The adaptation of Italy's regulations to the European Union's directives is beginning to affect the environmental field as well. The implications are many and involve some industrial fields in an interesting way. In particular, residues having a high content of energy, as non-conventional fuels, in cement kilns can now be used also in Italy. Such method, furthermore, is already being widely used in several foreign countries such as Germany, United States, Austria, Switzerland, Belgium, Holland, Japan and France.  
Cement works, in fact, have the technology and the experience necessary to exploit the potentialities of more organic and consistent regulations with a new project - already being developed in some Italian works - that makes it possible to combine safe energy saving and costs with the protection of the environment.  

Waste disposal thermal process and cement works: a possible alliance  

Among the various waste disposal methods, the thermal process is one of the most valid solutions. Because of their repercussions on the environment, dumps are not an acceptable solution any more and the search for sustainable alternatives in the short term is becoming increasingly urgent.  
The thermal decomposition of molecules in incineration plants takes place through a high-temperature (normally 900° C or over) oxidation, and is used to destroy polluting organic and toxic and noxious compounds, to reduce the volume of the residues and to regenerate energy.  
The thermal process can also be used in professional incinerators and during industrial processes that involve high temperatures where the three mentioned objectives are likely to be achieved. Among them - as stated previously - are cement works.  
Cement is derived from the fine grinding of limestone, clays, tufas, marls and schists (its chief components). The crude mixture passes inside a reactor where heat exchanges take place and trigger complex chemical reactions followed by a rapid cooling down. The result of this baking process is clinker, the basic product that is subsequently ground together with other secondary constituents to make it more suitable for different uses.  
The baking phase is the heart of the production of cement. Kilns reach a temperature equal to 1,450°C and absorb between 90 and 100% of the energy consumed as a whole by the entire process of the cement production.  
This consumption, that considerably affects costs, is the object of a particular attention and of initiatives aimed at its reduction. Cement works, then, are strongly interested to look for alternative energy sources.  
The 94/76 EU directive on dangerous waste incineration equated the role of professional incinerators to that of industrial plants burning residues as alternative fuel. As mentioned previously, in fact, when producing cement, the baking phase of clinker requires very high temperatures for a long time in a highly oxidising atmosphere of the gases. This creates even more favourable conditions than those existing in incinerators. In this case the law limits the caloric supply of residues to 40% of the total requirements of the plant's primary energy. During the cement production process, the reuse of residues can have two different aims:  
 - residues to be re-used in the crude mixture of the kiln firing to bake clinker (for example purple ore, iron oxides, exhausted sands and earth from foundries and so on);  
 - residues to be used as secondary constituents of cements (such as blast furnace slags, flying cinders, chemical gypsum, exhausted sands and earth from foundries and so on).  

What advantages?  

The thermal process used in cement kilns involves a large number of advantages both in terms of saving (economical and of raw materials) and of protection of the environment, for general applications and for professional incinerators in particular.  
First of all energy is almost completely regenerated: the thermal energy obtained from the residues replaces the one saved in conventional fuels with a ratio of 1:1. This value is far less meaningful in incinerators and sometimes is even equal to zero for old plants.  
As far as the environmental aspect is concerned, the quantities of the kilns' emissions remain unchanged, but the CO2 concentration is lower. The emissions of a special incineration furnace, furthermore, are eliminated.  
Using the quantities of residues allowed by the law as much as possible (equal to 40% of the total necessary energy), it would be possible to save 1,700.000 t/a of pit coal (a natural resource that cannot be renewed).  
Re-using cement kilns does not involve the formation of solid residues, dross or liquids and disposal-related problems that conventional kilns normally have to cope with.  
Cement-producing plants are submitted to constant controls that make the reuse process safe in terms of atmospheric pollution prevention.  
Furthermore, it must be noted that re-using residues in cement kilns does not change the cement characteristics that is perfectly sustainable with the environment and not harmful for human health.  
The interests of cement manufacturers to enhance the use of cement kilns for waste disposal is also supported by other observations: the uniform distribution of cement works across the country, the amount of investments to comply cement plants' kilns with the thermal process of the residues (that are considerable although always lower than those necessary to build new incinerators), the existing presence of plants to destroy dusts, in fact, make cement works potentially interesting to tackle the problem of waste disposal and its relationship with the environment.  
The effects on the environment are considerable.  
In the first place, risks to pollute the earth and the waters are not expected because the reuse (unlike in professional incinerators) does not entail the production of solid and liquid residues. Kilns are provided with plants that eliminate dusts suspended in emitted gases, the concentration of sulphur oxides in emitted gases is reduced thanks to some chemical and physical characteristics of the process. Normally, there also is a reduction of the percentage of nitric oxides in the emitted gases, dangerous organic compounds are almost completely destroyed, and there are no considerable increases of the emitted metals.  
Among the fuels of the future we can include (with further improvement of the separation process and the elimination of non-compatible components) urban solid waste and PDF (package-derived fuel) that is obtained from the waste of plastic materials with a high energy content.  
According to the information reported, the cement industry can now considerably contribute to reuse high-energy residues in order to better preserve natural resources that are not renewable and the environment itself.  
The regeneration of energy carried out in cement kilns, in fact, is a globally favourable operation as far as ecology and the environment are concerned and, as shown by its application in technologically advanced and environmentalist countries in Europe, United States and Japan, does not have negative health repercussions on people and on the plants' workers.  
Aware of the fact that the protection of the environment is a responsibility that cannot be postponed for the industrial sector as well, cement manufacturers can and intend to contribute considerably with their experiences and know-how to a consistent growth with the most advanced regulations and choices at a world level.