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Purpose: Nitrogen (N) fertilizer is a critical factor in achieving high rice yields, but it can also contribute to increased CH4 emissions from rice paddies. Determining how to utilize N fertilizer to effectively balance the contradiction between methane (CH4) emissions and rice yield remains an urgent need in the face of unstoppable climate change. Materials and methods: In this study, the response of CH4 fluxes in rice paddies to elevated carbon dioxide (CO2) concentration (e[CO2]) and reduced N application were investigated. The rice biomass and yield, CH4 fluxes, soil properties, and methanogenic characteristics were observed in control (CK) (ambient CO2 concentration + application of 250 kg N ha−1 urea), C+ (e[CO2] by 200 ppm + 250 kg N ha−1 urea), N− (ambient CO2 concentration + 150 kg N ha−1 urea), and C+N− (e[CO2] by 200 ppm + 150 kg N ha−1 urea) treatments. Results and discussion: The results revealed that the C+ and C+N− treatments significantly increased the CH4 emissions/yield by 20.0% and 18.8%, respectively, while the N− treatment significantly suppressed the CH4 emissions/yield by 13.3% compared to CK. The N− treatment weakened the promotion effect of C+ on the rice total biomass, the soil dissolved organic carbon (DOC) concentration and invertase activity, and the CH4 emissions/yield. Moreover, the C+N− treatment significantly reduced the soil DOC concentration and the abundance of the mcrA gene in the grain-filling stage compared to C+. Conclusions: Overall, under climate change conditions, N reduction can mitigate CH4 fluxes from rice paddies by affecting rice growth, soil methanogenic characteristics, and the C substrate. [ABSTRACT FROM AUTHOR]

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The livestock production sector plays a crucial role in food security and income generation and has an undeniable relationship with the environment. Like other agricultural sectors, it faces the significant challenge of climate change. However, the attention given to this issue has not been satisfactory given its importance. Thus, the primary aim of the current research is to assess the impact of temperature change, precipitation, CH4 emissions, gross fixed capital, and land use on the livestock production index as an indicator of food security in Iran. The modeling uses data from 1990 to 2020, employing the NARDL approach and Granger causality. The results show that a 1% increase in temperature can lead to an 8.06% decrease in livestock production (food security), while a 1% decline in temperature results in a 3.85% surge in livestock production. Precipitation has a direct relationship with food security; a 1% rise and drop in rainfall lead to an increase and reduction in livestock production by 0.8% and 1.02%, respectively. A 1% increase in gross fixed capital boosts food security by 0.47%, while a 1% decrease leads to a 2.32% reduction. A statistically insignificant relationship is seen between the positive CH4 shock and food security in the long run. However, the negative shock of this variable positively influences food security by 7.5%. Negative changes in land use will reduce livestock production. The Granger causality test proves a two‐way causal relationship between CH4 emissions and livestock production. A unidirectional causality is discovered from production to temperature and from land use to livestock production. To mitigate the impact of global warming on livestock production, strategic investments in infrastructure, livestock micro insurance, and informing producers about the consequences of climate change and solutions for addressing this phenomenon can be considered effective policies. [ABSTRACT FROM AUTHOR]

The SF6 gas tracer technique is extensively used to measure enteric CH4 emissions for scientific research in Latin-American countries. Although guidelines on how to properly implement this technique have been published, its use has been the subject of considerable uncertainty due to a high variation within measurements when compared to results obtained with other techniques. Therefore, a detailed evaluation of this technique is important to identify the main sources of variability. The aim of this study is to summarise the key factors contributing to this variation, as reported in studies conducted in Latin America (LA). The final dataset comprised 63 studies and the variables considered within our analysis were split into two main categories: (1) Production systems and animal-related factors driving enteric CH4 emissions and (2) Aspects related to the implementation of the SF6 gas tracer technique in research laboratories, such as: duration of the collection period, and mean permeation rate of the SF6 collection canisters, among others. The lack of specific details regarding the SF6 gas tracer technique in the compiled dataset from LA studies is notable. Despite this, the main sources of variation identified were related to both the duration of the sampling period and the SF6 permeation rate. [ABSTRACT FROM AUTHOR]

Crop straw and N fertilizer applications impact paddy rice yield and greenhouse gas (GHG) emissions. However, their interactive effects have not been well documented. This study investigated the effects of straw (S), no straw incorporation (NS), and three levels of N fertilization rates (N0, N1, and N2) on single rice (SR), double rice (DR), and rice-wheat (RW) cropping systems. Straw incorporation significantly increased total CH4 emissions by 118.6%, 8.0%, and 79.0% in the SR, DR, and RW, respectively, compared to the NS. The total GHG emissions in DR are significantly 72.6% and 83.5% higher than those in RW and SR, respectively. Compared to NS, straw incorporation significantly increased yield-scaled emissions by 27.8%, 15.0%, and 89.0% in SR, DR, and RW, respectively. Straw with N application significantly increased average rice yield over N1 and N2 by 39.4%, 50.0%, and 6.7% in SR, DR, and RW, respectively. There was a significant correlation between methyl coenzyme M reductase (mcrA) and CH4 emissions in rSR = 0.87 (p < 0.05) and rRW = 0.85 (p < 0.05), except in rDR = 0.06 (p > 0.05). This study scientifically supports straw incorporation combined with a moderate N application rate in rice-based cropping systems to maintain high rice yields and mitigate GHG emissions. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Inland waters are significant emitters of greenhouse gases for the atmosphere and play an important role in the global carbon cycle. With a vast land area in East Asia spanning a broad range of climatic conditions, China has a large number of natural and human‐made water bodies. These inland water systems are of global importance because of their high carbon emission fluxes. Over the past decades, China has experienced unprecedented environmental changes driven by rapid economic development, which have profoundly modified its inland water carbon biogeochemistry and associated emissions. This review focuses on carbon dioxide (CO2) and methane (CH4) emission dynamics from China's inland waters in response to global change. Major drivers of CO2 and CH4 emissions, including aquatic metabolism, hydrological and climatic factors, and prevailing human impacts, are examined. To advance our understanding of carbon emissions from China's inland waters, we further identify several critical knowledge gaps, such as inadequate research in headwater streams and the climate‐sensitive Tibetan Plateau aquatic ecosystems. Furthermore, insufficient understanding of carbon emissions from inland waters undergoing extensive human interventions (e.g., damming, flow regulation, pollution, and farming practices in aquaculture ponds) is highlighted. We suggest that future efforts should be made to better capture the spatiotemporal heterogeneity in dissolved CO2 and CH4 concentrations and fluxes across China as well as their long‐term trends. To overcome uncertainties in carbon sources and current flux estimates, future research to mechanistically understand carbon transport and transformation in Chinese inland waters and their underlying processes is particularly needed. Plain Language Summary: Inland waters (e.g., streams, rivers, lakes, reservoirs, and ponds) are important sources of greenhouse gases (i.e., CO2 and CH4) for the atmosphere, affecting the earth's carbon balance. With a vast land area (∼9.6 million km2) and diverse climate regions, China contains numerous natural and man‐made water bodies. Dissolved carbon dioxide (CO2) and methane (CH4) emissions from these inland water systems have been significantly disturbed by global climate change and human activities. This review focuses on the current research progress of CO2 and CH4 emissions from China's inland waters. Major factors controlling dissolved CO2 and CH4 emission dynamics are examined. Furthermore, we discuss the shortcomings of current research on inland water carbon emissions in climate‐sensitive regions and anthropogenically disturbed regions of China. There is a pressing need to strengthen the monitoring of aquatic CO2 and CH4 emissions over space and time and to gain a deeper understanding of the underlying mechanisms. Key Points: Chinese inland waters have significantly higher water‐to‐air carbon emission fluxes than lateral transport of carbon to the coastal oceanAquatic metabolism, hydrological and climatic factors, and human disturbance are main drivers regulating the aquatic carbon emissionsDynamics of CO2 and CH4 evasion from inland waters in China's climate‐sensitive and anthropogenically disturbed regions are understudied [ABSTRACT FROM AUTHOR]

