Waste Disposal and Recycling
For many years direct recycling by producers of surplus and defective materials constituted the main form of recycling. However, indirect recycling, the recycling of materials after their use by consumers, became the focus of activity in the 1990s. For some time, most solid waste has been deposited in landfills or dumps. Landfills are filling up, however, and disposal of wastes in them has led to environmental problems. Also, government (which had little authority over disposal of wastes until the 1970s) now has extensive regulatory powers.
A growing alternative to such disposal is recycling. Industry has found that when it undertakes serious recycling programs, the savings can sometimes be considerable. In addition to reducing manufacturing and materials costs, such programs can insulate the companies from liability for environmental violations. Agriculture, which is the cause of much environmental degradation, can use organic recycling, or the reuse of manure and crop residues (sometimes called "green manure").
Water, in one sense, is always recycled, inasmuch as there is a finite amount of it available on earth and it constantly moves through its cycle of evaporation, condensation, and precipitation. Deliberate programs for recycling water include use of wetlands as areas to filter harmful wastes from the substance, or using partly treated sewage for raising fish. Municipal sewage- and water-treatment plants, of course, are fundamental recycling agents.