Exploration of ‘hot-spots’ of methane and nitrous oxide emission from the agriculture fields of Assam, India

This study aimed to determine the emissions of methane (CH4) and nitrous oxide (N2O) from seven Tunisian livestock species and their evolution over eleven consecutive years (2008–2018). The species of animals used were cattle (dairy and others), sheep, goats, camelids, horses, donkeys and mules, and poultry. The estimations of CH4 and N2O emissions were based on the Intergovernmental Panel on Climate Change (IPCC) guidelines for national inventories, using Tier 1 and Tier 2 approaches, with its default emission factors (EFs). The Tier 2 approach was applied only for the calculation of EF to estimate CH4 emissions related to livestock manure management. CH4 emission represented more than 92% of the total greenhouse gas (GHG) from livestock emissions. Moreover, 53% of the total CH4 emissions from livestock were derived from cattle, followed by sheep, goats, other mammals (camelids, horses, mules, and donkeys), and poultry. During the period covered by the study (2008–2018), a slight and continuous decrease of both livestock population and total GHG emissions was observed, mainly in terms of CH4. In mammals, CH4 emissions were greater than N2O emissions, whereas in poultry, N2O emissions were up to 2.6 times greater than CH4 emissions. The aggressive drive of the government to increase cattle and sheep production might affect CH4 emissions in the future. Therefore, periodic estimations of GHG emissions from livestock are required to follow the time trends for more rational decision-making regarding livestock and GHG emissions policies.

The objective was to provide a systematic review of the literature on greenhouse gas (GHG) emissions from swine operations, with a meta-analysis that integrates results of independent studies. A total of 53 studies that measured GHG emissions from swine operations were included in the analyses. Results showed that the Intergovernmental Panel on Climate Change (IPCC) approaches were effective in estimating the overall CH4 and N2O emission levels from swine operations, but the variation of the measured emissions is not adequately captured. An overestimation by the IPCC approaches for CH4 emissions was observed for swine buildings with pit systems in European studies and the average percentage relative difference (PRD) between the measured and the IPCC values is -21.1%. The observed CH4 emissions from lagoons were lower than the IPCC estimated values and the average PRD is -33.9%. In North American studies the observed N2O emission factors for swine buildings with pit systems were significantly lower than the IPCC default values whereas in European studies they were significantly greater than the IPCC default values. The measured CH4 and N2O emissions were significantly affected by stage of production (P = 0.05 and <0.01, respectively) and geographic regions (P = 0.04 and 0.02, respectively). The IPCC approaches were effective in simulating the effect of temperature on CH4 emissions from outdoor slurry storage facilities whereas they could overestimate CH4 emissions from lagoons at low temperatures. The CH4 emissions from pits inside swine buildings were not significantly affected by average ambient temperatures. A positive relationship between diet CP content and CH4 emissions was confirmed in the meta-analysis. The obtained knowledge can be helpful in efforts to improve estimation of GHG emissions from swine operations.

Greenhouse gas (GHG) emissions from rice fields have huge effects on climate change. Low-cost systems and management practices to quantify and reduce GHGs emission rates are needed to achieve a better climate. The typical GHGs estimation processes are expensive and mainly depend on high-cost laboratory equipment. This study introduces a low-cost sensor-based GHG sampling and estimation system for rice fields. For this, a fully automatic gas chamber with a sensor-integrated gas accumulator and quantifier unit was designed and implemented to study its performance in the estimation efficiency of greenhouse gases (CH4, N2O, and CO2) from rice fields for two crop seasons. For each crop season, three paddy plots were prepared at the experimental site and then subjected to different irrigation methods (continuous flooding (CF), intermittent flooding (IF), and controlled intermittent flooding (CIF)) and fertilizer treatments to study the production and emission rates of GHGs throughout the crop growing season at regular intervals. A weather station was installed on the site to record the seasonal temperature and rainfall events. The seasonal total CH4 emission was affected by the effects of irrigation treatments. The mean CH4 emission in the CIF field was smaller than in other treatments. CH4 and N2O emission peaks were high during the vegetative and reproductive phases of rice growth, respectively. The results indicated that CIF treatment is most suitable in terms of rice productivity and higher water use efficiency. The application of nitrogen fertilizers produced some peaks in N2O emissions. On the whole, the proposed low-cost GHGs estimation system performed well during both crop seasons and it was found that the adaption of CIF treatment in rice fields could significantly reduce GHG emissions and increase rice productivity. The research results also suggested some mitigation strategies that could reduce the production of GHGs from rice fields.

