All the ruminal methane (CH4) emitted by ruminants (cattle, buffalo, sheep, camel goats and minor camelids) was calculated all over the world, standardized according to the size and therefore the quantity of methane emitted and was compared with the methane that could potentially be produced if the dejections were treated in anaerobic plants. Obviously we took into account the fact that not all types of breeding allow the recovery of dejections, for example grazing. This calculation was also made for other non-ruminant animals of zootechnical interest. The conversion of methane potentially used by anaerobic plants into electrical energy has also been calculated, considering both the various quantities of manure for each species and for each type of breeding and the yield in biogas and then in methane according to the various chemical composition. This calculation was also extended and separated also for non-ruminant species reared. To make the conclusions pragmatic, electrical energy and potentially powered homes were quantified.