This study aims to present a roadmap on which optimal solutions can be adopted for a sustainable water and energy management by focusing on the relationships among "Sustainable Development Goals (SDGs)", "Water‐Energy", "Innovation‐Technology" and "Capacity‐Generation" blocks. The findings reveal that technological innovations are the core of sustainable solutions. An optimal bundle for policy tools should take SDG3, SDG10, SDG11, SDG12, SDG16, CH4‐N2O emissions, access to clean fuels, wastewater treatment and COVID‐19 major drivers into account primarily to explain the water‐energy nexus. Among the five worst‐performing technologies are hydrogen, CCUS, fuel cells, energy efficiency and electromobility‐electric energy management. Considering the constructed four scenarios together; levelized cost of electricity, global horizontal irradiation and photovoltaic (PV) power output seasonality are the only significant PV potential indicators despite their low impacts. [ABSTRACT FROM AUTHOR]

The increase in temperature caused by global climate change has promoted the salinization of wetlands. Inland saline-alkaline wetlands have an environment of over-humidity and shallow water and are hot spots for CH4 emissions. However, there are few reports on the effect of salinity on CH4 emissions in inland saline-alkaline wetlands. This study conducted simulation experiments of increased salinity to investigate the impact of salinity, habitat, and their interactions on CH4 emissions, as well as to examine the response of methanogenic archaea to salinity. Overall, salinity inhibited CH4 emissions. But there were different responses in the three habitat soils. Salinity decreased the relative abundance of methanogenic archaea and changed the community structure. In addition, salinity changed soil pH and dissolved organic carbon (DOC) and ammonium (NH4+) concentrations, which were significantly correlated with methanogenic archaea. Our study showed that salinity changed the soil physicochemical properties and characteristics of the methanogenic archaeal community, affecting CH4 emissions. [ABSTRACT FROM AUTHOR]

• Frequent export of slurry for outside storage reduced overall methane emissions. • Methane reduction for barn + storage was 18–41% and 53–83% in summer and winter. • Funnel inserts in slurry pits effectively reduced in-house ammonia emissions. • Frequent removal delayed the development of methanogenic activity. Manure management is a significant source of methane (CH 4) and ammonia (NH 3), and there is an urgent need for strategies to reduce these emissions. More frequent export of manure for outside storage can lower gaseous emissions from housing facilities, but the longer residence time may then increase emissions during outside storage. This study examined CH 4 and NH 3 emissions from liquid pig manure (pig slurry) removed from the in-house slurry collection pits at three different frequencies, i.e., three times per week (T 2.3), once per week (T 7), or once after 40 days (T 40 , reference). The slurry from treatments T 2.3 and T 7 was transferred for outside storage weekly over four weeks, and slurry from treatment T 40 once after 40 days, in connection with summer and winter production cycles with growing-finishing pigs. The slurry was stored in pilot-scale storage tanks with solid cover and continuous ventilation. Compared to T 40 , the treatments T 2.3 and T 7 increased CH 4 emissions during outside storage, but in-house emissions were reduced even more, and the net effects on total CH 4 emissions from manure management (housing unit and outside storage) were reductions of 18–41% in summer and 53–83% in winter. The frequent slurry export for outside storage led to more NH 3 emissions, except for the treatment T 2.3 , which has slurry funnel inserts beneath the slatted floor. Measurements of in-vitro CH 4 production rates suggested that shorter residence time for slurry in pig houses delayed the development of active methanogenic populations, and that this contributed to the reduction of CH 4 emissions. [ABSTRACT FROM AUTHOR]

To improve the quality of soil, agriculture typically uses organic additions like wheat straw (WS). Water management (WM) methods such as alternative wetness and dryness irrigation (AWDI) in paddy rice farming can increase water use efficiency and reduce greenhouse gas (GHG) emissions. In this study, a randomized complete block design (RCBD) pot greenhouse experiment was conducted to assess the effects of WM (CFI (continued flooding irrigation) and AWDI), WS (15.0 and 30.0 ton ha−1), and their interaction (WS*WM) on CH4 emissions and rice yield in a paddy calcareous soil cultivated with rice. The largest CH4 emission occurred 30 and 70 days following rice planting. Single applications of WS at 15.0 and 30.0 ton ha−1 significantly increased CH4 emissions by 19.60% and 68.70% (P < 0.01), respectively, compared to the Control. Compared to CFI, the AWDI reduced CH4 emissions by 31.20% (P < 0.01). The correlations between AWDI and CH4 emissions in days after rice planting were significantly negative at the 0.01 level based on Pearson correlation. Adding WS in the AWDI significantly decreased CH4 emissions by 27.70 and 25.64% in 15.0 and 30.0 ton ha−1 added WS (P < 0.05), respectively, compared to sole WS. Both rates of WS resulted in a considerable increase in biomass and rice grain compared to the Control, while the AWDI had no significant effect on biomass and grain yield. Our data showed significant interaction between AWDI and WS on biomass. Our study shows that the AWDI saved 18.50% water compared to the CFI. [ABSTRACT FROM AUTHOR]

Distinguished features of cities influence the characteristics of CH4 emissions. A city-level emission inventory represents the characteristics of CH4 on a smaller scale, according to the special factors in each city. A city-level emission inventory was established to reveal the characteristics and source profile of CH4 emissions in the coldest province, which is a typical provincial cold region in northeast China. The dominant sources were identified for targeted cities. Rice cultivation, coal mining, oil and gas exploitation, and livestock are the dominant emission sectors. Emissions from other sectors, including wastewater disposal, biomass burning, landfill, etc. were also estimated. The provincial CH4 emissions increased gradually from 2003 to 2012, up to 2993.26 Gg with an annual increase rate of 2.85%; the emissions were 2740.63 in 2020. The emissions of CH4 in Harbin, Daqing, Jiamusi, and Hegang cities were higher than in the other nine cities, which were 337.23 Gg, 330.01 Gg, 328.55 Gg, and 307.42 Gg in 2020, respectively. Agriculture, including the rice cultivation, livestock, and biomass burning sectors contributed to 51.24–62.12% of total emissions, and the contributions increased gradually. Coal mining, oil and gas exploration, and fossil fuel combustion are energy-related sources, which contributed up to 37.91% of the total emissions, and the proportion kept decreasing to 23.87% in 2020. Furthermore, meteorological factors are especially relevant to the region, by which the differences of ambient temperature are over 60 °C (±30 °C). In the summer, CH4 emissions from the rice cultivation, biomass burning, livestock, and landfill sectors are obviously distinct from the heating period (winter), while few differences in CH4 emissions are found from wastewater disposal and the fossil fuel production sectors. [ABSTRACT FROM AUTHOR]

