Answer to Question 1
Until the 1960s, most MSW was burned in open dumps. The waste was burned to reduce its volume and lengthen the life span of the dump, but refuse does not burn well. Smoldering dumps produced clouds of smoke that could be seen from miles away, smelled bad, and created a breeding ground for flies and rats. Some cities turned to incinerators, or combustion facilities, as they are called today: huge furnaces in which high temperatures allow the waste to burn more completely than in open dumps. Without controls, however, incinerators were prime sources of air pollution. Public objection and air pollution laws forced the phase out of open dumps and many incinerators during the 1960s and early 1970s. Open dumps were then converted to landfills. In the United States in 2010, 54.2 of MSW was disposed of in landfills, 34.1 was recovered for recycling and composting, and the remainder (11.7) was combusted.
Answer to Question 2
Agriculture can use less water by using (1) a surge flow method, in which computers control the periodic release of water, or (2) drip irrigation systems. Industry and homes can use less water by using toilets that require less water, putting in xeriscaping, replacing leaking faucets, replacing faucets with low-flow alternatives, and using water displacement devices. Gray water (from sinks, showers, bathtubs, and laundry) can be used for irrigation.
Photograph illustrating the development of an embryo.
Emanuel Leutze’s Washington Crossing the Delaware (1851) is riddled with historical inaccuracies, mo
The United States, 1819
Primary causes of chronic liver disease in the United States.
Many countries do not produce enough food and need to import food from the United States
Human embryo at successive stages of development (not to scale).