Methane Carbon Dioxide Research Articles

Hydrogen activation on aluminium-doped magnesium hydride surface for methanation of carbon dioxide

Traditional catalysts for thermal hydrogenation of CO2 mainly focus on the catalytic activation of CO2 molecule, while the activation of H2 is often neglected. Herein, we report an Al-doped MgH2 nano-catalyst producing negative lattice H− as hydrogen source for CO2 hydrogenation. The Al-doped MgH2 nano-catalyst is synthesized with a reactive ball-milling method equipped with Al-based milling balls to dope Al on MgH2 surface. The surface doping of Al promotes the dissociation of H2 to lattice H− and helps the catalyst to achieve 88.4% CH4 selectivity and 27.1% CO2 conversion under H2/CO2 ratio 5/1 at 320 °C and 1.0 MPa. The atomic-doped-Al weakens the MgH bond and improves electron transfer on MgH2 surface, by which gives the lattice H− a high reactivity for CO2 hydrogenation. The delocalized large π bond of CO2 molecule is weakened by the combination of the lattice H− to the C atom of CO2 molecule, which promotes the formation of Mg formate, significantly influencing the hydrogenation route.

On the optimal design of load flexible fixed bed reactors: Integration of dynamics into the design problem

• Integration of critical dynamics into model-based reactor design approach. • Polytropic fixed-bed reactor is optimized for a worst case dynamic scenario. • Steady state and dynamic reactor models are coupled and solved simultaneously. • Limitations of conventional steady state design approach are overcome. • Methodology suitable for the design of flexible and dynamically operated reactors. The design of dynamically operated fixed bed reactors is a challenging task, especially for highly exothermic reactions. Fluctuations of process conditions such as inlet flow rate and composition can cause losses in product quality, wrong-way behavior or even a thermal runaway which damages reactor and catalyst. We present a methodology for the model-based design of dynamically operated, load flexible fixed bed reactors. Critical reactor dynamics are already considered during the reactor design and are integrated into the optimization problem. Instead of a steady state problem, the reactor is optimized for a worst case dynamic scenario. The optimization approach yields a design which allows for safe transitions from any flow rate to another within a pre-defined load range. The approach is introduced using the methanation of carbon dioxide as an important case study of high relevance for both research and society within the context of chemical energy storage of fluctuating renewable energy. A feasibility test demonstrates the safe reactor operation for a time horizon which includes a series of step-changes of the inlet flow rate as an approximation of a fluctuating hydrogen supply.

The Impact of Climate Change on Tourism: A Causality Analysis

Tourism industry is one of the primary sectors that contribute to economic growth of countries worldwide. Since it requires appropriate weather conditions and clean environment, climate changes can significantly affect the sector. Therefore, this study examines the causality and long-run relationship between the climate change and tourism sector in Turkey. To estimate the potential long-run relationship between variables, Granger-Causality test is applied to data from 1960 to 2016. The study uses World Development Indicator Data released by World Bank. For the analysis, carbon-dioxide emission, methane emission, energy use (oil equivalent), and forest land are standing for climate change indicators. International tourist arrivals and tourism revenues represent for tourism sector‘s variables. The findings show that there is a negative and significant coefficient of climate change on tourism sector. Also, in average, climatic change indicators have unidirectional and negative impact on international tourism revenue. Another finding is that climate change deteriorates to environment by augmenting carbon dioxide emission and methane emission. As a result, climatic change can weaken the tourism industry which can decrease the speed of Turkey‘s economic development. In the long run, this research can pioneer assessing the economic and environmental impacts of climate change in the tourism sector bases.

