As a proud Kindle owner I wondered if e-books were better for the environment than their paper brethren.

I found three papers that looked into this question: Environmental Implications of Wireless Technologies: News Delivery and Business Meetings by Michael Toffel, Screening environmental life cycle assessment of printed, web based and tablet e-paper newspaper by Asa Moberg, and Printed Scholarly Books and E-book Reading Devices: A Comparative Life Cycle Assessment of Two Book Options by Greg Kozak.

To determine which is best for the environment, lets compare the energy usage and co2 emissions of reading the New York Times for one year in paper vs. e-book form.

What is the impact of reading the paper form of the NY Times for 1 year?

Michael Toffel puts the weight of a year of NY Times at 236 kg (.65 kg a day). The Environmental Defense Fund's Paper Calculator shows that 1 kg of 50% recycled newsprint (uncoated groundwood) paper uses 30,000 BTU (31 MJ) of energy. 236 kg of paper would therefore use 7,316 MJ of energy.

Michael Toffel finds that to create, print, deliver and dispose of the newspaper emits 702 kg of co2 a year (using 50% recycled newspaper).

Aside #1: How many trees and how much land does a year of NY Times require?

This Depaul University analysis states that one pallet of paper (2,000 lbs) can be produced by 3.84 trees from which follows that each tree produces 237 kg of paper. Surprisingly, the 236 kg of paper needed each year to produce one year of NY Times papers would take almost exactly 1 tree.

The Depaul University analysis also states that over the course of 25 years, 1 acre of forested land can produce 120 trees (or 4.8 trees/acre/year or 12 trees/ha/yr). In one year, a hectare of land therefore produces 2,844 kg of paper (12 trees * 237 kg/tree) and 1 kg of paper requires 3.5 m2 yr of forest (1/2,844 ha/yr * 10,000 m2 per ha). The 236 kg of paper needed each year to produce the NY Times would require a dedicated 826 m2 of forest.

What is the impact of reading the digital version of the NY Times on the Kindle e-book for 1 year?

There are 3 stages to this: manufacturing the e-book, running the e-book and downloading the digital file over the cellular network.

The three papers give slightly different values for manufacturing an e-book. Michael Toffel puts it at 158 MJ and 8.8 kg of co2, Asa Moberg puts it at 190 MJ and 9 kg of co2 and Greg Kozak puts it at 261 MJ and 19 kg of co2. Using an average of the three, I will go with 200 MJ and 12 kg of co2. This is much lower than the 1,390 MJ (386 kWh) of energy and 60 kg of co2 to produce a mobile phone. Assuming an e-book lasts for 3 years, the impact of the manufacturing per year is 1/3 of the total or 67 MJ (18.6 kWh) and 4 kg of co2.

The impact of running an e-book is minimal. I find that I charge my Kindle for 2 hours at 6W every 3 days which works out to 1.5 kWh a year. The EIA states the average US power plant emits .6 kg of co2 per kWh. 1 year of running a Kindle causes 1.5 kWh * .6 kg/kWh = .9 kg of co2 emissions a year.

The Kindle uses the Sprint cellular system to download the new content each day. The NY Times Kindle edition has a size of approximately 334 kB and takes approximately 1 minute to download. Michael Toffel puts the impact of 1 minute of cellular time to be .014 kWh based on a 1999 study of the Sacramento cellular system. Over a year this would be 8 kWh and would release 5 kg of co2 (using the .6 kg of co2/kWh value from above).

The combined the result is 100 MJ (27.5kWh) and 10 kg of co2 a year for using an e-book to read the NY Times each day.

Aside #2 What if I read the newspaper on my computer rather than an e-book?

Asa Mosberg takes a look at that scenario in her paper and finds that it depends on how much time you spend reading the news. If you spend less than 30 minutes reading the news then you will use less energy and emit less co2 by using your computer. If you spend more than 30 minutes, then the electricity that it takes to run your computer and monitor uses more energy and emits more co2 than if you read a physical newspaper. Of course mileage can vary based on how efficiently your monitor and computer use electricity and what the source of your electricity is.

Conclusion

Reading the physical version of the NY Times for a year uses 7,300 MJ of energy and emits 700 kg of co2. Reading it on a Kindle uses 100 MJ of energy and emits 10 kg of co2.

The Kindle therefore saves 6,500 MJ and 690 kg of co2 a year. A gallon of gasoline has 131 MJ of energy and emits 8.8 kg of CO2, so switching to an e-book would be like saving 50 gallons of energy and 78 gallons of co2 emissions. A reduction of 690 kg of co2 is 3.5% of the average American's 20 metric tons of yearly emissions.

Americans use on average a bit over 700 lbs (320 kg) of paper and paper board a year, so cutting out 236 kg of paper would be a significant reduction of paper usage.

For the newspaper, the majority of the energy and emissions are due to the manufacturing of paper. The most significant step that can be done to reduce the impact of paper manufacturing is to use recycled paper. Michael Toffel concludes that emissions could be reduced 41% by doing using 100% recycled paper. But, even 100% recycled newspaper would use significantly more resources than an e-book.

Most of energy that an e-book uses in its lifetime is from the manufacture of the e-book. Keeping your e-book beyond 3 years is the best way to lower the environmental impact of reading an e-book. Also, using it for additional activities like reading books, magazines and blogs will also reduce the impact of using an e-book.

