Gas Production:  Methane gas production is directly related to solids destruction.  Digesters with comparable solids destruction levels will produce comparable levels of methane gas measured in BTU’s.  The actual gas volume produced by a digester will vary somewhat with the concentration of methane in the gas.  Digesters producing 50% methane gas (500 BTUs per cubic foot) must produce a higher gas volume than a digester producing 65% methane gas (650 BTUs per cubic foot) in order to achieve the same energy output (total BTU’s).

Not all digestible waste streams are equal in terms of the potential for methane gas production, and not all organic waste streams are suitable for anaerobic digestion by themselves.  Animal manure is well suited for digestion by itself or as an excellent buffer for other waste streams that are too acidic or basic for processing on their own but that have high energy potential.  By adding high energy substrates to animal waste in the correct proportion, methane gas production can be enhanced significantly.  The Andigen system is well suited for the controlled addition and digestion of supplemental substrates.

Gas Utilization:  Methane gas from an anaerobic digester can often be used as a direct replacement for natural gas.  It is typically necessary to make a simple modification to natural gas burners in order to accommodate the lower BTU content of biogas from digesters.  Compatibility is enhanced when digesters produce gas with a higher BTU content and lower H2S content as in the Andigen system.  When direct utilization of biogas is employed, a fraction of the BTUs produced must be used to heat the digestion process.  On average this would be less than 1/4^th of the energy, depending on the climate.

Biogas is also suitable for use in a combustion engine generator.  The high BTU content and low H2S content make the gas from the Andigen digester well suited for this application.  The actual kilowatt production is directly related to solids destruction as reflected in BTUs generated by the digester as methane gas, and the efficiency of the engine generation system.

When an engine generator is used, waste heat is also available from three sources, engine cooling water, engine exhaust and radiant heat.  These heat sources are more than enough to heat the digester.  On average, over 60% of the total of engine waste heat is available for other uses.