Energy efficiency

The overall energy input of the cement industry is made up of roughly 90% thermal energy, which is required primarily for the combustion process in rotary kilns, and approximately 10% electrical energy, most of which is accounted for by grinding processes. Use is now largely made of alternative fuels (including used tyres, waste oil, animal meal, plastic waste and sewage sludge) as a substitute for fossil fuels, lignite and hard coal in particular. These tend to contain less carbon and exhibit a high proportion of biomass. In this way, the German cement industry has managed to save an average of around 700 kg of CO₂ per tonne of alternative fuel employed and has thus achieved a considerable overall reduction in CO₂. At the same time, the inorganic constituents (ashes) of the alternative fuels can be recovered and used in the product (co-processing). And so the utilisation of alternative fuels also contributes towards the conservation of resources.

Electricity is a further crucial production factor for the cement industry. In view of the relatively high price of electricity in Germany, the annual power costs of the industry amount to roughly 50% of the total energy costs. It has therefore always been in the economic interests of the companies themselves to make efficient use of electricity, which is why all the cement plants in Germany employ energy management systems certified in accordance with ISO 50.001. Nevertheless, the power demand of the cement industry is likely to carry on increasing in the foreseeable future - despite ongoing efforts to improve efficiency. The reasons for this include product quality requirements, the use of CO₂ reduction technologies and the raising of environmental protection standards in production. In the light of the above, internationally competitive electricity prices and a reliable power supply are of essential importance to the German cement industry

Various process engineering innovations in the cement industry today permit the extremely efficient use of thermal energy. Developments in kiln technology, for example, have led to the introduction of dry process kilns equipped with cyclone preheaters. These days, more than 90 per cent of cement clinker is produced at such plants in Germany. Thanks to modern precalcining technology, it is now also possible to design shorter rotary kiln plants than used to be the case. This reduces the radiation losses of the plant. There are however thermodynamic limits to any further gains in efficiency. Another factor is that the construction of a kiln is extremely capital-intensive, which means that such plants tend to be used over the course of several decades.

The efficiency level with regard to power consumption is also very high nowadays. Nevertheless, the specific power requirement per tonne of cement has increased slightly in recent years. This is the result of opposing effects which more than offset the gains in efficiency achieved. One example of these effects is the increasing demand for high-performance CO₂-efficient cements in the building industry. Such cements require more intensive grinding, which translates directly into higher power consumption. More electrical energy is also being used in the cement industry on account of the regulations applying to exhaust gas cleaning with the aim of reducing nitrogen oxide emissions for example. The utilisation of additional filtration systems slows down the exhaust gas flow, so that a higher drive power is required to maintain the flow velocities.

Furthermore, the energy transition process requires demand-side flexibility on the part of industrial consumers. The frequent start-up and shutdown of production facilities associated with this also detracts from energy efficiency. Looking into the future, sophisticated CO₂ reduction technologies (e.g. carbon capture installations) in particular will lead to a further increase in the power consumption of the German cement industry.

Notwithstanding these successes and ongoing optimisation of the processes, the German cement industry remains an energy-intensive sector particularly reliant on a competitive and stable energy policy framework. This applies to both implementation of the energy transition in Germany and energy policy measures in the context of climate protection. At the heart of these considerations is the development of electricity and fuel costs, which are influenced not only by state levies and charges (e.g. energy/power taxes, EEG levy, national CO₂ price) but also by other cost factors (network charges, electricity market prices). It is therefore imperative to ensure a competitive and reliable power supply when introducing energy policy measures. In view of all this, the existing equalisation schemes remain absolutely essential for cement production in Germany. And all the more so given the decarbonisation measures currently being planned. One such measure for the cement industry will be carbon capture in the manufacturing process, a highly power-intensive and thus expensive technology. As far as fuel costs are concerned, state charges such as energy taxes as well as European and national emissions trading are major factors for the industry.