Valuable metals contained in electronics and green-technology products are being recycled at "discouragingly" low rates, raising the prospect of material shortages, according to a United Nations-sponsored report.

The U.N. report, released last week, found a wide disparity in metal recycling rates and very low rates among even highly prized metals, such as gold, from electronics. The study recommends using product designs that make recycling easier and addressing the problem of obsolete electronics. About 18 percent of TVs and PCs are recycled and about 10 percent of cell phones, according to the Environmental Protection Agency.

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Less than one third of about 60 metals had an end-of-life recycling rate over 50 percent and 34 elements had a recycling rate below 1 percent. In addition to creating a larger supply of metals, recycling is estimated to be two to 10 times more resource-efficient than smelting metals from ore, according to the study.

"In theory, metals can be used over and over again, minimizing the need to mine and process virgin materials and thus saving substantial amounts of energy and water while minimizing environmental degradation," said Achim Steiner, U.N. under-secretary general and executive director of the U.N. Environment Program, in a statement.

Lead, which is most commonly used in batteries, is the most recycled, with a rate around 80 percent. Iron and other components of stainless steel are recycled at over 50 percent, as are precious metals platinum, gold, and silver. Gold is recycled at a high rate from industrial use, but only 10 percent to 15 percent from electronics, such as cell phones.

Meanwhile, there are several metals considered vital to green-technology product manufacturing, including rare-earth minerals, which are essentially not recycled at all. Indium, for example, is used in semiconductors, LED lighting, medical imaging, and some solar photovoltaic cells. Other important metals for green technology include tellurium and selenium, which are used in thin-film solar cells, and neodymium and dysprosium, which are used as permanent magnets in hybrid cars and wind turbines.

There aren't shortages of metals important to energy-related products at this point, but it's difficult to evaluate available ore resources, according to Thomas Graedel, one of the report's eight authors and a professor of industrial ecology at Yale University.

"By failing to recycle metals and simply disposing of these kinds of metals, economies are foregoing important environmental benefits and increasing the possibility of shortages," he said in a statement. "If we do not have these materials readily available at reasonable prices, a lot of modern technology simply cannot happen."