How to deal with waste has been a problem since humans started producing it. As more and more people choose to live close together in cities, the waste-disposal（处理）problem becomes increasingly difficult.

       During the eighteenth century, it was usual for several neighboring towns to get together to select a faraway spot as a dump site. Residents or trash haulers（垃圾拖运者）would transport household rubbish, rotted wood, and old possessions to the site. Periodically（定期地）some of the trash was burned and the rest was buried. The unpleasant sights and smells caused no problem because nobody lived close by.
           Factories, mills, and other industrial sites also had waste to be disposed of. Those located on rivers often just dumped the unwanted remains into the water. Others built huge burners with chimneys to deal with the problem.

        Several facts make these choices unacceptable to modern society. The first problem is space.  Landfills(填埋场)are most needed in heavily populated areas. Such areas rarely have empty land suitable for this purpose. Property is either too expensive or too close to residential（住宅区的）neighborhoods. Long-distance trash hauling has been a common practice, but once farm areas are refusing to accept rubbish from elsewhere, cheap land within trucking distance of major city areas is almost nonexistent.

      Awareness（意识）of pollution dangers has led to more strict rules of waste disposal. Pollution of rivers, ground water, land and air is a price people can no longer pay to get rid of waste. The amount of waste, however, continues to grow.

       Recycling efforts have become commonplace, and many towns require their people to take part. However, even the most efficient recycling programs can hope to deal with only about 50 percent of a city’s reusable waste.