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To address the climate change caused by anthropogenic emissions of greenhouse gases into the atmosphere, it is essential to understand and quantitatively elucidate their cycling on the Earth's surface. This paper first presents an overview of the global cycling of three greenhouse gases, carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O), followed by a description of their variations in the atmosphere. This paper then presents the recent global budgets of these greenhouse gases estimated using two different approaches, top-down and bottom-up. Discussions on our current knowledge regarding the global cycling of the three gases are also presented.

Key long-lived greenhouse gases (CO2, CH4, and N2O) are perhaps among the best-studied components of the Earth's atmosphere today; however, attempts to predict or explain trends or even shorter-term variations of these trace gases are not always successful. Infrared spectroscopy is a recognized technique for the ground-based long-term monitoring of the gaseous composition of the atmosphere. The current paper is focused on the analysis of new data on CO2, CH4, and N2O total columns (TCs) retrieved from high resolution IR solar spectra acquired during 2009–2022 at the NDACC atmospheric monitoring station of St. Petersburg State University (STP station, 59.88°N, 29.83°E, 20 m asl.). The paper provides information on the FTIR system (Fourier-transform infrared) installed at the STP station, and an overview of techniques used for the CO2, CH4, and N2O retrievals. Trends of key greenhouse gases and their confidence levels were evaluated using an original approach which combines the Lomb–Scargle method with the cross-validation and bootstrapping techniques. As a result, the following fourteen-year (2009–2022) trends of TCs have been revealed: (0.56 ± 0.01) % yr−1 for CO2; (0.46 ± 0.02) % yr−1 for CH4; (0.28 ± 0.01) % yr−1 for N2O. A comparison with trends based on the EMAC numerical modeling data was carried out. The trends of greenhouse gases observed at the STP site are consistent with the results of the in situ monitoring performed at the same geographical location, and with the independent estimates of the global volume mixing ratio growth rates obtained by the GAW network and the NOAA Global Monitoring Laboratory. There is reasonable agreement between the CH4 and N2O TC trends for 2009–2019, which have been derived from FTIR measurements at three locations: the STP site, Izaña Observatory and the University of Toronto Atmospheric Observatory. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) is the third important long‐lived greenhouse gas next to carbon dioxide and methane and croplands are considered biogeochemical hotspots of soil N2O emissions. To reduce soil N2O and other greenhouse emissions, climate‐smart agricultural practices including biochar application have been applied. Many studies have been conducted with biochar application but results from these studies are not conclusive. To address this issue, meta‐analysis, a quantitative review that synthesizes results from multiple independent studies, has been widely used. The results from different meta‐analyses also differ but are seldomly evaluated. In this study, we evaluated meta‐analyses on the effects of biochar application on soil N2O emissions. A grand mean response ratio (RR) was further proposed to estimate an overall effect and the impacts of experiment setting, properties of biochar and soil, and agricultural practices. We found 18 meta‐analysis papers were published between 2014 and 2022. Sample size (publications or experiments) varied from less than 30 to more than 1000, with a mean sample size of 275. RR was calculated in all studies except one. While four meta‐analyses did not find a significant effect of biochar application on soil N2O emissions, all others reported reductions of soil N2O emissions, but the magnitude ranged from −10.5% to −54.8%. Synthesizing all results from these meta‐analyses, we found that biochar application overall significantly reduced the soil N2O emissions by 38.8%. The impacts increased with experimental duration till one and half years and reduced after that. Biochar application rate and C:N ratio had large influence on the effects of biochar application on soil N2O emissions. This study demonstrated that while meta‐analysis provides a more comprehensive and better estimation, the inconsistence among these studies may need to be further evaluated. A grand mean RR based on meta‐analyses could be more accurate and representative than single meta‐analysis. [ABSTRACT FROM AUTHOR]

The Congo basin is home to the second-largest tropical forest in the world. Therefore, it plays a crucial role in the regional water cycle, the global carbon cycle and the continental greenhouse gas balance. Yet very few field-based data on related processes exist. In the wake of global change, there is a need for a better understanding of the current and future response of the forest biome in this region. A new long-term effort has been set up to measure the exchange of greenhouse gasses between a humid lowland tropical forest in the Congo basin and the atmosphere via an eddy-covariance (EC) tower. Eddy-covariance research stations have been used for decades already in natural and man-made ecosystems around the globe, but the natural ecosystems of Central Africa remained a blind spot. The so-called "CongoFlux" research site has been installed right in the heart of the Congo Basin, at the Yangambi research center in DR Congo. This introductory paper presents an elaborated description of this new greenhouse gas research infrastructure; the first of its kind in the second-largest tropical forest on Earth. [ABSTRACT FROM AUTHOR]

This paper investigates the relationship between greenhouse gas emissions, energy consumption, and output growth among African OPEC countries (Libya, Nigeria, Angola, Algeria, Equatorial Guinea, and Gabon) using the panel autoregressive distributed lag model (PARDL) estimated by means of mean group (MG) and pooled mean group (PMG) for the period 1970–2016. The paper estimated three panel models comprising the components of greenhouse gasses which includes nitrous oxide, carbon dioxide (CO2), and methane and examined their relationship with economic growth and energy consumption. The findings of the study showed evidence of a positive impact of economic growth on both CO2 and methane emissions in the long run. Its impact on nitrous oxide emissions although positive was found to be statistically insignificant. Energy consumption was also found to produce an insignificant positive impact on CO2, methane, and nitrous oxide emissions in the long run. In the short run, economic growth exerts a significant positive effect on methane emissions; however, its effect on CO2 and nitrous oxide emissions although positive was found to be statistically insignificant. Energy consumption produces an insignificant impact on all components of greenhouse gasses in the short run. In addition, our empirical results showed the presence of a non-linear relationship between methane emissions and economic growth, confirming the existence of the environmental Kuznets curve (EKC) only in the case of methane emissions model. [ABSTRACT FROM AUTHOR]

It is widely acknowledged that greenhouse gases (GHG) like carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) play a key role in the development of global climate change. 17% of China's GHG came from the agricultural industry. For China's future development, it is essential to investigate low-carbon emission paths in planting fields, as one of the key components of agriculture. In this study, the IPCC method was used to estimate the total carbon emission from cultivation in Eastern China. The Tapio decoupling model was used to study the relationship between economic growth and carbon emission. An extended STIRPAT stimulus model was established to predict the carbon emission of the planting industry in East China with three development paths. The results show that carbon emission in East China has shown a fluctuating downward trend with a peak in 1999, which has strong decoupling characteristics with economic growth. Adjusting agricultural structure and raising the mechanization rate can remarkably reduce agricultural carbon emission. Compared to 2020, carbon emission in 2035 will decrease by 12.50%, 13.68%, and 14.32% with Baseline, Low-carbon, and Enhanced Low-carbon scenarios, respectively. Effective measures such as optimizing planting structure by adjusting rice area, promoting intensive mechanization, and improving fertilizer use efficiency can reduce carbon emission actively. [ABSTRACT FROM AUTHOR]

