already running low. For example, rhenium only occurs at seven parts per billion in the Earth’s crust, making it one of the rarest elements on the planet. However, its high melting point of 3,186 °C makes it valuable in the manufacture of jet engines. Demand for the metal is rising, with increasing air travel, but its rarity means increasing extraction is not simple. This is where recycling comes in; rhenium is one of the few metals that has witnessed a rise in recycling rates. It is likely that recycling will become a more viable option than extraction for other metals in future, saving energy, cutting greenhouse gases emitted to the atmosphere and reducing negative impacts on the environment. References External links www.resourcepanel.org www.unep.org United Nations Environment Programme Recycling Metals