Remains of human settlements through the ages are characterized by garbage. Early human encampments are surrounded by discarded bones, shells, and broken tools and weapons. While such material is a boon to archaeologists, the mountains of discarded materials produced by today's society threaten to consume available land near large cities, and they pollute the water supplies of both rural and urban environments. Nearly every object and material discarded by humans can be recycled, reducing the cost and danger of disposal and providing valuable resources for industry and the home. Recycling also restricts many dangerous substances to facilities designed to handle them.
The Emergence of Recycling
Many Americans remember when garbage disposal was as simple as placing the material in a can in the alley or, in the case of rural residents, feeding the pig, or tossing everything into a nearby ditch in the name, at least, of erosion control. Our ancestors lived lives much simpler and were much less encumbered by material possessions. Bottles, buttons, nails, and wood all passed through a progression of steps and were smelted, rewoven, reshaped, or burned. Few people anywhere lived in societies where many materials were simply thrown away. The largest furniture store now operating in the United States was founded by two immigrants who began their careers as rag and bottle pickers during the early 1900s.
Every bottle or jar in early America was recycled, and pieces were used for purposes as varied as arrowheads and grit for chickens. Birds, lacking teeth, must collect small rocks, or grit, in order to grind their food in the craw. Old-time farmers sometimes ground glass when oyster shell or other sources of grit were unavailable. Ground glass was also mixed with glue to make abrasives. The vast numbers of buffalo killed by Native American or European hunters left huge quantities of bones on the prairie, but early scavengers collected them and shipped them to plants where they were ground for fertilizer. Early-day cloth was collected and treated to reclaim fiber, which could be woven into string or rope. Most cities contain parks, and below many of these parks are landfills dating back as far as the 1800s. A lack of landfill space, increasing transportation costs, and tougher government regulations now diminish the use of landfills, and many smaller communities sport signboards denouncing the importation of waste from other cities or states.
Recycling falls into two categories: direct and indirect. Direct recycling is the reuse of components of manufactured materials before sale, often in the case of damaged or unsold products. Indirect recycling is the practice of recycling products or materials that consumers have used and discarded.
Shortages during World War I and World War II prompted scrap iron, fiber, and rubber drives, reclaiming many essential materials. The first items to be recycled through organized programs other than in wartime were milk and other beverage bottles. In days when milkmen placed bottles on doorsteps, the heavy bottles were returned, washed, and refilled dozens of times. During the 1940s and 1950s, families scavenged for soda and beer bottles and cans along highways, and many children supplemented or earned allowances by collecting bottles for the two-cent deposit. Plastic bottles and aluminum cans have largely replaced the reusable bottles of the twentieth century. Many states now mandate five- to ten-cent deposits on the plastic replacements. The scrap material drives of the World Wars brought the public's attention to the fact that many more fabrics, metals, and rubber items could be recycled.
The most commonly recycled material is water. Seldom destroyed in use, water serves as a medium for chemical reactions and as a heat transfer mechanism in steam or hot water systems, car engines, and various industrial processes. Moderately dirty water may be dumped directly into streams, injected into wells, or, in the case of cooling water from power plants, allowed to pass through wetlands to cool.
Water containing sewage is given primary treatment consisting of settling and filtration and secondary aeration treatment to allow oxidative bacteria to reduce the bacterial oxidative demand (BOD). Tertiary treatment with chlorine, chloramines, or ozone is used if the water is needed for consumption. In rural areas, sewage may pass through a cesspool for sedimentation and anaerobic bacterial action, and the effluent may be distributed through a series of pipes into a disposal field. Water that has low BOD is usually purified by bacterial action in soil so that after passing some distance through the ground, biodegradable substances are removed. It is particularly important that detergents be biodegradable and contain minimal amounts of phosphates and nitrates, as these substances, along with high BOD water, contribute to eutrophication, a rapid growth of bacteria. Eutrophication may consume so much available oxygen that fish and other organisms die.
Farms, ranches, and feedlots provide food but often are major sources of pollution. Modern feedlots store sewage in lagoons where solids can be collected. Effluent water from lagoons often contains microorganisms that serve as food in fish farms, and solids from the lagoons can be processed into fertilizer. The effectiveness of these operations is often determined by the size of the operation and the need for cleanup. Larger operations can afford more complex remediation equipment and tend to be more costeffective than small ones. Most large feedlots are located away from population centers whose residents often complain of the odors.
Federal, state, and municipal laws mandate that industries reclaim most pollutants, such as heavy metals or organic chemicals, from wastewater. Prior to this legislation, toxic chemicals often made their way into the water table. Reclaiming toxic substances protects the environment and, in many cases, provides a valuable source of materials needed for synthesis . In many cases, industries are located near other manufacturing plants that pass their waste to another plant, which uses it as a raw material.