Agricultural waste can have a catastrophic impact on climate change, as it contributes significantly to greenhouse gas (GHG) emissions if not managed sustainably. Swine-digestate-manure-derived biochar may be one sustainable way to manage waste and tackle GHG emissions in temperate climatic conditions. The purpose of this study was to ascertain how such biochar could be used to reduce soil GHG emissions. Spring barley (Hordeum vulgare L.) and pea crops in 2020 and 2021, respectively, were treated with 25 t ha−1 of swine-digestate-manure-derived biochar (B1) and 120 kg ha−1 (N1) and 160 kg ha−1 (N2) of synthetic nitrogen fertilizer (ammonium nitrate). Biochar with or without nitrogen fertilizer substantially lowered GHG emissions compared to the control treatment (without any treatment) or treatments without biochar application. Carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions were directly measured using static chamber technology. Cumulative emissions and global warming potential (GWP) followed the same trend and were significantly lowered in biochar-treated soils. The influences of soil and environmental parameters on GHG emissions were, therefore, investigated. A positive correlation was found between both moisture and temperature and GHG emissions. Thus, biochar made from swine digestate manure may be an effective organic amendment to reduce GHG emissions and address climate change challenges. [ABSTRACT FROM AUTHOR]

Crop straw and N fertilizer applications impact paddy rice yield and greenhouse gas (GHG) emissions. However, their interactive effects have not been well documented. This study investigated the effects of straw (S), no straw incorporation (NS), and three levels of N fertilization rates (N0, N1, and N2) on single rice (SR), double rice (DR), and rice-wheat (RW) cropping systems. Straw incorporation significantly increased total CH4 emissions by 118.6%, 8.0%, and 79.0% in the SR, DR, and RW, respectively, compared to the NS. The total GHG emissions in DR are significantly 72.6% and 83.5% higher than those in RW and SR, respectively. Compared to NS, straw incorporation significantly increased yield-scaled emissions by 27.8%, 15.0%, and 89.0% in SR, DR, and RW, respectively. Straw with N application significantly increased average rice yield over N1 and N2 by 39.4%, 50.0%, and 6.7% in SR, DR, and RW, respectively. There was a significant correlation between methyl coenzyme M reductase (mcrA) and CH4 emissions in rSR = 0.87 (p < 0.05) and rRW = 0.85 (p < 0.05), except in rDR = 0.06 (p > 0.05). This study scientifically supports straw incorporation combined with a moderate N application rate in rice-based cropping systems to maintain high rice yields and mitigate GHG emissions.

More than half of the world’s rivers experience occasional, seasonal, or permanent drying, and this may increase because of climate change. Drying, i.e. severe reduction in water flow even leading to streambed desiccation, can have a profound impact on the available aquatic habitat, biodiversity, and functions of rivers. Yet, to date, it is unclear whether similar drying events in comparable climate zones result in similar changes in ecosystem processes, such as river metabolism or greenhouse gas (GHG) emissions. Here, we synthesise the detected effects of drying on gross primary production (GPP) and ecosystem respiration (ER), as well as on the emissions of GHGs (CO _2 , CH _4 , and N _2 O) in rivers and streams. We examined the current available scientific literature detailing the impact of drying on these variables when measured either in the field or in the laboratory. We extracted data from 30 studies analysing GPP and ER responses, and data on GHG emissions from another 35 studies. Then, we conducted a meta-analysis to determine whether the magnitude and direction of the effects varied across the systems and climate zones studied, or according to the type (natural or human-induced) and severity of drying. In general, drying enhanced GPP (under low flows) and CH _4 emissions, and decreased CO _2 and N _2 O emissions. The hydrological phases throughout streambed drying (low water flow, isolated pools, or desiccation) had differential effects on metabolism and GHG emissions. The effects of drying were generally more severe when it induced desiccation, rather than just periods of low flow. Desiccation strongly reduced GPP, likely because of the die-off of algae, while its negative effect on ER was smaller. Greater decrease in GPP than in ER under desiccation would lead to increase in CO _2 emissions; our results showed accordingly that desiccation increased CO _2 emissions. Furthermore, the magnitude and direction of the effects varied depending on the study type. Experimental studies conducted in micro- and mesocosms demonstrated greater effects than field studies, thus the extrapolation of results from these to real conditions should be done with caution. Overall, the effects’ direction was inconsistent across climate zones, except for the Mediterranean climate zone, where drying was showing a negative effect on both metabolism and GHG emissions. Our synthesis may contribute to identifying the worldwide trends and patterns of drying on riverine functions associated to global change impacts on river and stream ecosystems.

Global wetlands are the largest and most uncertain natural source of atmospheric methane (CH _4 ). The FLUXNET-CH _4 synthesis initiative has established a global network of flux tower infrastructure, offering valuable data products and fostering a dedicated community for the measurement and analysis of methane flux data. Existing studies using the FLUXNET-CH _4 Community Product v1.0 have provided invaluable insights into the drivers of ecosystem-to-regional spatial patterns and daily-to-decadal temporal dynamics in temperate, boreal, and Arctic climate regions. However, as the wetland CH _4 monitoring network grows, there is a critical knowledge gap about where new monitoring infrastructure ought to be located to improve understanding of the global wetland CH _4 budget. Here we address this gap with a spatial representativeness analysis at existing and hypothetical observation sites, using 16 process-based wetland biogeochemistry models and machine learning. We find that, in addition to eddy covariance monitoring sites, existing chamber sites are important complements, especially over high latitudes and the tropics. Furthermore, expanding the current monitoring network for wetland CH _4 emissions should prioritize, first, tropical and second, sub-tropical semi-arid wetland regions. Considering those new hypothetical wetland sites from tropical and semi-arid climate zones could significantly improve global estimates of wetland CH _4 emissions and reduce bias by 79% (from 76 to 16 TgCH _4 y ^−1 ), compared with using solely existing monitoring networks. Our study thus demonstrates an approach for long-term strategic expansion of flux observations.

Biochar has been suggested as a soil supplement to improve soil fertility and mitigate methane (CH4) emissions from rice farming. On the other side, the world is covered in microplastics (MPs), which are tiny pieces of degraded plastic. Studies have paid little attention to the combined biochar and soil contamination caused by MPs, particularly the mechanism of their interactions with CH4 emissions. In this study, a pot greenhouse experiment with a randomized complete block design (RCBD) was carried out to examine the impact of polystyrene (PS), sugarcane bagasse biochar (SBB), and their interaction (PS*SBB) on the CH4 emission and rice yield in a rice-cultivated paddy calcareous soil. The largest CH4 emission occurred at 30 and 70 days following rice planting, which corresponds to the tillering and heading stages of rice growth. Adding SBB to our paddy soil samples reduced CH4 emissions. Our findings showed that applying PS at different rates greatly increased CH4 emissions in our soil samples under ambient conditions. Our results showed that adding SBB can partially offset the negative effects of PS in the soil. In comparison with when PS was applied alone, the co-application of SBB and PS reduced PS's stimulation of the global warming potential (GWP) by altering its impacts on the structure and function of the soil's microbial community and the carbon and nitrogen contents of the microbial biomass. We come to the conclusion that interactions between PS and the use of SBB have an impact on GWP, microbial community activities, and CH4 emissions. Both SBB rates resulted in a considerable increase in height, biomass, and rice grain as compared to control. Our findings indicated that PS negatively impacts rice height, grain yield, and biomass and that the addition of SBB can partially counteract PS's negative effects on the rice. Further study is needed to understand how various types of MPs interact with soil amendments to affect ecosystem function. [ABSTRACT FROM AUTHOR]

