Composting, or the planned rotting of organic material, done under anaerobic conditions with little to no oxygen creates methane gas as a byproduct. Methane is a highly flammable gas related to other gases, such as propane, which are used to power electrical generators. Capturing the methane gas released by compost is a way in which producers of large amounts of unneeded organic matter may become be self-sustaining. The production of the equivalent of one gallon of gasoline per day, however, requires the manure of approximately 46 swine or 5.5 cattle.
Create a sturdy, enclosed holding area for the composting material. This should be long and narrow. An example from a South African pig farm is a concrete tank 50-feet long, 11-feet wide and 5-feet high. The tank should have openings at both ends for the addition of new material and the removal of the finished compost. Hatches are distributed throughout the top for access to the interior. Attach a pipe to the ceiling through which to draw the lighter-than-air methane gas to a holding tank.
Fill the tank with sufficient organic material to begin composting. A tank that size can receive the daily waste product from approximately 800 pigs, or 95 cows for about 30 days.
Add more waste product daily and use it to push the previous day's waste further into the tank. The older material will continue to compost as the new material is put in.
Draw off the compost when the older material finally reaches the far side of the tank. It should be dark brown, crumbly, and filled with nutrients.
Continue to put waste in one end and draw out compost from the other end.
Collect the methane into a holding tank by drawing it through the pipe from the composting tank.
Use the methane as you would propane gas in powering a natural-gas electrical generator for the home, business or farm.
If done properly with a sealed tank there is no offensive odour to the composting.