Anaerobic ammonium oxidation (anammox), denitrifying anaerobic methane oxidation bacteria (DAMO) have received great attention for their excellent performance in nitrogen removal. However, not much study focused on the co-existence of anammox, DAMO, and denitrification in constructed wetlands, not to mention the advantage of their application in mitigating the necessary byproduct nitrous oxide (N₂O), methane (CH₄) from the biodegradation process. In this study, the result indicated the construction of integrated vertical constructed wetlands (IVCWs) contributed to the high-efficient stable simultaneous anammox, DAMO and denitrification (SADD) process for the nutrients removal, with denitrification being the least contributor to nitrogen reduction. Besides the succession of SADD process was largely the driver for the variation of N₂O, CH₄ emission. The structural equation method (SEM) further suggested that the three biological pathways of qnorB/bacteria, archaea/qnorB, and anammox/nirK accounted for the N₂O production, as were top-controlled by mcrA/DAMO in IVCWs. Besides the anammox-associated nitrifier denitrification was the main source for N₂O production. And that the trade-off effect between the CH₄ and N₂O production was exerted by the DAMO, while the influence was far from satisfactory under the methane constraints.

Polluted urban river systems might be a strong source of atmospheric methane (CH₄) and nitrous oxide (N₂O), but so far only a few urban river systems have been quantified with regard to their source strength for greenhouse gases (GHGs). In this study, we measured loads of dissolved inorganic nitrogen and organic carbon, dissolved oxygen (DO) concentrations, and fluxes of CH₄ and N₂O from an urban river in Beijing, China during the course of an entire year. Fluxes calculated using the floating chamber approach or via the diffusion method with measurements of river water GHG concentrations showed comparable temporal variations. However, the flux magnitude based on the diffusion method was found to strongly depend on the underlying parameterization of the gas transfer velocity. In view of the large differences while applying different methodologies to estimate surface water GHG fluxes further studies are still needed to prove and eventually quantify the systematic errors which are likely caused by either the chamber technique or the approaches of individual diffusion models. For both the floating chamber and the diffusion-based flux estimates, strong seasonal variations in CH₄ and N₂O fluxes from the river surface were observed, with fluxes ranging from 3 to 8374 μg C m⁻² h⁻¹ for CH₄ and 1–3986 μg N m⁻² h⁻¹ for N₂O. The CH₄ fluxes were strongly negatively correlated with the DO concentration (P < 0.01). The highest N₂O fluxes were observed at times with low CH₄ fluxes (i.e., in spring and autumn). Annual CH₄ and N₂O fluxes totaled 19.3–79.4 and 17.4–44.8 kg C (N) ha⁻¹ yr⁻¹, respectively. These high fluxes are in agreement with estimates from the few other studies carried out for urban river systems to date and indicate that urban polluted river systems are a significant regional source of atmospheric GHGs.

Both biochar (BC) and wood vinegar (WV) influence the nitrous oxide (N₂O) and methane (CH₄) emissions from agricultural systems. However, the impacts of BC and WV co-application on rice production, N₂O and CH₄ emissions are not well documented. We here conducted a two-year soil columns experiment with four treatments: WV (5 t WV ha⁻¹), BC (7.5 t BC ha⁻¹), WV + BC (5 t WV ha⁻¹ +7.5 t BC ha⁻¹) and a control (no treatment). The results showed that BC and WV + BC produced higher rice grain yield than the control by 14.1–15.9% in 2016 and by 4.1–5.2% in 2017, respectively. While WV increased rice grain yield by 11.2% in 2016, it had no significant influence on yield in 2017. Both WV and BC significantly mitigated N₂O emissions by 22.4–41.8% in 2016 and 22.4–36.9% in 2017, respectively. Interestingly, WV + BC treatment showed the highest N₂O mitigation efficiency, with a 52.9–62.8% mitigations in 2016 and 2017. Furthermore, the co-application of WV and BC significantly mitigated CH₄ emissions by 42.6% in 2016 and 35.3% in 2017, respectively, while applying WV or BC alone had no annually-consistent mitigation effect on CH₄ emissions. Overall, GWPt of rice growth cycle was most significantly suppressed by WV + BC with a 48.7–56.1% reduction, followed by WV and BC with 20.4–28.0% and 19.7–35.7% reductions, respectively. Consequently, the WV + BC treatment had the highest GHGI mitigation effect, averaging with 56.7% over two consecutive rice growth cycles. In conclusion, co-application of WV and BC is recommended for rice cultivation, which can both improve rice yield and minimize GHG emissions.