[Display omitted] • Shrubification releases more CO 2 and less CH 4 in rhizosphere soil. • Shrub rhizosphere soil has higher CO 2 and lower CH 4 production genetic potential than herb rhizosphere soil. • Shrubification influences rhizosphere soil C emissions via root exudates. • Shrub root exudates stimulate the genetic potential for labile C decomposition; • Herb root exudates promote the genetic potential for the methanogenesis process. As shrubs continue to expand in peatlands due to climate change, it is critical to examine the mechanisms underlying carbon dioxide (CO 2) and methane (CH 4) emissions. While the decrease in water levels during shrub encroachment into peatlands is known to increase soil carbon emissions, the role of the genetic potential of microbial metabolic processes mediated by root exudates in affecting rhizosphere soil carbon emissions is less well understood. Here, we conducted in situ field monitoring of shrub and herb peatlands, combined with laboratory incubation experiments involving the addition of root exudates. Using metagenomics and metabolomics technologies, we aimed to elucidate the microbiological mechanisms behind changes in carbon emissions. This study found that the rhizosphere soil under shrubs had a higher CO 2 emission rate with greater genetic potential for CO 2 production (19.36%), but exhibited a lower CH 4 emission rate conferring a lower genetic potential for CH 4 production (52.30%) than that under herbs. These differences were attributed to the distinct ways in which the root exudates of shrubs and herbs influence the structure and function of the microbial community, thereby favoring CO 2 and CH 4 emissions differently. Specifically, the relatively higher amounts of sugars and amino acids in shrub root exudates stimulate the genetic potential for cellulose and hemicellulose decomposition, leading to a 13.23% increase in CO 2 emissions. In contrast, the relatively higher amounts of lipids in herb root exudates promote the genetic potential for the acetic acid-type methanogenic process, resulting in a 33.50% increase in CH 4 emissions. Shrubification increased the genetic potential for labile carbon decomposition while decreasing the genetic potential for chitin and lignin decomposition, possibly promoting recalcitrant carbon conservation in the rhizosphere soil. Altogether, shrubification of herbaceous peatlands increases rhizosphere soil carbon emissions by regulating root exudates. It is recommended that appropriate ecosystem management measures be implemented to control shrub expansion, thereby optimizing carbon emissions from peatlands. [ABSTRACT FROM AUTHOR]

Atmospheric CH4 is the second largest anthropogenic contributor to global warming, however its emissions, components, spatiotemporal variations, and projected changes present large uncertainties from city to national scales. CH4 emissions from waste treatment account for >50 % of total anthropogenic CH4 emissions at the city scale, and considering the high sensitivity of CH4 emission factors (EFs) to temperature for biological process-based sources, such as waste treatment, large bias will occur when estimating future CH4 emissions under different global warming scenarios. Furthermore, the relationships between temperature and waste treatment CH4 emissions have only been determinized in a few site-specific studies, and these findings lack representativeness for the whole city scale, which contains various biophysical conditions and shows heterogeneous distribution. These factors increase the difficulty of evaluating city-scale CH4 emissions (especially from waste treatments), and the projected changes remain unexplored. Here, we conduct the first tower-based CH4 observation network with three sites in Hangzhou city, which is located in the developed Yangtze River Delta (YRD) area and ranks as one of the largest megacities in China. We found that the a priori total annual anthropogenic CH4 emissions and waste treatment emissions were overestimated by 36.0 % and 47.1 % in Hangzhou city, respectively. However, the total emissions in the larger region of Zhejiang Province or the YRD area was only slightly underestimated by 7.0 %. Emissions from waste treatment showed obvious seasonal patterns according to the air temperature. By using the constructed linear relationship between monthly waste treatment CH4 emissions and air temperature, we found that the waste treatment EFs increased by 38 %~50 % as the temperature increased by 10 °C. Together with the projected temperature changes from four climate change scenarios, the global warming-induced EFs in Hangzhou city will increase at rates of 2.2 %, 1.2 %, 0.7 % and 0.5 % per decade for RCP8.5, RCP6.0, RCP4.5 and RCP2.6 scenarios, respectively, and by 17.6 %, 9.6 %, 5.6 %, and 4.0 % at the end of this century, respectively. Additionally, the relative changes derived for the whole of China also showed high heterogeneity and indicated large uncertainty in projecting future national total CH4 emissions. Hence, we strongly suggest the temperature-dependent EFs and positive feedback between global warming and CH4 emissions should be considered in future CH4 emission projections and climate change models. [ABSTRACT FROM AUTHOR]

Using annual time-series data from 1970 to 2016, this study attempts to examine the effects of environmental degradation on agricultural efficiency in India. Autoregressive distributed lag (ARDL), fully modified OLS (FMOLS) models are used to explore the long-run influence of environmental degradation and other control variables such as labor force, metabolic energy, fertilizer usage, and farm machinery on agricultural efficiency. Also, dynamic OLS (DOLS) and canonical cointegration regression (CCR) methods are used to validate the robustness of the estimated ARDL and FMOLS results. The Granger causality approach is used to examine causation among variables. According to ARDL and FMOLS estimates, fertiliser use, farm machinery, and metabolic energy improve India's agricultural efficiency. Agricultural methane emissions, on the other hand, reduce agricultural production. Furthermore, the DOLS and CCR approaches validate the estimated ARDL and FMOLS outcomes, indicating that the results are robust and consistent. The study suggest that the government should modernize agricultural research and seed systems and market and input diversification to help farmers. [ABSTRACT FROM AUTHOR]

Rice is the main staple food worldwide, yet paddy fields are a primary source of artificial methane (CH4) emissions. Phosphorus (P) is a key element in the growth of plants and microbes, and P fertilizer input is a conventional agricultural practice adopted to improve rice yield. However, the impact of long-term P fertilizer addition on CH4 emissions in rice paddies is still unclear. To test this impact, a 36-yr field experiment with and without P fertilizer application treatments under a double-rice cropping system was used in this study to explore how continuous P application affects CH4 emissions and related plant and soil properties. The cumulative CH4 emissions were 21.2% and 28.6% higher without P fertilizer application treatment than with P fertilizer application treatment during the early and late season, respectively. Long-term P fertilizer application increased the rice aboveground biomass by 14.7–85.1% and increased grain yield by 24.5–138.7%. However, it reduced the ratio of root biomass to aboveground biomass. Long-term P fertilizer input reduced the soil NH4+ concentrations in both rice seasons but increased the soil DOC concentrations in the late season. The soil methanogenic abundance and CH4 production potential were similar without and with P fertilizer application treatments; however, the methanotrophic abundance and soil CH4 oxidation potential with P fertilizer application treatment were significantly higher than without P fertilizer application treatment. Our findings indicate that long-term P fertilizer input reduces CH4 emissions in rice fields, mainly by improving CH4 oxidation, which highlights the need for judicious P management to increase rice yield while reducing CH4 emissions. [ABSTRACT FROM AUTHOR]