Agriculture has become an important source of greenhouse gas emissions. This paper calculates the agricultural GHGs emissions of 30 provinces in China from 1997 to 2016, and analyzes the emission intensity of GDP of carbon dioxide, methane and nitrous oxide by club convergence. After using the DEA CCR model to divide the club, the absolute β-convergence analysis method is used to verify the emission trends of various greenhouse gases. The results showed that the carbon dioxide emission intensity showed obvious absolute β convergence in all three clubs. Methane and nitrous oxide only have absolute β convergence in one of the clubs, respectively, and there is divergence in other clubs. Since the emission trends of the three greenhouse gases in the clubs are different, the formulation of reasonable reduction target allocation plan should be more detailed and targeted, and more stringent emission reduction targets should be set for provinces with high GHGs intensity of GDP in order to reduce it rapidly. [ABSTRACT FROM AUTHOR]

There are many types of methods for monitoring atmospheric greenhouse gases, and the differences between the methods have introduced many uncertainties for the accurate monitoring of atmospheric greenhouse gases. In this paper, the monitoring methods of 7 long-lived greenhouse gases (LLGHG), including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6) and nitrogen trifluoride (NF3), which are regulated and controlled in the Kyoto Protocol and the Doha Amendment, were summarized, and the principle, characteristics and application research progress of each method were systematically studied. Besides, their application scope was analyzed, and the domestication research of relevant instruments was analyzed and prospected. At present, the monitoring methods of atmospheric greenhouse gases are developing towards automation and multi-component simultaneous rapid detection, and are accelerating its integration with new technologies such as big data and satellite remote sensing monitoring; top-down and bottom-up methods are used to provide strong data support for carbon peaking and carbon neutral management decisions in various countries. [ABSTRACT FROM AUTHOR]

Global climate change, especially global warming, has caused widespread concern in the international community. Increasing concentrations of greenhouse gases, such as carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) produced by human activities, are the main cause of global warming. According to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), agriculture is an important source of greenhouse gas emissions, so reduction of such emissions is of great significance to global climate change. There are many driving factors affecting agricultural greenhouse gas emissions. These factors are interrelated and interact with each other, so the mechanism of action is complicated. In this paper, first, the driving factors of agricultural greenhouse gas emissions and emission sources are introduced. Second, the factors influencing agricultural greenhouse gas emissions are analyzed and summarized. Third, to clarify the factors influencing agricultural greenhouse gas emissions, measures and countermeasures for reducing greenhouse gas emission are proposed, discussed, and compared. Finally, action mechanisms, action pathways, and long‐term reduction measures for agricultural greenhouse gases are described. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Constructed wetlands (CWs) are natural-like systems for wastewater treatment capable to remove both pollutants and nutrients without additional energy demand. In these systems, gaseous compounds are released into the atmosphere through microbial processes. Among these gases carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) are the most dangerous because they act as greenhouse gases (GHGs) and are well known as contributory factors to cause global warming. In this paper we reviewed 224 scientific articles (from 1980 to 2016) from the literature in order to analyze the most important factors that drive the quantity and type of GHGs production and emission from different CWs systems. Wastewater flow and composition, hydroperiod, environmental conditions and plant presence and species used to vegetate CWs have been considered. CWs typologies influence GHGs fluxes with lower CH 4 emissions from subsurface flow CWs than free water surface (FWS) ones and higher N 2 O emissions from vertical subsurface flow (VSSF) CWs than FWS ones. The inlet wastewater COD/N ratio of 5:1 has been found as the best ratio to obtain in the same time the lowest N 2 O emission and the highest nitrogen removal in FWS CWs. The inlet wastewater C/N ratio of 5:1 allows to obtain the lowest CO 2 and CH 4 emissions in VSSF CW treatment. Intermittent CWs bed wastewater loading decreases CH 4 and promote CO 2 and N 2 O emissions. Temperature is positively correlated with CO 2 , CH 4 and N 2 O emissions and solar radiation with CO 2 and CH 4 emissions. GHGs flux is affected by plant presence and species, and it is influenced both by the phenology and density of vegetation. Plant presence significantly increases the CO 2 emission respect to unvegetated condition in all CWs types, and increases N 2 O and CH 4 emissions in VSSF CWs. Considering the HSSF CWs plant presence significantly reduce the CH 4 emissions. Plant species richness effect on CH 4 emission has been investigates in a limited number of papers with not unique results, probably due to the different plant species and number used by authors, which may have influenced the CWs microbial population and activity. Considering plant species Zizania latifolia determine significant higher CH 4 and N 2 O emissions than Phragmites australis . No significant different CH 4 and N 2 O emissions have been found between P. australis and Typha latifolia . Significant lower N 2 O emissions determine the T. angustifolia than P. australis. Although plant presence, in some case, increases CW GHG emissions respect to unvegetated situation, the vegetation fixes atmospheric carbon by photosynthesis; as a consequence CWs act, in most cases, as sink of CO 2(eq) . [ABSTRACT FROM AUTHOR]

Abstract: Biochar application to soils may increase carbon (C) sequestration due to the inputs of recalcitrant organic C. However, the effects of biochar application on the soil greenhouse gas (GHG) fluxes appear variable among many case studies; therefore, the efficacy of biochar as a carbon sequestration agent for climate change mitigation remains uncertain. We performed a meta‐analysis of 91 published papers with 552 paired comparisons to obtain a central tendency of three main GHG fluxes (i.e., CO2, CH4, and N2O) in response to biochar application. Our results showed that biochar application significantly increased soil CO2 fluxes by 22.14%, but decreased N2O fluxes by 30.92% and did not affect CH4 fluxes. As a consequence, biochar application may significantly contribute to an increased global warming potential (GWP) of total soil GHG fluxes due to the large stimulation of CO2 fluxes. However, soil CO2 fluxes were suppressed when biochar was added to fertilized soils, indicating that biochar application is unlikely to stimulate CO2 fluxes in the agriculture sector, in which N fertilizer inputs are common. Responses of soil GHG fluxes mainly varied with biochar feedstock source and soil texture and the pyrolysis temperature of biochar. Soil and biochar pH, biochar applied rate, and latitude also influence soil GHG fluxes, but to a more limited extent. Our findings provide a scientific basis for developing more rational strategies toward widespread adoption of biochar as a soil amendment for climate change mitigation. [ABSTRACT FROM AUTHOR]

The article focuses on mitigation of greenhouse gas (GHG) emissions in agricultural sector in Spain. Topics discussed include emission of nitrous oxide (N2O) from agricultural soils due to application of manures and fertilizers, removal of carbon dioxide (CO2) by carbon which gets accumulated in plant biomass and diversity in climate of Spain affect production systems of livestock with their environment.

