a. Department of Geosystem, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656. Japan

Life Cycle Assessment (LCA) has been broadly discussed, recently. However, LCA data in the mining operation, which should be the starting point of the material how, isn't evaluated sufficiently.
The purpose of this study is to calculate and evaluate the amount of CO₂ emission, due to limestone production at Japanese limestone quarries based on three kinds of statistical data, and to compare the result with other types of open pit mines. In Japanese limestone quarries, principal mining method is bench-cut in which the deposit will be sliced down from top using orepass system.
Consequently, the total amount of CO₂ emission from limestone quarries in Japan is estimated to be 428,780 t in 1998, which equals to 2 .31 kg CO₂ /t of limestone. It has been varying between 2.1 to 2.3 kg-CO₂ /t during this 15 years and tends to increase slightly after 1991. 55.9% of CO₂ emission is caused by diesel fuel consumption, and 32.3% by purchased electric power consumption. The most part of CO₂ emission in the mining process is originated by the diesel fuel consumption.
For the limestone quarries producing more than million tons ore per 1 year, the diesel oil consumption rate at the most fuel efficient mines was 025 l/t, independently of the mining scale. The amount of CO₂ emission by the haulage operation at a Chilean copper mine was found out to be nine times more than that of a limestone quarry in Japan. The bench-cut mining method has a possibility to considerably decrease the energy consumption in mining compared to other mining methods.