The accordance in between these results can be better understood considering the efficiency in the biogas yield. In fact, if on one side the co-generation allows to save NRPE during digestion and upgrading, on the other side the consumption of produced biogas decreases the bio-methane yield at the end of the process. Instead, taking the electricity from the grid, also if increases the NRPE consumption during the process, increases also the amount of bio-methane produced. This increases the global avoided NRPE consumption, increasing the avoided NRPE consumption related to the use of fossil methane by the end users. The analysis can take into account just the efficiency of the process , or including also the use of the produced resource in the case of the present work, which considers the bio-methane production for automotive exploitation, the second criterion is more appropriate.