A General Method of Life Cycle Assessment

In previous Life Cycle Assessment (LCA) methods, environmental burden items to be analyzed, prior to a life cycle inventory analysis, were assumed as the main factors of environmental problems regardless of the product category. Next, the life cycle inventory analysis, in which the total amount of environmental burden items emitted during the life cycle of a product was calculated, and an environmental impact assessment were performed. The environmental impact assessment was based on the initially assumed environmental burden items. The process, in other words, was a particular solution based on this assumption. A general solution unconstrained by this assumption was necessary.

The purpose of this study was to develop a general method of LCA that did not require such initially assumed environmental burden items, and to make it possible to perform a comprehensive environmental impact assessment and strategically reduce environmental burden of a product. This could be achieved by combining scientific knowledge on environmental burden items that could cause environmental problems, database on the environmental burden items emitted during the material production and product assembly, and sales portfolio of the product.

The general method of LCA was applied to passenger cars. Dominant environmental burden items that could have environmental impact were identified to focus attention on their reduction.

In the life cycle of a passenger car, CO₂, SO_X, NO_X, and NMVOC were identified as dominant environmental burden items that could cause global warming, acidification, and formation of photochemical ozone. Efforts to reduce the environmental impact were focused on the improvement of fuel efficiency for a new car model. As a result, it was confirmed that the new car model emitted 5% less CO₂, 2% less SO_X, 3% less NO_X, and 2% less NMVOC than the predecessor.

The application of the general method of LCA to other products needs to be studied further. Additionally, new scientific knowledge on the environmental burden items needs to be reflected in the database.