school energy&environment

Climate and atmosphere

The greenhouse effect, the phenomenon that entails the overheating of the planet, is caused by the presence in the atmosphere of different substances, which are normally existing in nature in low concentrations but that are now produced in high quantities by human activities, especially in the last decades (combustion of fuels to move from one place to another, to make machinery work, fuels to produce electric energy, etc.). Among these substances, some have a stronger impact as methane (CH₄) and nitrous oxide (N₂O), others, as carbon dioxide (CO₂), affect less the greenhouse effect but are produced in great amount by humans. CO₂ is employed as benchmark to measure the extent of the impact of other molecules on global overheating (Global Warming Potential, GWP): it’s like a bargaining counter where the effect of CO₂ on climate change counts as 1 and the effects of methane and nitrous oxide are its multiples. Animal production plays a crucial role in terms of climate change as it’s accountable for 18% of global atmospheric GHG (Green House Gases) emissions produced on the whole by human activity. This share is even superior to GHG emissions generated by means of transport in the whole world!! In particular, cattle breeding produces 9% of global carbon dioxide emissions, especially as a consequence of land-use change as deforestation caused by the extension of pastures and farmed lands. The zootechnical sector, though, is accountable also for 37% of methane produced on the whole by human activities: this share is emitted mostly by ruminants and fermentation of cellulose that takes place in their stomach. We should take into account that methane is 23 times more powerful than carbon dioxide with regards to the overheating of Earth. Moreover, animal production contributes for 65% of nitrous oxide introduced on the whole by humans in the atmosphere (N₂O has a potential of overheating that is 296 times stronger than CO₂!) The greatest part of nitrous emitted by breeding farms comes from zootechnical waste, which is manure and slurry produced by livestock and fertilizers applied on farmed lands to feed raised animals: we could infact state that zootechnology is accountable for 75-80% of agricultural emissions of N₂O. Breeding eventually produces about two thirds of anthropogenic ammonia (NH₃) existing in gaseous form in the atmosphere. The agricultural sector is accountable for 94% of ammonia emissions related to anthropic activities that cause acid rain and acidification of ecosystems. In zootechnology, the passing of ammonia in the atmosphere is especially caused by the application of manure on farmed fields.