Due to the need to find solutions for managing plastic waste, various recycling techniques have been developed; since there are different types of plastics, the methods for separating and recycling them vary.Plastic recycling can be physical, chemical, or thermal; as a last resort, it can be disposed of in a landfill. The choice of any of these methods depends on the results of an ecobalance study (product life cycle analysis), which determines which type of recycling is the most environmentally sound.
For high-density polyethylene, the only method not recommended is chemical recycling, as it is neither economically nor environmentally feasible. Mechanical and thermal recycling are much better options.
Mechanical recycling
The mechanical recycling of HDPE consists of the reception and storage of the materials, selection of the plastic or identification, crushing of the same so that the product is in the form of pellets, to be able to incorporate it back into the production chain, closing the circle of clean production. It is recommended to wash the material prior to the selection of the plastic in order to eliminate impurities that can greatly affect the properties of the recycled HDPE.
The most important step is the sorting of the HDPE, which can be done at the recycling site called "selective collection" or at purpose-built sites. The different methods used for the sorting and identification of HDPE have already been described above.
This type of recycling is not as destructive as thermal recycling and is recommended when the HDPE is relatively free of contaminants.
Thermal recycling
This is a destructive method that consists of burning the plastic, transforming the waste into gases, ash and slag. The purpose of this is to obtain energy, since plastics are compounds with a high calorific value. To carry out this technique, it is necessary to first carry out ecobalance studies to determine if this type of recycling is favorable.
To carry out this energy recovery technique, it is necessary to have a strict control of the emission of polluting gases, because even with careful control, harmful gaseous products are emitted into the atmosphere.
Source: IVÁN ERNESTO ROCA GIRÓN Advised by: Ing. José Eduardo Calderón García