| Confined by the resource structure,the proportion of ammonia production from natural gas will gradually decrease in China that is the world’s largest ammonia producer country,which will further aggravate the resource and environmental problems.But China has the world’s largest recoverable shale gas reserves,which may be a new way for ammonia production in China.However,the stage of shale gas extraction may cause water shortages and air pollution.So it is necessary to evaluate the environmental impact of shale gas based ammonia production from the perspective of the life cycle.In this study,Life Cycle Assessment was used to quantify the energy consumption,water depletion and environmental impact of the life cycle of ammonia from shale gas,and it is compared with coal and residual oil based ammonia to study whether the shale gas route has environmental sustainability.Finally,Data Quality Indicator method and Monte Carlo simulation method were combined to discuss the uncertainty of the results.（1）In the life cycle of ammonia production from shale gas,the values of abiotic depletion and global warming potential are 2.957×104 MJ/ton NH3 and 3.040×102kg CO2-eq/ton NH3,respectively.In addition to water depletion,the stage of shale gas extraction is the main contribution stage for other selected impact categories.The generation of by-product steam has a positive environmental benefit on ozone layer depletion category throughout the life cycle.The disposal of water-based drilling mud and cuttings and the transport for the process of shale gas extraction are the key parameters.Among them,the disposal of water-based drilling mud and cuttings contributed 24.14%to eutrophication potential and 46.08%to human toxicity potential,respectively,and the transport of the stage of shale gas extraction accounted for 9.43%to global warming potential.In addition,although electricity（mainly hydroelectric power）has a good performance on ozone layer depletion category,it is the main source of acidification potential and water depletion.Especially on water depletion category,electricity contributed96.74%.If the way of electricity generation is changed to coal power generation and wind power generation,the water depletion will be greatly reduced.The results of uncertainty analysis showed that stable conclusion could not be drawn on human toxicity category,and other impact categories had low deviation from the mean value and high robustness.（2）By comparing the shale gas route with the coal route and the residual oil route,it is found that the shale gas route has significant environmental benefits,and the scenario analysis results also verify this conclusion.Among all selected environmental impact categories,the shale gas route is lower than 64%of the highest environmental impact route,and in which the global warming potential and energy consumption are reduced by 95.02%and 37.76%respectively compared with the coal route.To further reduce the environmental impact of the life cycle of ammonia production from shale gas,it is possible to increase the recovery rate of water-based drilling mud and fracturing flowback fluid,or increase the dehydration rate of water-based drilling mud,and deploy fracturing fluid on site.Due to the uncertainty of database,the robustness of coal ammonia route and residual oil route are not good on eutrophication potential and ozone layer depletion categories. |