Livestock contributes approximately one‐third of global anthropogenic methane (CH4) emissions. Quantifying the spatial and temporal variations of these emissions is crucial for climate change mitigation. Although country‐level information is reported regularly through national inventories and global databases, spatially explicit quantification of century‐long dynamics of CH4 emissions from livestock has been poorly investigated. Using the Tier 2 method adopted from the 2019 Refinement to 2006 IPCC guidelines, we estimated CH4 emissions from global livestock at a spatial resolution of 0.083° (~9 km at the equator) during the period 1890–2019. We find that global CH4 emissions from livestock increased from 31.8 [26.5–37.1] (mean [minimum−maximum of 95% confidence interval) Tg CH4 yr−1 in 1890 to 131.7 [109.6–153.7] Tg CH4 yr−1 in 2019, a fourfold increase in the past 130 years. The growth in global CH4 emissions mostly occurred after 1950 and was mainly attributed to the cattle sector. Our estimate shows faster growth in livestock CH4 emissions as compared to the previous Tier 1 estimates and is ~20% higher than the estimate from FAOSTAT for the year 2019. Regionally, South Asia, Brazil, North Africa, China, the United States, Western Europe, and Equatorial Africa shared the majority of the global emissions in the 2010s. South Asia, tropical Africa, and Brazil have dominated the growth in global CH4 emissions from livestock in the recent three decades. Changes in livestock CH4 emissions were primarily associated with changes in population and national income and were also affected by the policy, diet shifts, livestock productivity improvement, and international trade. The new geospatial information on the magnitude and trends of livestock CH4 emissions identifies emission hotspots and spatial–temporal patterns, which will help to guide meaningful CH4 mitigation practices in the livestock sector at both local and global scales. [ABSTRACT FROM AUTHOR]

Rice root aerenchyma (RA) and irrigation practices influence key physiological processes in rice paddies, affecting both yield and methane (CH 4) emissions. However, the interaction between RA and irrigation practices, and its implications for CH 4 mitigation, remains unclear, making it difficult to identify rice cultivars for CH 4 mitigation purposes. Here, we conducted a series of field and pot experiments to evaluate how RA affects grain yield and CH 4 emissions under two common irrigation regimes: continuous flooding (CF) and alternate wetting and drying (AWD). Our results show that the interaction between RA and irrigation regime significantly influenced both rice yield and CH 4 emissions. Under CF, increased RA formation was associated with higher rice yield and lower CH 4 emissions across a wide range of cultivars. These results could be explained by cultivars with well-developed RA increasing root oxygen loss, thereby stimulating CH 4 oxidation and promoting N availability to support plant growth. In AWD systems, no significant differences in rice yield, methanogenesis or methanotrophy were observed between cultivars with varying RA development. However, cultivars with well-developed RA increased CH 4 emissions by 28 %−32 % compared to those with less-developed RA, likely due to enhanced CH 4 transport from anaerobic deep soil layers to the atmosphere. Consistent with these findings, CH 4 emissions under AWD decreased when we inhibited RA development through root irrigation with brassinosteroids. In conclusion, we demonstrate that AWD in paddies can reverse the impact of RA on CH 4 emissions, highlighting the need for CH 4 mitigation strategies involving cultivar selection to account for variations in irrigation practices. [Display omitted] • AWD could significantly reduce CH 4 emissions compared with CF. • Developed RA stimulates CH 4 oxidation and reduces emissions in CF. • AWD produces more CH 4 in deep soil than in surface soil. • Developed RA promotes CH 4 transport and increases CH 4 emission under AWD. • Optimal cultivars for CH 4 mitigation strongly depend on water management practices. [ABSTRACT FROM AUTHOR]

• The high water table (HWT) enhances methanotrophic α-diversity, while the low water table (LWT) elevates methanogenic α-diversity. • Methanogens are dominated by methanoregula at the LWT site, and by methanobrevibacter and Methanoregula , and methanosarcina at the HWT site. • Methanotrophs are dominated by methylosinus at the LWT site, and by Methylocystis, methylosinus and methylocapsa at the HWT site. • HWT enhances the stability and complexity of ecological networks of methanotrophs and methanogens. • Temperature-dependent methane emissions vary with water table in the sub-alpine peatland. Methanogens and methanotrophs are important in regulating the peatland carbon cycle. The influence of hydrology on microbiota in different peatlands has been globally documented; however, the hydrological impact on methane-related microbial communities and methane (CH 4) emission remains underexplored in sub-alpine peatlands. Here, seasonal methanogenic and methanotrophic communities, as well as CH 4 emission, were determined at two sites with different water table levels from the Dajiuhu peatland, the largest intact sub-alpine peatland. Methane-related microbial communities varied with water table. A higher methanogenic and lower methanotrophic α-diversity were unveiled in samples with low water table (LWT), a reverse pattern was observed in high water table (HWT). Hydrogenotrophic methanogens dominated in samples with LWT, whereas hydrogenotrophic and aceticlastic methanogens dominated with HWT. Type II methanotrophs were predominant at both sites. Samples with HWT had higher gene copy numbers of methanogens (mcrA) and methanotrophs (pmoA) than those with LWT. Along the peat profile, methanogens and type II methanotrophs were enriched in samples at the depth of 10 - 15 cm and their abundances decreased toward deeper layers. Both type Ia and Ib methanotrophs were abundant in surface samples (0 - 5 cm). The HWT co-occurrence networks of methanogen and methanotroph were more stable and complex in contrast to those in LWT. Soil temperature was an important driver of seasonal variations in CH 4 emission at the LWT sites (0.03 - 1.61 mg m−2 h−1 for bare peat and 0.06 - 4.08 mg m−2 h−1 for peat covered with Sphagnum palustre) and HWT sites (0.25 - 0.78 mg m−2 h−1 for bare peat and 0.42 - 9.60 mg m−2 h−1 for peat covered S. palustre). The water table and vegetation affected the pattern of seasonal CH 4 emission. These results provide new insights in understanding the effect of hydrology on microbial functional groups and CH 4 emission within sub-alpine peatlands. [Display omitted] [ABSTRACT FROM AUTHOR]

Distinguished features of cities influence the characteristics of CH4 emissions. A city-level emission inventory represents the characteristics of CH4 on a smaller scale, according to the special factors in each city. A city-level emission inventory was established to reveal the characteristics and source profile of CH4 emissions in the coldest province, which is a typical provincial cold region in northeast China. The dominant sources were identified for targeted cities. Rice cultivation, coal mining, oil and gas exploitation, and livestock are the dominant emission sectors. Emissions from other sectors, including wastewater disposal, biomass burning, landfill, etc. were also estimated. The provincial CH4 emissions increased gradually from 2003 to 2012, up to 2993.26 Gg with an annual increase rate of 2.85%; the emissions were 2740.63 in 2020. The emissions of CH4 in Harbin, Daqing, Jiamusi, and Hegang cities were higher than in the other nine cities, which were 337.23 Gg, 330.01 Gg, 328.55 Gg, and 307.42 Gg in 2020, respectively. Agriculture, including the rice cultivation, livestock, and biomass burning sectors contributed to 51.24–62.12% of total emissions, and the contributions increased gradually. Coal mining, oil and gas exploration, and fossil fuel combustion are energy-related sources, which contributed up to 37.91% of the total emissions, and the proportion kept decreasing to 23.87% in 2020. Furthermore, meteorological factors are especially relevant to the region, by which the differences of ambient temperature are over 60 °C (±30 °C). In the summer, CH4 emissions from the rice cultivation, biomass burning, livestock, and landfill sectors are obviously distinct from the heating period (winter), while few differences in CH4 emissions are found from wastewater disposal and the fossil fuel production sectors.

