How green is our laptop?

[Ian Stirling]

Jim Gettys wrote:
> We've been very concerned about the "green" of our laptop, as we know
> that it may not be recycled properly.  Obviously, a smaller/lighter/more
> rugged/longer lived machine has a lot of advantages as well in this area
<snip>
> The very low power consumption of the machines means way less global
> warming due to electricity usage.

Beware, I'm bored, and have the Internet!

Say average child flatulence is 1l/day - sources I found said 200ml-2l, 
I'm assuming 1l, as diets high in vegetables are more likely to cause an 
increase.
Assuming that methane is 7%, this is about 150ml/day. (I found several 
sources saying 7-9%, though some dismissed it as 'trace'. No primary 
literature.)

Assuming the '20 times more potent than CO2' is accurate - equivalent to 
3l/day of CO2.
If we're talking 10Wh/day, how much of the food is used to produce 
electricity?
Well, if we're talking 1000Calories per day baseline food, that's 
4MJ/day, or around 1% before taking into account human efficiencies. As 
I see 25% as a rough 'maximum food conversion efficiency, that means 
somewhere on the order of 4% more food, or 120g of CO2 equivalent per day.
(I'm assuming that the food is being produced in a carbon neutral manner.)

Wow!

If you use this 120g of CO2 budget, and burn it in a modern gas power 
station, you get about 300Wh. Using a coal power station, 100Wh.
Using an figure for a poorly maintained diesel generator (and neglecting 
local emissions) it's still >90Wh.
I'd never have guessed.