Ebooks are becoming increasingly more ubiquitous as customers buy e-reading devices such as the iPad and Kindle. Advocates for environmentally friendly products may see this as good news, as it means fewer trees are being sacrificed for the production of paper books.
However, e-readers still have to run on electricity, which, unless it comes from a renewable source like solar or wind power, produces carbon dioxide, thus slowly contributing to climate change. Paper books are not without their own carbon footprint, so this all begs the question of which format ends up being more sustainable when you tally up all greenhouse gas emissions.
The answer is complicated. Essentially, the conclusion of most studies on the subject is that the more books you read, the more carbon you save with ebooks. One study detailed by Terrapass.com, however, found that readers would need to read an average of 23 books every year in order for digital books to be more environmentally friendly. That's a very high total for the average reader. Another study, as reported by the New York Times, stated that readers would offset the carbon footprint of switching to e-readers by reading three to four books every month for four years. Again, not an entirely realistic number, even for a bookworm.
As noted by environmental living site SCGH.com, probably the most environmentally responsible way to read would be to walk to the library, borrow a few books at a time, finish them and return them the next time you're in the area. In terms of reducing your carbon footprint, simply sharing already existing materials is a much more efficient method than buying new items, digital or not.