The main raw materials for cement manufacture are limestone and lime marl. Grinded cement is a hydraulic binder, and with the addition of water hardens in air. In the form of mortar and concrete it is an indispensable material in the construction industry. Cement is primarily produced using a dry process with rotary kilns and multistage cyclone pre-heaters with or without pre-calciners. Production is energy-intensive and costly. Depending on the quality, temperatures of up to 1450°C have to be reached in the rotary kiln. To optimise energy costs, low caloric secondary fuels are becoming increasingly important.