HDPE plastic is usually shredded, melted and then pelletized where the pellets are then used to create new HDPE products. It can theoretically be recycled indefinitely except that usually contamination appears from other plastic fibres and the contents of HDPE containers so that this is practically limited to 7-8 recycles. One company, Carbios, has developed an enzymatic approach to recycle PET to potentially allow infinite recycling, and they are attempting to expand their process to include other plastics.
For many non-food HDPE products it is cheaper to purchase recycled pellets to use in manufacturing than to use virgin plastics. If one considers plant containers etc to be of a lower utility than food containers then one could say that this is downcycling of the plastic.
Recycling HDPE has many benefits. For example, it is more cost efficient to produce a product from recycled HDPE than it is to manufacture ‘virgin’ plastic.
HDPE, like many plastic polymers, is produced using considerable amounts of fossil fuels and it takes a total of 1.75kg of oil to manufacture just 1kg of HDPE.
Because it is not autoclavable it is not possible to do non-destructive sterilization of food containers made from HDPE.