Sand is the most-consumed natural resource in the world after water and air. Modern cities are built out of it. In the construction industry alone, it is estimated that 25 billion tons of sand and gravel are used every year. That may sound a lot, but it’s not a surprising figure when you consider how everything you’re surrounded with is probably made of the stuff. But it’s running out. This is a scary fact to think about once you realize that sand is required to make both concrete and asphalt, not to mention every single window on this planet. The United Nations Environment Programme found out that from 2011 to 2013, China alone used more cement than the United States had used in the entire 20th century and in 2012, the world used enough concrete to build a wall around the equator that would be 89 feet high and 89 feet thick (27 by 27 meters).
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