A Review on Waste Management Options to Lessen Greenhouse Gas Emissions from Paper

China's CH4 and CO2 emissions: Bottom-up estimation and comparative analysis

In this study, a comparative analysis was presented to detect the quota of urban and rural areas from total greenhouse gas (GHG) emissions in 26 selected countries of the Middle East and Central Asia (MECA) during 1994–2014. For this purpose, 18 independent variables such as land area, population characteristics, energy use and consumption, gross domestic product (GDP), CO2 emissions, etc., were considered in addition to one dependent variable of total GHG emissions. Statistical modeling to investigate GHG emissions was constructed comprising the quantitative procedures of the correlation test and clustering analysis, which can be considered as the fundamental basis of each econometric analysis. The GHG emissions from the urban (rural) sector of total countries in 2014 were obtained as 3313.4 (1135.6) Mt of CO2 equivalents, which is about 74.5% (25.5%) of the total GHG emissions (4449.1 Mt of CO2 equivalents) in the MECA region. The correlation test between GHG emissions and urban indicators revealed the significant records (R from 0.745 to 0.981) compared with rural indicators (R from 0.337 to 0.890). Based on the clustering analysis of the countries, Cluster A, comprised of three countries of Iran, Saudi Arabia, and Turkey, was categorized as countries with very high contributing to the total GHG emissions in the MECA region (~ 43.3%). The quotas of emissions from urban and rural sectors in the Cluster A were estimated as 83.1% and 16.9% from the total GHG emissions in 2014 (1921.3 Mt of CO2), while the same quotas were predicted as 73.1% and 26.9% from the total GHG emissions in 2030 (1921.3 Mt of CO2). This study carried out comprehensive research on the GHG emissions from the urban and rural areas in a crucial region of the world, which is faced with the rising growth of population, urbanization, globalization, high-energy use, and fuel consumption.

This study investigates the effect of energy consumption on greenhouse gas (GHG) emissions in 33 African countries from 1995–2017. It contributes to the literature by investigating the effect of disaggregated measures of energy consumption (coal, oil and other liquids, renewable energy, and electricity) on GHG emissions (CO2, N2O, CH4, and total GHG emissions) in Africa and identifies the transmission channels through which energy consumption affects GHG emissions. The system GMM is used in the study as it accounts for possible endogeneity and the potential correlation between the error term and the country fixed effects. The results show that coal consumption significantly increases CO2, CH4, and total GHG emissions and reduces N2O emissions. Oil consumption increases CO2 and total GHG emissions but reduces N2O and CH4 emissions. Renewable energy consumption reduces CO2 and CH4 emissions but increases N2O emissions. Finally, electricity consumption promotes CO2, N2O, CH4 and total GHG emissions in Africa. Further analyses show that foreign trade and economic growth are the channels through which oil consumption increases GHG emissions. The adverse effect of electricity is through urbanization. Renewable consumption could decrease GHG emissions through sustainable urbanization and trade policies. The findings suggest that countries should gradually reduce coal consumption and encourage renewable energy consumption, which has the lowest impact on the environment.

Climatic temperature controls the geographical patterns of coastal marshes greenhouse gases emissions over China

