Hybrid Life Cycle Assessment Of GHG Emission And Methane Slip From LNG Power River-Sea-Going Ship

With the continuous activity of human economic activities,the attendant en-vironmental problems are becoming more and more serious,especially the global greenhouse effect and various meteorological natural disasters.At the same time,global warming has also caused the hole in the Arctic ozone layer to expand.According to the research of scholars from Russia and the United States,they find that some ancient bacteria have been found in the melting ice layer of the Arctic Circle,which further indicates that environmental problems have increasingly affected the normal life of human beings.According to the IMO(International Maritime Organization)report,the greenhouse gas emissions from the shipping industry have accounted for 3% of the global carbon emissions.Fortunately,environmental issues have been highly valued by the shipping industry,and the shipping industry is also constantly exploring new technologies,such as developing new ship types,using More efficient and clean energy,for instance LNG energy,hydrogen energy,etc.,especially LNG energy is sought after by the shipping industry.LNG is mainly composed of hydrocarbons,so that the content of sulfide and nitrogen in the emissions is greatly reduced.Without considering the leakage of methane,the industrybelieves that LNG can reduce greenhouse gas emissions by 8% compared to fuel oil.Our country’s river-sea going ships have also carried out "oil-to-gas" projects in order to reduce greenhouse gas emissions from ships in my country’s inland river basins.As a systematic and comprehensive environmental impact assessment method,the life cycle assessment method(Life Cycle Assessment,LCA)is highly praised by the shipping industry.It can comprehensively evaluate the environmental impact of a product or service from the "cradle" to the "grave".However,the traditional process-oriented life cycle assessment method(Process Life Cycle Assessment,P-LCA)has some disadvantages,for examples,the process data acquisition is difficult,the data collection volume is large,and the system boundary has truncation errors,which greatly increases the evaluation difficulty and evaluation speed.The input-output evaluation method(Input Output Life Cycle Assessment,IO-LCA)was originally used in the economic field,taking the national economy as the boundary,eliminating stage errors,and all data are easy to obtain.Most of the data are from the"National Input-Output Table","China Energy Statistical Yearbook" ".The idea of hybrid life cycle is to integrate the input-output evaluation method and the process life cycle method,and use the respective advantages of the two methods to improve the evaluation speed and accuracy.In this paper,the hybrid life cycle method(Hybrid Life Cycle Assessment,Hybrid-LCA)is used to analyze the greenness of the "oil to gas" of the river-ocean going ships.For the complex raw material production stage,IO-LCA is used for evaluation,which has fast evaluation speed and high effect.For the operation stage supported by detailed data,P-LCA is adopted to make the evaluation personalized.First of all,this paper mainly introduces the characteristics of LNG power technology of the river-sea going ships.This paper also analyzes the characteristics of the LNG main engine and the requirements for the LNG power reconstruction of the ship main engine,and also propose some safety matters and characteristics of bunkering.This paper focuses on the reason of methane slip from LNG main engine in the operation process.Secondly,this paper analyzes the traditional LCA method and points out some shortcomings and deficiencies of traditional LCA.For example,it is very difficult to analyze and collect data on the upstream stage,and the efficiency is very low,and it often consumes a lot of manpower,material and financial resources.In this paper,a hybrid life cycle method in the field of ships is constructed,and the environmental impact of the upstream stage is analyzed by the input-output method(IO-LCA).At the same time,the boundary error of the system is eliminated by taking the national economy as the boundary.The traditional process LCA method can be used for the downstream stage(i.e.ship operation and recovery stage)where it is easy to collect data.Using the idea of hybrid LCA,an efficient and accurate life cycle assessment method for ship field can be constructed.Finally,this paper analyzes the emission characteristics of LNG and HFO by using the idea of hybrid LCA.Throughout the study,the situation of methane leakage is mainly considered.Through the analysis,it points out that if the methane leakage rate in the whole life cycle reaches 1.6%,then the greenhouse gas emission of LNG energy is equivalent to that of HFO.If the methane leakage rate is further increased,when the leakage rate reaches 4%,LNG energy greenhouse gas emissions will exceed HFO by nearly 42%.