Assessing The Environmental Impacts Of Urban Transport Infrastructure Via Life Cycle Assessment

Urban is a major source of greenhouse gases(GHG)which emits more than 70% CO2 equivalent.The environmental impacts during urban construction have been the puzzles of environmental governance and the focus fields in abroad and China.Urban transport infrastructure,as one of the most important infrastructure,provided convenience services to the resident as well as consumed a large amount of resources and energy,emitted GHG.Shenzhen,as the national low carbon city,national ecological city and the first pilot city of low-carbon transportation,has formed integrated traffic network and assess the environmental impacts of transport infrastructure in Shenzhen is significant to the development of low carbon city and energy saving.This study tries to assessing the environmental impacts of urban transport infrastructure via life cycle assessment based on field surveys,LCA software and statistic data.The accounting model of carbon emissions in transport infrastructure sector was established and the scope and system boundary was defined and the whole life cycle was separated into 4 stages: materials using;construction;repair and demolition.Inventory analysis was conducted of different transport infrastructure(including roads,metro and bridges)to quantify the life cycle carbon emissions based on the accounting model.Shenzhen was selected as a case study to quantify and forecast the annual carbon emissions in urban transport infrastructure sector.And the emission factors of which could be having an enormous influence and contribution were analyzed.The calculations results of 1 km Shenzhen transportation infrastructure show that the carbon emissions 1 km expressway was more than 2.7 thousand tons and that the most GHG was discharged in the material using stage.The carbon emissions of 1 km first class road to fourth class road were between 1 to 2 thousand tons which were lower than expressway.The carbon emissions of 1 km bridge was 3.2 thousand tons and 1 km metro was around 80 thousand tons and where the material using stage contributed more than 90% to the whole life cycle carbon emissions.In the view of Shenzhen,the calculating model was established based on the previous calculating data of 1 km different transport infrastructure.The annual carbon emissions from the year of 2006 to 2013 in urban transport infrastructure of Shenzhen were calculated.The annual carbon emissions were around 2 million tons in a stable state most of which was resulted from the construction of metro,accounting for 80% of the total annual carbon emissions.According to the 13 th Five Year Plan of urban metabolism in Shenzhen,the total carbon emission in transport infrastructure part will reach 10 million tons from 2016 to 2020.Based on this result,suggestions in materials manufacturing technique,transport infrastructure planning and pavement structure type selection were raised.To summarize,this study is a preliminary research in the life cycle environmental impacts of transport infrastructure in Shenzhen.A streamlined life cycle assessment method was built for quantifying the life cycle carbon emissions for transport infrastructure in Shenzhen and the result obtained provide an sufficient dimensioning of carbon emission in transport infrastructure and this study can provide suggestions in energy saving and can be considered as an opportunity for research and study of other cities' carbon emissions of transport infrastructure in China.