How this calculator works
A printed book has a footprint from growing and pulping the paper, printing, binding and distribution, typically between 1 and 3 kg of CO2e for a paperback. An e-reader has almost none of that per book, but its manufacture concentrates the impact of a screen, a battery, a plastic case and electronics into one device. Dividing the device footprint by the per-book footprint gives the number of books you have to read before the reader pays off. The device figures here, about 168 kg for a dedicated e-paper reader, 200 kg for a tablet and 80 kg for a phone, are rounded estimates from life cycle studies. Reading on a phone you already own is almost free in carbon terms, though the manufacturing of the phone is shared with everything else it does. Libraries and second-hand books cut printed-book emissions further because one copy serves many readers.
Formula
books over the device life = books per month x 12 x years kept. printed-book emissions = books x footprint per book. break-even = device footprint / footprint per book. The chart plots the two cumulative footprints against the number of books read; the printed line rises with every book and the device line starts at its manufacturing footprint and stays flat.
Worked example
An e-paper reader at 168 kg CO2e, kept for 4 years, reading 2 books a month: 2 x 12 x 4 = 96 books. The printed equivalent is 96 x 2.7 = 259.2 kg CO2e, so the reader saves 91.2 kg over its life. The break-even is 168 / 2.7 = 62.2 books, reached after about 2.6 years at this reading rate.
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Frequently asked questions
Does reading on a phone or tablet count?
If you already own the device, the marginal emissions of reading one more book are tiny, mainly the electricity to charge the screen. The footprint of the device is shared across everything you do with it, so it is reasonable to attribute little of it to books.
What about audiobooks?
Streaming an audiobook uses data centre and network energy, but a few hundred megabytes per book is small compared with a printed book. The listening device matters far more than the stream.
Are library books almost free?
In carbon terms, close to it. The book is shared across many readers, so the manufacturing emissions are divided by the number of loans. The trip to the library, if you drive, can outweigh the book saving.
Why do the device figures vary so much between studies?
They depend on the screen type, the size of the battery, the manufacturing location and the electricity mix. Studies also disagree about whether to count the mining of rare metals and the shipping of finished devices. Treat the number as a range of roughly 100 to 250 kg, not a precise figure.
Sources
- Environment and Climate Change Canada: emission factors and reference values for greenhouse gas quantification (national inventory edition, updated annually)
- Moberg et al. (2010), Printed and tablet e-paper newspaper from an environmental perspective, Environmental Impact Assessment Review
- US Environmental Protection Agency: paper and paperboard life cycle