Meta Analysis of Life Cycle Greenhouse Gas of Automobiles

Abstract

Meta-analysis is a method that integrates multiple existing studies through statistical processing and is typically used in academic fields such as medical care, psychology, and education surveys. Some studies exist in which they apply meta-analysis to Life Cycle Assessment（LCA）results of automobiles, but the vehicle types and target life cycle stages are limited. In this study, we applied the meta-analysis method to the life cycle of automobiles classified by vehicle type and energy sources to estimate greenhouse gas（GHG）emissions. A literature review of 27 peer-reviewed articles was conducted to extract the LCA data that were used in this study. The life cycle stages were classified into four stages: Battery, Other production, Use, and Disposal. The results showed that GHG emissions during the use stage represented approximately 80% of the entire life cycle for gasoline, diesel, and hybrid vehicles. For plugin hybrid vehicles and electric vehicles charged with electricity from electricity mix or fossil fuel generation methods the use stage accounted for approximately 50-70% of the entire life cycle. Moreover, the results showed that GHG emissions could be reduced by approximately 75-80% if gasoline and diesel vehicles are replaced by electric vehicles that are powered by electricity generated from renewable energy. However, when electric vehicles are powered by electricity generated from fossil fuels, the GHG emissions can be equivalent to gasoline and diesel vehicles. The results also showed that the amount of GHG emissions depend significantly on the travel scenarios and the source of electricity generation. Therefore, the selection of these factors are of major importance when conducting an LCA study of automobiles.