Salt-affected soils contain high levels of soluble salts (saline soil) and exchangeable sodium (alkali soil). Globally, about 932 million ha (Mha), including 831 Mha of agricultural land, is salt-affected. Salinity and sodicity adversely affect soil microbial diversity and enzymatic activities, and thereby carbon and nitrogen dynamics and greenhouse gas (GHG) emissions from soils. In this review article, we synthesize published information to understand the impact of salinity and sodicity on GHG production and emissions from salt-affected soils, and how various reclamation amendments (gypsum, phosphogypsum, organic manure, biochar, etc.) affect GHG emissions from reclaimed soils. Nitrous oxide (N2O) and methane (CH4) emissions are of greater concern due to their 298 and 28 times higher global warming potential, respectively, compared to carbon dioxide (CO2), on a 100-year time scale. Therefore, CO2 emissions are given negligible/smaller significance compared to the other two. Generally, nitrous oxide (N2O) emissions are higher at lower salinity and reduced at higher salinity mainly due to: (a) higher ammonification and lower nitrification resulting in a reduced substrate for denitrification; (b) reduced diversity of denitrifying bacteria lowered down microbial-mediated denitrification process; and (c) dissimilatory nitrate reduction to ammonium (DNRA), and denitrification processes compete with each other for common substrate/nitrate. Overall, methane (CH4) emissions from normal soils are higher than those of salt-affected soils. High salinity suppresses the activity of both methanogens (CH4 production) and methanotrophs (CH4 consumption). However, it imposes more inhibitory effects on methanogens than methanotrophs, resulting in lower CH4 production and subsequent emissions from these soils. Therefore, reclamation of these soils may enhance N2O and CH4 emissions. However, gypsum is the best reclamation agent, which significantly mitigates CH4 emissions from paddy cultivation in both sodic and non-sodic soils, and mitigation is higher at the higher rate of its application. Gypsum amendment increases sulfate ion concentrations and reduces CH4 emissions mainly due to the inhibition of the methanogenesis by the sulfate reductase bacteria and the enhancement of soil redox potential. Biochar is also good among the organic amendments mitigating both CH4 and N2O emission from salt-affected soils. The application of fresh organic matter and FYM enhance GHG emissions for these soils. This review suggests the need for systematic investigations for studying the impacts of various amendments and reclamation technologies on GHG emissions in order to develop low carbon emission technologies for salt-affected soil reclamation that can enhance the carbon sequestration potential of these soils.

Integrative effects of soil tillage and straw management on crop yields and greenhouse gas emissions in a rice–wheat cropping system

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Prescribed fires or wildfires are common in natural ecosystems. Biochar input during fires can impact soil greenhouse gas (GHG) emissions, including methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O). Meadows are functionally important ecosystems due to their large carbon (C) and nitrogen (N) stocks and potential to mitigate GHG emissions. The effects of biochar on meadow GHG emissions may be sensitive to whether it is derived from more than one type of vegetation, especially with N addition and warming. To further our understanding of how input of fire-derived biochar affects meadow soil GHG emissions, especially under the context of N deposition and warming, we conducted this study to examine potential non-additive effects of these factors. We collected soils from meadows dominated by Miscanthus sinensis and Arundinella hirta at Wugong Mountain (Jiangxi, China). Biochar was produced by pyrolyzing the aboveground vegetation of each of the two species at 450 °C for 1 h. Mixed biochar was produced by 1:1 ratio. Soil GHG emissions and N transformations were measured by incubating soils with biochar (control, M. sinensis biochar, A. hirta biochar, mixed biochar) and N addition (control vs. 6 g m−2) treatments at different temperatures (10, 15, 20, or 25 °C). Biochar input consistently increased both CH4 and N2O flux, but only A. hirta and mixed biochar decreased CO2 emission rates. Mixed biochar imposed non-additive effects on cumulative CH4 and CO2 emissions. Biochar decreased soil nitrification rates and increased the temperature sensitivity of soil N2O emission rates. The results indicated that biochar input during fires in meadows impacts soil GHG emissions and N transformations. Input of biochar into meadow soil following fire impacted GHG emissions, and mixing biochar derived from different species imposed non-additive effects on CH4 and CO2 emissions. The variable and non-additive biochar effects on soil GHG emissions showed that fire-induced alterations in meadow soil GHG emissions will depend on the species composition of the local plant community. The effects of biochar on meadow soil GHG emissions after fires should be considered in future budgets of meadow soil GHG emissions and prediction of prescribed fire impacts on meadow ecosystems under the context of N deposition and warming.

Meta-analysis of GHG emissions stimulated by crop residue return in paddy fields: Strategies for mitigation

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

Nitrous oxide and methane emissions from coffee agroforestry systems with different intensities of canopy closure

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.

