here is my responce to this report
www.environment-agency.gov.uk/commondata/acrobat/nappies_1072099.pdf
you will see that this is May 2005 and one of the biggest (the biggest?) studies of its kind. Also the one that most people refer to.
You can read all 130ish pages, + 50 pages of appendix if you like.... OR i will summarise it for you for people who cant be bothered.
ANYWAY
they assume that 1/3 of people wash their nappies at 90c (i disagree!) table5.7
they assume 10% of nappies are ironed (5.14.7)
they assume 60% of nappies are tumble dried.... (if you look it says their survey sugested that 19% of people tumble dry their nappies but because 75% of household use a dryer they decided to use a figure of 60% (off the top of their heads basicaly)(9.3.2)
they assume 50% of people add softner to their nappies . im sure anyone who uses nappies KNOWS that you do NOT ever add softner to nappies cause it stops them from absorbing.... (also consider the enivironmental impact of the softner.... and of manufacturing the softener.... and of driving to sthe supermarket to by the softener and of the softener going down the drain etc etc) (5.14.5)
It also assumes most people SOAK their nappies and allows 10 litres of water per day.... on top of 75 litres per washing machine load.... a large overestimate on the amount of water most modern machines, having recently got a new washing machine trust me i KNOW, so 85 litres of water per day (5.14.2)
They assume that people have 47.5 'terry nappies' nappies per 6 months (9.3.5)...
and then asses the full environmental impact of manufacturing all that cotton to make 47.5 nappies per 6 months.... and its the MANUFACTURE and water used during manufacture that is basically the major environmental 'problem / issue with' washables
also they acknowledge and justify this figure and in the same sentence say that actually only an average of 40 nappies are bought for the LIFE of the child (personally i cant believe that is an accurate average.... does anyone know anyone with more than 40 nappies?... EVERY person i know has LOADS less)
Its is assumed that 12 nappies are washed at a time (5.14.7) and that it takes a WHOLE HOUR to iron 12 cotton nappies.... and they use that figure of electricity... ie an iron on for an hour to iron 12 cotton squares..... Maybe 12 seconds would be more accurate? or 0 seconds for ironing nappies!]
FOR disposable nappies they assume just over 4 (4.05) nappies per day... this is a LOW estimate IMO especially when you consider new born babies (9.1)
In the summary they conclude that reusable users should reduce they energy they use washing and drying nappies.
SO..... they DO over estimate the washing temperatures, water use, tumble dryer use and iron....
they also allow for FAR too many nappies being manufactured (washables) and asses the environmental impact of the commercial manufacture of the cotton...
(no mention of bamboo which is a much more environmentally friendly material and becoming increasing popular with washable nappies)
then there is the fact that loads of people who choose washables are 'environmentally aware' people who are likely to be using less than 'conventional' washing detergents... such as soap nuts or eco balls, and are likely to be using more energy efficient machines, due to the way they think.
the fact that they only allow for 12 nappies being washed per load then 60% tumble dried (when only 19% of their survey suggested they tumble dried their nappies, AND allowed 1 hour of electric for the iron per load).... yet allow for the manufacture of nearly 200 nappies PER CHILD just shoes how ridiculous this whole study was!
{they also allow for nappies to be travel half way around the world to England.... yet several main brands of washables ARE made here in the uk}
and with 2nd babies etc they DONT need to be manufactured... which IS the main issue with washables
don?t forget we bin 8 MILLION disposables per day and for every £1 a parents spends on nappies the tax payer has to spend 10p disposing of them