In recent years, there has been a sharp increase in interest in the development of environmentally friendly technology for burning methane gas hydrate. In addition to solving energy problems, gas hydrates will help to make significant progress in solving environmental problems. The use of gas hydrate combustion technology is shown to reduce harmful emissions. In this work, experimental studies on the combustion of double hydrate powder of propane-methane have been performed at five different ways of combustion organization. Powder heating was realized using: 1) induction heating; 2) radiation and convective heating; 3) using a hot metal body; 4) combustion without forced gas flow and 5) combustion in the presence of forced and free air convection. Currently there has been neither a comprehensive study of the combustion of double gas hydrates, nor a comparison of the combustion efficiency for different methods; besides, no data on emissions have been obtained. The maximum dissociation rate is implemented with the use of induction heating. Using a gas analyzer the concentration of gases during the gas hydrate combustion has been measured. Comparison of different ways of combustion allows optimizing the combustion efficiency of gas hydrates.

About 11% of the global anthropogenic greenhouse gases (GHGs) emissions result from agricultural practices. Dairy manure (DM) application to soil is regarded as a best management practice due to C sequestration and improvement of soil physiochemical properties. However, GHGs emissions from the soil following the DM application could offset its advantages. Biochar (BC) is known to affect N transformation and GHGs emissions from soil. There had been considerably less focus on the BC amendment and its effects on GHGs emissions following DM application under field conditions. The objectives of this study were; i) to determine the temporal patterns and cumulative GHGs fluxes following DM and inorganic nitrogen (IN) application and, ii) to investigate BC amendment impact on DMY, GWP, direct N₂O emission factor (EFd) and the response of CH₄ emissions (RC) in DM based silage corn. To achieve these objectives a two-year field experiment was conducted with these treatments: 1) DM with high N conc. (DM₁: 0.37% N); 2) DM with low N conc. (DM₂: 0.13% N); 3) IN; 4) DM₁+BC; 5) DM₂+BC; 6) IN + BC; and 7) Control (N₀); and were laid out in randomized complete block design with four replications. BC amendment to DM₁, DM₂ and IN significantly reduced cumulative CO₂ emission by 16, 25.5 and 26.5%, CH₄ emission by 184, 200 and 293% and N₂O emission by 95, 86 and 93% respectively. It also reduced area-scaled and yield-scaled GWP, EFd, RC and enhanced DMY. Thus, BC application showed great potential to offset the negative effects of DM application i.e GHGs emissions from the silage corn cropping system. Further research is needed to evaluate soil organic carbon and nitrogen dynamics (substrates for GHG emissions) after DM and BC application on various soil types and cropping systems under field conditions.

CH₄ oxidation in landfill cover soils plays a significant role in mitigating CH₄ release to the atmosphere. Oxygen availability and the presence of co-contaminants are potentially important factors affecting CH₄ oxidation rate and the fate of CH₄-derived carbon. In this study, microbial populations that oxidize CH₄ and the subsequent conversion of CH₄-derived carbon into CO₂, soil organic C and biomass C were investigated in landfill cover soils at two O₂ tensions, i.e., O₂ concentrations of 21% (“sufficient”) and 2.5% (“limited”) with and without toluene. CH₄-derived carbon was primarily converted into CO₂ and soil organic C in the landfill cover soils, accounting for more than 80% of CH₄ oxidized. Under the O₂-sufficient condition, 52.9%–59.6% of CH₄-derived carbon was converted into CO₂ (CECO₂₋C), and 29.1%–39.3% was converted into soil organic C (CEₒᵣgₐₙᵢc₋C). A higher CEₒᵣgₐₙᵢc₋C and lower CECO₂₋C occurred in the O₂-limited environment, relative to the O₂-sufficient condition. With the addition of toluene, the carbon conversion efficiency of CH₄ into biomass C and organic C increased slightly, especially in the O₂-limited environment. A more complex microbial network was involved in CH₄ assimilation in the O₂-limited environment than under the O₂-sufficient condition. DNA-based stable isotope probing of the community with ¹³CH₄ revealed that Methylocaldum and Methylosarcina had a higher relative growth rate than other type I methanotrophs in the landfill cover soils, especially at the low O₂ concentration, while Methylosinus was more abundant in the treatment with both the high O₂ concentration and toluene. These results indicated that O₂-limited environments could prompt more CH₄-derived carbon to be deposited into soils in the form of biomass C and organic C, thereby enhancing the contribution of CH₄-derived carbon to soil community biomass and functionality of landfill cover soils (i.e. reduction of CO₂ emission).

