RESUMEN

The environmental impact of livestock is often evaluated separately from the other agricultural activities involved in an integrated system, such as that of the rearing of Piemontese cattle in the area of origin of the breed. The most frequently used assessment methods (e.g. Footprint approaches or a Life Cycle Assessment) are in fact often used, through a product-based approach, to analyse a single productive process, but such methods do not consider the production of agro-ecological services, and they neglect the interactions that characterise complex systems. Moreover, such methods often only consider the negative aspects of the environmental impact and misrepresent less intensive agriculture practices. However the current gaps in knowledge about the carbon sequestration of agricultural ecosystems, which are complex and integrated systems, require further investigation and other types of analysis tools. A carbon (C) balance of 1223 Piemontese breed beef farms, located in North-West Italy, has been calculated to evaluate whether such a method could be applied to overcome the aforementioned limitations, to evaluate whether it could be used to describe a complex and integrated system, to highlight the relationships that exist between rearing and agricultural activities and to characterise their environmental roles. Conducting a mass balance involves considering the input and output material flows and their accumulation within a system. Thus, the data necessary to quantify the C input, output and internal fluxes of a system at the farm gate, pertaining to the vegetable and animal production processes (productive factors, crop yields, animal performances, productions and sales, reuses), were collected from official documentation, and were then completed and verified through site visits. The mass balance of the system was transformed into C fluxes using stoichiometric coefficients. The fluxes evaluated for the balance were then used to estimate the changes in the C stocks to highlight not only the C emissions or losses from the system, but also their contributions towards reducing environmental hazards. A sensitivity analysis was carried out to evaluate the uncertainty and the robustness of the obtained results. The net C exchange from plants was the flux that contributed the most, amounting to 94.3 % of the inputs, and this was followed by soil losses and animal gases released through respiration and enteric fermentation, which amounted to 42.8 and 36.2 % of the outputs, respectively. The C stored and released by the considered system was calculated considering the C fluxes. Plant, animal and soil storage sites were included in the system, whereas the air site was left out. A constant C content was assumed for the soil. The productive activities of the selected group of beef farms in the Consortium were calculated to remove 96.1 103 t of C from the atmosphere (air site) over a period of one year, and that this amount of C was transferred to plant growth and agricultural products (plant site) and to an increase in live weight (LW) of the animals (animal site). The rates of the stored C to agricultural and wooded areas and to the LW of the animals slaughtered in one year were 1.18 t ha-1 and 2.24 t C t-1 LW, respectively. The sensitivity analysis demonstrated that the C balance was always positive, even for the worst scenario. This study has shown that the examined beef production system, when analysed as an integrated and complex system, can be considered an important C sink and that it is necessary to reconsider the role that livestock, and ruminants in particular, play in the global greenhouse effect.