It is difficult to numerically define mileage in terms of CO2 emissions since even the Ministry of Economy, Trade and Industry (in Japan) is currently evaluating methods for converting mileage to emissions and establishing the accuracy of these methods. Conventional soy inks use soy oil made by extracting raw soy bean grown and harvested in the United States or in other countries. The rice bran oil used in rice ink, however, is 100% domestically produced, so the mileage incurred for importing the raw soy bean and soy oil is drastically reduced.

Printing companies using rice ink are entitled to use the mark on the right to prove to customers that their printed matter is environmentally friendly.