We show new results from an updated version of the Fast atmOspheric traCe gAs retrievaL (FOCAL) retrieval method applied to measurements of the Greenhouse gases Observing SATellite (GOSAT) and its successor GOSAT-2. FOCAL was originally developed for estimating the total column carbon dioxide mixing ratio (XCO2) from spectral measurements made by the Orbiting Carbon Observatory-2 (OCO-2). However, depending on the available spectral windows, FOCAL also successfully retrieves total column amounts for other atmospheric species and their uncertainties within one single retrieval. The main focus of the current paper is on methane (XCH4 ; full-physics and proxy product), water vapour (XH2O) and the relative ratio of semi-heavy water (HDO) to water vapour (δD). Due to the extended spectral range of GOSAT-2, it is also possible to derive information on carbon monoxide (XCO) and nitrous oxide (XN2O) for which we also show first results. We also present an update on XCO2 from both instruments. For XCO2 , the new FOCAL retrieval (v3.0) significantly increases the number of valid data compared with the previous FOCAL retrieval version (v1) by 50 % for GOSAT and about a factor of 2 for GOSAT-2 due to relaxed pre-screening and improved post-processing. All v3.0 FOCAL data products show reasonable spatial distribution and temporal variations. Comparisons with the Total Carbon Column Observing Network (TCCON) result in station-to-station biases which are generally in line with the reported TCCON uncertainties. With this updated version of the GOSAT-2 FOCAL data, we provide a first total column average XN2O product. Global XN2O maps show a gradient from the tropics to higher latitudes on the order of 15 ppb , which can be explained by variations in tropopause height. The new GOSAT-2 XN2O product compares well with TCCON. Its station-to-station variability is lower than 2 ppb , which is about the magnitude of the typical N2O variations close to the surface. However, both GOSAT-2 and TCCON measurements show that the seasonal variations in the total column average XN2O are on the order of 8 ppb peak-to-peak, which can be easily resolved by the GOSAT-2 FOCAL data. Noting that only few XN2O measurements from satellites exist so far, the GOSAT-2 FOCAL product will be a valuable contribution in this context. [ABSTRACT FROM AUTHOR]

Earth's climate largely depends on carbon and nitrogen exchange between the atmosphere and tropical peatland ecosystems. Permanently wet peatlands take up carbon dioxide in plants and accumulate organic carbon in soil but release methane. Man-made drainage releases carbon dioxide from peat soils. Carbon and nitrous gas exchange and their relationships with tropical peatland conditions are poorly understood. We analysed natural peat swamp forests and fens, moderately drained and dry peatlands under a wide variety of land uses. The tropical peat swamp forests were large greenhouse gas sinks while tropical peatlands under moderate and low soil moisture levels emitted carbon dioxide and nitrous oxide. Carbon dioxide uptake of 160 mg m–2 h–1 dominated the net greenhouse gas budgets overall, while nitrous oxide emission of 90 mg CO2-equivalent m–2 h–1 on average was the second most important contributor (ahead of average methane emissions of 36 mg CO2-equivalent m–2 h–1) across the whole tropical peat moisture range. [ABSTRACT FROM AUTHOR]

Shallow lakes and ponds undergo frequent temporary thermal stratification. How this affects greenhouse gas (GHG) emissions is moot, with both increased and reduced GHG emissions hypothesised. Here, weekly estimations of GHG emissions, over the growing season from May to September, were combined with temperature and oxygen profiles of an 11 ha temperate shallow lake to investigate how thermal stratification shapes GHG emissions. There were three main stratification periods with profound anoxia occurring in the bottom waters upon isolation from the atmosphere. Average diffusive emissions of methane (CH 4) and nitrous oxide (N 2 O) were larger and more variable in the stratified phase, whereas carbon dioxide (CO 2) was on average lower, though these differences were not statistically significant. In contrast, there was a significant order of magnitude increase in CH 4 ebullition in the stratified phase. Furthermore, at the end of the period of stratification, there was a large efflux of CH 4 and CO 2 as the lake mixed. Two relatively isolated turnover events were estimated to have released the majority of the CH 4 emitted between May and September. These results demonstrate how stratification patterns can shape GHG emissions and highlight the role of turnover emissions and the need for high-frequency measurements of GHG emissions, which are required to accurately characterise emissions, particularly from temporarily stratifying lakes. [ABSTRACT FROM AUTHOR]

A field campaign was conducted using six treatments under the summer rice-winter wheat cultivation system to evaluate the response of soil greenhouse gas (GHG) emissions to long-term differentiated fertilisation regimes. The treatments included control, phosphorus plus potassium, nitrogen only, nitrogen plus phosphorus (NP), nitrogen plus potassium, and NP plus potassium (NPK). Compared to the control, mineral fertilisation increased CH4 emissions during the rice season by 69% to 175%. Phosphorus amendment also enhanced seasonal CO2 emissions by 21% to 34% when compared with the treatments without receiving P, while combined use of P and potassium suppressed seasonal N2O emission to the same level of control. Net CO2 and N2O emissions from the dried fallow and wheat seasons and CH4 emissions from the flooding rice season dominated annual budgets of individual GHGs. All of the soils under different treatments were net sources of global warming and the overall net global warming potential ranged from 9 799 to 14 178 kg CO2 eq/ha/year with CO2 emission contributing 52% to 76%, CH4 contributing 20% to 40% and N2O occupying the rest. The annual maximum grain yields and minimum GHG intensity was observed at the NPK treatment, suggesting it to be the environmental-friendly optimum fertilisation regime. [ABSTRACT FROM AUTHOR]

This paper presents results of greenhouse gas (GHG) measurements in the pre-filling phase of three hydroelectric reservoirs in Brazil: Belo Monte Hydroelectric Complex, Batalha Hydroelectric Plant and Santo Ant"nio Hydroelectric Plant. In contrast to most of the estimates available in the literature on hydroelectric reservoirs, which take into consideration only gross emissions, these data will enable the calculation of the net emissions of the hydroelectric reservoirs studied. Carbon dioxide and methane flux measurements were carried out in terrestrial (in different types of soil and vegetation) and aquatic (rivers, lakes and marshes) ecosystems before the reservoir flooding. In each reservoir, four measurement campaigns were carried out in order to represent different rainfall regimes and river water levels. The median values of CH 4 emissions were 9.97 ± 3.55 mg CH 4 m−2 day−1 and 11.34 ± 1.62 mg CH 4 m−2 day−1 for pasture and forest, landuse types, respectively. For CO 2 emission was 10,448.41 ± 3036.48 mg CO 2 m−2 day−1 and 8004.50 ± 1314.98 mg CO 2 m−2 day−1 for pasture and forest lands, respectively. The median fluxes for N 2 O were near zero, and 0.78 ± 0.56 mg N 2 O m−2 day−1 for pasture and 0.67 ± 0.29 mg N 2 O m−2 day−1 for forest. The study showed that the terrestrial areas prior reservoir creation act as potential emitters of greenhouse gases. Hydropower sites under construction, where hydroelectric reservoirs have not been installed yet create a great opportunity to carry out gas flux measurements in the pre-filling phase. The results can be further compared with the same measurements after the dam closure in order to more precisely estimate the net reservoir emissions. In the case of reservoirs already built, off course the possibility of taking pre-filling phase measurements no longer exists. However, the results of the present study allow for reassessment of the available flux estimates for such reservoirs. [ABSTRACT FROM AUTHOR]

