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 sorting 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 high-density polyethylene involves receiving and storing the materials, sorting or identifying the plastic, and shredding it into granules so that it can be reintroduced into the production chain, thereby closing the clean production cycle. It is recommended that the material be washed prior to plastic sorting in order to remove impurities that could significantly affect the properties of the recycled high-density polyethylene.
The most important step is the sorting of high-density polyethylene, which can be done at the recycling site—a process known as “selective collection”—or at facilities built specifically for that purpose. The various methods used to sort and identify high-density polyethylene have already been described above.
This type of recycling is not destructive, unlike thermal recycling, and is recommended when high-density polyethylene is relatively free of contaminants.
Thermal Recycling
This is a destructive method that involves burning plastic, transforming the waste into gases, ash, and slag. The goal is to generate energy, since plastics are compounds with a high calorific value. To implement this technique, it is necessary to first conduct life cycle assessments to determine whether this type of recycling is beneficial.
To implement this energy recovery technique, strict control of pollutant gas emissions is necessary, because even with careful monitoring, harmful gaseous byproducts are released into the atmosphere.
Source: IVÁN ERNESTO ROCA GIRÓN Advised by: José Eduardo Calderón García, Engineer