Air contains around 21% oxygen and 79% nitrogen. The nitrogen is useless for the combustion process but at high temperature produces nitrogen oxides (NOx). Thus using pure oxygen instead of air helps to reduce the energy needed for the combustion (it is no longer necessary to heat up the nitrogen) and prevents the formation of NOx.
AGC Glass Europe developed in addition a unique system, called "Hot-Oxycombusion", that re-uses heat from the flue gases to preheat the natural gas before it is injected into the furnace. This yields additional energy savings.
The furnace located in Boussois (France) was the first float furnace in Europe to operate fully on oxycombustion and the first in the world to have the natural gas and oxygen preheated. This furnace proved to be the most ecological float furnace in the world. After three years of employing the method at full scale in Boussois, the plant’s furnace emission targets have been met, and even exceeded: CO2, NOx and SOx, emissions were reduced by 15%, 83% and 34.5% respectively. Furthermore, the plant’s furnaces consumed 25% less energy.