As the amount of waste produced in the United States increases, new methods of disposal are needed to replace the old ones. In the past, waste was often placed in dumps, where waste was left open to the atmosphere and free to blow around. This resulted in bad smells and frequent fires that would burn uncontrollably, releasing pollutants into the atmosphere. In addition, verminous creatures such as roaches, flies, mosquitos, rats, etc. would live in the dump increasing the chance for the spread of disease. A large quantity of organic waste was also fed to hogs. This led to the spread of trichinosis and more stringent regulations on the treatment of waste before it could be fed to the hogs. Other waste was dumped in the ocean. Today ocean dumping and dumps are illegal, and hog-feeding is impractical. As a result, the most common disposal method for municipal solid waste is the sanitary landfill. Incinerators are also used in some localities, but are now being phased out due to air pollution problems and public pressure.

The sanitary landfill of today is designed to minimize pollution problems. To prevent water from moving through the landfill and into groundwater, runoff systems are installed to collect drainage and keep the landfill as dry as possible. When water does move through the landfill picking up pollutants, it is referred to as leachate. If it picks up heavy metals or some toxic organic chemicals, it can contaminate nearby groundwater sources. To prevent the movement of leachate, clay and plastic liners are often installed at the base of the landfill before the solid waste is put in. To prevent trash from blowing around and to reduce smells and the spread of disease, the solid waste is covered with clean fill material throughout the day. Finally, a methane recovery system is installed. In the past, methane levels would build up in the lower layers of the landfill where they could leak into nearby sewer systems or basements. When ignited, they caused explosions.

Even biodegradable waste does not biodegrade appreciably in a landfill. Aerobic microorganisms (ones that require oxygen) are primarily responsible for rapid biodegradation. When the waste is initially put in, plenty of oxygen is available and they begin biodegradation. As time goes on and waste is further compacted, they run out of oxygen and the site become anaerobic. Anaerobic organisms (ones that do not require oxygen for respiration) can continue biodegradation, but they work much slower, especially in the high temperatures evolved from the biodegradation process. As a result, it takes an extremely long time for the waste to biodegrade. Compost piles work differently. They are turned over frequently, which keeps them aerobic and releases excess heat. In addition, they use both microorganism and animals such as earthworms as the decomposers. Although the piles are kept moist, they do not smell. Anaerobic bacteria put off the bad smell associated with rotting materials.

Once the landfill is filled, it must be maintained for another 30 years by law. This includes methane removal and constant monitoring of water quality in the surrounding area. These areas are usually converted into parks or golf courses because they settle unevenly making them unsuitable for structures.

Most of this exploration depends on students having an introductory knowledge of the above concepts. They will learn other issues involved in waste disposal by completing case studies and questions, debates, research, role playing games, writing environmental impact statements, and laboratory experiments. This unit also includes information on hazardous waste disposal, environmental law, disposal alternatives, and community responses (NIMBY). Pick and choose your favorite parts and adjust them for learning level as required. Depending on the exercise, you can introduce more chemistry, have them design their own experiments,...