Here is a home version of the biogas digester converting pony manure into usable gas for cooking and heating.

Powell's thoughts:

1.  This video doesn't show that you regularly have to clean out the solids from the digester.  But overall I thought the inventor covered everything except initial digester constriction.

2.  Such methane digesters can provide heating and gas light but do not have enough energy to drive a generator or motor.

3.  It could be used to drive a propane engine if modified---but methane only has a third as much energy per unit burned as propane so it takes three times as much for the same output.  And it would need to be compressed.

4.  Any manure or finely chopped vegetation would work.

 

5.  It might be a good idea to build a 3 wall sandbag bunker retainer wall around the dome with the open side facing away from the home as a blast barrier.  And to make sure a emergency pressure relief valve was on the dome.

 

6.  Might consider a cheap greenhouse cover to raise the temp of the digester (as well as paint exposed surface black) as it will increase the efficiency.

 

see also:
http://diy.edibleplanet.org/biogas-diy-methods-to-turn-that-waste-gas-into-useful-energy

http://agroindustriindonesia.blogspot.com/2010/09/home-made-biogas.html

http://home.btconnect.com/engindia/biogas.htm

http://www.small-farm-permaculture-and-sustainable-living.com/methane_generator.html

http://www.motherearthnews.com/diy/methane-gas-energy-generator-zmaz75mazgoe.aspx#axzz2RcLLsAeq