Purpose: Nitrogen (N) fertilizer could promote rice root growth and alter methane (CH4) emissions in paddy fields. This study investigated the mechanism of different N application rates and timing affecting CH4 emissions, focusing on the interactions between rice root growth, soil properties, and CH4-related microbes in the rhizosphere. Methods: N fertilizer was applied only as basal and tillering fertilizer (BF) in 2016–2017 and applied as panicle fertilizer (PF) as top-dressing in 2018–2019. A validation experiment was conducted in 2020 to compare the soil chemical properties and CH4 production and oxidation in rhizosphere soil with those in soil with root effects eliminated by removing rice aboveground parts. Results: Based on the local high-yielding BF rate, applying PF had a more significant effect on CH4 mitigation than increasing BF application rate. PF notably increased the rice root biomass, carbon substrates in root exudate (including organic acids) during rice reproductive growth phase (RGP), and the dissolved organic carbon and dissolved oxygen concentration in rhizosphere soil, simultaneously promoting the abundance and potential activities of methanogens and methanotrophs. A mantel test and the validation experiment confirmed that the increase of CH4 oxidation activity and a high ratio of methanotrophs to methanogens in rhizosphere soil driven by rice root was the main reason for CH4 mitigation after N application. Conclusion: An appropriate PF rate can stimulate rice root growth, root exudation, and oxygen secretion, increasing the CH4 oxidation in rhizosphere soil that contributes significantly to the CH4 mitigation in paddy fields. [ABSTRACT FROM AUTHOR]

Summary: Forty percentage of UK peatlands have been drained for agricultural use, which has caused serious peat wastage and associated greenhouse gas emissions (carbon dioxide (CO2) and methane (CH4)). In this study, we evaluated potential trade‐offs between water‐table management practices for minimizing peat wastage and greenhouse gas emissions, while seeking to sustain romaine lettuce production: one of the most economically relevant crop in the East Anglian Fenlands. In a controlled environment experiment, we measured lettuce yield, CO2, CH4 fluxes and dissolved organic carbon (DOC) released from an agricultural fen soil at two temperatures (ambient and +2°C) and three water‐table levels (−30 cm, −40 cm and −50 cm below the surface). We showed that increasing the water table from the currently used field level of −50 cm to −40 cm and −30 cm reduced CO2 emissions, did not affect CH4 fluxes, but significantly reduced yield and increased DOC leaching. Warming of 2°C increased both lettuce yield (fresh leaf biomass) and peat decomposition through the loss of carbon as CO2 and DOC. However, there was no difference in the dry leaf biomass between the intermediate (−40 cm) and the low (−50 cm) water table, suggesting that romaine lettuce grown at this higher water level should have similar energetic value as the crop cultivated at −50 cm, representing a possible compromise to decrease peat oxidation and maintain agricultural production. [ABSTRACT FROM AUTHOR]

Context: East Asia is a crucial region in the global methane (CH4) budget, with significant contributions from the livestock sector. However, the long-term trend and spatial pattern of CH4 emissions from livestock in this region have not been fully assessed.Methods: Here, we estimate CH4 emissions from 10 categories of livestock in East Asia during 1961 – 2019 following the Tier 2 approaches suggested by the 2019 Refinement to the IPCC 2006 Guidelines.Results: livestock-sourced CH4 emission in 2019 was 13.22 [11.42 – 15.01] (mean [minimum%maximum of 95– confidence interval] Tg CH4 yr-1, accounting for an increase of 231% since 1961. The contribution of slaughtered populations to total emissions increased from 3% in 1961 to 24% in 2019. Spatially, the emission hotspots were mostly distributed in eastern China, South Korea, and parts of Japan, but they tend to shift northward after 2000.Conclusion: It is necessary to use dynamic emission factors and include slaughtered populations in the estimation of livestock CH4 emissions. Regions including Northern China, Mongolia, and South Korea deserve more attention in future CH4 mitigation efforts. [ABSTRACT FROM AUTHOR]

Agricultural waste can have a catastrophic impact on climate change, as it contributes significantly to greenhouse gas (GHG) emissions if not managed sustainably. Swine-digestate-manure-derived biochar may be one sustainable way to manage waste and tackle GHG emissions in temperate climatic conditions. The purpose of this study was to ascertain how such biochar could be used to reduce soil GHG emissions. Spring barley (Hordeum vulgare L.) and pea crops in 2020 and 2021, respectively, were treated with 25 t ha−1 of swine-digestate-manure-derived biochar (B1) and 120 kg ha−1 (N1) and 160 kg ha−1 (N2) of synthetic nitrogen fertilizer (ammonium nitrate). Biochar with or without nitrogen fertilizer substantially lowered GHG emissions compared to the control treatment (without any treatment) or treatments without biochar application. Carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions were directly measured using static chamber technology. Cumulative emissions and global warming potential (GWP) followed the same trend and were significantly lowered in biochar-treated soils. The influences of soil and environmental parameters on GHG emissions were, therefore, investigated. A positive correlation was found between both moisture and temperature and GHG emissions. Thus, biochar made from swine digestate manure may be an effective organic amendment to reduce GHG emissions and address climate change challenges.

In recent years, the global trade in liquefied natural gas (LNG) has experienced significant growth, leading to a rise in the effect of embodied methane (CH _4 ) emissions between economies. This study investigates the spatiotemporal evolution of these CH _4 emissions embodied within the global LNG trade and examines the associated network characteristics between the years 2011 and 2021. The findings reveal a substantial increase of 43.3% CH _4 emissions embodied in global LNG trade, reaching a peak of 2.75 Tg in 2021, which equates to a monetary value exceeding 5 billion USD in terms of natural gas. Over the study period, these emissions aggregated to a total of 1987.92 Mt CO _2 -eq and 718.06 Mt CO _2 -eq, based on the respective global warming potential values over 20 year and 100 year timeframes. Our investigation of this complex network reveals the emergence of multiple robust hub economies, which have exerted significant influence over the dynamics of supply-demand in embodied CH _4 trade, as well as the structure of trade communities. Notably, the Asia-Pacific trading community has exhibited exceptional growth and prominence in this market. Such growth is directly related to an increase in embodied CH _4 emissions and their overall standing within this community’s network. The US has steadily attained dominance within an export-oriented community, which encompasses economies in South and North America, as well as certain regions of Europe. Moreover, the redistribution of LNG-related CH _4 emissions among economies is significantly impacted by the intensity of production emissions and the volume of LNG trade. This reveals the potential of these hub economies to drive substantial reductions in CH _4 emissions by implementing targeted energy and climate policies, which they have launched. Reinforcing coalitions and fostering closer collaboration within these communities can provide a robust foundation for technological advancements and transformative changes in trade structures.