Greenhouse gas emission from direct seeding paddy field under different rice tillage systems in central China

The objective of the project is to provide a systematic review of the literature on GHG emissions from swine operations, including both a qualitative review and a meta-analysis that integrates results of various independent studies. Results showed that variation of the CH4 and N2O emission rates from swine operations has not been adequately captured by the Intergovernmental Panel on Climate Change (IPCC) approaches. For CH4 emissions, the differences between the IPCC estimated emission rates and measured values were significantly influenced by type of emission source, geographic region and measurement methods. In North American studies, the results indicated an overestimation by the IPCC approaches for CH4 emissions from lagoons and the discrepancy mainly occurred at lower temperatures. In European studies, the results indicated an overestimation of the IPCC approaches in swine buildings with pit systems. For N2O emissions, an overall underestimation of the IPCC approaches was observed in European studies but not in North American studies. Swine buildings generated much higher CO2 emissions than manure storage facilities while CH4 and N2O emissions were not different. Lagoons generated significantly higher N2O emissions than slurry storage basin/tanks, while CH4 and CO2 emissions were not different. Farrowing swine emitted more CH4 and CO2 emissions as compared with other swine categories, while gestating swine had greater N2O emissions. North American studies reported significantly higher CH4 emissions from swine operations than European and Asian studies. Diet CP was not significant on GHG emissions, while temperature were significant on CH4 emissions from lagoons or slurry storage facilities.

A review on the main affecting factors of greenhouse gases emission in constructed wetlands

Energy supply utilities release significant amounts of greenhouse gases (GHGs) into the atmosphere. It is essential to accurately estimate GHG emissions with their uncertainties, for reducing GHG emissions and mitigating climate change. GHG emissions can be calculated by an activity-based method (i.e., fuel consumption) and continuous emission measurement (CEM). In this study, GHG emissions such as CO2, CH4, and N2O are estimated for a heat generation utility, which uses bituminous coal as fuel, by applying both the activity-based method and CEM. CO2 emissions by the activity-based method are 12–19% less than that by the CEM, while N2O and CH4 emissions by the activity-based method are two orders of magnitude and 60% less than those by the CEM, respectively. Comparing GHG emissions (as CO2 equivalent) from both methods, total GHG emissions by the activity-based methods are 12–27% lower than that by the CEM, as CO2 and N2O emissions are lower than those by the CEM. Results from uncertainty estimation show that uncertainties in the GHG emissions by the activity-based methods range from 3.4% to about 20%, from 67% to 900%, and from about 70% to about 200% for CO2, N2O, and CH4, respectively, while uncertainties in the GHG emissions by the CEM range from 4% to 4.5%. For the activity-based methods, an uncertainty in the Intergovernmental Panel on Climate Change (IPCC) default net calorific value (NCV) is the major uncertainty contributor to CO2 emissions, while an uncertainty in the IPCC default emission factor is the major uncertainty contributor to CH4 and N2O emissions. For the CEM, an uncertainty in volumetric flow measurement, especially for the distribution of the volumetric flow rate in a stack, is the major uncertainty contributor to all GHG emissions, while uncertainties in concentration measurements contribute a little to uncertainties in the GHG emissions.Implications:Energy supply utilities contribute a significant portion of the global greenhouse gas (GHG) emissions. It is important to accurately estimate GHG emissions with their uncertainties for reducing GHG emissions and mitigating climate change. GHG emissions can be estimated by an activity-based method and by continuous emission measurement (CEM), yet little study has been done to calculate GHG emissions with uncertainty analysis. This study estimates GHG emissions and their uncertainties, and also identifies major uncertainty contributors for each method.

ABSTRACTAgricultural fields, including rice (Oryza sativa L.) paddy fields, constitute one of the major sources of atmospheric methane (CH4) and nitrous oxide (N2O). Organic matter application, such as straw and organic fertilizer, enhances CH4 emission from paddy fields. In addition, rice straw management after harvest regulates CH4 emissions in the growing season. The interaction of tillage times and organic fertilizer application on CH4 and N2O emissions is largely unknown. Therefore, we studied the effects of fallow-season tillage times and fertilizer types on CH4 and N2O emissions in paddy fields in Ehime, southwestern Japan. From November 2011 to October 2013, four treatments, two (autumn and spring) or one (spring) in the first year, or two (autumn and spring) or three (autumn, winter, and spring) in the second year times of tillage with chemical or organic fertilizer application, were established. Gas fluxes were measured by the closed-chamber method. Increasing the number of tillage times from one to two decreased succeeding CH4 emission and the emission factor for CH4 (EFCH4) in the rice-growing season, suggesting that the substrate for CH4 production was reduced by autumn and spring tillage in the fallow season. Higher EFCH4 [1.8–2.0 kg carbon (C) ha−1 d−1] was observed when more straw was applied (6.9–7.2 Mg ha−1) in the second year. Organic fertilizer application induced higher CH4 emission just after the application as basal and supplemental fertilizers, especially at a lower straw application rate. This indicated that EFCH4 in the organically managed fields should be determined individually. Organic fertilizer application with two tillage times induced N2O efflux during the rice-growing season in the second year, but N2O emissions were not affected by winter tillage. Although paddy fields can act as an N2O sink because of reduced soil conditions when straw application was high, application of organic C and nitrogen as fertilizer can enhance N2O production by the denitrification process during the growing season, especially in the ripening stage when soil anaerobic conditions became moderate. These results suggest that negative emission factors for N2O (EFN2O) can be applied, and EFN2O of organic fertilizer should be considered during the estimation of N2O emission in the paddy field.

