It takes an enormous quantity of energy to print, transport, count and sort the dollar bills in your wallet. The U.S. Bureau of Printing and Engraving cranks out $750 million in new currency each day, trucking the paper from its Massachusetts manufacturing plant to be printed in Washington and then to secret distribution points, where it's held before it's carted off to banks. When you pay with a credit or debit card, in contrast, all you're doing is moving electrons, as e-money moves between accounts-so it has to be the greener alternative, right? Not so fast.
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