It takes 37 gallons of watch to make the beans needed for one cup of coffee.

from: http://en.wikipedia.org/wiki/Coffee

Another issue concerning coffee is its use of water. According to New
Scientist, using industrial farming practices, it takes about 140
liters (37 US gal) of water to grow the coffee beans needed to produce
one cup of coffee, and the coffee is often grown in countries where
there is a water shortage, such as Ethiopia.[45] By using sustainable
agriculture methods, the amount of water usage can be dramatically
reduced, while retaining comparable yields. For comparison, the United
States Geological Survey reports that one egg requires an input of 454
liters (120 US gal) of water; one serving of milk requires an input of
246 liters (65 US gal) of water; one serving of rice requires an input
of 132 liters (35 US gal) of water; and one glass of wine requires an
input of 120 liters (32 US gal) of water.[46]

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