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Developed regions of the world represent a major atmospheric methane (CH4) source, but these regional emissions remain poorly constrained. The Yangtze River Delta (YRD) region of China is densely populated (about 16% of China's total population) and consists of large anthropogenic and natural CH4 sources. Here, atmospheric CH4 concentrations measured at a 70-m tall tower in the YRD are combined with a scale factor Bayesian inverse (SFBI) modeling approach to constrain seasonal variations in CH4 emissions. Results indicate that in 2018 agricultural soils (AGS, rice production) were the main driver of seasonal variability in atmospheric CH4 concentration. There was an underestimation of emissions from AGS in the a priori inventories (EDGAR—Emissions Database for Global Atmospheric Research v432 or v50), especially during the growing seasons. Posteriori CH4 emissions from AGS accounted for 39% (4.58 Tg, EDGAR v432) to 47% (5.21 Tg, EDGAR v50) of the total CH4 emissions. The posteriori natural emissions (including wetlands and water bodies) were 1.21 Tg and 1.06 Tg, accounting for 10.1% (EDGAR v432) and 9.5% (EDGAR v50) of total emissions in the YRD in 2018. Results show that the dominant factor for seasonal variations in atmospheric concentration in the YRD was AGS, followed by natural sources. In summer, AGS contributed 42% (EDGAR v432) to 64% (EDGAR v50) of the CH4 concentration enhancement while natural sources only contributed about 10% (EDGAR v50) to 15% (EDGAR v432). In addition, the newer version of the EDGAR product (EDGAR v50) provided more reasonable seasonal distribution of CH4 emissions from rice cultivation than the old version (EDGAR v432). [ABSTRACT FROM AUTHOR]

Municipal solid waste (MSW) landfills are the third largest source of anthropogenic methane (CH4) emission. Evaluating the CH4 emission and energy generation potential of MSW landfills facilitates the development of appropriate measures for mitigation and recovery of CH4. This study evaluated the CH4 generation, CH4 emissions and potential energy generation capacity of Jiangcungou MSW landfill, Xi'an, China, during its operation and closure period using three inventory models, including the IPCC default method (DM), IPCC first‐order decay (FOD), and US EPA Landfill Gas Emissions Mode (LandGEM). Based on the DM, FOD and LandGEM models, the total estimated CH4 emissions in 1994–2060 were 755.0, 348.9, and 344.9 Gg, respectively. There is a huge potential for electricity generation after the closure of the landfill, and the potential energy generation for 2020 was 688.3 MkW h and 599.7 MkW h. However, the actual electricity generation ranged from 12.4% to 74.1% and 14.2% to 61.8% of the potential electricity generation during the operation period (2004–2017) for the FOD and LandGEM methods, respectively. Improving the efficiency associated with LFG collection and gas engine from the landfill after closure can be an effective measure to mitigate greenhouse effects and increase investment payments. [ABSTRACT FROM AUTHOR]

Rice is the main staple food worldwide, yet paddy fields are a primary source of artificial methane (CH4) emissions. Phosphorus (P) is a key element in the growth of plants and microbes, and P fertilizer input is a conventional agricultural practice adopted to improve rice yield. However, the impact of long-term P fertilizer addition on CH4 emissions in rice paddies is still unclear. To test this impact, a 36-yr field experiment with and without P fertilizer application treatments under a double-rice cropping system was used in this study to explore how continuous P application affects CH4 emissions and related plant and soil properties. The cumulative CH4 emissions were 21.2% and 28.6% higher without P fertilizer application treatment than with P fertilizer application treatment during the early and late season, respectively. Long-term P fertilizer application increased the rice aboveground biomass by 14.7–85.1% and increased grain yield by 24.5–138.7%. However, it reduced the ratio of root biomass to aboveground biomass. Long-term P fertilizer input reduced the soil NH4+ concentrations in both rice seasons but increased the soil DOC concentrations in the late season. The soil methanogenic abundance and CH4 production potential were similar without and with P fertilizer application treatments; however, the methanotrophic abundance and soil CH4 oxidation potential with P fertilizer application treatment were significantly higher than without P fertilizer application treatment. Our findings indicate that long-term P fertilizer input reduces CH4 emissions in rice fields, mainly by improving CH4 oxidation, which highlights the need for judicious P management to increase rice yield while reducing CH4 emissions.

We present a Pt/ZrO2 catalyst that can operate in the harsh conditions of methane oxidation without being deactivated by SO2. XPS analysis of 1%Pt/ZrO2 catalyst revealed the presence of stable Pt2+–Pt4+ and Pt2+–Zr4+ bifunctional catalytic sites of dipolar nature at the Pt–ZrO2 interface. These sites increase the probability of CH4 polarization, increasing the strength of their collision with the catalyst surface, lowering the C–H bond energy and facilitating the abstraction of the first hydrogen in adsorbed CH4. The resistance of the catalyst to deactivation by sulfur poisoning is explained considering the stronger interaction of SO2 with Pt2+–Zr4+ dipolar sites, presenting a higher dipolar electric potential than Pt2+–Pt4+, on which CH4 adsorption and oxidation occur. [ABSTRACT FROM AUTHOR]

This study examines the link between environmental indicators and output volatility unlike the previous literature that mainly emphasized the importance of carbon emissions and economic growth nexus. Output uncertainty is considered a serious global issue as it undermines economic gains and quality of life. This study scrutinizes the impact of greenhouse gas emissions on output volatility in 155 countries over the period 1971- 2017. The empirical analysis is based on Pooled Ordinary Least Squares, Random and Fixed Effects Models. The empirical results confirm that carbon dioxide (CO2), nitrogen oxide (NOX), methane (CH4), and total greenhouse gas (GHG) emissions are positively contributing to amplify global output volatility. Moreover, the Principal Component Analysis (PCA) of pollutant indicators also confirms the main results. Comparatively carbon emissions are contributing more to augment output volatility. A comparative analysis also reveals that all pollutants augment output volatility more in agricultural economies. The results of Granger causality confirm the bidirectional causality between environmental degradation and output volatility providing an evidence of endogeneity problem. To address it, the system GMM estimator is used by incorporating the instruments in output volatility model and the results of system GMM are also consistent with main findings. Findings of the study imply that a promising path of sustainable growth can be achieved by adopting the alternative ways of energy resources that produce less pollutant relative to greenhouse gasses.

Abstract We quantify the impact of atmospheric transport and limited marine boundary layer sampling on changes in global and regional methane burdens estimate using tracer transport model simulations with annually repeating methane emissions and sinks but varying atmospheric transport patterns. We find the 1σ error due to this transport and sampling effect on annual global methane increases to be 1.11 ppb/year and on zonal growth rates to be 3.8 ppb/year, indicating that it becomes more critical at smaller spatiotemporal scales. We also find that the trends in inter‐hemispheric and inter‐polar difference of methane are significantly influenced by the effect. Contrary to a negligible trend in the inter‐hemispheric difference of measurements, we find, after adjusting for the transport and sampling, a trend of 0.37 ± 0.06 ppb/year. This is consistent with the emission trend from a 3‐D inversion of the measurements, suggesting a faster increase in emissions in the Northern Hemisphere than in the Southern Hemisphere.

East Asia is a crucial region in the global methane (CH4) budget, with significant contributions from the livestock sector. However, the long-term trend and spatial pattern of CH4 emissions from livestock in this region have not been fully assessed. Here, we estimate CH4 emissions from 10 categories of livestock in East Asia during 1961−2019 following the Tier 2 approaches suggested by IPCC (2019). Our results show that livestock-sourced CH4 emission in 2019 was 13.22 [11.42−15.01] (mean [minimum−maximum of 95% confidence interval] Tg CH4 yr-1, accounting for an increase of 231% since 1961. From 1961 to 2019, the emissions increased first and then stabilized after 2000. The contribution of slaughtered livestock to total emissions increased from 3% in 1961 to 24% in 2019 as a result of a significant increase in the slaughtered population. Spatially, the emission hotspots were mostly distributed in eastern China, South Korea, and parts of Japan, but they tend to shift northward after 2000. This latest long-term inventory can help to understand CH4 budget and to assess CH4 mitigation potential at national and regional levels.

