Controversial plans to mine the floor of the Pacific Ocean should not go ahead before Earth's 'urban mines' have been exploited, say campaigners.
They made the call following a conference in London this month (31 July-1 August) on deep-sea mining attended by industry leaders and global investors.
Each year silver and gold worth US$21 billion is used in personal computers, mobile phones, tablets and similar devices, creating precious metal 'deposits' that are up to 50 times richer than ore mined from the ground, says Natalie Lowrey, a campaigner with the US-based Ocean Foundation.
Recycling this metal, as well as that found in infrastructure like bridges and cables, is known as urban mining.
"If industrial nations took action and invested in urban mining, there would be less environmental impact, we could rid landfills of reusable materials, lower energy costs and conserve natural resources," says Lowrey.
The Solwara 1 project, which was to be the world's first deep-sea mine in Papua New Guinea, is currently on hold, but deep sea mining is a likely prospect for the near future. Projects have been planned in the Pacific Ocean and the Red Sea, for example, and countries such as India are also surveying ocean floors for mineral riches.
The International Seabed Authority is set to grant the first deep-sea mining licences in 2016. Approximately 1.5 million square kilometres of the Pacific Ocean floor has already been approved for exploration, according to statistics from the Ocean Foundation.
But this nascent industry is encountering fierce opposition from environmental groups who argue that its consequences could be catastrophic.
Lowrey questions why an industry with unknown ramifications is being pursued when metals that have already been mined are sitting in landfills.
While the demand for rare-earth minerals and the specialty metals used to make electronic devices is one of the key factors driving up metal prices — and making deep-sea mining potentially profitable — it is precisely these products that lack infrastructure for recycling.
"The vast majority of these discarded electronics are shipped to Africa and Asia for low-tech recycling, which in effect is dumping e-waste for smash-and-burn scavenging by impoverished populations," says Lowrey.
According to a recent report from the UN Environment Programme, less than one per cent of the metals commonly used in electronics, such as gallium, tellurium and tantalum, are recycled. 
These metals are classed as "criticial raw material" by the European Union because of their importance to modern society.
Barbara Reck, an industrial ecologist at Yale University, says that devices are often not designed for recycling, with a typical mobile phone containing 30-40 different metals in such tiny quantities that they are difficult to extract, or in alloys that cannot be broken up.
But, she says, the main reason is that devices are tossed into landfills at the end of their productive life, rather than being collected for reprocessing. "They are being thrown away with the other waste from home."
With proper infrastructure, Reck estimates that the urban mining of e-waste could meet up to 50 per cent of the demand for specialty metals, so ores would still be needed if current consumption rates continue or increase.
But Reck adds that urban mining is "in the short and medium term the more feasible solution" when compared with the costs of developing infrastructure for deep-sea mining.
Developing formal channels for recycling would also solve the problems associated with the informal mining of e-waste in countries such as China, India and Nigeria, says Deepali Sinha Khetriwal, an urban ecology researcher with the UN University.
She says that these unregulated practices often leave workers and communities exposed to dangerous toxins, and that the unrefined processes lose metal.
"It's not scientific. It's not safe. It's not even efficient. They lose a lot of the material value in this way," she adds.
But she says that e-waste could prove a valuable source of metals in developing countries if the dangerous smelting work is moved to regulated facilities, and the labour-intensive sorting of e-waste is done by trained workers.
"E-waste recycling can not only be a source of good jobs but could also reduce the environmental burden of getting raw material from primary sources," Khetriwal concludes.
Link to UNEP report