paper towels or electric drier?

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What’s less harmful for the environment: using a paper towel to try your hands or running an electric drier for 20 seconds? Some of the paper towels can be recycled (but not all, and that also takes some energy, and some trees are cut down to make paper), on the other hand the heat form the drier is lost forever. Has there been any study on this topic? I see both advertized as "ecologic" but which one is and which one is not?