Nitrogen (N) deposition has been conventionally thought to decrease forest soil methane (CH₄) uptake, while the biome specific and dose dependent effect is poorly understood. Based on a meta-analysis of 63 N addition trials from 7 boreal forests, 8 temperate forests, 13 subtropical and 4 tropical forests, we evaluated the effects of N addition on soil CH₄ uptake fluxes across global forest biomes. When combining all N addition levels, soil CH₄ uptake was insignificantly decreased by 7% in boreal forests, while N addition significantly decreased soil CH₄ uptake by 39% in temperate forests and by 21% in subtropical and tropical forests, respectively. Meta-regression analyses, however, indicated a shift from a positive to a negative effect on soil CH₄ uptake with increasing N additions both in boreal forests (threshold = 48 kg N ha⁻¹ yr⁻¹) and temperate forests (threshold = 27 kg N ha⁻¹ yr⁻¹), while no such shift was found in subtropical and tropical forests. Considering that current N deposition to most boreal and temperate forests is below the abovementioned thresholds, N deposition likely exerts a positive to neutral effect on soil CH₄ uptake in both forest biomes. Our results provide new insights on the biome specific and dose dependent effect of N addition on soil CH₄ sink in global forests and suggest that the current understanding that N deposition decreases forest soil CH₄ uptake is flawed by high levels of experimental N addition.

Coastal wetlands are widely recognized as atmospheric methane sources. However, recent field studies suggest that some coastal wetlands could also act as methane sinks, but the mechanism is not yet clear. Here, we investigated methane oxidation with different electron acceptors (i.e., oxygen, nitrate/nitrite, sulfate, Fe(III) and Mn(IV)) in four coastal wetlands in China using a combination of molecular biology methods and isotopic tracing technologies. The geochemical profiles and in situ Gibbs free energies suggest that there was significant nitrite-dependent anaerobic oxidation of methane (nitrite-AOM) in the sub-surface sediments; this was subsequently experimentally verified by both the microbial abundance and activity. Remarkably, the methanotrophic communities seemed to exist in the sediments as layered structures, and the surface aerobic methane-oxidizing bacteria were able to take up atmospheric methane at a rate of 0.10–0.18 nmol CH₄ day⁻¹ cm⁻², while most, if not all, sedimentary methane was being completely consumed by anaerobic methanotrophs (23–58% by methane oxidizers in phylum NC10). These results suggest that coastal methane sinks might be governed by diverse microbial communities where NC10 methane oxidizers contributed significantly. This finding helps to better understand and predict the coastal methane cycle and reduce uncertainties in the estimations of the global methane flux.

A mass balance approach to quantify methane (CH4) emission of four co-located landfills by means of airborne measurements and dispersion modelling was proposed and assessed. By flying grids at different heights above the landfills, atmospheric CH4 densities and wind components were measured along the edges and inside the study atmospheric volume, in order to calculate mass flows in the along- and across-wind directions. A steady-state Gaussian dispersion model was applied to build the concentration fields associated to unit emission from each landfill, while the contribution of each one to the total emission was assessed using a General Linear Model approach, minimizing the difference between measured and modeled mass flows. Results showed that wind spatial and temporal variability is the main factor controlling the accuracy of the method, as a good agreement between measured and modeled mass flows was mainly found for flights made in steady wind conditions. CH4 emissions of the entire area ranged from 213.5 ± 33.5 to 317.9 ± 90.4 g s−1 with a mean value of 252.5 ± 54.2 g s−1. Contributions from individual sources varied from 17.5 to 40.1 g m−2 day−1 indicating a substantial heterogeneity of the different landfills, which differed in age and waste composition. The proposed method was validated against tower eddy covariance flux measurements made at one of the landfills, revealing an overall agreement within 20%.

The rate of deforestation in Brazil increased by 29% between 2015 and 2016, resulting in an increase of greenhouse gas emissions (GHG) of 9%. Deforestation fires in the Amazonia are the main source of GHG in Brazil. In this work, amounts of CO2, CO, main hydrocarbon gases and PM2.5 emitted during deforestation fires, under real conditions directly in Brazilian Amazonia, were determined. A brief discussion of the relationship between the annual emission of CO2 equivalent (CO2,eq) and Paris Agreement was conducted. Experimental fires were carried out in Western Amazonia (Candeias do Jamari, Rio Branco and Cruzeiro do Sul) and results were compared with a previous fire carried out in Eastern Amazonia (Alta Floresta). The average total fresh biomass on the ground before burning and the total biomass consumption were estimated to be 591 ton ha−1 and 33%, respectively. CO2, CO, CH4, and non–methane hydrocarbon (NMHC) average emission factors, for the four sites, were 1568, 140, 8, and 3 g kg−1 of burned dry biomass, respectively. PM2.5 showed large variation among the sites (0.9–16 g kg−1). Emissions per hectare of forest were estimated as 216,696 kg of CO2, 18,979 kg of CO, 1,058 kg of CH4, and 496 kg of NMHC. The average annual emission of equivalent CO2 was estimated as 301 ± 53 Mt year−1 for the Brazilian Amazonia forest. From 2013, the estimated CO2,eq showed a trend to increase in Amazon region. The present study is an alert and provides important information that can be used in the development of the public policies to control emissions and deforestation in the Brazilian Amazonia.