According to New Scientist, the streets are literally paved with riches. A team at the University of Birmingham has set up a company called Roads to Riches to recover platinum from our catalytic converters that ends up as road dust. The best platinum mines in South Africa have 2-10 ppm of platinum in their ore. Street sweepings have 1 ppm, but are much easier and less expensive to mine. Birmingham University's Angela Murray calculates that £64 million of platinum metals are swept from UK roads every year and dumped.
In fact, the riches may be even greater, since roadside soils have concentrations may be 100 to 1,000 times greater, according to the University of Natural Resources and Life Sciences in Vienna. That's one of the reasons that academics like Helen Parker at the University of York, UK, are experimenting with 'hyper-accumulating' plants grown in soil rich in the platinum metals. Besides roadside plants, they have also found that seaweed can successfully capture gold, coppy, nickel, zinc and platinum group elements.
A team at Linkoping University in Sweden has another lucrative strategy. They estimate that there is between 90,000 and 400,00 tonnes of copper power cables worth $630 million beneath Swedish cities. Using this scrap metal instead of mining the copper would save 360,000 tonnes of CO2. In Japan, the source of riches is industrial waste sludge. In Nagano, these effluent flows have gold concentrations of up to 2.9 kg per tonne, nearly five times greater than conventional gold ores. This has also been a practice in India's major cities for some time, where gold is extracted from waste sludge in the jewellery districts.
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