Electronic structure modulating for supported Rh catalysts toward CO2 methanation

Methanation of carbon dioxide is a promising approach to ameliorate greenhouse effect. Rhodium based catalysts have been intensively investigated due to its ability in cleavage of CO bond, but the role of support in the catalysts was underestimated. In this regard, we explored the methanation of CO2 over Rh catalysts with three metal oxide supports (TiO2, Al2O3, and ZnO). It was found that Rh/TiO2 exhibited the highest catalytic activity with product yield of 455 mmol gcat-1 h−1 (CH4 and CO) at 370 °C and 2 MPa, which is 2 and 14 times higher than Rh/A12O3 and Rh/ZnO, respectively. Moreover, the CH4 selectivity over Rh/TiO2 was higher than 95 %. The superior catalytic performance of Rh/TiO2 can be mainly attributed to its unique electronic structure associated with stronger Rh-TiO2 interaction and the existence of Ti3+ ions on TiO2.

Simulating the Potential Sequestration of Three Major Greenhouse Gases in China’s Natural Ecosystems

The greenhouse gases sequestrated by ecosystems are of great relevance to global carbon cycle and climate regulation. However, it is time-consuming and laborious to conduct sampling analysis, and it is also difficult to analyze the variation of potential sequestration of various ecosystems for greenhouse gases in China. This study used six 5-year periods of land use data for China between 1990 and 2015 to analyze the changes of three natural ecosystems (forest, grassland, and wetland). Correspondingly, the potential sequestration of the three ecosystems for three major greenhouse gases (carbon dioxide CO2, methane, and nitrous oxide) during the 25 years were simulated through a greenhouse gas value (GHGV) model. The GHGV model was found to be a reliable alternative to calculating the carbon sequestration of natural ecosystems in China. The total greenhouse gas sequestration of China’s natural ecosystems remained at around 267 Pg CO2-equivalent; however, the greenhouse gas sequestration had decreased by 3.3 Pg CO2-equivalent between 1990 and 2015. Comparison of the simulation results of the GHGV model based on the localized parameters and the model default parameters revealed that the simulated potential sequestration of the greenhouse gases for forest and wetland ecosystems (but not the grassland ecosystem) were smaller when run with localized parameters than the model default parameters. Moreover, the carbon sequestration of natural ecosystems was greater than the amount of anthropogenic carbon emissions, but the potential sequestration of natural ecosystems for greenhouse gas has become increasingly limited. Our study reveals the model can act as an important supplement for assessing the potential sequestration of the greenhouse gases for ecosystems at a regional scale.

Thermochemical and electrochemical aspects of carbon dioxide methanation: A sustainable approach to generate fuel via waste to energy theme

Sustainable generation of green energy and fine chemicals from carbon dioxide (CO2) is the most desirable and promising route for justifying the atmospheric CO2 build-up and carbon sequestration. This additionally serves to mitigate or defer global warming and avoid serious climate change. Renewable carbon is a possible source to reduce CO2 emission and avoid the combustion of coal and petroleum products. In this context, there is a dire need to introduce modern industrial procedures to develop new carbon recycling strategies for CO2, like spent carbon from CO2. The role of diverse industrial processes for the proper utilization of renewable carbon would fruitfully simulate the natural procedure. For the past few decades, both heterogeneous and homogeneous catalysis approaches have been useful for the conversion of CO2. Still, unfortunately, none of them addressed the current safety needs, cost-effectiveness, efficiency, reaction conditions, and selectivity. This review signifies the thermochemical and electrochemical approaches for the useful conversion of CO2, in the presence of catalyst material, to some high-value products of industrial interests, such as fuels (methane). Furthermore, several suitable examples are discussed to represent the potential and perspective of these technologies. In summary, a highly efficient conversion of CO2 to fuels and related high-value chemicals would fulfill the rising demands of diverse sectors of the modern world.