In eutrophic freshwater ecosystems, submerged macrophyte communities are replaced by phytoplankton or free-floating plants. In isolated wetlands, vegetation shift occurs over short time scales and leads to water deoxygenation and chemically reduced sediments, conditions that favor the generation, accumulation and degassing of greenhouse gases (GHGs, i.e. CH 4 , CO 2 and N 2 O) to the atmosphere. However, the relationship between primary producer's growth forms, hydrological connectivity and GHGs concentration is poorly studied in the literature. A set of 18 freshwater wetlands including isolated and river-connected oxbow lakes, marshes and ponds with different vegetation growth forms was therefore monitored monthly on the annual scale. Potential GHGs diffusive fluxes towards the atmosphere were calculated and compared with direct measurements reported in peer-reviewed papers within a meta-analysis. Our results demonstrate a strong link between the colonization of free-floating plants and the onset of hypoxic conditions and accumulation of dissolved methane. Methane and carbon dioxide concentration peaked in late summer, when floating-leaved and free-floating vegetation covered 100% of the water surface. Carbon dioxide accumulation was particularly evident at hydrological connected wetlands, where nitrate pollution was likely responsible for the concomitant increment of dissolved nitrous oxide. As an increasing number of studies focuses on unravelling environmental drivers of GHGs emission from small lakes and ponds, we encourage to systematically consider the vegetation growth forms and the hydrological connectivity as major drivers of GHGs accumulation and evasion rates. • Eutrophic small waterbodies are supersaturated in greenhouse gases. • Free-floating plants dominance favors hypoxic conditions and accumulation of CH 4 and CO 2. • In hydrologically connected wetlands nitrate loads favor N 2 O supersaturation. • Vegetation shift and nitrate input lead to increased GHG emissions. [ABSTRACT FROM AUTHOR]

Waste stabilization ponds (WSPs) are a cost-efficient method to treat municipal and non-toxic industrial effluents. Numerous studies have shown that WSPs are a source of greenhouse gas (GHG). However, most reports concerned anaerobic ponds (AP) and few have addressed GHG emissions from facultative (FP) and aerobic/maturation ponds (MPs). In this paper, GHG emissions from three WSP in series are presented. These WSPs were designed as anaerobic, facultative and aerobic/maturation and were treating agricultural wastewater. CH4fluxes from 0.6±0.4 g CH4 m−2 d−1in the MP, to 7.0±1.0 g CH4 m−2 d−1in the (AP), were measured. A linear correlation was found between the loading rates of the ponds and CH4emissions. Relatively low CO2fluxes (0.2±0.1 to 1.0±0.8 g CO2 m−2 d−1) were found, which suggest that carbonate/bicarbonate formation is caused by alkaline pH. A mass balance performed showed that 30% of the total chemical oxygen demand removed was converted to CH4. It has been concluded that the WSP system studied emits at least three times more GHG than aerobic activated sludge systems and that the surface loading rate is the most important design parameter for CH4emissions. [ABSTRACT FROM AUTHOR]

Terrestrial ecosystems may act as a source or a sink for the atmospheric greenhouse gases, carbon dioxide (CO), methane (CH), and nitrous oxide (NO), depending on land use and management. This paper reviews the literature on carbon, CH, and NO fluxes from terrestrial ecosystems in China, and analyzes its national greenhouse gas budget. Carbon storage in biomass and soils in Chinese terrestrial ecosystems decreased in the past 300 years, due to deforestation and expansion of cultivated land, and reached a minimum in the late 1970s. Since then, carbon storage has increased at an estimated rate of 0.19 to 0.26 Pg C yr, mainly owing to reforestation and afforestation. CH emission from natural wetlands decreased from 6.65 Tg CH yr in 1990 to 5.71 Tg CH yr in 2000 owing to the decrease in wetland area. CH emission from flooded rice fields was 7.41 Tg CH yr. At the same time, aerobic soils took up atmospheric CH at a rate of 2.56 Tg CH yr. Nitrous oxide emission from forestlands, grasslands, and farmlands was positively correlated with precipitation at a national scale, and the emission rate was positively correlated with the CH uptake rate of forestlands and grasslands ( P<0.01). Natural NO sources were estimated to be 419 Gg N yr and anthropogenic sources (from farmlands) to be 292 to 476.3 Gg N yr, with a mean of 372.6 Gg N yr. The integrated budget of greenhouse gasses indicates that Chinese terrestrial ecosystems act as a small net sink for global warming potential (GWP), ranging from 0.04 to 0.32 Pg CO-eq yr, in a striking contrast to terrestrial ecosystems globally, which are a source of 2.75 to 6.78 Pg CO-eq yr. The ratios of anthropogenic to natural sources of CH and NO are much larger in Chinese terrestrial ecosystems than they are in global averages, reflecting greater human disturbance of terrestrial ecosystems in China. [ABSTRACT FROM AUTHOR]

Abstract Agriculture is a significant source of anthropogenic greenhouse gas (GHG) emissions, and beef cattle are particularly emissions intensive. GHG emissions are typically expressed as a carbon dioxide equivalent (CO 2 e) 'carbon footprint' per unit output. The 100-year Global Warming Potential (GWP 100) is the most commonly used CO 2 e metric, but others have also been proposed, and there is no universal reason to prefer GWP 100 over alternative metrics. The weightings assigned to non-CO 2 GHGs can differ significantly depending on the metric used, and relying upon a single metric can obscure important differences in the climate impacts of different GHGs. This loss of detail is especially relevant to beef production systems, as the majority of GHG emissions (as conventionally reported) are in the form of methane (CH 4) and nitrous oxide (N 2 O), rather than CO 2. This paper presents a systematic literature review of harmonised cradle to farm-gate beef carbon footprints from bottom-up studies on individual or representative systems, collecting the emissions data for each separate GHG, rather than a single CO 2 e value. Disaggregated GHG emissions could not be obtained for the majority of studies, highlighting the loss of information resulting from the standard reporting of total GWP 100 CO 2 e alone. Where individual GHG compositions were available, significant variation was found for all gases. A comparison of grass fed and non-grass fed beef production systems was used to illustrate dynamics that are not sufficiently captured through a single CO 2 e footprint. Few clear trends emerged between the two dietary groups, but there was a non-significant indication that under GWP 100 non-grass fed systems generally appear more emissions efficient, but under an alternative metric, the 100-year global temperature potential (GTP 100), grass-fed beef had lower footprints. Despite recent focus on agricultural emissions, this review concludes there are insufficient data available to fully address important questions regarding the climate impacts of agricultural production, and calls for researchers to include separate GHG emissions in addition to aggregated CO 2 e footprints. Highlights • Multi-gas footprints are typically converted to a total carbon dioxide equivalent. • Different carbon dioxide equivalence metrics emphasize different climate behaviours. • Reporting emissions of all gases as a combined total loses important information. • Disaggregated data could not be retrieved from most (71%) full beef LCAs. • Relative emissions intensity is highly dependent on metric choice. [ABSTRACT FROM AUTHOR]

