No matter how much we reduce our waste, it’s a fact of life that many consumer products must be purchased with a disposable container. However, these materials can be kept out of the waste stream by promoting recycling, the process of returning the raw materials present in a form of waste back to the manufacturer to be used again. Commonly recycled materials include glass, plastics, metal, paper, and cardboard (Figure 12.20).

Recycling has a number of benefits. When a disposable product, such as an aluminum can, is recycled, both raw material and energy are conserved. Less source material, bauxite ore in this case, must be mined and processed. The amount of energy needed to melt and mold recycled material is much less than when starting with raw ore. Finally, the product is kept out of the waste stream for at least one more round of use.

One way to increase recycling rates is to require deposits on bottles and cans. The state of Michigan, for example, imposes a 10-cent deposit on all its recyclable beverage containers, the highest of any state. This deposit is returned to the customer when the container is recycled. In response to this incentive, the recycling rate for these containers in Michigan from 1990 to 2012 was 97%—more than double the national average. Over this period more than $9 billion in deposits were paid by consumers and refunded. Of the approximately $300 million in unclaimed deposits, 75% was returned to the state government to fund environmental programs, and beverage retailers retained 25%.

One recent development is take back laws, which typically require manufacturers of televisions, computers, and other electronics to pay for e-waste recycling programs. Such laws have been passed in 24 states, including New York and Texas. California’s Electronic Waste Recycling Act is similar, but it requires consumers to foot the bill for recycling, paying a special fee to retailers when they purchase certain devices. Utah lacks a take back law, but it does require manufacturers to participate in e-waste recycling programs and to inform consumers.

Dismantling electronic equipment into constituent components and scrap metals is called demanufacturing. Although the process can be dangerous when conducted informally, without the oversight of environmental or health regulators, it has the potential to separate hazardous waste from valuable materials that can be recycled. Several electronics recycling centers have emerged in urban centers, supporting the view that demanufacturing could be a vital source of jobs and income.

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The problem of waste disposal in Philadelphia, now managed in a more integrated fashion, is much less pressing than during the time of the Khian Sea. City ordinances were passed to support a goal of a 50% recycling rate. Although this goal has not yet been reached, recycling rates have steadily improved, as they have across the United States. From 1960 to 2013, the amount of MSW recycling increased from just 6% to 25%. Over this same period, the amount of waste composted increased to 9% and the amount burned for energy recovery rose to 13%. As a consequence, the amount of MSW ending up in landfills across the country fell from 94% to 53% between 1960 and 2013 (Figure 12.21).

While the progress made in reducing disposal rates across the United States is encouraging, some cities are doing better than others. For example, San Francisco has succeeded in reducing the amount of solid waste ending up in landfills to just 20% of the total generated. The city has achieved this low level of waste disposal by emphasizing the key elements of integrated waste management: reducing and reusing, recycling, and composting. To facilitate these management goals, residents have access to three refuse bins, one for recyclable materials, one for compostable materials (e.g., food and garden wastes), and one for solid waste destined for the landfill (Figure 12.22).

Based on San Francisco’s waste handling system and other measures, an independent study has ranked it as the “greenest city” in North America. However, the city’s ultimate goal is zero waste. While no municipality has yet attained this goal, Europe’s greenest city, Copenhagen, Denmark, with a disposal rate of only 2% of the waste generated, comes close. Like San Francisco, Copenhagen stresses waste reduction and reuse, recycling, and composting. In addition, any waste that cannot be recycled or composted is burned to generate energy in electrical power plants.

After removing everything that can be recycled or composted, the remaining trash can be burned to reduce the waste volume by up to 90%. Less waste volume means less landfill space is needed. However, incineration is economically viable only where space for landfills is highly restricted. Incineration facilities are expensive to build and pollution control systems are essential for reducing hazardous emissions. One potential source of environmental impact is the ash produced by incinerators. There are two forms of ash produced by incinerators. Fly ash is made of lighter, noncombustible material that is normally sent airborne during incineration. Bottom ash is the heavier, noncombustible material left over after incineration. Fly ash has a high concentration of toxins, and incinerators are required to have filters and electrostatic precipitators, similar to those in coal-fired power plants, to collect fly ash and prevent it from being released into the air. Many substances that will not burn (e.g., heavy metals and dioxins) will be left behind in bottom ash.

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Once recyclable metals have been recovered from incinerator ash, the residual is sent to a disposal site. The EPA requires regular testing of ash from incinerator waste for the presence of hazardous waste. When the presence of hazardous substances exceeds certain thresholds, the ash must be treated as hazardous waste and disposed of in specially designed hazardous waste disposal sites. Otherwise, in the United States, ash in these plants is disposed in sanitary landfills designed to accept standard MSW. Several European countries use nonhazardous incinerator ash for highway building and other construction.

While properly built and managed incinerators are costly, they can be used to recapture some of the chemical energy that remains in MSW by including a steam-powered turbine in the system (Figure 12.23). Increasingly, MSW is being recognized as a valuable energy resource. According to the EPA, in 2013 there were 86 “waste-to-energy” power plants in the United States using MSW to generate electricity. The agency estimates these plants burned 32.7 million tons of MSW—approximately 13% of the total municipal solid waste stream during that year.

These power plants must have the latest pollution control systems to avoid releasing hazardous wastes into the air. Similar plants are in operation in Europe. For example, two waste-to-energy power plants in Oslo, Norway (Figure 12.24), which are paid to accept solid waste from the United Kingdom and elsewhere, make additional income by selling electrical power and heat to consumers. The two plants have a combined capacity to process 410,000 metric tons of waste annually, with an energy equivalent of over 100,000 metric tons of oil.