Mathematical Modeling of Landfill Gas (MSW)—Production of Gas with Methane Gas Content from Landfills (MSW)

The municipal solid waste (msw) is a source of landfill gas (msw)—with methane gas content. Preoccupations for landfill gas (msw) management date back since 1976 when, at a landfill (msw) in California (USA), it turned out practically that the landfill gas (msw) with methane gas content contains a gas with high caloric value that can be collected and used for economic purposes. The landfill gas (msw) contains methane gas (30% - 60% volume), carbon dioxide (45% - 50% volume), hydrogen sulfide and other gases. Methane gas, carbon dioxide, nitrous oxide and other gases are listed in Kyoto Protocol as high greenhouse gases. Their ecological-rational management is both a national and global preoccupation. In terms of greenhouse gases, especially methane gas, the landfill (msw) is held responsible for 3.5% - 5% of the total global greenhouse gases. Practically, the quantitative estimation of the methane gas in a municipal solid waste landfill can be done by measuring the landfill gas (msw) flow in an extraction-collection well. In Romania, a quantitative estimation relationship of methane gas from deposits (msw) was made, approaching the problem in a different way. This paper presents the calculation formula, the working algorithm, the municipal waste landfill equation and the NOMOGRAMA of a municipal solid waste landfill (msw). The NOMOGRAMA allows us to define the values for parameter -m- (number of months needed for an amount of municipal solid waste (msw) to degrade, starting with the year from which the landfill gas (msw) emission with methane gas content is calculated). Taking into account the environmental conditions for each location of municipal solid waste landfill, the calculation uses various indexes and approximations, while the fundamental parameter remains -m- defined by the NOMOGRAMA of the municipal solid waste landfill (msw). A municipal solid waste landfill (msw) is a conglomerate of waste with various biodegradation periods between 2 - 3 years and 5 - 10 - 30 years. Degradation of waste (msw) in to dissolved organic carbon will take place in a number of months defined -m- starting with the year from which the methane gas emission with the NOMOGRAMA of the municipal solid waste landfill (msw) is calculated. The -m- values for the year of the quantitative emission of methane gas can be also done analytically, which requires good experience in the ecologic-rational management of the municipal solid waste (msw).

Enhanced conjugated linoleic acid and biogas production after ruminal fermentation with Piper betle L. supplementation

ABSTRACT: Piper betle L. is edible plant richer in polyphenols that might improve feed utilization in rumen diet. The objective of the present study was to investigate the effect of various Piper betle L. powder (PL) doses on in vitro rumen microorganisms, ruminal biogas and fermentation end-product production, and biohydrogenation including lipolysis-isomerization. The completely randomized design used five levels of PL supplementation (0, 25, 50, 75 and 100 mg DM) incubated with 400 mg of a basal substrate of Pangola hay and concentrate (50:50). The matrix compounds (g/kg DM) of 0.27 catechin, 0.11 rutin, 3.48 quercetin, 0.41 apigenin, 0.04 myricetin, 0.27 kaempferol, 0.76 eugenol and 0.22 caryophyllene derived from PL altered the fermentation pattern, with an increase in degradable nutrients and total volatile fatty acids and acetogenesis without shifting pH during fermentation. These values promoted in vitro gas production, with higher carbon dioxide and lower methane production. Although, hydrogen recovery from lipolysis-isomerization in biohydrogenation was limited, PL successfully promoted stearic acid (C18:0) accumulation by changing the biohydrogenation pathway of fatty acids, causing more C18:1 trans-11 rather than C18:2 trans-11, cis-15. Consequently, this resulted in more conjugated linoleic acid (CLA) cis-9, trans-11, CLA trans-10, cis-12 and CLA trans-11, cis-13. Enhanced PL supply increased total bacteria and fungal zoospores due to a reduction in rumen protozoa. In conclusion, our results demonstrated that PL is a feed additive with potential for ruminants, promising improved ruminal fermentation and biohydrogenation, while reducing methane production.

A short review on carbon dioxide (CO2) methanation process

In this new modern era, global warming induced climate change has capture researcher’s attention due to its huge threat towards human civilization. CO2 is major parts of GHGs that contribute to global warming. The increasing of CO2 concentration in the atmosphere will rise the temperature of the earth surface. Currently, various effort has been done to utilize CO2 as raw material to generate a value-added chemical. Sabatier process is a process which generated methane (CH4) and water (H2O) utilizing Nickel (Ni)-based catalysts from CO2 and H2. Therefore, various effort has been done in the last 10 years. Despite of all the works done, the process still can’t be used in large-scale. This is because, the process is a complex process. Therefore, during low temperature the desirable of catalyst with high activity and stability is very crucial in order to achieve the optimum efficiency, cost-effectiveness, and sustainability of the catalyst while sustain the long-term CH4 production without producing any adverse by-products for industrial application. In addition, the sources of CO2 and H2 must be generated from industrial wastage or renewable feedstock, in order to consider the CO2 methanation process as a promising future technique to generated synthetic methane.

