Comparative life cycle assessment of three representative feed cereals production in the Po Valley (Italy)

The cultivation of three different cereals e wheat, triticale and maize (five classes: 300, 400, 500, 600 and 700) e dedicated to grain production for feed purposes was assessed to quantify their environmental profiles and identify the most sustainable crop from an environmental perspective. The most critical processes throughout the life cycle of the cropping systems were also identified. These cereals were chosen because they are the most widespread cereal crops in the Po Valley (Lombardy region), the most important agricultural area in Italy. The standard framework of the Life Cycle Assessment (LCA) was followed to assess the environmental performance of the different cropping systems. Several impact categories were evaluated, including climate change (CC), ozone depletion (OD), terrestrial acidification (TA), freshwater eutrophication (FE), marine eutrophication (ME), human toxicity (HT), photochemical oxidant formation (POF), terrestrial ecotoxicity (TEC), freshwater ecotoxicity (FEC), marine ecotoxicity (MEC), water depletion (WD), fossil depletion (FD) as well as land use as an indicator. The results showed that the maize class 300 was the cereal with the worst environmental profile in the base case, considering economic allocation and no environmental burdens related with digestate production. This scenario presented the most intensive agricultural practices and the lowest biomass yield in comparison with the other crops. In contrast, the maize classes 600 and 700 were the cereal crops with the best environmental profiles in most impact categories. The lower requirements of fertiliser (and thus, fertilisation activities) as well as the higher biomass yield were responsible of these favourable results. However, according to the environmental results, the selection of the best biomass source depends on several methodological assumptions such as the functional unit and the allocation criteria considered (between the grain and the straw) as base for the calculations. Thus, the results of a sensitivity analysis showed that the choice of a mass allocation instead of economic one caused lower environmental impacts in all the categories. Moreover, the consideration or not of the environmental burdens related to the digestate production (the main organic fertiliser used) was also a critical step in the environmental evaluations. The inclusion of environmental loads related to digestate production caused a notable increase in the impact of all the cropping systems regardless the cereal and the impact category. This conclusion could be extrapolated to other systems that exclude the additional burdens allocated to the production of organic fertilisers.