Methane (CH4) is a greenhouse gas with a warming potential 28 times that of dioxide of carbon (CO2) and Africa alone contributes more than 1/3 of global methane emissions. Considering the fact that Africa has the second largest hydro-forest basin in the world after the Amazon and is highly dependent on agriculture, this study examines the effects of economic growth on environmental quality in an Environmental Kuznets curve (EKC) framework. It empirically tests the relationship between CH4 emissions and GDP per capita (GDPC) for six countries of Central African Economic and Monetary Community (CEMAC) over the period 1980 to 2018. Using the Driscoll-Kraay standard errors technique as well as panel Granger non-causality test, the results point out cointegration between CH4 emissions and GDPC, show that there is bidirectional causality between the two variables and support evidence of EKC hypothesis. Policymakers should strengthen sustainable strategies for growth and environment. [ABSTRACT FROM AUTHOR]

The practice of co‐incorporating rice straw and leguminous green manure (such as Chinese milk vetch) into paddy soils has become increasingly popular in the last 10 years, although its effect on soil CH4 emissions and microbial community structure is poorly understood. In this study, data from a 2‐year pot experiment were used to reveal the effects of the co‐incorporation of rice straw and Chinese milk vetch on CH4 emissions and methanogenic and methanotrophic communities in paddy soil. Five treatments were chosen: CK (unamended control), CF (inorganic fertilizer), FM (inorganic fertilizer and Chinese milk vetch, 20 g 10 kg−1 dry soil, 4.5 t ha−1), FR (inorganic fertilizer and rice straw, 20 g 10 kg−1 dry soil, 4.5 t ha−1) and FMR (inorganic fertilizer and Chinese milk vetch and rice straw mixture, 5 + 15 g 10 kg−1 dry soil, 1.125 + 2.375 t ha−1). Overall, the soil CH4 emissions in the 2 years under all residue treatments (104.4–122.8 and 83.3–133.3 g CH4 m−2) were higher than those in CK (57.0 and 20.7 g CH4 m−2) and CF (71.8 and 21.9 g CH4 m−2) treatments. The FMR treatment decreased CH4 emissions when compared with FM and FR, especially in the second year. A higher abundance of methanogens (mcrA gene copies) was found under the plant residue‐treated soils (4.35 × 108 g−1 dry soil on average) and FM increased the abundance of methanotrophs (pmoA gene copies, 2.68 × 106 g−1 dry soil). Application of plant residues changed the methanogenic and methanotrophic community structures in comparison with CF (e.g., markedly increased the populations of Methanobacteriales and Methylomonas and suppressed Methanomicrobiales and Methylobacter populations). Methane emissions were significantly and positively related to the mcrA and pmoA gene copy numbers, as well as the mcrA/pmoA ratio. The partial least squares path model (PLS‐PM) indicated that the rice plant biomass (path coefficient = 0.64), the abundance of methanogens (path coefficient = 0.57) and the community structure of methanotrophs (path coefficient = −0.59) were determinants of CH4 emissions. Among the three residue‐treated soils, FMR showed the lowest CH4 emissions and was associated with a slight decrease in the mcrA/pmoA ratio and a significant increase in the Type I/Type II methanotrophs ratio. Thus, we recommend the co‐incorporation of Chinese milk vetch and rice straw as a sustainable fertilization pattern to improve the growth of rice and minimize CH4 emissions. Highlights: Residue application improves rice productivity (except for FR), soil fertility and CH4 emissions.Co‐incorporation of MV and RS reduces CH4 emissions in comparison with pure MV or RS addition.Residue application changes the community structure of methanogens and methanotrophs.The methanogenic abundance and the methanotrophic community structure determine the CH4 emissions. [ABSTRACT FROM AUTHOR]

The use of sugarcane straw is a promising option to enhance bioenergy production. But the implications of straw removal for soil greenhouse gas (GHG) emission are not yet fully understood due to scarcity of studies under Brazilian conditions. Four field experiments were designed to assess soil N2O and CH4 emissions derived from nitrogen (N) fertilization under scenarios of sugarcane straw removal in São Paulo state, Brazil. Our focus was also to derive the direct N2O emission factor (EF) that represents the regional conditions of sugarcane production, taking into account the data obtained from this study and those from the literature. In each field study, four straw removal rates (no removal (NR); low removal (LR)—removal of 5 Mg ha−1; high removal (HR)—removal of 10 Mg ha−1; and total removal (TR)—removal of 15 Mg ha−1) were arranged in a randomized block design. This study shows a clear evidence that CH4 fluxes are very low for all assessed sites regardless of straw removal rates, indicating a predominance of CH4 consumption by the soil. Cumulative N2O emissions ranged from 0.20 to 4.09 kg ha−1 year−1 and were significantly affected by straw removal in two sites, indicating that straw removal reduces N2O emissions. The average direct N2O EFs obtained from this study and from the literature were 0.28, 0.44, 0.70, and 0.56% for TR, HR, LR, and NR treatments, respectively, which are consistently lower than the EF of 1% suggested by the IPCC. Based on our regional-specific EF (Tier 2), the direct N2O emissions derived from N fertilization under scenarios of straw removal showed a reduction of at least 50% in relation to IPCC approach. Our findings are a step forward in providing regional-specific data to reduce the high level of uncertainty concerning N2O emission assessments of sugarcane ethanol in Brazil, but further studies are needed to evaluate how straw removal for bioenergy production and the associated changes in soil organic carbon stocks affect the GHG balance of sugarcane. [ABSTRACT FROM AUTHOR]

Background and aims: Urea is widely used in rice farming systems to improve the nitrogen (N) availability and crop yield, yet its influence on CH4 emissions remains unclear. The present study aimed to identify the potential microbial mechanisms resulting in the N fertilizer-induced effects on CH4 emissions from paddies. Method: A field experiment was conducted with (N1, 100 kg N ha−1) and without (N0) N fertilization. CH4 emission rate was measured every 3–7 day using the static chamber-gas chromatography method. Quantitative PCR (qPCR) and Illumina MiSeq sequencing approaches were employed to investigate the community composition and structure of methanogenic archaea and methanotrophic bacteria in rice rhizosphere soil at three time points (tillering stage 17d, heading stage 47d and mature stage 67 d). Results: Urea application significantly stimulated the CH4 emissions from paddies, partially due to the decrease of redox potential (Eh) around the root region and the reduction of dissolved oxygen (DO) concentration at the soil-water interface. qPCR indicated a sharp increase in methanogenic archaeal 16S rRNA and methanotrophic bacterial pmoA gene copies with urea fertilization. Next-generation sequencing of these amplicons revealed that the diversity of both methanogenic and methanotrophic communities was decreased by urea input. Additionally, urea fertilization stimulated the genera Methanoregula (methanogen) and Methylococcus (type I methanotrophs) and inhibited the genus Methylocystis (type II methanotrophs). Conclusions: Urea fertilization changed oxygen state of the paddy soil and water and thus changed the community structure of methanogens and methanotrophs, which resulted in increased CH4 emissions. [ABSTRACT FROM AUTHOR]