A Robust Titanium Isophthalate Metal-Organic Framework for Visible Light Photocatalytic CO <sub>2</sub> Methanation

Isophthalic acid (IPA), a feedstock linker, has been considered so far to build series of topical metal-organic frameworks (MOFs) of diverse structures with various di- and trivalent metal ions, such as CAU-10(Al), owing to its facile availability, unique connection angle/mode and a wide scope of functional groups attached. Constructing MOFs from IPA and tetravalent metals, typically Group 4 metals, would be of a great interest due to expected higher chemical stability. In particular, titanium-IPA frameworks possessing photoresponse is alluring, in relation to the known challenge of synthesizing new Ti-MOFs. Here, we have synthesized the first Ti-IPA MOF, denoted as MIP-208, via a solvothermal process that efficiently combines the use of preformed Ti8 oxoclusters and in situ acetylation of 5-NH2-IPA linker. MIP-208 has helical chains of cis-connected corner-sharing TiO6 polyhedra as the inorganic building units, which are interconnected to each other leading to a 3D ultramicroporous framework. Solid-solution mixed linkers strategy was then successfully applied resulting in a series of multivariate MIP-208 structures with tunable chemical environment and sizable porosity. Finally, the excellent thermal and hydrolytic stabilities of MIP-208 allowed its use for the photocatalytic carbon dioxide (CO2) methanation, showing the best result among the pure MOF catalysts. Ruthenium oxide nanoparticles were further photodeposited on MIP-208 forming a highly active and selective composite catalyst, MIP-208@RuOx, to largely improve the photocatalytic performance, which features a notable visible light response, an excellent stability and recycling ability.

Climate impact assessment of a pig manure storage system substituted with anaerobic digestion - a case study in Santa Catarina, Brazil

Brazil currently holds the fourth-place on pig meat production as well as in exports. The major pig industries are located in the state of Santa Catarina. The most common pig manure management in the state is the open tank storage with subsequent crop application of the manure. This study aimed to assess and compare the climate impact when substituting current management (reference scenario) with an anaerobic digestion scenario for energy and biofertilisation purposes at a small piglet production farm in Santa Catarina State. It was conducted as a consequential life cycle assessment (CLCA) focused on greenhouse gas emissions (methane, nitrous oxide and fossil carbon dioxide). The emissions, in each one of the studied scenarios, were dominated by methane from manure storage and direct carbon dioxide from managed soil. The anaerobic digestion scenario showed considerable reduction of the global warming potential (81%) compared to the reference scenario. The electricity and heat production in the anaerobic digestion scenario contributed to the reduction of total greenhouse gas emissions and supplied farm electricity and heat demands. The sensitivity analysis showed that parameters and emission factors for greenhouse gas emissions are important to consider in the assessment of environmental performance of manure management.

Climate impact assessment of a pig manure storage system substituted with anaerobic digestion - a case study in Santa Catarina, Brazil

Brazil currently holds the fourth-place on pig meat production as well as in exports. The major pig industries are located in the state of Santa Catarina. The most common pig manure management in the state is the open tank storage with subsequent crop application of the manure. This study aimed to assess and compare the climate impact when substituting current management (reference scenario) with an anaerobic digestion scenario for energy and biofertilisation purposes at a small piglet production farm in Santa Catarina State. It was conducted as a consequential life cycle assessment (CLCA) focused on greenhouse gas emissions (methane, nitrous oxide and fossil carbon dioxide). The emissions, in each one of the studied scenarios, were dominated by methane from manure storage and direct carbon dioxide from managed soil. The anaerobic digestion scenario showed considerable reduction of the global warming potential (81%) compared to the reference scenario. The electricity and heat production in the anaerobic digestion scenario contributed to the reduction of total greenhouse gas emissions and supplied farm electricity and heat demands. The sensitivity analysis showed that parameters and emission factors for greenhouse gas emissions are important to consider in the assessment of environmental performance of manure management.

