Technology giant Apple wants to "one day" end the need to mine materials from the earth to make its gadgets, the company said in its annual environmental responsibility report out Thursday."Traditional supply chains are linear. Materials are mined, manufactured as products, and often end up in landfills after use. Then the process starts over and more materials are extracted from the earth for new products."We believe our goal should be a closed-loop supply chain, where products are built using only renewable resources or recycled material."The company's research concluded that recycled aluminum should come from Apple products rather than from recycling facilities because of the high grade needed for the metal.Apple has been encouraging customers to return used products for recycling and has melted down iPhone aluminum enclosures to make mini computers used in its factories. "For tin, we took a different approach," the tech giant said. "Unlike aluminum, there is an existing market supply of recycled tin that meets our quality standards." As a result, Apple has been using recycled tin for its iPhone 6s.The ultimate aim is "to one day end our reliance on mining altogether," said Apple, without settling a date.Apple did not disclose the amount of recycled products currently used in its products. The tech giant said 96 percent of the electricity at its global facilities comes from renewable energy and that its new corporate campus is powered entirely by renewable energy.