How are landfill gas and sewage gas generating systems treated, as opposed to bio-digester generating systems, within GGAS?
Despite possibly having similar fuel sources for the derivation of its resultant methane gas, landfill gas and sewage gas fuelled generating systems receive a slightly different treatment under the Generation Rule, than generating systems using ‘manufactured methane’ as fuel (such as bio-digesters). The treatment differs on the basis that generation from landfill gas and sewage gas derives its energy from existing waste disposal methods (and accordant waste stream inputs) that have historically released (and in some cases, may continue to do so) fugitive methane emissions to the atmosphere. As such, these types of generating systems utilise Equation 16 of the Generation Rule to calculate the amount of fugitive methane emissions directly avoided through the use of the fuel. On the other hand, bio-digesters are seen as diverting existing waste streams (that may possibly have been disposed of via less intensive methane formation methods than bio-digestion), thus in effect, ‘artificially’