Biofuels are fuels produced from biomass, mostly in liquid form, within a time frame sufficiently short to consider that their feedstock (biomass) can be renewed, contrarily to fossil fuels. This paper reviews the current and future biofuel technologies, and their development impacts (including on the climate) within given policy and economic frameworks. Current technologies make it possible to provide first generation biodiesel, ethanol or biogas to the transport sector to be blended with fossil fuels. Still under-development 2nd generation biofuels from lignocellulose should be available on the market by 2020. Research is active on the improvement of their conversion efficiency. A ten-fold increase compared with current cost-effective capacities would make them highly competitive. Within bioenergy policies, emphasis has been put on biofuels for transportation as this sector is fast-growing and represents a major source of anthropogenic greenhouse gas emissions. Compared with fossil fuels, biofuel combustion can emit less greenhouse gases throughout their life cycle, considering that part of the emitted CO2 returns to the atmosphere where it was fixed from by photosynthesis in the first place. Life cycle assessment (LCA) is commonly used to assess the potential environmental impacts of biofuel chains, notably the impact on global warming. This tool, whose holistic nature is fundamental to avoid pollution trade-offs, is a standardised methodology that should make comparisons between biofuel and fossil fuel chains objective and thorough. However, it is a complex and time-consuming process, which requires lots of data, and whose methodology is still lacking harmonisation. Hence the life-cycle performances of biofuel chains vary widely in the literature. Furthermore, LCA is a site- and time-independent tool that cannot take into account the spatial and temporal dimensions of emissions, and can hardly serve as a decision-making tool either at local or regional levels. Focusing on greenhouse gases, emission factors used in LCAs give a rough estimate of the potential average emissions on a national level. However, they do not take into account the types of crop, soil or management practices, for instance. Modelling the impact of local factors on the determinism of greenhouse gas emissions can provide better estimates for LCA on the local level, which would be the relevant scale and degree of reliability for decision-making purposes. Nevertheless, a deeper understanding of the processes involved, most notably NO emissions, is still needed to definitely improve the accuracy of LCA. Perennial crops are a promising option for biofuels, due to their rapid and efficient use of nitrogen, and their limited farming operations. However, the main overall limiting factor to biofuel development will ultimately be land availability. Given the available land areas, population growth rate and consumption behaviours, it would be possible to reach by 2030 a global 10% biofuel share in the transport sector, contributing to lower global greenhouse gas emissions by up to 1 GtCO eq · year (IEA, 2006), provided that harmonised policies ensure that sustainability criteria for the production systems are respected worldwide. Furthermore, policies should also be more integrative across sectors, so that changes in energy efficiency, the automotive sector and global consumption patterns converge towards drastic reduction of the pressure on resources. Indeed, neither biofuels nor other energy source or carriers are likely to mitigate the impacts of anthropogenic pressure on resources in a range that would compensate for this pressure growth. Hence, the first step is to reduce this pressure by starting from the variable that drives it up, i.e. anthropic consumptions. [ABSTRACT FROM AUTHOR]

A new analytical inversion method has been developed to determine the regional and global emissions of long-lived atmospheric trace gases. It exploits in situ measurement data from three global networks and builds on backward simulations with a Lagrangian particle dispersion model. The emission information is extracted from the observed concentration increases over a baseline that is itself objectively determined by the inversion algorithm. The method was applied to two hydrofluorocarbons (HFC-134a, HFC-152a) and a hydrochlorofluorocarbon (HCFC-22) for the period January 2005 until March 2007. Detailed sensitivity studies with synthetic as well as with real measurement data were done to quantify the influence on the results of the a priori emissions and their uncertainties as well as of the observation and model errors. It was found that the global a posteriori emissions of HFC-134a, HFC-152a and HCFC-22 all increased from 2005 to 2006. Large increases (21%, 16%, 18%, respectively) from 2005 to 2006 were found for China, whereas the emission changes in North America (-9%, 23%, 17%, respectively) and Europe (11%, 11%, -4%, respectively) were mostly smaller and less systematic. For Europe, the a posteriori emissions of HFC-134a and HFC-152a were slightly higher than the a priori emissions reported to the United Nations Framework Convention on Climate Change (UNFCCC). For HCFC-22, the a posteriori emissions for Europe were substantially (by almost a factor 2) higher than the a priori emissions used, which were based on HCFC consumption data reported to the United Nations Environment Programme (UNEP). Combined with the reported strongly decreasing HCFC consumption in Europe, this suggests a substantial time lag between the reported time of the HCFC-22 consumption and the actual time of the HCFC-22 emission. Conversely, in China where HCFC consumption is increasing rapidly according to the UNEP data, the a posteriori emissions are only about 40% of the a priori emissions. This reveals a substantial storage of HCFC-22 and potential for future emissions in China. Deficiencies in the geographical distribution of stations measuring halocarbons in relation to estimating regional emissions are also discussed in the paper. Applications of the inversion algorithm to other greenhouse gases such as methane, nitrous oxide or carbon dioxide are foreseen for the future. [ABSTRACT FROM AUTHOR]

Abstract: Ruminant livestock systems contribute to global warming through the emission of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2). This paper discusses a general framework for a whole-farm approach to develop cost-effective GHG mitigation strategies. A dairy farm is a complex system with different interacting components. Generally, whole-farm approaches distinguish at least an animal component and a soil–crop component. Whole-farm models should be able to give an accurate representation of the internal cycling of materials and its constituents as well as the exchange between the farming system and its environment. The paper gives an overview of current whole-farm models that are able to simulate GHG emissions for dairy farms. These models are DairySim, FarmGHG, SIMSDAIRY and FarmSim. All models are able to calculate CH4 and N2O emissions, but differences appear in the ability to calculate CO2 emissions, economics and other parameters. The effects of selected mitigation strategies are demonstrated with some of the models. It is concluded that a whole-farm approach is a powerful tool for the development of cost-effective GHG mitigation options as it reveals relevant interactions between farm components. Model calculations underlined the relationship between farm gate N surplus and GHG emissions, and thus the possibility to use N surpluses as an indicator for GHG emissions. [Copyright &y& Elsevier]