Aside #3: What if you compared books rather than newspaper reading with an e-book?

For many people, the Kindle and other e-books will be a replacement for physical books rather than newspapers. Eco-Libris states that 3.09 billion books were sold in the US in 2006, or approximately 10 per American. Alibris finds that the average book sold weighs 340 g. The 3.4 kg of books the Average American purchases leads to 105 MJ and 10.2 kg of co2 (at 31 MJ/kg of paper and 3 kg of co2/kg of paper). The yearly value for using a Kindle to read the newspaper daily was 100 MJ and 10 kg of co2. It is basically a wash between using physical books and the Kindle. If you purchase more than 10 books a year and are unlikely to loan those books out when you are done with them, then the Kindle will come out ahead.

How you get the books is also important to the analysis, for if you drive to the book store the extra gasoline burnt is likely to tip the scales in favor of the Kindle.

Assumptions

It took me so long to actually write this up that I found out that Erika Engelhaupt has written a similar article to this one in Environmental Science and Technology. I agree with her that "Our world has become such a complicated place that every purchasing decision can become a Ph.D. dissertation topic, as I quickly learned." Trying to determine whether e-books are better for the environment quickly gets complicated and full of assumptions that can completely change the conclusion. Here are the most important assumptions in this analysis.

Number of people that read the newspaper: I assumed just one person reads the paper. Michael Toffel's research shows that on average 2.6 people read each NY Times paper. Asa Moberg assumes 2.4 people read each paper. If you are living in a house where 4 people read the paper each day, the impact of the paper can be split 4 ways.

Kg of co2 emitted per kg of paper: There are a ton of different estimates. I used Michael Toffel's value of around 3 kg of co2 per kg of 50% recycled paper. He also gives a value of 1.74 if the paper is 100% recycled. Asa Moberg puts it at .96 with 60% recycled paper. Greg Kozak uses a value of 6.33. This Green Press Initiative document that puts it at 7.14 for 0% post-consumer recycled, 5.5 for 50% recycled and 3.9 for 100% recycled, while this other Green Press Initiative document puts it at 1.6 million tons of co2/ 540,000 tons of paper = 2.96. The Green Press Initiative has yet a third value from this webpage that puts it at 73 billion lbs of co2 / 8.7 million metric tons of paper = 3.8 (this includes addition of forest carbon loss). Finally, the Environmental Defense Fund's Paper Calculator lets you put in your own assumptions and for Uncoated Groundwood (newsprint), 50% recycled emits 5.1 and 100% recycled 3.7. The higher values would make the e-book look even better.

Most of these estimates for co2 emissions from paper assume that some of the disposed paper ends up in a land fill and is turned into methane by microbes. Methane is 20 times as strong as a greenhouse gas as co2 is and the methane emissions translate into higher co2 equivalent emissions. But, another possibility is to store or bury the newspaper in a way that methane isn't released. In this way the carbon in the paper is sequestered. This report suggests that trees can be grown as a way to sequester carbon, and one way to do so would be to sequester newspapers. I am not sure what the impact on this analysis would be if this were to occur.

MJ of energy per kg of paper: The Paper Calculator shows a value of 31 MJ per kg of paper, while Asa Moberg finds a value of 10.4 MJ per kg and Greg Kozak comes up with 110 MJ.

Kg of paper per tree: The amount of paper that one tree produces is estimated at 237 kg by this Depaul University analysis. The Green Press Inititive states that 95 million trees can produce it takes 6 million metric tons of virgin fiber or 63 kg of paper/tree. Using the lower value would mean more trees would be needed to produce one years worth of NY Times.

Manufacturing of e-books: The numbers for the manufacture of e-books was not done on e-ink readers as no numbers were yet available. I don't know how this would impact the results.

Impact of the cellular system: I used Michael Toffel's estimate. Another estimate of the impact of using a cellular system is found in this report from 2004. It puts the impact of downloading 1 Gb over a UMTS cellular system in Switzerland to be 939 MJ of energy and 27 kg of co2. But, if you take out the impact of the cellular phone and the administration of the cellular system (business trips for cellular employees), what remains is just 20% of that total or 188 MJ (52kWh) and 5.4 kg of co2. Downloading a 334 kB file daily racks up 121 MB a year or 975 Mb, slightly less than 1 Gb. Therefore, this report would estimate the impact of using the cellular system at 183 MJ and 5.2 kg of co2. This is much more energy and about the same amount of co2 as the other estimate I used. Not clear to me which estimate is better, or how things have changed in the cellular commuications business since each report was written.

Ignored aspects of the e-book life cycle: I don't know how much energy it takes to run the servers from which the newspaper file is downloaded from, but given how efficient servers are today, I don't believe a single 334 kB file download a day is significant. Also I am not sure how much energy and emissions the engineers that developed the Kindle and the engineers who created the software for the Amazon website used. Should the energy they use while working in their offices or when flying on business trips be included?

Impact of how electricity is generated: While the average American power plant emits .6 kg of co2 per kWh of power produced, it varies greatly, as low as .013 kg in Idaho (hydro-power) and as high as 1.0 kg in North Dakota (coal, I assume). Where you get your power from changes the values.

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