions of carbon dioxide from fossil fuel consumption.
TL;DR: In this paper, the Arctic bottom water temperatures and their future evolution projected by a climate model were analyzed and it was shown that the resulting warming is spatially inhomogeneous, with the strongest impact on shallow regions affected by Atlantic inflow.
Abstract: Vast amounts of methane hydrates are potentially stored in sediments along the continental margins, owing their stability to low temperature – high pressure conditions. Global warming could destabilize these hydrates and cause a release of methane (CH 4) into the water column and possibly the atmosphere. Since the Arctic has and will be warmed considerably, Arctic bottom water temperatures and their future evolution projected by a climate model were analyzed. The resulting warming is spatially inhomogeneous, with the strongest impact on shallow regions affected by Atlantic inflow. Within the next 100 years, the warming affects 25% of shallow and mid-depth regions containing methane hydrates. Release of methane from melting hydrates in these areas could enhance ocean acidification and oxygen depletion in the water column. The impact of methane release on global warming, however, would not be significant within the considered time span.
TL;DR: Anaerobic oxidation of methane (AOM) by sulfate has been recognized as a critical process to maintain this greenhouse gas stability by limiting methane flux to the atmosphere.
Abstract: Anaerobic oxidation of methane (AOM) by sulfate has been recognized as a critical process to maintain this greenhouse gas stability by limiting methane flux to the atmosphere. We show geochemical evidence for AOM in deep lake sediments and demonstrate that AOM is likely driven by iron (Fe) reduction. Pore-water profiles from Lake Kinneret (Sea of Galilee, Israel) show that this sink for methane is located below the 20-cm depth in the sediment, which is well below the depths at which nitrate and sulfate are completely exhausted, as well as below the zone of methanogenesis. Iron-dependant AOM was verified by Fe(III)-amended mesocosm studies using intact sediment cores, and native iron oxides were detectable throughout the sediments. Because anaerobic Fe(III) respiration is thermodynamically more favorable than both sulfate-dependent methanotrophy and methanogenesis, its occurrence below the zone of methane production supports the idea that reduction of sedimentary iron oxides is kinetically or biologically limited. Similar conditions are likely to prevail in other incompletely pyritized aquatic sediments, indicating that AOM with Fe(III) is an important global sink for methane.
TL;DR: The deep-sea oil spill in the Gulf of Mexico released large quantities of oil and gaseous hydrocarbons into the deep ocean as discussed by the authors, and it is estimated that up to 500,000 t of gases such as methane were released into the ocean.
Abstract: The deep-sea oil spill in the Gulf of Mexico released large quantities of oil and gaseous hydrocarbons into the deep ocean. Calculations using published estimates of the volume of oil released suggest that up to 500,000 t of gases such as methane were released into the deep ocean.
TL;DR: In this article, a 5.9-kW stationary diesel engine was converted into spark ignition mode and run on compressed natural gas (CNG), methane enriched biogas (Bio-CNG) and Biogas produced from biomethanation of jatropha and pongamia oil seed cakes.
TL;DR: In this paper, the authors investigated the effect of charred biomass on carbon mineralization in rice fields and showed that the addition of charred rice residue to paddy fields resulted in a transient increase in carbon mineralisation rates.
Abstract: Rice paddy soils are characterized by anoxic conditions, anaerobic carbon turnover, and significant emissions of the greenhouse gas methane. A main source for soil organic matter in paddy fields is the rice crop residue that is returned to fields if not burned. We investigated as an alternative treatment the amendment of rice paddies with rice residues that have been charred to black carbon. This treatment might avoid various negative side effects of traditional rice residue treatments. Although charred biomass is seen as almost recalcitrant, its impact on trace gas (CO 2 , CH 4 ) production and emissions in paddy fields has not been studied. We quantified the degradation of black carbon produced from rice husks in four wetland soils in laboratory incubations. In two of the studied soils the addition of carbonised rice husks resulted in a transient increase in carbon mineralisation rates in comparison to control soils without organic matter addition. After almost three years, between 4.4% and 8.5% of the black carbon added was mineralised to CO 2 under aerobic and anaerobic conditions, respectively. The addition of untreated rice husks resulted in a strong increase in carbon mineralisation rates and in the same time period 77%–100% of the added rice husks were mineralised aerobically and 31%–54% anaerobically. The 13 C-signatures of respired CO 2 gave a direct indication of black carbon mineralisation to CO 2. In field trials we quantified the impact of rice husk black carbon or untreated rice husks on soil respiration and methane emissions. The application of black carbon had no significant effect on soil respiration but significantly enhanced methane emissions in the first rice crop season. The additional methane released accounted for only 0.14% of black carbon added. If the same amount of organic carbon was added as untreated rice husks, 34% of the applied carbon was released as CO 2 and methane in the first season. Furthermore, the addition of fresh harvest residues to paddy fields resulted in a disproportionally high increase in methane emissions. Estimating the carbon budget of the different rice crop residue treatments indicated that charring of rice residues and adding the obtained black carbon to paddy fields instead of incorporating untreated harvest residues may reduce field methane emissions by as much as 80%. Hence, the production of black carbon from rice harvest residues could be a powerful strategy for mitigating greenhouse gas emissions from rice fields.
