Environmental performance of sorghum, barley and oat silage production for livestock feed using life cycle assessment

The role of environmental consequences derived from cereal production in agricultural systems is widely recognised. Life Cycle Assessment (LCA) has been considered as a useful tool to support environmental decision-making in agricultural systems. In this study, the quantification and identification of the environmental impacts derived from two different double cropping systems comprising winter and summer crops for silage production (forage sorghum, barley and oat) was performed following an attributional LCA perspective in accordance with ISO 14040 standards. Primary data of cereal production for dairy cattle feeding were obtained from a representative year. Only secondary data were used for background processes. Four different functional units were considered to report the environmental profiles: 1 t dry matter silage (base case), 1 ha, 1 t crude protein and 1 MJ metabolisable energy. According to the results, the combination of sorghum with barley presented better environmental results than sorghum with oat when the impacts were reported for mass and energy based functional units, which is attributed to the biomass yield (23% higher) achieved under similar agricultural practices. When the functional unit of 1 ha was taken, the scenario of sorghum and oat was more beneficial due to lower requirements of diesel and herbicides for the agricultural activities per cultivation area. Regardless the functional unit considered, both field preparation and biomass harvesting were the agricultural stages which reported the largest contributions to the environmental impacts (similar to 99%) due to on-field emissions associated to manure application, diesel use in agricultural machinery and seed production. If the crops are separately assessed, sorghum cultivation system would be the best option due to the highest biomass yield, followed by barley and oat considering 1 kg dry matter silage as functional unit. However, when 1 ha was considered to report the results, the barley system was the worst alternative due to the highest seed ratio and diesel requirements (high input-output system). Environmental results must be interpreted within limitation of assumptions accepted by LCA community. Variations on climate and soil parameters as well as nutrients uptake by crops should be analysed and required in further research in order to reduce uncertainties. (C) 2016 Elsevier B.V. All rights reserved.