The increasingly stricter nationally specific environmental protection constraints require not only that chaff and other particles be filtered out, but also the treatment of the exhaust gasses generated during the roasting and grinding process. During roasting, chiefly volatile carbon compounds (Cx), carbon monoxide (CO) and carbon dioxide (CO2) are produced, during grinding carbon dioxide is produced.

The latter can be recycled to a greater part as a protective gas for the conveyor equipment and silos in the ground coffee process. The impurities in roaster exhaust air are usually eliminated through thermal and/or catalytic combustion. Today, catalytic combustion is state-of-the-art; precious metals such as platinum serve as the catalyser. The combustion process takes place at temperatures between 450 and 600°Celcius.

PROFORTE:
The energy required for exhaust air combustion can be distinctly reduced using regenerative thermal oxidation. In this process, the heating energy released during the flameless combustion of the pollutants is stored in a ceramic bed and then most of it released back into the process, which thereby attains a thermal efficiency rate of 95 to 98 percent. Due to the high process temperature of 900 to 1,000°Celcius, the pollutant emissions are far below the prescribed limiting values.