Paper, Steel, and Aluminum
Paper, in the form of used newspapers, packing materials, and telephone books, may be burned for energy, but it still makes up 30 percent to 45 percent of the average landfill. Landfilled paper requires decades to decay and may release methane, a greenhouse gas that is twenty times as deleterious as carbon dioxide. Most paper could be reused or converted to materials used for blown insulation. Nearly 40 percent of office paper and newspapers is now recycled. Two problems occur in recycling paper. Each time paper is reprocessed, the fibers break and become shorter. Office copiers work best with long-fiber paper that has higher tensile strength and produces less dust. Fiber from used paper is often blended with new fibers to produce the desired qualities. A second problem in recycling office paper is the demand for white paper. Used paper pulp often contains ink or other colored materials that must be removed. Some inks and adhesives can be removed by flotation, and bleaching then whitens the pulp. Older methods of chlorine bleaching produced toxic dioxin. Oxygen and hydrogen peroxide are now used to whiten paper and are considered less damaging to the environment. Use of colored papers for printing and copying greatly decreases the need for bleaching.
Steel is widely recycled. Soon after steel was first produced, damaged steel items were recycled into new products. Today, 68 percent of used steel is recycled. The basic oxygen process of steel manufacture uses 25 percent scrap as starting material, and nearly 100 percent of the starting material for steel production by the electric arc process is scrap. Many states have "clunker" laws that require that the purchase of a new car be accompanied by turning in a junked car, and most municipalities have programs for collecting and recycling used auto parts and furniture.
Aluminum is one of the most commonly recycled metals. Although many aluminum products are still discarded, 65 percent of aluminum materials are recycled; 95 percent less energy is needed to produce aluminum from recycled cans than from aluminum ore.
Plastics and Oil
Plastics make up only about 8 percent of the volume in the average landfill but represent a huge investment of energy and raw materials. Most plastics produced from petroleum materials by polymerization of monomers such as ethylene or vinyl chloride are thermoplastic materials and can be cleaned, melted, and re-formed. Thermosetting plastics can also be cut into pieces that are mixed with other plastics or used as fillers. High-density polyethylene (HDPE) and polyethylene terephthalate (PETE) are the most widely reused plastic materials, but polyvinyl chloride (PVC), polypropylene, and polystyrene account for 5 percent of the recycled plastics. In 2001 80 million pounds (36 million kilograms) of plastics were recycled in the United States. Recycled plastic materials are used in the production of bottles, fabrics, flowerpots, furniture, plastic lumber, injection molded crates, and automobile parts.
According to the Environmental Protection Agency, Americans discard 120 million gallons (454 million liters) of oil each year as a result of automobile oil changes. Virtually all this oil can be recycled, and most states require recycling. Used motor oil contains particulate matter and some chemical substances that must be removed during re-refining. As much as 80 percent of used motor oil is used with little change as a fuel for ships or industrial heating equipment, but this practice probably poses a greater danger to the environment than burning refined oil.
Batteries, Rubber, and Paint
Used lead-acid automobile batteries represent a major hazard to the environment. Most landfills accept batteries but place them aside for recycling, which includes collecting and neutralizing the acid, removing the cases, and resmelting the lead plates. Fragments of cases can be recycled into new battery cases, and resmelted lead is used to cast new battery plates. In New Zealand alone, 500,000 lead-acid storage batteries are recycled each year.
Rechargeable batteries from power tools, telephones, and most other devices can be recycled. Nonrecyclable batteries often contain mercury or other toxic metals that are harmful to the environment, but in the early twenty-first century, most were still discarded in landfills.
Rubber products pose a special problem in the environment, and their dumping in landfills usually requires a special fee. Discarded in piles or buried, they occasionally catch fire and produce noxious gases. In developing countries, many used or damaged automobile tires are repaired or disassembled to make other products. Granulated rubber produced from
discarded tires can be used to make floor mats and rubber wheels, and it can be used as a component of asphalt-paving materials. Used rubber can be heated to reclaim petroleum products, treated chemically to obtain components used as filler in manufacturing rubber products, or incinerated as a source of energy.
Many recyclable materials consist of mixed materials that pose special problems. Discarded automobile oil filters contain steel, fiber, and contaminated petroleum. Oil filters are crushed and heated to remove oil, and the metal reclaimed. Discarded household appliances contain large amounts of steel but must often be dismantled, with other materials removed. A special fee is charged at recycling centers to discard most appliances. Fluorescent lamps contain small amounts of mercury that can be reclaimed. Used computers and television sets contain usable materials and, often, some toxic materials that can be collected for safe disposal.
The small amounts of paint generated by the average household cannot be recycled economically, but most municipalities sponsor paint exchange programs and collect oil-based paints. Spent fuel rods from nuclear power plants can be recycled to reclaim unused uranium, and some spent uranium is used to produce armor-piercing bullets. Yard waste from households is often recycled and made into mulch for farming and gardening. Discarded Christmas trees are used to form mulch or are immersed in lakes as a habitat for fish.
Ehrig, R. J., ed. (1992). Plastics Recycling: Products and Processes. New York: Hanser Publishers.
American Plastics Council. Information available from http://www.plastics.org .
Environmental News Network. Information available from http://www.enn.com .
United States Environmental Protection Agency. Information available from http://www.epa.gov .