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Briefly: United Airlines are giving their 11,000 pilots iPads in an effort to increase efficiency, etc. They're making manuals and other documents electronic.
As a side-benefit, they claim, there will be a big reduction in greenhouse gas emissions: 3,208 metric tons per year.
However, nowhere have I seen the emissions generated by the manafacture and distribution of 11,000 iPads taken into account.
What might the net increase or reduction in greenhouse gas emissions be? I suggest assuming an iPad is good for 3 years, but I leave that up to you.
According to Apple's Own Information an iPad2 causes 105kg of greenhouse gases from start to finish. Multiply that by 11,000 and you have 1,155 metric tons. Being their own publicised information, it could be highly idealised. Also, this doesn't include additional resources needed by the airline to roll out the devices.