| Emissions of greenhouse gas caused by human activities are considered to be one of the important causes of global climate change,and how to alleviate the growing problem of greenhouse gas emissions is the current research focus.As the second largest greenhouse gas,methane has higher warming potential and larger emission reduction space.As the most important greenhouse gas emitter,China faces great pressure and has responsibility in the field of emission reduction.There has been some research on methane emission in China,but in general,there are still many deficiencies in methane inventory construction and emission characteristics analysis.Based on the existing methods and studies,this study builds the complete methane emission inventory of sub-area and sub-department from 2000 to 2014 in China,and estimates the emission from 2015 to 2020 by an artificial neural network model.Based on the analysis of the time series and spatial distribution of methane emissions in China,this paper concludes the regulations and trends of methane emissions in various sectors.Finally,based on the conclusions,this study provides specific strategies and basis for the further implementation of methane emission reduction in China.This study consists nine parts.As part one,the introduction part sums up the research background and the status quo of the study,and elaborates the research methods and technical routes of this paper at the same time.From part two to part eight,it makes researches on the waste,wastewater,animal husbandry,rice field,biomass,coal mining and all the anthropogenic methane emissions respectively.Each part consists four sections,and from the emission inventory construction,future emission prediction,emission characteristics analysis and emission reduction direction to discuss and analyze methane emissions.In part nine,it summaries and prospectes the research results of this paper.The main findings and results are as follows:(1)Methane emissions of the waste disposal departments increased from 1141.10 Gg to 1748.62 Gg from 2000 to 2014.Emissions will continue to grow steadily from 1838.24 Gg to 2003.07 Gg from 2015 to 2020.The more developed large provinces are the main emission areas.In comparison with 2000,2010 and 2020,there is a shift from the east and south to the northeast and the centralwest for emission intensive areas.For methane emission reudction,it should be targeted at intensive areas to formulate targeted policies.Meanwhile China should pay more attention to landfill and recycling of waste to achieve methane emission reduction.(2)Methane emissions from wastewater increased from 1349.01 Gg to 3430.02 Gg from 2000 to 2014.Methane from industrial wastewater treatment is the most important emission source.Emissions from 2015 to 2020 will increase from 3875.30 Gg to 5212.75 Gg,and methane emissions from domestic wastewater will continue to increase.In terms of spatial distribution,there will be a transition for emission intensive areas from eastern and coastal areas to inland areas such as the central and southwestern regions.In view of methane emission reduction in wastewater,it is necessary to consider the characteristics of different types of wastewater and the differences of emission in different regions,at the same time,through the development of technical means and applications to solve the problem of methane emissions in wastewater treatment.(3)From 2000 to 2014,the methane emission from livestock decreased from 12629.04 Gg to 11770.83 Gg,and enteric fermentation of beef cattle was the main source of methane emission.From 2015 to 2020,the amount of methane from enteric fermentation will decrease,while the emissions of methane from manure management will remain stable.It is worth noting that there are differences in methane emissions based on food consumption and livestock breeding,and there is a phenomenon of emission transfer among provinces.The emission reduction of methane in livestock should first consider the emission characteristics of different livestock types and breeding areas,and pay attention to the impact of the consumption market on livestock breeding at the same time.In addition,China should pay attention to the phenomenon of methane emission transfer.(4)From 2000 to 2014,methane emission from rice paddied was rather stable and slightly decreased from 5854.6 Gg to 5680.06 Gg.From 2015 to 2020,methane in rice paddy fields did not fluctuate much,slightly decreased from 5813.56 Gg to 5741 Gg.The concentration of emissions is mainly in the southern region,where plants double cropping rice.From the perspective of irrigation and fertilization,the methane emission from paddy fields can be greatly reduced by improving irrigation water and irrigation methods,fertilization methods and fertilizer types.In addition,the cultivation and promotion of high-yield and low-emission rice can achieve methane emission reduction from the source.(5)From 2000 to 2014,the methane emission from biomass combustion increased from 1433.60 Gg to 2177.39 Gg,and straw combustion was the main source of methane emission in rural China.Methane emissions will drop slightly from 2291.99 Gg to 2217.76 Gg between 2015 and 2020.In terms of spatial distribution,the region with large population and low level of urbanization is the main emission area.For methane emissions from biomass combustion,China should make adjustments and improvements to the fuels and stoves that used in large rural areas.On the other hand,there is still a need to strengthen the management of open burning phenomenon and the recovery of biomass such as straw.(6)As the main source of methane emissions,from 2000 to 2014,methane emissions from coal mining increased from 5359.69 Gg to 15181.63 Gg.It is estimated that from 2015 to 2020,methane emissions will decrease from 13711.71 Gg to 7288.74 Gg due to the rapid growth of methane recovery.The spatial distribution of methane emission from coal mining is relatively fixed,mainly concentrated in Shanxi,Guizhou,Anhui,Henan and Inner Mongolia.Whether China could ensure the efficiency of coal mining and methane recovery is the key to achieve methane emission reduction.(7)From 2000 to 2014,anthropogenic methane emissions in China increased from 27510.07 Gg to 39503.27 Gg,coal mining,enteric fermentation and rice paddies were the main sources of methane emissions.For a variety of reasons,such as data and methods,most institutions overestimated anthropogenic methanogenesis emissions from China to varying degrees.From 2015 to 2020,methane emission is expected to decrease from 37945.58 Gg to 31411.58 Gg due to the rapid growth of methane recovery and utilization in coal mines.From the spatial distribution,because of the dense areas of coal mining,animal husbandry and paddy fields are basically fixed,anthropogenic methane emission intensive areas are also relatively stable and concentrated.By comparing with carbon dioxide emissions in China and considering the changes of methane emissions per capita and GDP,the situation of anthropogenic methane emissions in China is relatively optimistic.For further methane emission reductions,this study suggests that China can take actions from the following aspects: implement emission reduction strategies targetedly according to the dynamic emission characteristics of different sectors;upgrade the recovery and reuse of methane from a technical and market perspective;reduce uncertainty in methane inventories and account for emissions by using a variety of methodologies;start from the people’s daily life,and call for the whole people to implement energy conservation and emission reduction. |
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