Study On Temporal And Spatial Variation Characteristics And Driving Factors Of Embodied Carbon Emissions In China's Infrastructure

Since the Industrial Revolution,global CO₂ concentration has been increasing,and the global warming problem has caused widespread concern.There is a consensus among governments to control and mitigate CO₂ emissions.As the largest carbon emitter,China is facing tremendous pressure due to its rising total carbon emissions and high growth rate.Since China's reform and opening up in the late 1970s,the expansion of infrastructure construction leads to a large amount of consumption in construction materials and energy which cause environmental impacts and emit CO₂.Among them,building carbon emissions account for about 40%of total social emissions,which has been confirmed by many research institutions and scholars.As a major carbon emitter,infrastructure has an obligatory responsibility for carbon emission reduction.The overall target of national carbon emission reduction needs to be finally assigned to each province,and with the promotion and implementation of carbon emission trading market,each province will carry out infrastructure carbon quota allocation.According to the average lifetime of buildings in China,houses built in the early 1990s are facing demolition and reconstruction,and a new round of infrastructure construction may begin.How can we objectively and accurately set the baseline of infrastructure embodied carbon emissions without accurately verifying the value in different provinces?How to be fair and transparent?This will inevitably leads to conflicts of interest in regional development.Based on the above research background,we divide China's infrastructure into three major systems:building,road and railway.We calculate their embodied carbon emissions from the national and provincial levels,and analyses the characteristics of spatial-temporal distribution and regional differences,and decompose the driving factors affecting infrastructure embodied carbon emissions in different provinces from two dimensions of time and space.On this basis,we provide data support and policy guidance for regional and differentiated infrastructure development plan.?1?Infrastructure embodied carbon emissions in China and 31 provinces from1997 to 2016 are calculated by the material flow analysis model?MFA?.The results show more than 90%of the embodied carbon emissions come from buildings,but the average annual growth rate of the transportation embodied carbon emissions is faster,and the share is also increasing year by year.The embodied carbon emissions of urban and rural buildings are almost the same in 1997.By the end of 2016,the embodied carbon emissions of urban buildings are about 2.2 times that of rural buildings.The growth rate of embodied carbon emissions of different types of buildings ranked from large to small as follows:urban non-residential building>urban residential building>rural residential building>rural non-residential building.The embodied carbon emissions of urban steel-concrete structure,rural steel-concrete structure and rural brick-wood structure buildings are increasing,while the embodied carbon emissions of urban brick-concrete structure and rural whole-wood structure buildings are gradually decreasing.Among the eight common building materials,carbon emissions from steel and cement increased the fastest,while wood and brick increased the slowest.More than 94.3%of the transportation embodied carbon emissions come from road.Among the four kinds of transportation construction materials,cement contributes the most transportation embodied carbon emissions,and asphalt has the fastest annual growth rate.?2?We analyze the time-varying trend of embodied carbon of buildings and transportation in China from 1997 to 2016 by Linear Tendency Estimation Method.The results show that the provinces with extremely rapid-growing,rapid-growing and relatively rapid-growing of building embodied carbon emissions mainly concentrate in coastal regions and developed regions,while the medium-growing provinces are mostly in the central,western and northeastern regions.The slow-growing provinces are mainly located in the underdeveloped regions in the northwest and southwest of China.The rapid-growing and relatively-rapid growing of transportation embodied carbon emissions is similar to buildings.Medium-growing provinces are the most widely distributed,slow-growing provinces are more dispersed,with municipalities directly under the Central Government and minority autonomous regions as the main ones.Using global Moran's I index and LISA index to analyze the spatial autocorrelation of the per capita building carbon emission intensity and the per unit area transportation carbon emission intensity.The results show that during the whole research period,the per capita building carbon emission intensity of Moran's I experiences significant increase and decrease.The?high-high agglomeration?provinces are located in the northern and eastern coastal areas.The?low-low agglomeration?provinces are mostly concentrated in the northwest and southwest regions.The Moran's I of the per unit area transportation carbon emission intensity shows interval upward and downward,but the spatial agglomeration phenomenon is obviously strengthened.Finally,the?low-low agglomeration?area of Xinjiang-Inner Mongolia-Gansu-Qinghai-Ningxia-Tibet-Sichuan-Yunnan is formed.The?high-high agglomeration?area changes from Beijing-Tianjin-Hebei and Shanghai-Jiangsu to Shanghai-Jiangsu-Zhejiang.?3?The absolute difference of embodied carbon emissions of buildings and transportation measured by standard deviation show an increasing trend year by year;the relative difference of buildings embodied carbon emissions measured by coefficient of variation also show an increasing trend,while the relative difference of transportation embodied carbon emissions show a decreasing trend.The Gini coefficient and Theil index are used to analyze and study the regional differences of the per capita building carbon emission intensity and the per unit area transportation carbon emission intensity in eight economic regions.The results show that the difference index of the per capita building carbon emission intensity decrease first and then increase,and the overall trend is slowly rising.Before 2002,the differences mainly come from the intra-regional.Since 2003,inter-regional differences have become the main source of the total differences.The difference index of per unit area transportation embodied carbon emission intensity fluctuates before 2007,but it dosen't change much;thereafter,it shows a downward trend.The difference mainly comes from the inter-regional.?4?Combining Kaya identity and LMDI index decomposition model,five driving forces affecting the embodied carbon emissions of infrastructure are decomposed from the temporal dimension.The results show that the investment scale and economic effect are the main driving forces for the increase of embodied carbon emissions of infrastructure from national and provincial infrastructure,while the main reasons for the decrease are the technological level and investment benefit.In most provinces,the main driving forces of embodied carbon emissions from buildings and transportation are roughly the same as those at the national level.A multiple-region spatial decomposition model is constructed to decompose six driving forces affecting the embodied carbon emissions of infrastructure from the spatial dimension.The results show that population scale and provincial area are the main driving forces for the difference between the embodied carbon emissions of provincial and the national average.Technological level,investment effect,investment scale and economic effect are the important factors that cause the difference of embodied carbon emissions between provinces.The provinces with high population-intensive and provincial-scale have greater potential growth space of infrastructure embodied carbon emissions.Developed provinces should pay more attention to the role of technology and investment efficiency in mitigating and suppressing embodied carbon emissions.Based on the above conclusions,it can be seen that although the embodied carbon emissions of China's infrastructure are relatively large at present,from the perspective of development,China has only spent 30 or 40 years to complete the century-long infrastructure construction and embodied carbon emissions of some developed countries.Because of the long-term effectiveness,the existing infrastructure will provide long-term services for China's economic development and people's production and living needs.So the state and local government should have a forward-looking awareness when planning investment and low-carbon economic development path.Provinces should be treated differently according to local resource characteristics and development orientation.For the eastern coastal regions with high embodied carbon emissions,it is necessary to strengthen the maintenance of infrastructure,prolong the lifetime of infrastructure,and avoid large demolition and construction caused by some human factors.For the western inland regions with low carbon emissions,the role of green building materials and low carbon construction technology should be strengthened to reduce material and energy consumption and carbon emissions.At the same time,balance the regional disparity of infrastructure embodied carbon emissions caused by population and economic development level.