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人类对各种资源的需求不断增长,而自然资源的储量是有限的,所以,世界各国都很重视二次资源的开发利用。从垃圾中回收有用物质很有意义。若要直接从矿石中得到有色金属,必须经采矿、选矿、冶炼等很多工序,耙费大量人力、物力和财力。而从垃圾中回收二次资源的成本较低。如苏联从垃圾中回收铝和铜的成本比直接从矿石中冶炼便宜约60％,从垃圾中回收铝省电95～96％,回收铜省电84％。美国从垃圾中回收的铁占总产量的7％,铝占8％,锡占19％。
The demand of various kinds of human resources is constantly increasing while the reserves of natural resources are limited. Therefore, all countries in the world attach great importance to the development and utilization of secondary resources. Recycling useful materials from garbage makes sense. To get non-ferrous metals directly from the ore, must be a lot of manpower, material and financial resources by mining, beneficiation, smelting and many other processes. The recovery of secondary resources from garbage is less costly. For example, the cost of recycling aluminum and copper from rubbish in the Soviet Union is about 60% cheaper than smelting directly from ore, 95-96% in aluminum recovered from refuse, and 84% in copper recovery. Iron recovered from the rubbish in the United States accounts for 7% of the total output, with aluminum accounting for 8% and tin accounting for 19%.