The purpose of this processing is to compare the emissions of greenhouse gases produced by farmed animals and the carbon dioxide fixed by the crops of the various plants used for their feeding. Starting from the collection of FAO data, the CO2 fixed by the main crops of zootechnical interest was calculated. The biomass produced and the CO2 set by them were calculated using the "Calvin-Benson cycle" and then subtracted from the atmosphere. All the emissions related to ruminal fermentations and the management of the dejections in the various types of farms were also calculated. A balance has been made and the ratio between the emissions due to the animals and their dejections and the CO2 set by the crops destined for their feeding has been calculated. The relationship and the incidence of the various species bred on the emissions related to the dejections have been calculated. The results obtained showed that the contribution of the atmospheric emissions of the farms is compensated by the vegetation used by the animals themselves.