Simulation of a NGCC Power Generation Plant for the Production of Electricity from CO2 Emissions Part II: SNGCC Power Plant

The objective of the first part of the investigation was to use Aspen Plus software and the Redlich-Kwong-Soave equation of state in order to simulate an adiabatic methanation reactor for the production of synthetic natural methane (SNG) using 1 kg/hr of carbon dioxide. In this paper, we define the Synthetic Natural Gas Combined Cycle (SNGCC) as a combined cycle power plant where the fuel is synthetic natural gas (SNG) produced by a methanation reactor. The feed of the methanation reactor is the recycled stream of carbon dioxide of a CO2 capture unit treating the flue gas of the SNGCC power plant. The objective of the second part of the investigation is the utilization of Aspen plus software with SRK equation of state for the simulation of the SNGCC power plant. The metallurgical limitation of the gas turbine was fixed at 1300°C in this investigation. For effective absorption by amine solutions, the molar percentage of CO2 in the flue gas should be higher than 10%. Moreover, in order to reduce technical problems linked to oxidative degradation of amine in the CO2 capture plant, the percentage of O2 in the flue gas should also be lower than 5%. To reach this goal, the primary air for combustion has 10% excess air (compared to stoichiometric air) and 37% of the flue gas leaving the SNGCC is recirculated as the secondary air for cooling the turbine. As a result, the concentration of CO2 and O2 of the flue gas entering the CO2 capture unit were respectively equal to 10.2% and 2.01%. The simulation results of the SNGCC power plant indicate that 6.6 MJ of electricity are produced for each kg of carbon dioxide recycled from the CO2 capture unit of the power plant. In other terms, the production of the 24.88 kg/hr of synthetic natural gas (SNG) consumes 62.36 kg/hr of recycled carbon dioxide and 16.4 kg/hr of hydrogen. The SNG produced by the methanation reactor of the power plant generates 114 kW of electricity. It is assumed in this paper that the hydrogen needed for the methanation of carbon dioxide is a product of a catalytic reforming plant that produces gasoline from heavy naphta fraction of an atmospheric distillation unit of crude oil.

Thermodynamics of the carbon dioxide plus nitrogen plus methane (CO2 + N2 + CH4) system: Measurements of vapor-liquid equilibrium data at temperatures from 223 to 298 K and verification of EOS-CG-2019 equation of state

Vapor-liquid equilibria (VLE) data of the ternary mixture of CO2 + N2 + CH4 were measured at the isotherms 223 K, 253 K, 273 K, 283 K, and 298 K and for pressures in the range of 0.8 MPa–9.3 MPa. The 62 experimental dew or bubble point data points have been measured using an analytical technique. For each temperature, the ratio between N2 and CH4 mole fraction in the total composition has been close to constant, enabling the data to be visualized as quasi phase envelopes. Estimated standard measurement uncertainties (k = 1) better than 14 mK in temperature, 1.5 kPa in pressure, and 0.06 mol% in composition are reported, yielding a total uncertainty in terms of composition better than 0.07 mol%. The experimental data were compared to the EOS-CG-2019 model, which is a state-of-the-art Helmholtz energy-based equation of state for the mixture of CO2 + N2 + CH4. All deviations between model and experimental data points are below 0.5 mol% for liquid compositions and 1.0 mol% for vapor compositions. The deviations between model and experimental points in the ternary mixture of CO2 + N2 + CH4 follow the same trends seen in earlier reports between model and experimental data for the binary mixtures of CO2 + N2 and CO2 + CH4. In addition, the model was analysed with respect to other thermophysical properties available in the literature. To a large extent, the results presented in this work validate the assumption that the thermodynamic properties of the multicomponent system CO2 + N2 + CH4 can be described purely based on the pure component and binary mixture contributions.

