Often, conventional exhaust air purification processes such as catalytic afterburning are used for exhaust air purification in roasting plants. Although this achieves a high separation efficiency, it has a high consumption of fossil fuels. Thermal afterburning is thus very cost-intensive and also has a negative impact on the company’s eco-balance and CO₂ footprint.
Another problem is that this thermal treatment of coffee beans, which takes place in discontinuous operation, generates emissions in two substeps, the roasting process itself and the subsequent cooling with fresh air. These emissions consist of a variety of aromatic-smelling organic compounds, which are measured as VOC content or odor units. The exhaust air is contaminated with oily and pasty aerosols, vapors, particulates, and other contaminants. In addition to the exhaust air pollution caused by particles, aerosols, other solids or liquids, roasting plants are confronted with the strong odor pollution of the production exhaust air.