In reply to AllanMac:
> What makes you so sure?
Well you could do a back of the fag packet calculation.
Service road 20km x 4m x 1m = 80,000m3
Turbine bases 25m dia x 3m = 70,000m3
Turbines lets say 50
150,000m3 total
Let's say that's 33% by mass carbon, peat is very boggy after all and hydrogen is light
Carbon weighs ~2T/m3
That's 0.33*150,000*2 = 100,000T of carbon
CO2 is ~1/3 carbon 2/3 oxygen, carbon and oxygen weigh very roughly the same so 100kt of carbon makes 300,000T of CO2 which certainly sounds like a lot but this is of course assuming all the peat disturbed is oxidised, most of it will just be moved aside making the bog slightly deeper locally. Also it may not actually be a very big number. Let's see.
A decent size land based turbine makes 5MW peak, that's 250MW from 50 of them but with a load factor of maybe 30% so let's say 80MW average over what, 25 years (a guesstimate but it seems reasonable).
365days *24Hours *25years = 220,000 Hours
80M*220K = 1.7x10^13 WattH
x60x60 to get Joules generated over the instalations's life: 6.3x01^16 Joules
Methane has an energy density of 55MJ/kg so assuming 100% conversion efficiency that's basically 1.2 million Tons of natural gas saved.
Actual conversion efficiency is more like 40% at best so that's 2.8MT of natural gas which is mostly carbon by weight (C4H10), let's say 2.5MT carbon.
As we saw before, CO2 is roughly 3 times the weight of the carbon used to make it so that's: 7.5MTon of carbon dioxide not released because of those 50 turbines.
So is 300,000T a big number? Undoubtably yes but most of that peat we accounted for won't become CO2 as a result of the build and even if it somehow did, 7,500,000 is a much bigger number!
Interesting exercise, I didn't know which way that would go when I started out on it.
Obviously one also has to manufacture the turbines and concrete but that goes for thermal stations too which have broadly comparable lifetimes and material demands.
jk
Post edited at 14:05