Evaluation of environmental impacts of important field crops by Life Cycle Assessment (LCA) in Khorasan-e Razavi Province

Agriculture is responsible for food production and consequently food security in one hand but on the other hand is the cause of many environmental externalities. Synthetic chemicals and other environmental pollutants have increased these externalities in the form of soil acidification and salinization, emission of greenhouse gases, nitrogen leaching to ground water, and eutrophication.
Many attempts have been made to evaluate the impacts of such phenomenon on the surrounding environment of which ‘Life Cycle Assessment (LCA)’ (‘cradle-to-grave’) is the most comprehensive one.
Due to increasing use of chemical inputs in agriculture in Khorasan-e Razavi province and its consequent environmental effects, LCA seems to be an appropriate tool to quantify such impacts. The objective of this study was to assess the environmental impacts of important field crops production in Khorasan-e Razavi Province by LCA.
This study was conducted to assess the environmental impact of production of important crops such as wheat, corn, sugar beet, canola, tomato, potato, melon, water melon and cucumber in Khorasan-e Razavi Province. In order to evaluate the relevant environmental effects, LCA methodology in compliance with ISO14044 was used and two factors concerned to resource consumption and contaminants emissions were computed. In this regard, four phases, which are goal and scope definition, inventory analysis, impact assessment, and interpretation, were designed to assess life cycle index. To make the various inputs and outputs comparable, it was necessary to relate these data to a common functional unit, which represent the main function of the system. Therefore, all resource consumption and emissions was related to one ton of economical yield. Three main categories as impacts on environment including global warming, acidification, and eutrophication (terrestrial and aquatic) were defined. To compare the indicators, they were normalized. For the normalization, the indicator results per functional unit were related to the respective indicator results for defined reference area. Finally, an index called environmental index (EcoX) was calculated. Cronbach's alpha was used for assessing the reliability of questionnaire.
The results showed that the largest share of greenhouse gas emissions in global warming category was related to CO2. The highest and the lowest global warming potential per functional unit were found for canola (1342.01 kg CO2 equivalents/ one ton of economical yield) and sugar beet (27.25 kg CO2 equivalents/ one ton of economical yield), respectively. The maximum and minimum aquatic eutrophication potential per functional unit were calculated for canola (0.59 kg PO4 equivalents/ one ton of economical yield) and sugar beet (0.01 kg PO4 equivalents/ one ton of economical yield) with, respectively. The highest and lowest EcoX were computed for canola with 0.67 Ecox/ one ton of economical yield) and sugar beet (0.01 EcoX/ one ton of economical yield), respectively..
The results revealed that, agricultural production systems with high levels of economical yield do not always contradict with environmental safety. In other word, high yield in agriculture and environmental stewardship is not divergent. Therefore, one of the appropriate approaches to decline the environmental impact of agricultural production is to achieve higher yield per unit of area by increasing resource use efficiency. In order to reduce environmental effect and obtain an environmental friendly for production systems in Khorasan-e Razavi province, different ecological approaches could be proposed such as nitrogen application on the basis of crops demands to provide utmost uptake and consequently decline nutrients leaching, decrease acidification and eutrophication impacts, and decrease global warming potential.