Method to roast coffee beans

A system for roasting coffee beans in a room, said system comprising:

• a roasting apparatus, and
• a smoke treating unit configured to treat the smoke produced by the roasting apparatus, said smoke treating unit comprising at least one filtering device configured for filtering particulate matters or VOCs, said filtering device being able to filter a pre-determined maximal amount of particulate matters or VOCs before being cleaned,
• a control system configured to control the roasting process by:
• wherein at each roasting operation implemented in the roasting apparatus, the method comprises the steps of:
• obtaining directly or indirectly the quantity of beans roasted during said roasting operation and the level of roasting applied to the beans during said roasting operation,
• determining the amount of particulate matters or VOCs retained in said filtering device during said roasting operation based on said obtained quantity of beans roasted and on said obtained level of roasting,
• determining the global amount of particular matters or VOCs retained in said filtering device during all the roasting operations implemented since the last cleaning operation of the filtering device, and
• estimating the number of roasting operations still able to be implemented before said global amount is equal to the pre-determined maximal amount of particulate matters or VOCs able to be retained by the filtering device.