Update: So it looks like my estimates for the carbon dioxide emissions were way off. I guess iPad’s components must be particularly carbon-unfriendly per unit mass; if I had to speculate, it’s due to a higher component weight to frame weight than on the computers considered here. Updated results at the end of this post; you can follow along using the original text, substituting in the new values for manufacturing. It looks like my estimates for power adapter efficiency and power consumption are pretty much spot on, though.
His reasoning is that it will help him pay for “content” without damaging the Earth –specifically, he’s talking about reading the newspaper, magazines, and e-books in the iPad, instead of buying them in paper version.
I suspected, and told him, that on the whole this would probably mean an *increase* in environmental damage, rather than a decrease. He’s not convinced.
Jorge then adds the question that prompted the creation of this blog: “Who is right?”
So will buying an iPad to replace print materials reduce carbon emissions or just result in more iWaste?
Waste attributable to the iPad
To calculate the net change in CO₂ by using an iPad instead of using paper, regardless of how often the iPad is used for reading, the entire manufacturing waste should be taken into account. Why? Simple cost-benefit analysis: compare the status quo CO₂ emissions to the alternative. In most cases, the iPad will be an addition to one’s computing family. But if one buys an iPad in lieu of an iPod Touch, iPhone, or similar device, one could instead look at the difference in manufacturing environmental impact. Here, we’ll look at the first case, the worst-case scenario; the entire CO₂ cost of manufacturing the iPad needs to be considered.
We’ll simplify the results of Williams ‘04, as we did in To Print or Not to Print?: manufacturing a computer results in 10 times its weight of CO₂ being produced. The iPad weighs 0.73 kg, so we end up with 7.3 kg of CO₂ produced as a result of manufacturing. We’ll ignore shipping and packaging, although we should note that toting around an iPad is more energy intensive than carrying a few sheets of paper. Unless toting a heavy book around is the alternative, once the iPad is purchased, a rise in emissions due to transportation will result.
We will assume the average reading rate per page is 5 pages per minute. This rate includes pages that would have been ignored if used in its printed form (e.g., the sports section in my copy of The Globe and Mail). We will assume the supplied USB power adapter is used and that it is 80% efficient.
The iPad runs for 10 hours on a 25 Wh battery while surfing the web with Wi-fi. Since the MacBook Air really does get the advertised battery life, I will assume that this isn’t just 10 marketing hours. This means the iPad uses a meagre 2.5W! We assumed a reading time of 5 minutes per page, so that means reading a page requires 0.26 Wh, after factoring in losses from the USB power adapter. Using numbers for power generation in Ontario, that works out to 0.12 g of CO₂ per page. The results of the calculations in To Print or Not to Print? give us a figure of 2 g of CO₂ per side of printed text on recycled paper with recycled toner. From here, all we need to do is solve for x: 2x = 7300 + 0.12x. Our break-even point, x, is therefore about 3883. To be safe, we’ll say 4000 pages (or, really, sides).
At an average reading rate of 5 pages per minute, if owning an iPad saves 4000 sides of paper from use, it’ll have resulted in a net reduction of CO₂ (remember, there are other unwanted byproducts we didn’t consider). At 5 minutes per page, that’s 333 hours of reading. If one owns an iPad for 24 months, that’s about half an hour of reading each day. Will the iPad’s battery hold up to that? Well, considering it runs for about 10 hours on a charge, that’s about 33 discharge cycles. If the battery is the same as the new type used in the MacBook Airs and MacBook Pros, that’s only a tiny fraction of Apple’s estimate of a lifespan of 1000 charges. A faster reader is a more environmentally-friendly reader on an iPad! Reading more dead tree media quickly makes you more like a beaver in the print world.
It impresses me that it doesn’t take much reading (in my books, anyway) for an iPad to pull ahead of print, even after accounting for its manufacturing. Me? I’ll stick to my iPod Touch and laptop until the iPad can serve all my computing needs which, considering my primary computer is a MacBook Air, probably won’t take much beyond letting me run my own apps. But to return to the original question: Jorge, the iPad? Not bad.
Update: After crunching the new numbers from Marek, it looks like one needs to read 35000 pages to break even. Somewhat fortunately, for someone who otherwise would read a newspaper or magazine, this includes the pages that one skips over. However, that’s still a very large amount of reading. I will have to retract that “not bad” verdict — at least from an emissions perspective.