Mitigating greenhouse gas emissions from irrigated rice cultivation through improved fertilizer and water management

Greenhouse gas (GHG) emissions from rivers and lakes have been shown to significantly contribute to global carbon and nitrogen cycling. In spatiotemporal-variable and human-impacted rivers in the grassland region, simultaneous carbon dioxide, methane and nitrous oxide emissions and their relationships under the different land use types are poorly documented. This research estimated greenhouse gas (CO2, CH4, N2O) emissions in the Xilin River of Inner Mongolia of China using direct measurements from 18 field campaigns under seven land use type (such as swamp, sand land, grassland, pond, reservoir, lake, waste water) conducted in 2018. The results showed that CO2 emissions were higher in June and August, mainly affected by pH and DO. Emissions of CH4 and N2O were higher in October, which were influenced by TN and TP. According to global warming potential, CO2 emissions accounted for 63.35% of the three GHG emissions, and CH4 and N2O emissions accounted for 35.98% and 0.66% in the Xilin river, respectively. Under the influence of different degrees of human-impact, the amount of CO2 emissions in the sand land type was very high, however, CH4 emissions and N2O emissions were very high in the artificial pond and the wastewater, respectively. For natural river, the greenhouse gas emissions from the reservoir and sand land were both low. The Xilin river was observed to be a source of carbon dioxide and methane, and the lake was a sink for nitrous oxide.

The study is focused on impact of manure application, rice varieties and water management on greenhouse gas (GHG) emissions from paddy rice soil in pot experiment. The objectives of this study were a) to assess the effect of different types of manure amendments and rice varieties on greenhouse gas emissions and b) to determine the optimum manure application rate to increase rice yield while mitigating GHG emissions under alternate wetting and drying irrigation in paddy rice production. The first pot experiment was conducted at the Department of Agronomy, Yezin Agricultural University, Myanmar, in the wet season from June to October 2016. Two different organic manures (compost and cow dung) and control (no manure), and two rice varieties; Manawthukha (135 days) and IR-50 (115 days), were tested. The results showed that cumulative CH4 emission from Manawthukha (1.084 g CH4 kg-1 soil) was significantly higher than that from IR-50 (0.683 g CH4 kg-1 soil) (P<0.0046) with yield increase (P<0.0164) because of the longer growth duration of the former. In contrast, higher cumulative nitrous oxide emissions were found for IR-50 (2.644 mg N2O kg-1 soil) than for Manawthukha (2.585 mg N2O kg-1 soil). However, IR-50 showed less global warming potential (GWP) than Manawthukha (P<0.0050). Although not significant, the numerically lowest CH4 and N2O emissions were observed in the cow dung manure treatment (0.808 g CH4 kg-1 soil, 2.135 mg N2O kg-1 soil) compared to those of the control and compost. To determine the effect of water management and organic manures on greenhouse gas emissions, second pot experiments were conducted in Madaya township during the dry and wet seasons from February to October 2017. Two water management practices {continuous flooding (CF) and alternate wetting and drying (AWD)} and four cow dung manure rates {(1) 0 (2) 2.5 t ha-1 (3) 5 t ha-1 (4) 7.5 t ha-1} were tested. The different cow dung manure rates did not significantly affect grain yield or greenhouse gas emissions in this experiment. Across the manure treatments, AWD irrigation significantly reduced CH4 emissions by 70% during the dry season and 66% during the wet season. Although a relative increase in N2O emissions under AWD was observed in both rice seasons, the global warming potential was significantly reduced in AWD compared to CF in both seasons (P<0.0002, P<0.0000) according to reduced emission in CH4. Therefore, AWD is the effective mitigation practice for reducing GWP without compromising rice yield while manure amendment had no significant effect on GHG emission from paddy rice field. Besides, AWD saved water about 10% in dry season and 19% in wet season.