TL;DR: In this article, a series of Ni−CeO2 catalysts with different La loadings is prepared by combustion synthesis and tested as catalysts in CH4 tri-reforming reaction at 800°C under atmospheric pressure with a GHSV of 30,000h−1.
Abstract: The objective of the present work is the study of CH4 tri-reforming process (simultaneous carbon dioxide reforming, steam reforming and oxygen reforming) that can contribute to the CO2 abatement producing synthesis gas with the desiderate H2/CO ratio. A series of Ni–CeO2 catalysts with different La loadings is prepared by combustion synthesis and tested as catalysts in CH4 Tri-reforming reaction at 800 °C under atmospheric pressure with a GHSV of 30,000 h−1. It has been found that during tri-reforming reaction the activity of Ni–ceria catalysts can be enhanced by an appropriate amount of La doping (10 at.%), the CH4 and CO2 conversion increases from 93% and 83% to 96% and 86.5%, respectively. The activity enhancement appears to be related to synergic effect of nickel–lanthana–surface oxygen vacancies of ceria via interfacial active sites that contribute to increase the nickel dispersion and create a basic site distribution on the surface able to interact with CO2.
TL;DR: In this paper, high pressure adsorption phenomena are discussed for different gases on HKUST-1 (Cu 3 (BTC) 2, commercially available product Basolite TM C300).
TL;DR: The findings of this factorial experiment point to a formerly unknown participation of desert soils in the global methane cycle.
Abstract: Methanogenesis is traditionally thought to occur only in highly reduced, anoxic environments. Wetland and rice field soils are well known sources for atmospheric methane, while aerated soils are considered sinks. Although methanogens have been detected in low numbers in some aerated, and even in desert soils, it remains unclear whether they are active under natural oxic conditions, such as in biological soil crusts (BSCs) of arid regions. To answer this question we carried out a factorial experiment using microcosms under simulated natural conditions. The BSC on top of an arid soil was incubated under moist conditions in all possible combinations of flooding and drainage, light and dark, air and nitrogen headspace. In the light, oxygen was produced by photosynthesis. Methane production was detected in all microcosms, but rates were much lower when oxygen was present. In addition, the δ13C of the methane differed between the oxic/oxygenic and anoxic microcosms. While under anoxic conditions methane was mainly produced from acetate, it was almost entirely produced from H2/CO2 under oxic/oxygenic conditions. Only two genera of methanogens were identified in the BSC-Methanosarcina and Methanocella; their abundance and activity in transcribing the mcrA gene (coding for methyl-CoM reductase) was higher under anoxic than oxic/oxygenic conditions, respectively. Both methanogens also actively transcribed the oxygen detoxifying gene catalase. Since methanotrophs were not detectable in the BSC, all the methane produced was released into the atmosphere. Our findings point to a formerly unknown participation of desert soils in the global methane cycle.
TL;DR: Investigation of a two-stage anaerobic hydrogen and methane process for increasing bioenergy production from organic wastes revealed that by changing the HRT(hydrogen):HRT(methane) ratio of the two- stage process from 3:12 to 1:14, 6.7%, more energy could be obtained.
01 Jan 2011
TL;DR: In this article, the authors synthesize available knowledge on biogeochemical cycling of CO 2 and CH 4 in estuarine environments, with a particular emphasis on the exchange with the atmosphere.
Abstract: Estuaries profoundly transform the large amounts of carbon delivered from rivers before their transfer to the adjacent coastal zone. As a consequence of the complex biogeochemical reworking of allochthonous carbon in the sediments and the water column, CO 2 and CH 4 are emitted into the atmosphere. We attempt to synthesize available knowledge on biogeochemical cycling of CO 2 and CH 4 in estuarine environments, with a particular emphasis on the exchange with the atmosphere. Unlike CH 4 , the global emission of CO 2 to the atmosphere from estuaries is significant compared to other components of the global carbon cycle.
TL;DR: In this paper, the authors presented geological and geochemical criteria to recognize secondary microbial methane in conventional petroleum reservoirs and estimated that ∼65,500 tcf of secondary microbial gas could have been generated in existing worldwide accumulations of oil and bitumen through their geological history.