Reusing glass bottles can require more energy than their initial manufacture as they have to be sterilized. Incineration is a source of greenhouse gases and toxic chemicals like dioxins and lead. Landfill sites are a possible source of toxic chemicals and produce large quantities of methane gas. They must be managed so that pollutants do not seep into groundwater and should therefore be kept dry, but this slows down the rate of decomposition. Tyres constitute another problem, as their resilience and indestructible nature become distinct disadvantages when it comes to disposal.
Tyres are virtually non-degradable and spread noxious fumes when burnt.
Western Europe, the US and Japan combined produce around 580 million tyres a year. The ocean has long served as a dumping-ground for human beings' waste, such as dredge spoil and sewage sludge. However, direct dumping at sea is one of the fastest ways for toxic compounds to enter the food chain. Increased international concern over this practice led to the 1972 London Convention on the Dumping of Wastes at Sea, which restricted further ocean dumping. Further research needs to be carried out on the effects of these various waste management options to determine the extent to which they positively benefit the environment.