If you look at the energy expenditures for maintaining a library over a decade, let alone a century, a paper book would be far more environmentally friendly. I

If you look at the energy expenditures for maintaining a library over a decade, let alone a century, a paper book would be far more environmentally friendly. I'm not so sure. The longer a book is in existence, the more expensive it is to maintain. Over time, books fall prey to dust, mites, mold, acids used to treat the paper. As books wear out, you upgrade to newer printings. Very similar things happen to computer files; bit rot, format support, etc. From an energy standpoint, there's a lot more up front energy needed to produce a book than an e-book. After it's created and read, an e-book sits on a hard drive or a flash drive, unused, and thus uses little to no energy for storage. Physical books, on the other hand, require dusting and cleaning, which requires energy in the form of a fed human being and/or a vacuum cleaner. In in depth comparison between the two types of libraries would be very interesting. Even after typing all of that, I'm not sure which one would come out on top.