Anaerobic digestion and milking frequency as mitigation strategies of the environmental burden in the milk production system

The aim of the study was to assess, through a cradle to farm gate Life Cycle Assessment, different mitigation strategies of the potential environmental impacts of milk production at farm level. The environmental performances of a conventional intensive dairy farm in Northern Italy (baseline scenario) were compared with the results obtained: from the introduction of the third daily milking and from the adoption of anaerobic digestion (AD) of animal slurry in a consortium AD plant The AD plant, fed only with animal slurries coming also from nearby farms. Key parameters concerning on-farm activities (forage production, energy consumptions, agricultural machines maintenance, manure and livestock management), off-farm activities (production of fertilizers, pesticides, bedding materials, purchased forages, purchased concentrate feed, replacement animals, agricultural machines manufacturing, electricity, fuel) and transportation were considered. The functional unit was 1 kg fat and protein corrected milk (FPCM) leaving the farm gate. The selected environmental impact categories were: global warming potential, acidification, eutrophication, photochemical oxidation and non-renewable energy use. The production of 1 kg of FPCM caused, in the baseline scenario, the following environmental impact potentials: global warming potential 1.12 kg CO2 eq; acidification 15.5 g SO2 eq; eutrophication 5.62 g PO43- eq; photochemical oxidation 0.87 g C2H4 eq/kg FPCM; energy use 4.66 MJ eq. The increase of milking frequency improved environmental performances for all impact categories in comparison with the baseline scenario; in particular acidification and eutrophication potentials showed the largest reductions ( -11 and -12%, respectively). In anaerobic digestion scenario, compared to the baseline one, most of the impact potentials were strongly reduced. In particular the most important advantages were in terms of acidification (-29%), global warming (-22%) and eutrophication potential (-18%). The AD of cow slurry is confirmed as an effective strategy to mitigate the environmental impact of milk production at farm level. (C) 2015 Elsevier B.V. All rights reserved.