In the last years we have to think about the question of emission reduction. One of the biggest producer of these emission is industry, where the cement industry comes under it. The effort of cement-workers and other manufacturers of building materials is the reduction of harmful oxides in our air, including CO2, which is one of a group of unfavourable oxides.This paper deals with the study possibility of partial compensation limestone by FBC-ash. The expected effect is the reduction of CO2 emissions and saving limestone. Following the previous stage of the research a recipes were designed for Portland clinker burning limestone-based and FBC ash, it was carried out laboratory burning and on produced cements were made basic technological tests.