Light packaging constitutes approximately 21% by weight of the municipal waste generated in Catalonia, according to PROGREMIC 2001-2006 data.

Light packaging can be divided into three basic groups:

• Metals: Mostly iron, brass and aluminium cans, which usually contain foodstuffs. This group also includes spray cans.

• Drinks cartons: This type of packaging comprises a layer of card (73%), two of polyethylene (21%) and one of aluminium (6%). Some are composed of only paper (90%) and polyethylene (10%).

• Plastics: Plastics are natural or (mostly) artificial polymeric compounds, processed by applying heat and pressure. The great diversity of types used to manufacture packaging makes them difficult to identify and recycle. The characteristics of the plastic are determined by the length, structure and elements of the molecular chain, along with the additives used. Technically, plastics are divided into two large groups, thermostable plastics and thermoplastics. The plastics most commonly used for packaging are thermoplastics such as PET, HDPE, PVC, LDPE, PP and PS:
  
  
  • PET: Polyethylene terephthalate. A thermoplastic material obtained from phthalic acid monomers and ethylene glycol. It is one of the materials most commonly used to make packaging, as it is very strong and light. 
  • HDPE: High density polyethylene. A highly shock-resistant material, at low temperatures, impermeable and an electric insulater. It is used to make packaging for cleaning products and beverages.
  • PVC: Polyvinyl chloride. A plastic compound of chlorine and ethylene. It requires the use of many additives to obtain the necessary flexibility and protection against radiation and high temperatures, which means it is highly pollutant, hence it is hardly ever used to make packaging.
  • LDPE: Low density polyethylene. Formed from the polymerisation of ethylene molecules in high pressure conditions, it is soft, flexible plastic with little resistance to temperature. It is used to make carrier bags, rubbish bags and in film form to wrap products.
  • PP: Polypropylene. A low density thermoplastic obtained from propene. It has similar characteristics to polyethylene, although it exceeds them at high temperatures.
  • PS-EPS: Polystyrene and expanded polystyrene (eg: trays). It is easily mouldable, shiny, fireproof, light and impermeable. It is used mainly as packaging for fresh dairy products, such as yoghurt.