Trace gas sensing using diode-pumped collinearly detected spontaneous Raman scattering enhanced by a multipass cell

A simple but highly effective method for enhancement of spontaneous Raman scattering from gases is described. It employs a multimode blue laser diode that receives feedback from a near-concentric bidirectional multipass cavity in such a way as to generate a circulating power on the order of 100 W for a sample volume of 10 m m 3 . The feedback, provided via a volume Bragg grating, reduces the laser bandwidth to 4 c m − 1 . Spectra of spontaneous Raman scattering from ambient atmospheric air, detected collinearly with the pump, were recorded with a limit of detection below 1 ppm. The performance of the setup is further illustrated through detection of acetone, methane, and isotopic carbon dioxide in breath.

Investigating Trends in Atmospheric Compositions of Cool Gas Giant Planets Using Spitzer Secondary Eclipses

Abstract We present new 3.6 and 4.5 μm secondary eclipse measurements for five cool (T ≲ 1000 K) transiting gas giant planets: HAT-P-15b, HAT-P-17b, HAT-P-18b, HAT-P-26b, and WASP-69b. We detect eclipses in at least one bandpass for all planets except HAT-P-15b. We confirm and refine the orbital eccentricity of HAT-P-17b, which is also the only planet in our sample with a known outer companion. We compare our measured eclipse depths in these two bands, which are sensitive to the relative abundances of methane versus carbon monoxide and carbon dioxide, respectively, to predictions from 1D atmosphere models for each planet. For planets with hydrogen-dominated atmospheres and equilibrium temperatures cooler than ∼1000 K, this ratio should vary as a function of both atmospheric metallicity and the carbon-to-oxygen ratio. For HAT-P-26b, our observations are in good agreement with the low atmospheric metallicity inferred from transmission spectroscopy. We find that all four of the planets with detected eclipses are best matched by models with relatively efficient circulation of energy to the nightside. We see no evidence for a solar-system-like correlation between planet mass and atmospheric metallicity, but instead identify a potential (1.9σ) correlation between the inferred CH4/(CO + CO2) ratio and stellar metallicity. Our ability to characterize this potential trend is limited by the relatively large uncertainties in the stellar metallicity values. Our observations provide a first look at the brightness of these planets at wavelengths accessible to the James Webb Space Telescope, which will be able to resolve individual CH4, CO, and CO2 bands and provide much stronger constraints on their atmospheric compositions.

Cleat-scale modelling of the coal permeability evolution due to sorption-induced strain

Coal permeability is known to be affected by the sorption-induced strain. Indeed, coal swells with gas sorption and shrinks with desorption, which is likely to modify the cleat aperture and thus the permeability. Coal permeability evolution is crucially important for either Coalbed Methane production (CBM) or Carbon dioxide Capture and Storage (CCS).A model is developed at the scale of the fractures to take into account the hydro-mechanical couplings observed experimentally. It is implemented in the finite element code Lagamine. This numerical model is developed at the scale of the fractures and the matrix blocks. Fractures are modelled with interface elements specially adapted to manage sorption/desorption by taking into account the Langmuir's isotherm (Langmuir, 1918). In the matrix blocks, the sorption strain is assumed proportional to the adsorbed gas content. Depending on the boundary conditions, sorption strain affects the stress state and thus the fracture aperture. Contrary to macroscale models (Bertrand et al. 2017), this model does not require the use of shape factors since the geometry can be explicitly represented. The implementation of the model is validated by comparison with the analytical solution on a simple geometry. The model is finally used to simulate gas injection on a representative elementary volume (REV) made up few matrix blocks. This modelling highlights the interests of a numerical approach to compute the permeability evolution compared to a porosity-based model.

