Friday, August 22, 2008

Urban mining

A tonne of cell phones contains more gold than a tonne of ore from a typical gold mine. An average gold mine produces 5 grams of gold per tonne of rock whereas cell phones contain 150 grams or more per tonne. In addition a tonne of cell phones contains 100 kg of copper and 3 kg of silver, as well as other valuable metals—all of which have been soaring in price.

The quantity of precious metals to be found in discarded electric devices has led to a new phenomenon—urban mining—which seeks to recover these increasingly valuable resources before they are sent to a landfill. The company Eco-Systems in Japan—which has few natural resources—is trying to recover these precious metals from the tens of millions of cell phones and other electronic gadgets that are thrown away every year. Says Nozumo Yamanaka, manager of Eco-Systems, “To some it’s a mountain of garbage, but for others it’s a gold mine.”

Hazel Prichard, a geologist at the University of Cardiff, is working on ways to collect platinum—which comes off of catalytic converters in cars—from the dust that is collected by street sweepers. "I get excited every time I see a street cleaner," she says. Platinum is a vital component not only of catalytic converters but also of fuel cells - and
supplies are running out. It has been estimated that if all the 500 million vehicles in use today were re-equipped with fuel cells, all the world's sources of platinum would be exhausted within 15 years.

The same goes for many other rare metals such as indium, which is being consumed in unprecedented quantities for making LCDs for flat-screen TVs, and the tantalum needed to make compact electronic devices like cell phones.

The metal gallium, which along with indium is used to make indium gallium arsenide, is the semi-conducting material at the heart of a new generation of solar cells that promise to be up to twice as efficient as conventional designs.

That is why the efforts of people like Hazel Prichard to find ways to urban mine these precious metals is of vital importance to any technological fix for the looming problems of peak oil and global warming.