Dairy systems in Europe contribute to the emissions of the greenhouse gases (GHGs) nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2). In this paper, the effects of improved nitrogen (N) management on GHG emissions from Dutch dairy farms are determined. The GHG emissions are calculated using the panel on climate change (IPCC) methodology for the Netherlands, an updated and refined IPCC methodology, and a full accounting approach. The changes in dairy farming over the last 20 years, and the consequences for N management are described using detailed farm-level data, collected in 1985, 1997 and 2002. The selected years represent distinct stages in the implementation of N policies. The changes in N management have reduced the GHG emissions. A reduction of the N surplus per kilogram milk with 1 g N reduced the GHG emissions per kilogram milk with approximately 29 g CO2-equivalents. The reduction of the N surpluses was mainly brought about by reduced fertilizer use and reduced grazing time. The use of updated and refined emission factors resulted in higher CH4 emissions and lower N2O emissions. On average, the overall emission was 36% higher with the refined method. Full accounting, including all direct and indirect emissions of CH4, N2O and CO2, increased the emission with 36% compared with the refined IPCC methodology. We conclude that the N surplus at farm level is a useful indicator of GHG emissions. A full accounting system as presented in this study may effectively enable farmers to address the issue of emissions of GHGs in their operational management decisions. Both approaches serve their own specific objectives: full accounting at the farm level to explore mitigation options, and the IPCC methods to report changes in GHG emissions at the national level. [ABSTRACT FROM AUTHOR]

The debate as to whether carbon dioxide, methane, nitrous oxide and other greenhouse gas emissions will become subject to increasing regulation, increased restrictions, and probably to some form of carbon tax, has moved from a simple "yes" or "no" to "when". Wastewater treatment plants will be significantly impacted by increased energy costs and by specific regulations and/or penalties associated with emissions of methane and nitrous oxide. In this paper, the greenhouse gases emissions of different wastewater process options are estimated. The paper outlines the increasing need for wastewater treatment plants to factor greenhouse gas mitigation issues into their medium-as and long-term strategies, and identifies anaerobic greenhouse gas processes as being at the core of such strategies. Further, the paper identifies a number of key research challenges to be addressed if such strategies are to play a larger role in attenuating the likely impacts of GHG mitigation requirements on wastewater treatment plant design and operation. [ABSTRACT FROM AUTHOR]

In addition to national inventories of emissions of greenhouse gases, there are inventories for most, but not all, states constituting the United States. This paper analyzes the state inventories to see if reported emissions of carbon dioxide, methane, and nitrous oxide are additive. Considerable reanalysis of the state inventories is required before they can be added to yield a larger-scale inventory. Some specific sources were considered by some states but not by others. Estimation techniques evolved over time as inventories were produced, and there are instances of both double-counting (two states reporting the same emission) and omission (neither state reporting the same emission), where interstate transfers of energy or materials occurred. Nevertheless, the inventories, when adjusted for obvious double-counting or omissions, are probably approximately additive, although it is difficult to quantify the extent to which this is true. Email: cushmanrm@ornl.gov --> [ABSTRACT FROM AUTHOR]

• Urban wastewater, mine water and agricultural inputs dominated GHG generation. • Anthropogenic urban nutrient sources disproportionality increased GHGs in summer. • Low oxygen and high riverine residence time increased nutrient impacts on GHGs. • A source-to sea methodology enabled easy identification of GHG sources and sinks. • Load appointment modelling enabled separation of point and diffuse GHG sources. There is growing global concern that greenhouse gas (GHG) emissions from water bodies are increasing because of interactions between nutrient levels and climate warming. This paper investigates key land-cover, seasonal and hydrological controls of GHGs by comparison of the semi-natural, agricultural and urban environments in a detailed source-to-sea study of the River Clyde, Scotland. Riverine GHG concentrations were consistently oversaturated with respect to the atmosphere. High riverine concentrations of methane (CH 4) were primarily associated with point source inflows from urban wastewater treatment, abandoned coal mines and lakes, with CH 4 -C concentrations between 0.1 - 44 µg l−1. Concentrations of carbon dioxide (CO 2) and nitrous oxide (N 2 O) were mainly driven by nitrogen concentrations, dominated by diffuse agricultural inputs in the upper catchment and supplemented by point source inputs from urban wastewater in the lower urban catchment, with CO 2 -C concentrations between 0.1 - 2.6 mg l−1 and N 2 O-N concentrations between 0.3 - 3.4 µg l−1. A significant and disproportionate increase in all GHGs occurred in the lower urban riverine environment in the summer, compared to the semi-natural environment, where GHG concentrations were higher in winter. This increase and change in GHG seasonal patterns points to anthropogenic impacts on microbial communities. The loss of total dissolved carbon, to the estuary is approximately 48.4 ± 3.6 Gg C yr−1, with the annual inorganic carbon export approximately double that of organic carbon and four times that of CO 2, with CH 4 accounting for 0.03%, with the anthropogenic impact of disused coal mines accelerating DIC loss. The annual loss of total dissolved nitrogen to the estuary is approximately 4.03 ± 0.38 Gg N yr−1 of which N 2 O represents 0.06%. This study improves our understanding of riverine GHG generation and dynamics which can contribute to our knowledge of their release to the atmosphere. It identifies where action could support reductions in aquatic GHG generation and emission. [Display omitted] [ABSTRACT FROM AUTHOR]

Simulations using global coupled climate models predict a climate change due to the increasing concentration of greenhouse gases and aerosols in the atmosphere. Both are associated with the burning of fossil fuels. There has been considerable debate if this postulated human influence is already evident. This paper gives an overview on some recent material on this question. One particular study using optimal fingerprints (Hegerl et al., 1996) is explained in more detail. In this study, an optimal fingerprint analysis is applied to temperature trend patterns over several decades. The results show the probability being less than 5% that the most recently observed 30 year trend is due to naturally occurring climate fluctuations. This result suggests that the present warming is caused by some external influence on climate, e.g. by the increasing concentrations of greenhouse gases and aerosols. More work is needed to address the uncertainties in the magnitude of naturally occurring climate fluctuations. Also, other external influences on climate need to be investigated to uniquely attribute the present climate change to the human influence. [ABSTRACT FROM AUTHOR]

