Energy recovery is the reclamation of energy, usually in the form of heat from the incineration of waste. The process gives materials, which cannot be recycled economically a genuine post-consumer use. For 'contaminated' waste, such as expanded polystyrene (EPS) fish boxes or horticultural trays, energy recovery is a safe and environmentally sound means of generating real value from used packaging materials. The combustion of EPS in an energy recovery incinerator does not produce any harmful gases – the incineration emissions are carefully cleared and controlled. Incineration of EPS and all plastics waste is endorsed by the plastics industry as a safe and environmentally beneficial disposal method where the incinerator conforms to regulations for safety and pollution abatement. In a modern incinerator, EPS releases most of its energy as heat, aiding in the burning of other garbage and emitting only carbon dioxide, water vapour and a trace of non-toxic ash. Plastics, such as EPS, in effect 'borrow' the energy available from petroleum that is used to produce them and then 'return' it when it is used as a fuel in the waste-to-energy conversion. The calorific value of EPS available for heat recovery is higher than that of oil and so EPS provides a valuable source of energy in incinerators.