## 3 Description of the Case Study Company  
The case study company deals with the recovery and processing of waste into alternative fuels, RDFs (refuse-derived fuels) [37]. RDFs are created as a result of the transformation of waste the energy potential of which is sufficient to obtain energy or the properties of which allow it to be processed into products that can be used for energy. RDF is a specific type of fuel, characterized by high calorific value and homogeneous particle size. Its production consists in separating the combustible fraction (paper, plastics, textiles, wood, rubber) from municipal waste by sorting it and subjecting it to a multi-stage process of shredding followed by briquetting [38]. The production of alternative fuels is an excellent way to minimize the overall amount of waste and to obtain energy, the recipients of which in Poland are cement plants. Therefore, the examined plant is located in the Cement Plant Chem. It specifically deals with the production of rubber granules using the material resulting from the recycling of the used car tires and other rubber components. A sample of the final product is presented in Figure 1.  
Waste is delivered to the indicated plant by trucks or vans. After entering the plant and undergoing a qualitative assessment, the waste in the form of tires is weighed using a truck scale and then it is directed to the unloading storage yard. The technological line for the processing of rubber waste consists of a pre-shredding section, proper grinding as well as magnetic and pneumatic separation. The technological line includes shredders, granulators, sets of special sieves, belt conveyors, mixers, and magnetic and pneumatic separators [37]. The preliminary shredding section includes machines and devices responsible for the initial shredding of waste into the 20-40 mm fractions (pre-shredders), then, in the proper shredding section, through the sets of granulators and specialized grinders, proper shredding takes place, resulting in the appropriate fractions of 0.01-30 mm granules, combined with simultaneously isolating rubber, wire and textile cord to separate devices for further processing [32]. The isolated raw materials are directed to the machine groups responsible for the production of final products. The shredded rubber is directed to mills and pneumatic separators in order to clean it and eliminate undesirable impurities. Then, it is packed in collective packaging. The steel wire is directed to magnetic separators and then to other grinding devices and a sieve classifier which cleans the wire of impurities. The cleaned wire (steel cord) is directed to the places of temporary storage in the storage yard [37]. The textile cord is isolated throughout the process with the use of pneumatic separators, and then, in part, it is directed to cleaning on devices used for the production of a stabilizing additive for mineral-asphalt mixtures. After cleaning, the cord is used for further processing in the machine called homogenizer where the filling emulsion and mineral filler are added to the textile cord. After adding the substrates, the mixing of the whole takes place. The mass prepared in this way is transported to the granulator where it is granulated into pellets [37]. At each of the stages of separation and cleaning of rubber, steel cord, and textile cord in the technological process, waste is generated in the form of low-quality rubber and other solid impurities derived from processing. The waste is an excellent quality alternative fuel that is processed in the combustion process in the cement plant. The general overview of the process is presented in Figure 2.  
The company processes a total of approx. 47,000 tons of waste per year, including used tires as well as plastics and rubber. In connection to the functioning of the installation, the waste in the form of ferrous metals and alternative fuels is generated.