Paddy fields are a major emission source of greenhouse gases (GHGs) [for instance, methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2)] among agricultural fields. Biochar has been deemed a potential candidate for the reduction of GHGs in paddy fields. However, there is no consistent conclusion that biochar can simultaneously reduce emissions of CH4, N2O, and CO2. Herein, we proposed the FeN3-doped biochar (FG) as an excellent material for GHGs restriction in paddy fields via the first-principles calculation. The computation results indicated that the FG exhibited satisfactory adsorption ability for CH4, CO2, and N2O, which improved the adsorption energies to −1.37 , −1.54, and −2.91 eV, respectively. Moreover, the density of state (DOS) analyses revealed that the factor responsible for FeN3-doped biochar to exhibit excellent adsorption ability was the occurrence of drastic energy up- or down-shift of the electron for Fe d, C p, O p, or N p orbital upon adsorption of CH4, CO2, or N2O. Our study suggested an advanced modified biochar material for reducing the GHGs emissions in paddy fields, in addition to exploring the adsorption properties and mechanisms of FeN3-doped biochar for GHGs mitigation, which provided a strategy to explore biochar modification and efficient emission reduction materials. Article highlights: • FeN3-doped biochar was first proposed for GHGs mitigation in paddy fields. • FeN3-doped biochar exhibited excellent GHGs adsorption ability. • FeN3-doped biochar improved physico-chemical adsorption ability for GHGs. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the emission factor of N2O, CH4, and the volatilization of NH3 for the combination of feces or urine with increasing doses of ammonium nitrate in tropical palisade grass pastures. The emission of greenhouse gases was assessed in eight treatments combining feces and urine with doses (75 and 150 kg of N ha−1) of ammonium nitrate, (32% N). The emission factor of N2O was 0.11, 0.19, and 0.17% for feces, urine, and 75 kg N ha−1 year−1 (as ammonium nitrate) and showed an additive linear effect when feces or urine were combined with increasing doses of N fertilizer. The emission factor of CH4 of feces (0.18 kg CH4 animal−1 year−1) was similar irrespective of combination with ammonium nitrate. The N loss by volatilized NH3 has a decreasing linear effect (p < 0.05) for the combination of feces or urine with ammonium nitrate. We concluded that N2O and CH4 emission factors of feces and urine in tropical climate conditions are lower than those reported by the IPCC. However, their N2O emission factors are sharply enhanced when combined with ammonium nitrate. These results may contribute to improvements in national and regional greenhouse gas inventories of livestock production. [ABSTRACT FROM AUTHOR]

High-precision observations provide an efficient way to calculate greenhouse gas emissions from agricultural fields and their spatial and temporal distributions. Two high-resolution laser heterodyne radiometers (LHRs) were deployed in the suburb of Hefei (31.9°N 117.16°E) for the remote sensing of atmospheric CO2, CH4 and N2O above rice paddy fields. The atmospheric transmittance spectra of CO2, CH4 and N2O were measured simultaneously in real time, and the atmospheric total column abundance was retrieved from the measured data based on the optimal estimation algorithm, with errors of 0.7 ppm, 4 ppb and 2 ppb, respectively. From July to October, the abundance of CO2 in the atmospheric column that was influenced by emissions from rice fields increased by 0.7 ppm CH4 by 30 ppb, and by 4 ppb N2O. During the rice growth season, rice paddy fields play a role in carbon sequestration. CH4 and N2O emissions from paddy fields are negatively correlated. The method of baking rice paddy fields reduces CH4 emissions from rice fields, but N2O emissions from rice fields are usually subsequently increased. The measurement results showed that LHRs are highly accurate in monitoring atmospheric concentrations and have promising applications in monitoring emissions from rice paddy fields. In the observation period, rice paddy fields can sequester carbon, and CH4 and N2O emissions from rice fields are negatively correlated. The LHRs have strong application prospects for monitoring emissions from agricultural fields. [ABSTRACT FROM AUTHOR]

The major greenhouse gases in streams and rivers, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), can contribute significantly to regional greenhouse gas (GHG) budgets, and each appears to be responding to multiple drivers. Recent work suggests that tropical water bodies may be hot spots of GHG emissions due to high primary productivity in their watersheds, but tropical streams and rivers have historically been underrepresented in studies of GHG concentration and emissions. We use a five-year record of weekly water chemistry and dissolved gas data from eight tropical watersheds of varying lithology and redox conditions in the Luquillo Mountains of Puerto Rico to examine controls on GHG variability and estimate gas flux. Streams were frequently supersaturated in all three gases indicating that streams in this tropical landscape are sources of GHGs to the atmosphere. Concentrations of CO2 and N2O were associated with lateral inputs from the surrounding landscape, whereas CH4 concentrations correlated with in-stream oxygen availability and lithology. Our results underscore the importance of including tropical sites in global syntheses and budgets and the role of both in-stream biological and physical processes as well as landscape attributes that contribute to the export of gases to the fluvial network and atmosphere. [ABSTRACT FROM AUTHOR]

The rewetting of drained peatlands supports long-term nutrient removal in addition to reducing emissions of carbon dioxide (CO 2) and nitrous oxide (N 2 O). However, rewetting may lead to short-term nutrient leaching into adjacent water and high methane (CH 4) emissions. The consequences of rewetting with brackish water on nutrient and greenhouse gas (GHG) fluxes remain unclear, although beneficial effects such as lower CH 4 emissions seem likely. Therefore, we studied the actively induced rewetting of a coastal peatland with brackish water, by comparing pre- and post-rewetting data from the peatland and the adjacent bay. Both the potential transport of nutrients into adjacent coastal water and the shift in GHG fluxes (CO 2 , CH 4 , and N 2 O) accompanying the change from drained to inundated conditions were analyzed based on measurements of the surface water concentrations of nutrients (dissolved inorganic nitrogen, DIN, and phosphate, PO 43-), oxygen (O 2), components of the CO 2 system, CH 4 , and N 2 O together with manual closed-chamber measurements of GHG fluxes. Our results revealed higher nutrient concentrations in the rewetted peatland than in the adjacent bay, indicating that nutrients leached out of the peat and were exported to the bay. A comparison of DIN concentrations of the bay with those of an unaffected reference station showed a significant increase after rewetting. The maximum estimated nutrient export (mean ± 95 % confidence level) out of the peatland was calculated to be 33.8 ± 9.6 t yr -1 for DIN-N and 0.24 ± 0.29 t yr -1 for PO 4 -P, depending on the endmember (bay vs. reference station). The peatland was also a source of GHG in the first year after rewetting. However, the spatial and temporal variability decreased, and high CH 4 emissions, as reported for freshwater rewetting, did not occur. CO 2 fluxes (mean ± SD) decreased slightly from 0.29 ± 0.82 g m -2 h -1 (pre-rewetting) to 0.26 ± 0.29 g m -2 h -1 (post-rewetting). The availability of organic matter (OM) and dissolved nutrients were likely the most important drivers of continued CO 2 production. Pre-rewetting CH 4 fluxes ranged from 0.13 ± 1.01 mg m -2 h -1 (drained land site) to 11.4 ± 37.5 mg m -2 h -1 (ditch). After rewetting, CH 4 fluxes on the formerly dry land increased by 1 order of magnitude (1.74 ± 7.59 mg m -2 h -1), whereas fluxes from the former ditch decreased to 8.5 ± 26.9 mg m -2 h -1. These comparatively low CH 4 fluxes can likely be attributed to the suppression of methanogenesis and oxidation of CH 4 by the available O 2 and sulfate in the rewetted peatland, which serve as alternative electron acceptors. The post-rewetting N 2 O flux was low, with an annual mean of 0.02 ± 0.07 mg m -2 h -1. Our results suggest that rewetted coastal peatlands could account for high, currently unmonitored, nutrient inputs into adjacent coastal water, at least on a short timescale such as a few years. However, rewetting with brackish water may decrease GHG emissions and might be favored over freshwater rewetting in order to reduce CH 4 emissions. [ABSTRACT FROM AUTHOR]

