Actually, bits do pollute, and more than you might think. Server farms consume astonishing amounts of power.

For example: In the United States, Google currently operates 12 data centers. Each data center consumes approximately 20 megawatts of power per month, representing a little over $2 million of electricity per month per data center. That is approximately half the total output from a very large coal-fired power plant (which is not to say that Google uses coal; they attempt, where possible, to locate their data centers where hydroelectric power is available).

That's not true of Facebook. Facebook operates nine US data centers; the largest, near my home in Oregon, occupies more than 300,000 square feet and consumes a whopping 60 megawatts(!) of power, which is provided by a coal-fired plant in Boardman, Oregon. The 585 megawatt Boardman plant is the worst single source of pollution on the West Coast (it was built long before EPA clean air regulations), and PG&E had actually planned to close the plant before Facebook announced plans to build their data center here. Facebook will be consuming more than 10% of the plant's total peak electrical output.

Apple's new iCloud data center in North Carolina has the capacity to scale to 100 megawatts of power(!!), though Apple won't say how much power it's currently consuming. Roughly half of the power fed to the NC data center comes from coal.

It would be an interesting research project to do a cradle-to-grave energy and environmental impact assessment of data shipped on DVDs vs. data held in data centers and shipped over the Internet. A single-time, single-use download of Lion from Apple's data center would probably come out ahead of a Lion DVD, but given that it's not easy for average non-technical users to burn installers themselves (and doing so would still require considering the manufacture, shipping, and disposal cost of a blank DVD), I bet that a user who has multiple computers to upgrade to Lion may download a copy for each computer, rather thanusing just one DVD on all of them. In an institutional setting, that might shift the environmental cost onto digital downloads away from DVDs.

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