I was watching a programme on Sky the other evening about the production of methane from cow (and other manure) and was prompted to look on the web.
As an introduction for those of you unware of what is involved here is one site I found (complete with a link to a High School science project type model):
Along with some more technical data:
And some engines designed to operate with gaspower (although normal petrol engines can be adapted very easily):
And some statistics for the USA from 1997:
Obviously, a GM would need to put in a bit of effort to come to some conclusions about how farm production in his area had fared. The key questions would be (off the top of my head):
1) How many animals were still alive? While the units in the examples owned hundreds of cows smaller scale collection of cowpoo (and indeed, pig or chicken droppings) would also work.
2) Ability to collect the droppings and put them in the digester.
3) Source of water to add to the droppings to create a slurry (apparently an 8% solution of poo is best).
4) Ability to maintain the digester at the optimum temperature (the bacteria work best within certain temperature ranges).
Once you have the methane then obviously it can be used to generate electricity, power vehicles or (possibly best option) burnt directly for heating purposes. The slurry once it has gone through the digester can be used as fertiliser.
One of my first campaigns was based upon the attempt by a village to produce a large still to provide fuel for a large generator (which was another whole set of adventures) - obviously a biogas digester like this would be another option for a group to utilise.
I thought this was one of those alternative technologies which is basically simple enough to translate into TW2000 situations.