Vertebrate herbivore excrement is thought to influence nutrient cycling, plant nutrition, and growth; however, its importance is rarely isolated from other aspects of herbivory, such as trampling and leaf removal, leaving questions about the extent to which herbivore effects are due to feces. We hypothesized that as a source of additional nutrients, feces would directly increase soil N concentrations and N2O emission, alleviate plant, and microbial nutrient limitations, resulting in increased plant growth and foliar quality, and increase CH4 emissions. We tested these hypotheses using a field experiment in coastal western Alaska, USA, where we manipulated goose feces such that naturally grazed areas received three treatments: feces removal, ambient amounts of feces, or double ambient amounts of feces. Doubling feces marginally increased NH4+-N in soil water, whereas both doubled feces and feces removal significantly increased NO3−-N; N2O flux was also higher in removal plots. Feces removal marginally reduced root biomass and significantly reduced productivity (that is, GPP) in the second year, measured as greater CO2 emissions. Doubling feces marginally increased foliar chemical quality by increasing %N and decreasing C:N. Treatments did not influence CH4 flux. In short, feces removal created sites poorer in nutrients, with reduced root growth, graminoid nutrient uptake, and productivity. While goose feces alone did not create dramatic changes in nutrient cycling in western Alaska, they do appear to be an important source of nutrients for grazed areas and to contribute to greenhouse gas exchange as their removal increased emissions of CO2 and N2O to the atmosphere. [ABSTRACT FROM AUTHOR]

The electricity sector is the biggest emitter of greenhouse gases in Bangladesh, and the country has the target to reduce these emissions and follow an environmentally sustainable development strategy. In this study, we explore how population growth, affluence and energy technology factors affect the emissions of carbon dioxide, methane and nitrous oxide emissions from the electricity sector in Bangladesh. This study employs an extended stochastic impacts by regression on population, affluence and technology model, using ridge regression for the analysis, covering a period from 1995 to 2014. The study also examines the presence of the environmental Kuznets curve (EKC) with respect to greenhouse gas emissions. We find that the chief drivers of carbon dioxide, methane and nitrous oxide emissions are population, affluence, urbanization and the carbon intensity of fuels. Energy intensity affects carbon dioxide and methane emissions. Transmission losses do not have a significant positive influence on emissions of any of the gases except carbon dioxide. Our results also show that there is no evidence of the EKC with respect to greenhouse gases in the electricity sector. Our study suggests that Bangladesh should have policies promoting a cleaner energy mix, reduce the use of fossil fuels, and increase energy efficiency technologies to counter the polluting effects of a growing power sector. [ABSTRACT FROM AUTHOR]

With the increasing popularity of biochar as a soil amendment worldwide in recent years, a question of concern arises as to whether the application of biochar would suppress or stimulate greenhouse gas (GHG) emissions. In this study, published data extracted from independent individual studies were systematically selected, statistically processed, graphically presented and critically analyzed to understand biochar's influences on the emissions of CO2, CH4 and N2O—the three major GHGs emitted in agricultural fields. The results revealed not only the significant importance of biochar's pyrolysis temperature for its impacts on GHG emissions, but also the dissimilar influences on the generations of different GHGs. The application of biochar, in general, stimulated the emissions of CO2 and CH4 to various extents. With biochar pyrolyzed under relatively lower temperatures (e.g., <500 °C), higher application rates generally resulted in more stimulated CO2 and CH4 emissions; whereas those pyrolyzed under relatively higher temperatures (e.g., >550 °C) became less stimulative (and sometimes even suppressive) for CO2 and CH4 emissions, especially when applied at higher rates. Nevertheless, the response of N2O emission to biochar application contrasted with those of CO2 and CH4. The results may contribute to better regulations for biochar application in combating GHG emissions in agriculture. [ABSTRACT FROM AUTHOR]

The influences of ammonia (NH3) and greenhouse gas (GHG) emissions from livestock on environment recently become a major concern of the worldwide. The objective of the study was to evaluate the effects of Yucca schidigera extract (YSE) on ammonia emission in manure and the release of green-house gases including methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) in artificial rumen of cows. Addition of YSE significantly decreased ammonia nitrogen (NH3-N) concentration (P < 0.01) and increased the percentage of total nitrogen (N) (P < 0.005) in manure incubation. The populations of total aerobic bacteria were significantly decreased by the addition of YSE with 1% and 2% (P < 0.05), while the populations of Lactobacilli were significantly increased in dose-dependent manner (P <0.001) in manure. In 1-12 h and 13-24h of ruminal fermentation in vitro, the yields of CH4, CO2 and N2O were dose-dependently reduced by the addition of YSE (P < 0.05). Results showed that YSE inhibit ammonia emission in manure and the release of green-house gases in artificial rumen of cows. [ABSTRACT FROM AUTHOR]

Agricultural production systems are known to be large contributors to global greenhouse gas (GHG) emissions and many studies have focused on the mitigation of GHG emissions from open-field and other traditional crop production practices. Little attention has been given to direct emissions from non-traditional production systems such as aquaponics. Here we determine direct GHG emissions (CO2, CH4, N2O) from a pilot-scale biofloc, decoupled aquaponics facility. We also determine how emissions from unit operations differ based on a set of environmental and operational parameters e.g. temperature, feeding rate, suspended solids, plant height, water flow rate, and nitrate levels. Major unit operations included a biofloc fish tank stocked with tilapia, a solids settling clarification system, and a climate-controlled greenhouse in which cucumber plants were grown in substrate culture. The study was separated into three seasons. In the summer of 2019, different pH treatments for cucumber irrigation water were tested. In the fall of 2019 and winter of 2020, emissions from perlite versus pine bark substrates were tested during cucumber production. Measurements indicated that aerial GHG emissions in intensively aerated areas of the fish tank were 4.7 to 46.8 times higher than those in areas with low-intensity aeration. High methane emissions (up to 44.8 g m-2 d-1) from the clarification system indicated anaerobic activity. Results from plant production showed a negative relationship between pH and N2O efflux (p=0.0001) while the choice of plant growth substrate had no significant effect on direct GHG emissions. Overall, carbon sequestration in plants could offset 40% to 62% of direct GHG emissions from the aquaponics system. This study provides insight into operational parameters that affect direct GHG emissions from aquaponics systems and provides data to support life cycle assessments. [ABSTRACT FROM AUTHOR]