ENVIRONMENTAL SCIENCE 14th Edition A Study of Interrelationships

Outline 18.1 Kinds of Solid Waste 18.2 Municipal Solid Waste 18.3 Methods of Waste Disposal

18.1 Solid Waste Solid waste is generally made of objects or particles that accumulate on the site where they are produced. They are typically categorized by the sector of the economy responsible for producing them. Mining wastes are generated in three ways: Waste material is left on the surface Milling tailings are dumped on the land or stored in ponds. Waste or tailings drainage often contains hazardous materials. Agricultural waste - Includes waste from raising animals as well as crop and tree harvesting. 90% is used as fertilizer or other forms of soil enhancement. Industrial solid waste consists of solid waste other than mining. Estimated to be between 200-600 million metric tons annually. Demolition waste Sludge Combustion ash Municipal solid waste consists of all the materials people in a region no longer want. 210 million metric tons annually. Mostly temporary use items (packaging, paper goods, magazines, newspapers, etc.) The Unites States produces nearly 230 million metric tons of municipal solid waste annually. This equates to 2 kg (4.4 lbs) of trash per person per day; per capita waste has increased 70% since 1960.

Municipal Solid Waste Generation Rates

18.2 Municipal Solid Waste Nations with a higher standard of living tend to produce more municipal solid waste per person than less-developed countries. Large metropolitan areas have the greatest difficulty dealing with solid waste.

The Changing Nature of Trash

Composition of Trash in the United States 2011

18.3 Methods of Waste Disposal Historically, waste disposal was by dumping solid wastes outside of city or village limits. To minimize the volume of waste, the dump was often burned; practice is still employed in remote or sparsely populated areas in the world.

18.3 Methods of Waste Disposal Five techniques are now used in waste disposal: Landfills Incineration Source reduction Composting Recycling

Landfills Municipal solid waste landfill - typically constructed above an impermeable clay layer, lined with an impermeable membrane and includes mechanisms for dealing with liquid and gas materials generated by the contents of the landfill. Traditionally this has been the primary method of waste disposal. Cheap and convenient Problems associated with poorly designed landfills incuded gw contamination, methane gas release - redesigned to reduce the amount of waste entering landfills. New landfills have an impermeable liner and complex bottom layers to trap contaminant-laden leachate. Monitoring systems are necessary to detect methane gas production and groundwater contamination. In some cases, methane is collected and used to generate electricity. New landfills currently cost up to $1 million per hectare ($400,000 per acre) to prepare.

A Well-Designed Modern Landfill

18.3 Methods of Waste Disposal The number of landfills is declining. Many small landfills that were not meeting regulations have been closed. Capacity has been reached. New landfills often resisted due to public concerns over groundwater contamination, odors, rodents, and truck traffic.

Incineration Incineration - burning refuse in a controlled manner. About 12% of U.S. municipal solid waste is incinerated. Most incinerators are designed to capture heat, which is then used to make steam to produce electricity. The production of electricity partially offsets disposal costs. Most incinerators burn unprocessed municipal solid waste. This process is referred to as mass burn technology. Incinerators drastically reduce the amount of municipal solid waste. Up to 90% by volume and 75% by weight. Primary risks of incineration involve air quality problems, concentrated toxicity and disposal of ash. Construction costs in North America in 2010 ranged from $50-$400 million. U.S. EPA has not looked favorably on construction of new waste-to-energy facilities. It has encouraged recycling and source reduction as more effective solutions to deal with solid waste.

Disposal Methods Used in Various Countries

Composting Composting uses natural processes of decomposition to transform discarded organic materials—grass clippings, leaves, food waste, or soiled paper—into compost, a humus-like material. With proper management of air and water, composting can transform large quantities of organic material into compost over a short period of time. Small-scale composting can be accomplished in the backyard, mixing green materials (grass clippings, vegetable scraps, etc.) and brown materials (dry leaves, twigs, soiled paper towels).

Composting About 3,800 composting facilities are currently in use in the United States. Most municipal programs involve one of three composting methods: Windrow systems Aerated piles Enclosed vessels

Source Reduction The simplest way to reduce waste is to prevent it from ever becoming waste in the first place. Source reduction is the practice of designing, manufacturing, purchasing, using and reusing materials so that the amount of waste or its toxicity is reduced. Design changes - Since the 2-liter soft drink bottle was introduced in 1977, weight has been reduced by 25%, keeping 250 million pounds of plastic have been kept out of the waste stream. Manufacturing processes reduce waste and increase efficiency. Purchasing decisions - Choose reduced packaging and plan quantities accordingly. Using materials to avoid waste generation Reduce use of hazardous materials. Follow label directions carefully and use the smallest amount necessary. Reusing items - Delay or prevent entry of items into waste collection stream.

Source Reduction Most businesses and manufacturers have a strong economic incentive to ensure they get the most from all materials they use. Any activities that reduce the amount of waste produced, reduce the: Cost of waste disposal Amount of raw materials needed Amount of pollution generated

Recycling Recycling is one of the best environmental success stories of the late 20th century. In the United States, recycling (including composting) diverted about 35% of solid waste stream from landfills and incinerators in 2011.

Recycling Beverage Container Deposit-Refund programs provide an economic incentive to recycle. Disposable containers are an increasing problem. In 1990 the average US citizen disposed of 550 drink containers. In 2010 this had risen to 784, about a 43 percent increase. Beverage containers currently constitute 25 percent of household trash. In a deposit-refund program a cash value in the form of a deposit is placed on the glass, aluminum, or plastic beverage container. Thus, consumers have an incentive to return their containers for the redemption value.

Recycling All provinces and most territories in Canada and at least 12 countries in Europe have bottle bills. In the United States, 10 states currently have beverage container deposit laws. They have recycling rates of 70 percent or more on containers covered by their laws. The average for the United States is about 35 percent. Mandatory recycling laws provide a statutory incentive to recycle. Many states and cities have passed mandatory recycling laws. Some of these laws simply require that residents separate their recyclables from other trash. Some are aimed at businesses and require them to recycle certain kinds of materials such as cardboard or batteries. Some forbid the disposal of certain kinds of materials in landfills. Those states and cities with mandatory recycling laws understandably have high recycling rates

Recycling Rates

Recycling Curbside recycling provides a convenient way for people to recycle. In 1990, 1,000 U.S. cities had curbside recycling programs. In 2011, 9,800 programs served 70 percent of the U.S. population. . Cities with curbside recycling tend to have much higher recycling rates than cities that lack such programs. In the U.S., curbside pick-up of recyclables is increasingly the norm, but rates remain low. Recycle Bank was founded in 2004. Families on a garbage route are issued a container with a computer chip. Recyclables are weighed and the family earns points redeemable at merchants like CVS pharmacy. Recycle Bank launched in Philadelphia in 2006. Recycle rates rose from 7% to 90%. In 2008 Recycle Bank started a pilot program in N.Y at Columbia University. Students recycle and claim their points.

Recycling Challenges There are many technical and economic problems associated with recycling. Plastics are recyclable, but technology differs from plastic to plastic. Milk containers tend to be high-density polyethylene (HDPE), while egg containers are polystyrene (PS), and soft-drink bottles are polyethylene terephthalate (PET). Increasing Plastic Volume in Trash