Effects of water management on greenhouse gas emissions from farmers' rice fields in Bangladesh

Methane (CH4) and nitrous oxide (N2O) are two extremely important greenhouse gases in the atmosphere. Nitrogen fertilizer is an important factor affecting CH4 and N2O emissions in rice fields. Rational application of nitrogen fertilizer can not only promote high yields of rice but also reduce greenhouse gas emissions. Existing studies have shown that nitrogen reduction and optimal application can effectively improve the nitrogen use efficiency of rice on the basis of ensuring the yield and reduce the loss of N2O caused by nitrification and denitrification of excessive nitrogen in soil. Fertilization times and fertilizer types have significant effects on CH4 and N2O emissions in paddy fields. In this study, a field experiment was conducted for two consecutive years (2019-2020) to study the effects of fertilizer application on CH4 and N2O emissions from rice fields by setting up four treatments consisting of no fertilizer (CK), customary fertilizer application by farmers (CF), twice fertilizer (TT), and 20% replacement of chemical fertilizer by organic fertilizer (OF) using static chamber-gas chromatography. Additionally, the effect of integrating rice yield and integrated global warming potential (GWP) on the greenhouse gas emission intensity (GHGI) per unit of rice yield was analyzed to explore fertilizer application for yield increase and emission reduction in a typical rice growing area in the middle and lower reaches of Yangtze River. The results showed that:① compared with those of CK, the fertilizer treatments reduced CH4 emissions by 14.6%-25.1% and increased N2O emissions by 610%-1836% in both years; ② compared with those of CF, both the TT and OF treatments showed a trend of increasing CH4 emissions and reducing N2O emissions. CH4 emissions increased by 1.8% (P>0.05) and 14.0% (P<0.05), respectively. The annual average of N2O emissions decreased by 63.3% (P<0.05) and 49.2% (P<0.05) in both the TT and OF treatments, respectively. ③ Compared with that of CK, both fertilizer applications increased rice yield and reduced GHGI; compared with that of CF, the OF and TT treatments increased the average annual rice yield by 17.0% and 10.7%, respectively, and reduced GHGI by 6.8% and 13.7%, respectively. The OF treatment had a better yield increase than that of the TT treatment, and the TT treatment had a slightly better emission reduction than that of the OF treatment. In terms of combined yield and GHG emission reduction, both twice fertilizer (TT) and 20% replacement of chemical fertilizer by organic fertilizer (OF) could reduce the intensity of GHG emission per unit of rice yield and achieve yield increase and emission reduction while ensuring rice yield.

Methane emissions along biomethane and biogas supply chains are underestimated

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The methodology 1 provided by the Intergovernmental Panel on Climate Change (IPCC) guidelines is widely used for estimating CH4 and N2O production by cattle, but the reference value is only distinguished between developed and developing countries, with large uncertainties. The objective of this study was to calculate the CH4 and N2O emissions factor by dairy and beef cattle, and the emissions in the Hubei province according to the recommendations of IPCC (2006) using regional farm management data. CH4 emission factors from enteric fermentation in Hubei province was 81.560 kg CH4/head/year for dairy cattle with CH4 emissions of 930.844 kg. CH4 and N2O emission factors from manure management were 0.408 kg/head/year and 1.307 kg/head/year for dairy cattle. The greenhouse gas emissions from breeding cows in Hubei Province in 2012 was 950.418 kg. In general, CH4 emission estimates using Tier 2 (IPCC, 2006) were slightly lower than those from Tier 1, mainly due to use of lower emission factors, especially for CH4 emitted from manure management The main CH4 emission source was enteric fermentation, being 99.512% of livestock CH4 emissions. Direct emission was the largest component of total N2O emission (56.695%).

Biochar improved rice yield and mitigated CH4 and N2O emissions from paddy field under controlled irrigation in the Taihu Lake Region of China

Methane (CH4) and nitrous oxide (N2O) are the two most important greenhouse gases (GHG) from flooded paddy fields in Indonesia. This review aims to characterise CH4 and N2O emissions from flooded paddy fields by published data analysis and to examine the potential of biochar from rice straw (RSB) and rice husk (RHB) to mitigate the emissions in Indonesia. A comparison of various box-plot datasets of CH4 emissions showed that the different types of flooded paddy field soil cause varying amounts of CH4 emissions from various regions in Indonesia. Sequentially, CH4 emissions of flooded paddy fields from highest to lowest are Alluvial of Kalimantan and Sulawesi, Andisols of Java, Ultisols of Sumatra, Alfisols of Java and Bali and Inceptisols of Java and Bali, with a mean of 1062, 505, 446, 135 and 64 kg ha-1 season-1, respectively. The organic amendments application combined with chemical fertilisers is the principal driver of anthropogenic CH4 emissions from paddy fields. However, N chemical fertiliser application contributes only about 0.37% of the N2O flux, 0.69 kg ha-1 season-1. The produced biochar number was insufficient effectively to reduce CH4 and N2O emissions, at least 20 tonnes ha-1 year-1, in addition to the pyrolysis process to produce biochar, releasing CH4 emissions. Yet, with its recalcitrant properties and continuous application, RSB and RHB potentially reduce CH4 and N2O emissions from paddy fields.