A partial life cycle assessment approach to evaluate the energy intensity and related greenhouse gas emission in dairy farms

Dairy farming is constantly evolving towards more intensive levels of mechanization and automation which demand more energy consumption and result in higher economic and environmental costs. The usage of fossil energy in agricultural processes contributes to climate change both with on-farm emissions from the combustion of fuels, and by off-farm emissions due to the use of grid power. As a consequence, a more efficient use of fossil resources together with an increased use of renewable energies can play a key role for the development of more sustainable production systems. The aims of this study were to evaluate the energy requirements (fuels and electricity) in dairy farms, define the distribution of the energy demands among the different farm operations, identify the critical point of the process and estimate the amount of CO2 associated with the energy consumption. The inventory of the energy uses has been outlined by a partial Life Cycle Assessment (LCA) approach, setting the system boundaries at the farm level, from cradle to farm gate. All the flows of materials and energy associated to milk production process, including crops cultivation for fodder production, were investigated in 20 dairy commercial farms over a period of one year. Self-produced energy from renewable sources was also accounted as it influence the overall balance of emissions. Data analysis was focused on the calculation of energy and environmental sustainability indicators (EUI, CO2-eq) referred to the functional units. The production of 1 kg of Fat and Protein Corrected Milk (FPCM) required on average 0.044 kWhel and 0.251 kWhth, corresponding to a total emission of 0.085 kg CO2-eq). The farm activities that contribute most to the electricity requirements were milk cooling, milking and slurry management, while feeding management and crop cultivation were the greatest diesel fuel consuming operation and the largest in terms of environmental impact of milk production (73% of energy CO2-eq emissions). The results of the study can assist in the development of dairy farming models based on a more efficient and profitable use of the energy resources.