Surfactant‐Free Sol–Gel Synthesis Method for the Preparation of Mesoporous High Surface Area NiO–Al2O3 Nanopowder and Its Application in Catalytic CO2 Methanation

A group of nickel‐based catalysts with different weight percentages of Ni are synthesized using a novel surfactant‐free sol–gel method, and the prepared catalysts are used in the methanation of carbon dioxide. The results indicate that the surfactant‐free sol–gel method is highly effective to prepare nickel‐based catalysts with high Brunauer–Emmett–Teller (BET) area in the range of 269.2–297.3 m2 g−1. The increment in nickel content from 15 to 30 wt% increases the size of the Ni crystals from 3.7 to 4.2 nm, weakens the interaction between nickel oxide and alumina, and improves the reducibility of the catalysts. The catalyst with 30 wt% Ni possesses the best catalytic performance in CO2 methanation reaction with 73.98% CO2 conversion and 99% CH4 selectivity at 350 °C. High catalytic stability is also observed for these catalysts.

Adaptation Approaches for Direct Seeded Rice to Reduce Greenhouse Gas Emission in the Perspective of Climate Change

A field experiment was conducted at research farm, Bihar Agricultural University, Sabour, India during 2017 and 2018 to gain insight crop phonology mediated greenhouse gas emission under different tillage and nitrogen management practices in direct seeded rice (DSR). The experiment was conducted in split plot design with two tillage viz. zero tillage (ZT) and conventional tillage (CT) as main plot and four nitrogen management practices viz. 100% nitrogen through neem coated urea (S1), SPAD based nitrogen management (S2), 75% through neem coated urea + 25% nitrogen through vermicompost, (S3) and ¼ nitrogen as basal and rest in equal three splits at 20, 40, 60 DAS (S4) as sub plot, in three replication. The highest yield (4.69 t ha-1), net return (Rs 46440 ha-1) and B:C ratio (1.44) were recorded from zero tilled DSR. Further, highest yield (4.82 t ha-1), net return (Rs 44880 ha-1) and B:C ratio (1.36) was obtained under split application of nitrogenous fertilizers among other subplot treatments. The range of methane (0.57- 1.47 mg m-2 hr-1) carbon dioxide (0.32- 0.61 mg m-2 hr-1) and nitrous oxide (19.58- 38.79 µg m-2 hr-1) emission was recorded lowest in zero tilled plots and split application of nitrogenous fertilizer also emitted lowest values of 1.59 mg m-2 hr-1 methane, 0.86 mg m-2 hr-1 carbon dioxide and 46.76 µg m-2 hr-1 nitrous oxide at maximum tillering stage of crop growth. Moreover, methane and nitrous oxide emission was gradually decreased from maximum tillering to harvesting stage. Zero tilled DSR with split nitrogen fertilizer application ascribed lowest greenhouse gas intensity among the other crop establishment and nitrogen management options. Thus, zero tilled method of crop establishment with split application of nitrogenous fertilizer could be a remunerative and environmentally stable method for direct seeded rice cultivation.

Rapid expansion of northern peatlands and doubled estimate of carbon storage

Northern peatlands are an integral part of the global carbon cycle—a strong sink of atmospheric carbon dioxide and source of methane. Increasing anthropogenic carbon dioxide and methane in the atmosphere are thought to strongly impact these environments, and yet, peatlands are not routinely included in Earth system models. Here we present a quantification of the sink and stock of northern peat carbon from the last glacial period through the pre-industrial period. Additional data and new algorithms for reconstructing the history of peat carbon accumulation and the timing of peatland initiation increased the estimate of total northern peat carbon stocks from 545 Gt to 1,055 Gt of carbon. Further, the post-glacial increases in peatland initiation rate and carbon accumulation rate are more abrupt than previously reported. Peatlands have been a strong carbon sink throughout the Holocene, but the atmospheric partial pressure of carbon dioxide has been relatively stable over this period. While processes such as permafrost thaw and coral reef development probably contributed some additional carbon to the atmosphere, we suggest that deep ocean upwelling was the most important mechanism for balancing the peatland sink and maintaining the observed stability. Northern peatlands are estimated to store more than 1,000 Gt of carbon, almost doubling previous estimates, according to a reconstruction of historical peat carbon accumulation.