I been engineering a digester/seperator/compression system for some time, if you ever feel up to it I can send you my yahoo addy and can talk about it.
the digester is a continuous flow type, new material goes in, old goes out (Used as fertilizer)
the gase is collected in a large accumulater tank, for my test system it iwll be a 100lbs propan tank. To the tank is a pressur edifriential switch, it will turn on at 10psi and off at 3 psi (this will come later)
the take off pipe will be at the top, on the bottom there will be a valve with a timer and a flame sensor (This will take plying with to find the ideal cycle time) it is to remove the co2 via stratazition of the gass layers as pressure builds, it will open till it detects a flame meaning all co2 has been vented
the off take will go through a scrubber drying system then to a refrigeration compressor (The switch controls this!) it will pump into a very larg propane tank and pressurize it to 300psi
each segment is designs as a modual, and self containes as such so back ups can be put in place easily. My dream is to have 4 2000l propane tanks in perallel pressurized to 300psi, I think this will be a fair bit of reserve fuel for winters when usage would be at its most, the system is intended to suply up to 10 people.